TOS-KURIM CNC Upgrade

[JimJam]

Hi Guys,

Stumbled across this site yesterday after doing some research, some awesome info on here!

I currently have an old TOS-KURIM converted knee mill which uses an Anilam Crusader II and analog Indramat drivers for the DC motors. When I bought it everything was working fine but three years in storage while I sorted a home for it seems to have finished it off!

I've had enough of putting hours into trying to fix it and decided it may just be better to upgrade it to something more modern.

My plan is to rip everything out and replace all motors, and electronics and use something along the lines of MACH/Centroid to run it.

That's as far as the plans gone though, I've got plenty of experience running machines but not building them! I'm a bit overwhelmed with all the different motors and the sizes and control boards etc.

Any help would be awesome on what I need for a low budget install, this is purely a home machine for odd jobs so doesn't need to be amazing. I have access to much better machines at work for anything serious.


Thanks,

Jamie

[JAZZCNC]

Hi Jamie,

Some pictures of the machine will help to get a feel for what you have. I've not seen or heard of TOS-KURIM and a quick google showed me a gantry Mill with a boat on it.!!! . .Pretty sure your not milling boats...Lol

Provided the machines not too massive then you might get away with some large Closed-loop mains driven steppers. They are very powerful and a lot cheaper and simpler than AC servo's. They won't give the speeds servos will but they will do the job if your not chasing high feeds.

Centroid Acorn would be a good match for the controller.

[JimJam]

haha! definitely not going to be getting any boats in the garage any time soon! I've added some photos to help give you an idea of size but its not really much bigger than a standard Bridgeport to be honest. table length is a little over a metre..

27814
27815
27816
27817


Ok that's great, I'll have a look into those.

The other things is I am almost certain the motors I have on it are still working well, so is it possible to leave them on and swap out the existing drivers for something newer/more reliable? apologies for my lack of knowledge on this...

Thanks again

[JAZZCNC]

That should be a simple upgrade you have most of the hard work done in the form of mountings etc, just a few adaptor plates for different size frames with motors will sort it.
I'm presuming you don't want to CNC the Knee.?

You just need to decide if want servos or steppers.? Quite a lot more work in setting up along with big learning curve involved with servos but they do give higher feeds, more power along with smoother operation and accuracy.
The downside is they also cost more money and require a higher level of the controller to get full use out of them. They can be much more temperamental than steppers and very unforgiving on poor wiring quality or practices.

Steppers, on the other hand, are much simpler to set up with hardly any learning curve involved and quite a bit cheaper. They can be run on a lower level of controller.
The downside is they are limited to roughly 1200 to 1500Rpm so feeds are lower. Resolution is lower compared to servo's but still more than enough for milling at this level.

Choosing the correct drives and size is critical with large steppers because you don't have lots of spare power as you do with servos. So if you take this route then look for 220V Mains powered Drives rather than lower AC/DC drives running say 80Vac or 100Vdc.

I've used these many times and they are a great set up with lots of power and provide reasonable torque even at high feeds. More than enough for your machine.

https://www.aliexpress.com/item/32799187522.html?spm=2114.12010612.8148356.3.3cac6 f37OxW5VA

Hope this helps, got any questions just ask.

[Boyan Silyavski]

It depends really on the servo drives and motors you have. Depends if they work properly and the cabling works properly. Meaning what type of signal the servo drives work with and if the board is closing the loop or the servo drives.

If the board is closing the loop probably you will need new modern servo drives and board, suitable to your machine.


Find the drives and motor names and you can start from there.


Most of all solution will depend what type or style of machine and manual control you will like to have as an end result. A big fancy display and a lot of buttons and dros to play with, or just bring an USB stick, stick it in the machine, zero and play / thats me/

[JAZZCNC]

The other things is I am almost certain the motors I have on it are still working well, so is it possible to leave them on and swap out the existing drivers for something newer/more reliable? apologies for my lack of knowledge on this...

Can't answer that without knowing more about the motors and the drives.
They are probably DC Brushed motors and It's quite possible you can get away without drives but it will probably require a different controller that uses +/-10V analog signals and these get expensive quick and are not so popular as Step/Dir controllers. You can get DC Brushed drives which accept Step/Dir signals but they are often not cheap.
It's often cheaper and better to just replace them as a set with modern AC motors and use a Step/Dir controller.

[JAZZCNC]

Most of all solution will depend what type or style of machine and manual control you will like to have as an end result. A big fancy display and a lot of buttons and dros to play with, or just bring an USB stick, stick it in the machine, zero and play / thats me/

Aww no Boyan it's a milling machine for god's sake don't start muddy the waters by suggesting to using one of those DDVS stand alone things will be ok for this machine.! . . It needs more control that those things allow.! :thumbdown:

[Boyan Silyavski]

Aww no Boyan it's a milling machine for god's sake don't start muddy the waters by suggesting to using one of those DDVS stand alone things will be ok for this machine.! . . It needs more control that those things allow.! :thumbdown:

I was going to say that it needs from the advanced standalone controllers or a good software/hardware solution. But now that you say it, DDSV could do the job fine :joker: Now you dont tell me that Mach3/4 is the way to go

[JimJam]

Ok that's brilliant, I've decided to just ditch the old motors now and start again. Not knowing the true condition or specifications of the original motors I would rather not put more money into them and still be no further forward if they don't work.

So based on my knowledge (lack of) and limited use it will have, it looks like I'm going to be better off heading down the stepper route.

The link you sent through with the motor and driver, I would require three of those (one for each axis), plus a control board of some kind, and a PC based control system... Am I somewhere on the right lines here for all the stuff I need for a basic setup?

Regarding PC control Software, what are the preferred options available? I don't want anything too fancy, just something that will jog axis, display DRO, and run code...

Thanks for all your help so far :thumsup:

[JimJam]

Steppers, on the other hand, are much simpler to set up with hardly any learning curve involved and quite a bit cheaper. They can be run on a lower level of controller.
The downside is they are limited to roughly 1200 to 1500Rpm so feeds are lower. Resolution is lower compared to servo's but still more than enough for milling at this level.

Choosing the correct drives and size is critical with large steppers because you don't have lots of spare power as you do with servos. So if you take this route then look for 220V Mains powered Drives rather than lower AC/DC drives running say 80Vac or 100Vdc.

I've used these many times and they are a great set up with lots of power and provide reasonable torque even at high feeds. More than enough for your machine.

https://www.aliexpress.com/item/32799187522.html?spm=2114.12010612.8148356.3.3cac6 f37OxW5VA

Hope this helps, got any questions just ask.

Crikey these are hard to come by in the UK! plenty of 80V and 100V ones around but no luck on any mains powered ones!

is that link you posted somewhere you've bought stuff from before?

[JAZZCNC]

is that link you posted somewhere you've bought stuff from before?

Yes I buy from them all the time. Don't worry about buying from China as they are trustworthy and well proven with many users in UK.

Also if you buy them thru the Aliexpress link I gave you then your protected by Aliexpress guarantee, they basically don't pay the seller until you have received them and say you are happy. They still charge you upfront but do not pass the money on until you are happy.

Edit: You will get charged VAT and Admin fee of around £15-20 on top of that price when they enter this country. You don't get charged Import duty.

[Muzzer]

CNCdrive sell a step/dir DC servo for brushed motors. I've got 2 of them on my Shizuoka and they have been a great experience. These are about £100 each, which hardly breaks the bank. They also avoid the need to mess about with a perfectly good installation.

http://shop.cncdrive.com/index.php?productID=366

[JimJam]

CNCdrive sell a step/dir DC servo for brushed motors. I've got 2 of them on my Shizuoka and they have been a great experience. These are about £100 each, which hardly breaks the bank. They also avoid the need to mess about with a perfectly good installation.

http://shop.cncdrive.com/index.php?productID=366

oh ok, that does sound like another possible route to take then. So with those drives, I would just need to buy a breakout board to link up to a PC and some control software and I would have a useable machine? providing my motors are still good...

If I did take this route the current setup uses linear scales for position feedback, would that be easy enough to incorporate into this type of system somehow?

[Boyan Silyavski]

oh ok, that does sound like another possible route to take then. So with those drives, I would just need to buy a breakout board to link up to a PC and some control software and I would have a useable machine? providing my motors are still good...

If I did take this route the current setup uses linear scales for position feedback, would that be easy enough to incorporate into this type of system somehow?

You will need separate DROs which are not expensive. Can not be integrated on a cheap or middle priced board. This could be done on very expensive boards only like the Galil and such that support double control loops

[Muzzer]

Yes, there's no magic solution to backlash and accuracy. The idea of closing the loop with external DRO scales sounds pretty neat but as Boyan says, it's only very expensive controllers that support that concept. And an expensive system using such a controller probably has very little mechanical nonlinearity and/or backlash to start with.

If you have a basic system with loads of backlash, no controller in the world will be able to able to make sense of the nonlinear behaviour in a sensible way. Imagine trying to drive a car down a windy road with half a turn of lost movement on the steering wheel, then trying to fix that by adding some form of simple closed loop.

Your system is either going to be worn out in which case you need to either live with it or fix it - or it's in good shape in which case you should just fit a modern controller and get on with life. Sounds as if it's quite a decent machine to start with. Apart from bragging rights, what accuracy do you think you actually need? 10-20um? That's still 50th - 100th of a mm. I would start by measuring what I have and take it from there.

[JAZZCNC]

If I did take this route the current setup uses linear scales for position feedback, would that be easy enough to incorporate into this type of system somehow?

I've got a feeling Jamie means the machine is using linear scales rather than encoders for position feedback, which the Anilam Crusader II controller would allow. And wants to know if the scales can be used with the CNCdrive.! Am I correct Jamie.? . . . If not the ignore me and listen to the others because it's correct what they say.!

[JimJam]

I've got a feeling Jamie means the machine is using linear scales rather than encoders for position feedback, which the Anilam Crusader II controller would allow. And wants to know if the scales can be used with the CNCdrive.! Am I correct Jamie.? . . . If not the ignore me and listen to the others because it's correct what they say.!

Yes exactly as you say, sorry I probably didn't explain that very well. I meant that it is currently using linear scales and wasn't sure how it would give positional feedback to the controller if using the CNCdrive muzzer posted without encoders on the motors..

Apologies again for not understanding what's probably the real basics for you guys! Appreciate your patience and sharing your knowledge.

[Muzzer]

You could try connecting the DRO encoders to a DC servo drive but unless you had near-zero backlash, the drive could be almost impossible to tune. This also assumes the encoder signal is a compatible (TTL A/B quadrature) type. If you have no backlash, it might be a workable solution.

Do the Indramat motors have encoders built in already? If not and the linear encoder doesn't work out, you'd need to fit a rotary encoder to each of the motors so the CNCdrives could work with them. You can buy suitable Haidenhain clone encoders from China for peanuts. Failing that, you'd probably be looking at acquiring some proper AC servos which would cost a lot more and need mechanical buggerage to fit them where the Indramats were. Not sure I'd want to waste my time and money fitting steppers to a decent machine like this.

Be aware that early analogue DC brushed systems often had tachometers mounted in the motors. They can't be used as encoders, as they only report speed, not position. However, you could remove them and use the freed up space to mount encoders.

[JAZZCNC]

You could try connecting the DRO encoders to a DC servo drive but unless you had near-zero backlash, the drive could be almost impossible to tune. This also assumes the encoder signal is a compatible (TTL A/B quadrature) type. If you have no backlash, it might be a workable solution.

Don't think these will be your typical magnetic linear encoders you see used on DRO's. These will be full blown Glass linear scales that are much more accurate and commonly used on high end machines.

If it was me I'd get the details of the Linear scales and drop CNCdrive an email asking if they can be used. I think they will be able to be used but you might need to convert from Single ended to Differential, which isn't a big issue. But they will be the one's to tell you, but they will need details.

Regards Steppers or Servo's then like I said if you want it cheap go with steppers as they will get the job done, maybe not as fast or smooth, but still done and reliable along with simple.!

[Voicecoil]

. Imagine trying to drive a car down a windy road with half a turn of lost movement on the steering wheel, then trying to fix that by adding some form of simple closed loop.

I can identify with that having once borrowed a friends Series 1 LandRover that had 30...40 degrees play in the steering wheel before anything happened :confusion:

[Muzzer]

When you say full blown glass linear scales, that's what most of your Chinesium scales are these days. I have several sets, for my smaller mill and my lathe. They are both single ended TTL output, which is what the CNCdrive servos are looking for - I have those drives on my Shizuoka, so I'm familiar with them. They would certainly connect up OK but whether they'd be happy driving an old machine with backlash would remain to be seen.

The accuracy is down to what you want to pay. I think mine are the basic 5um ones from HXX in Shenzhen but you can get resolution down to 0.1um from them and others.

It's possible that high end ones might have differential outputs which are more noise immune, in which case you'd need a line driver to TTL converter.

Whatever encoder you end up with, the driver needs to know how many pulses per rev. This will be a function of the ballscrew pitch, belt reduction ratio and linear encoder resolution but the sums are very simple.

[JimJam]

Ok, so some info I have found about the motors which also seems to match what's on the motor plates (photo attached):

permanent magnet DC servo motors
2000RPM
170V DC
tachometer mounted on rear (I think.. photo attached), but no idea of what output this gives...

with regards to the backlash and scale accuracy asked previously..
They are Anilam linear scales with 0.01mm resolution, again no idea of output type but photo attached if anyone might recognise it.

Done some measurements on the backlash, it's a lot worse than I thought to be fair!
X: 0.15mm
Y:0.04mm
Z:0.06mm

On a side note, the X axis moves faster than the pitch of the ball screw, does that mean there will be some kind of gearbox on the ball screw itself?

Like I say accuracy isn't of too high importance with this, I can sneak high accuracy stuff into lunch breaks at work if I do need that.
The main type of work I will be doing on it is very agricultural low tolerance stuff that I can't always get away with at work :whistle:! In all honesty I don't really need CNC functionality for most of it, its just a nice bonus to have!

With all that taken into account, Is a stepper setup going to be best for me? I know its probably not the best end result for the machine but it will keep it nice and simple for me to convert and use for now.

It would be nice to keep all the original motors but its sounds like it may be a bit more complicated to get running?

Or will this be realistically unusable as a CNC with that amount of backlash until I get that sorted?

[Muzzer]

That is a tacho you are looking at. They have no purpose nowadays, what with digital drives. You should try to remove it to see what the end of the rotor shaft looks like. A rotary encoder typically has a small (6mm or so) shaft and creates negligible torque drag, so mounting one in place of the tacho could be quite simple. Something like this Chinesium clone would be suitable https://www.ebay.com/itm/OMRON-Rotary-Encoder-E6B2-CWZ1X-2000P-R-E6B2CWZ1X-5VDC-New-in-box-Free-shipping/332386539771

One of those CNCdrive brushed servo drivers would be fine for a motor like that and the encoder would connect directly to it. https://www.cncdrive.com/DG4S_16035.html The bigger one is rated at 160V / 45A and although your motor is rated at 100A, it's a beast (47Nm!), so you can probably manage very nicely with half of that. The advantage of going this route would be minimal messing with the mechanical parts. You can probably just leave the encoders where they are for now unless you could hook them up with one of the Chinesium DRO displays just to frighten yourself.

This would be a good time to get a parts list / exploded / section view / manual for the machine. There's a good chance TOS would still have documentation, or you might find a user who could scan one for you. Then you can see how to dismantle it and how it works.

I would expect that the ballscrews will be fitted with double ballnuts, so you'd have some degree of adjustment for taking up some of the backlash. There's likely to be two ballnuts with a shim between them. You can fit additional shims to reduce backlash, possibly without having to even remove the ballscrew. Going to the extreme of fitting bigger ball bearings would likely require you to dismantle the machine, which is quite a large beast.

[JimJam]

Sounds like we might have a plan here then, I think you've convinced me to keep the motors on it and go for those drivers.

So in terms of parts I need to purchase:

-Three servo drives (the ones you linked me to)
-Three Rotary encoders for back end of motors ( I'll make them fit somehow I'm sure!)
-Breakout board to link drivers to PC? (this is where I start getting a bit confused...)
-PC control software (any recommendations that would be compatible with all these parts?)

I must be missing lots of other stuff I'm sure?


Before I order anything I think I'll give it a bit of a strip down and try and sort out some of the backlash issues. Good idea about the machine drawings, I'll see what is around.

[Muzzer]

I'd agree it's probably the plan with least effort, least cost and best performance although there may doubtless be other opinions. I don't have any particular technology to promote, having closed loop steppers, DC brushed servos and AC servos on my machines. But my Shizuoka is similar to your TOS ie old and solidly built with old but well specified motors, so it sounds very similar in many ways. The controller on that thing also came from the ark.

Almost any controller will do as long as it outputs step and direction signals and has some spare IO. My machines have Centroid Acorn (the Shiz) and Newker 990MDCa (Bridgeport) and they both have their pros and cons. Can't comment on other controllers from personal experience but I've heard UCCNC also good. They are from the same place as the DC servos (CNCdrive).

I quite like the Acorn but it requires a PC to run on and the cost adds up by the time you've got the full cream licence and expansion board. The Newker is pretty good value at under £400 being fully self contained but the Chinglish has been a bit of a hurdle. I prefer the Acorn of the 2 but as I say, I have little experience beyond them unless you count a near miss with LinuxCNC.

Would be interesting to see the manual if you can find one. I have one for my Shiz and it made rebuilding it considerably easier than it might otherwise have been.

[JimJam]

Just having a look at the centroid Acorn kit and its not too bad price wise but probably a little more than I can stretch at the minute.

The UCCNC looks to be a good option with good reviews considering the price.

would this combination get the mill running:

3 of these: https://www.cncdrive.com/DG4S_16035.html
1 of these: https://www.cncdrive.com/AXBB.html
Software: https://www.cncdrive.com/UCCNC.html
plus one 5VDC and 24VDC power supply
and the three motor encoders

Think I'm finally getting my head around it thanks to you guys!

[Muzzer]

Know what you mean about Acorn. By the time you've coughed up for the digitising (probing) version and the expansion board, you are at $1000 before you even find a PC to run it on. Then the wireless MPG is another $240. It works well and the support forum is very good, so I'm very happy with it. Depends if you have the dosh available.

The AXBB looks pretty interesting. No experience of them but they seem to have all the bumps in the right places and the pricing looks attractive.

FWIW, they also seem to sell several different encoders. Presumably they will be compatible with the controllers and the pricing seems similar.

That looks about right for the kit of parts. I assume you have a main PSU from the original system that can supply the bulk power at around 140Vdc or so? I ended up getting a 120V 3kW isolation transformer from Screwfix and removing some turns from the secondary to get the right output, as the original 3 phase transformer was the size of a house..

[JimJam]

I did see the encoders on there as well, probably just worth getting it all from them, as you say it should all be compatible then!

I've sent them over an email to check it is all going to work how I need, will have to wait and see if they get back to me or not though.

I hadn't thought about the main power supply actually, good point! The current set up has a fairly substantial transformer unit that appears to output various voltages, I know there is a supply at around 140V in the unit supplying the current drives but can't remember if its DC, will have to check!

[Muzzer]

If it's like mine, the DC was supplied from a massive three phase transformer. The winding would need to be about 100Vac so that you end up with around 140Vdc off load. Here's how I did mine, way back when https://mightyshiz.blogspot.com/2017/03/turn-it-up-new-servo-drivers-can-handle.html I welded the cores back up afterwards with the MIG.

One additional component I bought was the braking module http://shop.cncdrive.com/index.php?productID=260. This allows you to decelerate quickly without risking overvoltage damage to the servo drivers. This clamps the voltage at around 180V. I must admit I haven't ever checked to see if it cuts in on my system but I didn't plan to risk my drivers to find out. One braking module would be enough per system.

[JimJam]

Just had a look through your web page, some good stuff on there, really useful!

My transformer isn't quite the size that came on yours! I think I will repurpose what I have if possible. I found a 'specification sheet' for the transformer that seems to suggest that when used with the motors I have it should be set up to output 150V... but I may be reading it completely wrong! attached photo.

The braking module seems like a good idea for the price of it, better than potentially spending another £300 on new drivers if they go bang!

[Muzzer]

That's handy - you should be able to reuse that. It appears that the left hand three connections are for the secondary (black-black and blue-blue), forming the centre-tapped secondary. You will note that the centre tap is currently connected to ground. If you have 150Vac, you will need to remove turns from the secondary (taking the same number of turns off each leg) but luckily the secondary is on the outside and you won't even need to dismantle the transformer to do so. If it's 150Vdc, it should be fine as it is. The 3kW isolation transformer I used is about £140 https://www.screwfix.com/p/carroll-meynell-3300va-step-down-isolation-transformer-110v/43658 - depends how much weight and space you want to free up.

I originally tried to fit everything in the original operator console but that was a daft idea. Much better to have a cabinet on the side of the machine where you can work on it, with a remote display. With my Acorn system, the PC, display and keyboard etc are on a desk alongside so I can run Fusion (and music) and operate the machine from there. You soon get a stiff neck if you mount the console at the machine around head height.

[JimJam]

Bugger! turns out its 150Vac after all, so that will require some work as well! So with getting the DC output you need to use the centre tap and wire in some diodes or something like that?? to make a rectifier?? I've not done much in the way of electronics since my engineering apprenticeship if you couldn't tell! that was over 10 years ago and I didn't know that much then either!

Yeah I think I will try and get everything in the cabinet that's already on the side of the machine and then just use a laptop on a bench beside the machine for now. I did see someone had a nice setup with a mini PC in the cabinet and a touchscreen monitor mounted beside the machine, that looked like a nice setup which I may look into for a future project. Need to make sure I can get the thing working first though!

[Muzzer]

You should be able to find and reuse the old bridge rectifier and large electrolytic cap(s) from the old system. Alternatively, you could get new replacements from somewhere like CPC Farnell (Part of the Farnell group but cheaper than Farnell and RS).

To reduce the transformer secondary voltage from 150Vac to 100Vac you'd need to remove 1/3 of the turns from each of the secondary windings. Ideally you'd remove the same number of turns from each side rather than remove 2/3 of one and none from the other. You could power it up (carefully!) and use a voltmeter to check where you are if you are not sure how may turns to remove.

You don't need to connect the centre tap to ground but somewhere you may want to connect the secondary (well, 150Vdc) to ground to stop it floating. Some industrial systems leave the circuit floating so that it can tolerate one fault to ground without the system bombing out. It's not a massive consideration here, though.

You can get those tiny NUC / SFF PCs these days that fit on the back of a monitor or inside the cabinet. But as I said, I like to be able to sit down and it's handy to be able to use the same PC to make last minute CAD changes and regenerate the g code.

[JimJam]

Ah ok that will be handy, I'll try and see if I can work out where it is tomorrow then.

Ok that sounds within my ability I would think, Ill have to drop it off the machine and have a proper look at it. Although this is turning into what looks to be a long term project now so I may bite the bullet and go for something a bit more modern like you suggested the other day, when money permits.

Found more issues today as well, Z axis ball screw is heading for the bin! crack in screw itself and lots of wobble! I could probably have just cut the crack out and machined the feature back on the end but I don't think its worth it with the play that it has.. that said there is no way I'm getting a direct replacement so going to have to buy something and modify it to match the existing.

[JimJam]

Started making some progress finally!

X and Y axis ball nuts rebuilt with new oversize bearings, and also new AC bearings on the screw shafts seems to have sorted the backlash issues!

Started moving on to the electrical side of things and I've come to a bit of a halt already trying to work out the transformer..

In the attached picture, the right three wires should be the primary coil supply, so according to the diagram on the transformer that's either 415V or 380V supply going in? And on the left are either end of the two secondary coils which are labelled as 2 x 140V...


So I guess what I'm trying to verify is that I will really only need to connect my 415V AC supply to the primary, and then remove some winding from both secondary coils until I achieve 100V across them?


I have also attached a photo of how it was wired in the current setup, I got a little confused with what appeared to be a 140V leg attached to ground? everything the same colour wire makes it so confusing!!

[Muzzer]

One of the windings is across 1 and 2 - it's the winding at the top of the RH photo. The other winding is between 3 and 4 and is wound on the bottom of the photo. They are connected in series, so that you end up with double the voltage of each winding, from end to end. The centre of the combined winding is grounded. You could remove that unless you want your system voltage hard connected at its midpoint - at least this way the DC is at a known potential.

Looks as if you have both 380Vac and 415Vac primary taps.

If you are going to use a 415Vac connection, the primary would be connected across any 2 of the 3 phases of the 415Vac mains. However, if you were to connect it across single phase 240Vac, you'd get proportionally less output voltage. That might actually be handy here.

If you had 2 x 140Vac connected in series and full wave rectified them, you'd end up with 1.414 x 280Vac, which would be almost 400Vdc. You probably don't want that! If those really are 140Vac each, your original rectifier must have been half wave rectifying the outputs with the 0V at the grounded centre tap, so that each winding only conducted half of the time, giving a final DC voltage of around 200Vdc.

If you were to connect up the 380Vac primary tap to single phase 240Vac you'd get 88-0-88 Vac, which would get you about 125Vdc if you used half wave rectification. That would be a simple solution if you don't mind a slightly lower max speed. Probably wouldn't be an issue really.

If you want to get closer to 140Vdc output with 380Vac or 415Vac input, yes you'd want to be seeing 100Vac on each winding and connect it up as it was originally ie half wave rectification. One diode on the end of each winding, each pointing to the electrolytic cap, with the "0V" cap negative taken from the centre tap. To do that, you'd need to cut the big black wires on the outside of the windings and remove equal turns from each until the output is 100Vac. That's about 30% of the wire.

Do you have either a schematic or a photo of the capacitor and rectifier(s)?

[JimJam]

If you were to connect up the 380Vac primary tap to single phase 240Vac you'd get 88-0-88 Vac, which would get you about 125Vdc if you used half wave rectification. That would be a simple solution if you don't mind a slightly lower max speed. Probably wouldn't be an issue really.


Do you have either a schematic or a photo of the capacitor and rectifier(s)?

This would probably be a sensible solution a least for now to get the system running.
That was going to be my next plea for help, I can't confidently say I have located the capacitors and rectifiers! I have attached a load of photos of the internals, if you wouldn't mind casting your expert eye over them that would be much appreciated.

[Muzzer]

Hmm, that seems to be a set of 3 SCR phase angle controllers rather than "normal" (to us) DC servo drives. These run from ac, so you can look and you can look but you won't find any big electrolytic caps anywhere. The 3 axis drives are those power modules in the 4th photo. You can see there are 6 of them in the 3rd photo. The drivers for the SCRs are in the 2nd photo. The date codes on the compts suggest the boards were built in 1980, so it's an old beast. Technically, they operate at 50Hz, rather than several kHz and vary the duty cycle to modulate the motor current / torque.

Bottom line is that there is no electrolytic cap(s) and the rectification is actually done by the SCRs (thyristors) and the SCRs are commutated (turned off) by the alternating voltage. The supply voltage is indeed two lots of 140V - but ac not dc. The labels on the axis / SCR controllers mention "2x140V", or 280Vac centre tapped in fact.

I think you can safely bin all the contents of the cabinet, as there is almost nothing you can reuse. Even the mains transformer is of questionable value to you. If I were you, I'd want to run the whole thing from 240Vac single phase and keep away from 415V, as there's really no benefit. You need 100Vac on the secondary, a simple bridge rectifier (600V) and an electrolytic cap rated at around 200Vdc.

The servo motors look like good machines and are indeed DC brushed motors. As I said earlier, you can get rid of the tachos and replace them with simple encoders. Indramat is nowadays part of Bosch Rexroth etc, so these drives and motors were probably designed like brick shithouses.

I'm not certain what those 3 transformer-like things are. They are labelled "Drossel" which means something like "choke", so probably line inductors to filter out the current lumps and improve the mains current waveform / power factor. Again, almost certainly of little or no value to you.

[JimJam]

You certainly know your stuff when it comes to this! Everything I have found dated suggests it was built in the 80s (1983 was the latest date I found) so its certainly not cutting edge technology in there!! I'm glad you said to bin it all, I'm sick of the sight of the inside of that cabinet!!

I'll have a play with the transformer today, if I don't get anywhere I'll look into something a bit more suitable..

so if I went single phase and got the 100Vac, would these do to get the DC:

https://cpc.farnell.com/multicomp-pro/kbpc3506/diode-bridge-rect-1-ph-600v-module/dp/SC15622

https://cpc.farnell.com/panasonic/eca2dhg101/capacitor-105c-100uf-200v/dp/CA04976?st=200Vdc%20capacitor

If single phase is the best option, would you completely get rid of the 415V and us a VFD to power the Spindle motor? or Could I still use the 3 phase supply with a relay or something to switch spindle power on from the controller? I know the controller module I bought shows a VFD on the wiring diagram so that may have to be the way to go anyway..

[Muzzer]

Yes, that's the right kind of voltage and current for the diode bridge - and CPC is a good place to buy stuff. A lot of their stuff is identical to Farnell (sister company) but inexplicably sometimes a lot cheaper. You need to bolt it to some form of heatsink but unless you plan to push the spindle to its limit and keep it there for hours, it won't need much. I just fastened mine to the steel backplate and it's been fine. I have something similar on mine which I scavenged from the original VFD in my 1983 Shizuoka.

I think I mentioned earlier that I repurposed a 110V site transformer for my machine. If you are feeling flush / tight for space, that's an option. https://www.screwfix.com/p/carroll-meynell-3300va-step-down-isolation-transformer-110v/43658

Here's my transformer / rectumfrier / VFD installation. The relay next to the rectumfrier is a time delay jobby to allow the caps to charge over a second or two. The caps themselves are hidden behind my Centroid Acorn board further down.
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For the caps, I used a couple of these in parallel https://cpc.farnell.com/vishay/mal210212103e3/capacitor-200v-10000uf/dp/CA05339?CMP=TREML007-005. You could probably get away with one if money is tight.

That cap you linked to is FAR too small. It needs to be about the size of a coke can, speaking technically.

Here's my cabinet. No, it's not a textbook example of cabinet installations but it works.
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Doesn't seem to matter what I do here, I can't get the photo orientation right. What's the trick? It seems to be using the iPhone metadata to determine the orientation.

[JimJam]

Just had a play with the transformer, with 240Vac through the 380V terminals it gave secondary reading of 95V on each and 190V across both... could be usable?

Thanks for the link to the caps, they look a bit more substantial!
would something like this bit a better solution for the bridge rectifier https://www.mouser.co.uk/ProductDetail/IXYS/VBO105-08NO7?qs=sGAEpiMZZMtQ8nqTKtFS%2FKGlmTW84eZI%252BDn %2Fkm7zBfw%3D

Thanks for the photos, very handy to be able to visualise the whole set up.

I have no idea on the photos, all of mine were rotated through 90 degrees as well! I tried everything I could think of but they just revert back to side ways!

[Muzzer]

That is a bit of a mother and IXYS is a "premium" brand. That first one you linked to from CPC would be absolutely fine. These diode bridges are generally very robust.

A better solution would now be to connect the 2 primaries in series and the 2 secondaries in series (as they are already).

I take it that the 380V windings are the brown and blue. Each contains 2 wires - one from each limb. You could separate them and connect them in series so that there is a (floating) centre tap formed by one brown and one blue. Then the voltage on each primary would be 120V and the voltage across the ends of the series connected secondaries would be your 95Vac. Then you would simply feed the 95Vac into a bridge rectumfrier and you would get your 130Vdc or so.

Apart from reterminating the wires, you are almost done. It's a rather large beast but there is no extra expense and alongside your 2 tonnes of cast iron, it's all relative!

[JimJam]

ok I'll stick with that first one I found, save a few quid as well!

I manage to un cover some terminal labelling hiding under the grime! pictures attached of which wires do what..

Yes, as you say, the 380 windings are terminals 1.3 (Brown) and 1.1 (Blue). So leave the secondary as is, and separate the pairs of blue and brown and have a single blue, blue and brown together, single brown..? Hopefully I'm not being dumb and that's what you mean!

At this stage I think the money saving out weighs keeping the size and weight down, at least for now. So I'll persevere with this lump seeing as its quite close to where I need it to be. your not wrong though, it must weight somewhere between 50-60kg easily.

[Muzzer]

.Yes, single blue, blue and brown together, single brown would work.

You can always swap the transformer out later when things are running and you are feeling flush. Keep your beer tokens for other stuff.

My original transformer is even bigger, as it's a 3-phase jobby. Which reminds me, I must get it down the scrappie when it reopens....

[JimJam]

Awesome, I'll get them swapped over today.

Yeah I probably will end up changing it long term to be honest, its not the nicest thing to look at beside the machine..

Yeah I would! probably fetch a fair amount in scrap for something that size!



Have you got any recommendations for relays, I've attached a wiring diagram for the controller I've bought which calls for a 24Vdc relay to switch the power for the drivers ( I think!).

Would a solid state work alright for this? or go for a non-latching type?

[Muzzer]

You could use an SSR but TBH, they can be a bit expensive. If you decide to go that route, make sure you buy a DC one, not an AC one. If you try to switch a DC load with an AC SSR, it will go on but you won't be able to turn it off. CPC have a very limited range but Farnell and RS have a lot more to choose from.

That schematic shows all of the axis drives passing through the relay. That would make it a BIG relay and switching DC is more tricky for the contacts than switching AC. If you go this route, you'll be needing a big clonker of a relay, possibly more of a contactor and make sure it's actually rated for the DC current and voltage you would switching in a fault condition. I haven't gone that route myself. I use the drive enable signal into the drivers to inhibit them if I need to use the e-stop or the controller / VFD get upset. If the worst comes to the worst, I could always kill the mains using the front panel isolator. Certainly, if you switch the high power DC loads, you probably won't want to be using an SSR unless your bank account is very healthy.

I have SSRs for the flood and air (300VAC type) and for the spindle gear solenoids (60VDC). My mains is switched with a front panel isolator and I have a time delay relay after that to soft start the 100VAC transformer / diode bridge / electrolytic circuit. The e-stop kills the drives and the Acorn and the VFD via the low voltage inhibit circuit. As I said, if that were to fail I'd kill the mains. This isn't an industrial safety critical system, just like the other systems here, so there's no point kidding yourself that there is one approach you must take.

If you go the route I went, there's no need for heavy relays in the power circuit. If not there are probably contactors out there that are in common usage for this kind of application that somebody here could recommend.

[m_c]

I wouldn't personally use an SSR for anything deemed critical, as a common SSR failure mode is to fail short circuit.
A suitably sized relay, or contactor is a more robust option.

That diagram you posted, it would appear the AXBB uses an output to power up the drives. Personally, I'd use that output as an enable signal to the drives, and have power controlled via a suitable e-stop system.

[Muzzer]

I'd agree it's better to run the enable signal to the drives rather than switch the DC. I don't see any role for an SSR here either, other than coolant etc.

As you say, it's simpler to run an AC side contactor on an e-stop circuit if you can be bothered, rather than switch the lower voltage DC side. Personally, I'd rather not throw everything out each time I hit the e-stop but that's a matter of preference.

[JimJam]

Great info, cheers!

So it certainly sounds like a better option to tweak that layout somewhat, guess I need to have a think of what I want out of the set up. worryingly I hadn't even thought about an E-stop system yet!! I would at a minimum hope to have an e stop to kill the motors and spindle, whilst keeping the system powered still.

We had a machine at work that had floor mounted E-stops and god knows why but they literally killed everything, PC included, so you lost all your datums and tool offsets. Most annoying when you accidentally kicked them!! I don't want that...

[Muzzer]

Personally I wouldn't want that. On my machines, the e-stop stops the spindle turning and the table moving. The most likely cause would be senior moment / finger trouble causing the tool to dive into something unauthorised, or the tool clogging up and breaking, or realising the speeds and feeds are somewhat ambitious. Mistakes have been made!

If you have a crash, there's no need to kill the whole machine. And if the whole thing really goes native, the isolation switch will stop any arguments. Unless you are planning to sell your equipment commercially, it's your call what you do. There's no right or wrong answer although as there are humans involved, I'm sure there are strong opinions in favour of all manner of different solutions.

[JimJam]

I’ve been having a look at what I have from the old system and if I could use any of it for the E stop circuit and how to go about it. Just wanted your opinions to see if this would work and not cause any damage to anything… or if its just stupid!

I’ve got at the moment a phase and neutral from the 3 phase supply coming into the cabinet that go into fuses, which then go into a large contactor. I was wondering if I could use that contactor set up with a momentary switch, E stop, and relay (which I have from the old setup which are all rated to 600Vac). Then on one of the switched terminals from the contactor could I then feed the 230Vac supply to the transformer which will power the drivers, and on another the supply that goes up to the spindle start button.

With the spindle I should mention it is currently still set up as it would have been when in manual operation. So it is not linked to the CNC side of the machine other than it used to run through a relay so you could only turn the spindle on when the pendant was powered up.

Just reading through what I have written, I guess I could just run the spindle feed through the same relay as the e stop and just switch the 230 through the contactor…

Hopefully someone can make sense of my awful explanation!

[m_c]

Officially all user buttons should be low voltage (IIRC in this context, it's sub 60V), which is why most control systems use 24VDC.

In an industrial setting, you would normally use a dedicated safety relay (essentially a relay with multiple contacts, that all get monitored, and should any fail, the relay won't activate).
However what happens when an E-stop gets pressed, is down to risk assessment. An E-stop should bring the machine to a stop in a safe and controlled manner. With modern servos, you would normally do that by triggering the servo drives fast stop input, then a few seconds later, remove drive power. This means the drive should bring the servo to a fast stop, then power down. If you simply cut power, the servo can keep moving then freewheel to an uncontrolled stop.

However, as it looks like you're using older DC servos, then you have to consider a servo runaway failure.
DC servos is one setup where I would seriously recommend where limit switches are part of the e-stop circuit, and the E-stop kills the drives as quickly as possible, as you really don't want a servo running past the limit switch under full power.

[JimJam]

Makes sense, hadn't thought of it like that! Maybe the E stop button I have was rated to 60V and not 600V then, need my eyes checking!!

Thanks for the info, better get back to the drawing board on this one then!

[Muzzer]

Yo JimJam - wondering how you are getting on - I expect you will have been cutting chips by now!

Let us know what you are up to on this!

Murray

[JimJam]

Hi Murray,

Still making some slow progress! Back at work now so I haven't had too much time to play with it.

Waiting on a few last electricary bits to arrive then I should have everything I need to get it going in some basic form! would be nice to see a bit of movement from it soon!

Being back at work means I might be able to knock up the adaptor bits I need to mount the encoders to the motors as well.

Did you have much trouble getting your motors and drivers set up and working properly? I forgot to order the USB programming stick for the drives, so it would be lovely if they just worked out the box. I have a sneaking suspicion that couldn't be further from reality though....

[Muzzer]

They may just work out of the box after a fashion (I don't recall) but it's unlikely the PID (tuning) settings will be magically anywhere near optimum.

Might be sensible to order a USB thing now, as you are going to need it at some point. It's their own interface as far as I can see so you can't just reuse something else.

[JimJam]

Yeah it would be silly not to get one for the price, think postage will be more than the costs of it! Just waiting for them to get the payment info to me and It'll be on the way, been about 10 days since I ordered it and not heard from them. hopefully they're doing alright over there!

Started getting everything mounted up in the cabinet now, changed the layout god knows how many times. The base plate's like swiss cheese now!!

Got the mounts for the encoders machined up to bolt to the motors, they add a bit more length than I would have liked but I didn't want to start modifying and shortening the motor shafts really so I'll just have to live with it. Once (if) it's up and running I'll make a cover to protect them a bit more.

Also finished the new pulley mount for the Z axis ball screw. (and yes, I did reassemble the ball screw the wrong way after machining it...that was rather annoying to assemble twice!)

Starting to get somewhere now though!

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28293
28294
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[Muzzer]

I enquired about buying something small from them once - think it might have been a line driver board - but never got a reply. You might need to give them another nudge until you get a response or you may not see it. Larger orders possibly attract their attention more easily.

Dunno if you are aware that there is a cncdrive forum - you may be able to contact them through that http://www.forum.cncdrive.com/

Those housings look the part. Good to have access to decent machines when doing this sort of work.

Looks as if you actually replaced the Z axis ballscrew / ballnut? Did you enjoy machining the hardened steel? Sparks everywhere?

[JimJam]

Yeah that did cross my mind, the initial order was quite a chunk of money and I had a reply within a few hours.. I'll give the forum a try, thanks for the link.

Thanks, it certainly makes things easier! Worth taking the extra effort to make them properly, hopefully less head aches with setting them up knowing they are machined properly so the alignment between them should be good.

I replaced them both in the end, the old screw was cracked and it was an odd size. Also needed new bearings as well so just replaced the lot. Can't beat a bit of hard machining, sparks were disappointing though! It was actually worryingly not that hard if I'm honest... looked to be case hardened around 3mm per side, the rest was really soft...

I guessed it wasn't going to be amazing quality based on the price, think its was £30 for the screw and nut... we'll see how it does.

[JimJam]

Starting to get somewhere with wiring it all up now, just a quick query before I do something stupid...

so the wiring instructions for the main plug from the drive to AXBB board are:

The pinout of the Main connector is listed below:

1) Step signal input
2) Direction signal input
3) Ground for Step and Direction signals (NOT for power)
4) 5V power input. (if this input is fed then the 7.pin should not be connected!)
5) Reset (input) and Stop input)
6) Error (output) and Stop input
7) DC power + (12V DC input for digital processor)
8) DC power – (ground for the 12V DC power supply)

Step 3 says NOT for power, but the wiring diagram shows it connected to the 0V of the 5VDC power supply...

[Muzzer]

I think all it means is that you shouldn't connect the power supply 0V to it as the main connection to the board - that needs to go in to 8). The tracks from 3) to the rest of the circuits are probably very thin and come via the processor. May get damaged if you try to run the power supply connection in through them. But when you run the step/dir signals to the stepper / servo drive, you should take the associated 0V from 3) to give you the three wires you need. Better noise immunity.

The digital / logic circuits on the board are powered from the 5V either directly from 4) or by an internal step-down regulator fed from 7). Which ever you choose, the associated 0V to the power supply should connect to 8), not 3).

Hope that make sense....

[JimJam]

Ahh yes, that makes perfect sense now you've said it!

I've got the one axis wired up and started to try and get it going, then it dawned on me I haven't got a clue what I'm doing!!

When its powered up the motor is quiet until you try to move the axis (by hand or by jogging on control software) then I just get a humming noise from the motor and that is all...

So I fired up the PID tuning software and its all nonsense to me, I cant even begin to understand how I would calculate the figures I need to enter...

I've attached a photo of what the settings are and the default values that were there.

The other thing is I'm not 100% on the wiring of the encoders, so it could also be that... or it could be the settings in UCCNC... could be any number of things with me involved!28472

[JimJam]

Stroke of luck managed to get the one axis working, when I looked into what all the parameters actually were I was able to get them down to somewhere useable, probably no where near perfect but at least it's a starting point!

[Muzzer]

Did you see this? http://www.cncdrive.com/downloads/help.pdf

Looks half sensible. I'll also see if I noted my own values somewhere for you to compare against.....

EDIT - that's annoying. I seem to have logged almost everything else I ever did on this machine but there's no trace of the PID settings in the servo tuning. Sorry about that. I seem to recall that you could plot the response in the software as you played with the numbers.

You start with I and D turned off (to zero) then turn up the P term until it gets unstable then back off. Then dial in some D term until it gets a bit nervous then back that off a bit. Play with turning P and D up together until it seems happy and the response is good. Finally dial up the I term until it starts hunting again. Then dial it back a bit and play with all 3 together until you are sick of it. Note down some of the settings that seem to be getting there because you will screw it up and forget what looked promising.

The I term doesn't make a lot of difference to the speed of response but you need it to eliminate steady state error. It's a bit of a black art and there's loads of bollocks talked about it but the above is the guts of it. There are autotuners in some of these programs but in my experience they are usually pretty crap. I've done several courses on digital control systems over the years and I still end up doing a lot of it by trial and error.

[JimJam]

Nope didn't see that one, thank you! I'll give that a go today.

I spent a couple of hours trying to look into understanding it and how it all works but it went straight over my head!

Had another strange issues yesterday.. when I connect the 5V DC power to all three drive units none of them work, but when I unplug one of them the other two work. it doesn't matter which one I unplug the others will then fire up. power supply issues? I am only using one unit to feed the three drives and the controller board....

I have got a 12V DC unit somewhere which I'm pretty sure can be used for the drive units, might give that a go see if that makes a difference.

[Muzzer]

Yes, sounds as if the 5V supply can't supply enough current to get more than 2 of them started up. There may be an inrush current surge at turn-on that is upsetting the PSU. As you say, feeding 12V into pin 7 is an alternative. It may also be safer if there's an internal regulator in each of the drives to drop it to 5V by the sounds of it. Pretty sure that's what I did for my 3 drives.

[JimJam]

Finishing up my degree has taken up the last couple of months, so progress has been pretty slow up to now.

I had the machine roughly wired up to test everything before spending the time making it look tidy, the machine was working great and ran through some programs with no problems. It needed a few tweaks to the settings to get the dimensional positions a little closer but I didn't want to spend too much time on that until it was together for the final time.

Since re wiring it I'm having a nightmare! I managed to get the transformer wiring wrong on the primary coil, so when I fired that up to check the DC voltage output the cabinet filled with some lovely black smoke from the braking circuit. luckily I had unplugged everything else at this point so I didn't cause too much damage (hopefully).
I didn't stick around to check the actual voltage that was being output from it but could this have potential caused damage to the bridge rectifier and capacitor?

I re wired the transformer and checked the voltage output and its back to what I was expecting, but since wiring the drivers and motors back up I'm having power issues with all three drivers when I try to tune them. They all seem to get an voltage error and go into error mode..
I don't know at this point if it's power supply to the drives that's the issue or if its referring to the power to the motors.. need to do a bit of reading on the error codes.


I also managed to snap the silly little pins the USB connection boards plugs into on one of the drives so that's going to need replacing/repairing!

So all in all I've taken a few steps back at the moment! :thumbdown:

[Muzzer]

If you have blown your braking module and the DC voltage is close to the max limit, you may be getting an overvoltage condition when you decelerate your axes. Slowing down / stopping movement will generate voltage on the bus. Perhaps you could try reducing the feed rates in the controller to start with and see if that helps.

What DC voltage have you got? You need a good 30-40V below the overvoltage threshold. That threshold is probably shown in the manual.

You may need to replace the braking module unless you want to see glacial feedrates. But first see if this is the issue by slowing things right down to reduce any overshoot. If you have a scope or DVM, you may be able to observe what is happening to the DC voltage when you decelerate.

[JimJam]

I think I'm on the low side on the DC voltage already at 130V, the drives are rated at 160V 36A. I haven't actually checked the Amps on mine though, cant imagine it being higher than that though?

The braking circuit didn't actually get damaged in use, it started smoking the second I turned on the power when I had the wires mixed on the transformer... I will get a new module on the way, like you say it will probably cause me more issues leaving a potentially (definitely) damaged unit wired up.

I'll try reducing the feed rates as well and see if that helps, it does seem that they initially start to move the axis a rotation or so then goes into error state.

I also had a rather scary issue with one axis, when I hit the reset button the axis just went into rapid on its own! Managed to hit the E stop before it done any mechanical damage to the machine ( hadn't wired up the limit switches at this stage) So i may have some encoder issues as well on that motor.

[Muzzer]

You may have that motor connected up incorrectly, as you say. If your A and B encoder wires are swapped over, it will think the motor is going in the opposite direction. That causes the servo to run away. Or you might have 2 or 3 of the phase connections swapped around.

130vdc doesn't sound bad. I don't recall precisely but I think the voltage clamp / braking module starts clipping at around 170V or so, so you shouldn't be seeing a problem.

Shouldn't take a lot of current to jog the axes. 35A should be more than enough. You would be overcoming a large force to require that sort of power, possibly break something. I've jogged my table against a hard end stop a couple of times. Luckily on my system, the drive trips before anything snaps but that's down to the design of your machine. You could really f*ck something up, like a ballscrew / ballnut or its mount / yoke. Worth seeing what would take the load in that event and convincing yourself it would be OK come the crunch.

Going into error when starting to move doesn't sound like overvoltage, which would only happen if you try to bring an axis to a rapid stop. I wonder if it's an encoder / motor issue?

I'd disconnect 2 of the drives and remove the belt / coupling from the third. Then try to run the servo just using the tuning software. No point getting the controller involved yet. When that works, reconnect the ballscrew and try tuning the response with the software. Finally, connect up the controller and see how it plays together.

[JimJam]

Right, so I've literally taken it right back to basics as you suggested disconnected all drivers except from the one. I was still having a weird issues where it would go into error state as soon as it was powered up, so I went back to the original 5Vdc PSU to power the drive rather than the 12Vdc and that solved that issue. Then I reset the firmware back to factory encase I had done something stupid along the way with the settings.

Then I connected the motor and the 130Vdc supply to the drive, and as soon as I hit the E-stop reset to power it up the motor continuously rotates until it reaches the max error in the settings.

At the moment I'm thinking either encoder is faulty (but all 3 do the same thing) or damaged drivers?

The only other thing I can think of that's different from previously is that I extended the encoder cables. I have double and triple checked the wiring is correct and swapping A and B has no effect. I extended it using CAT 5e cable, could this be causing some interference/noise giving a bad signal back to the drive?

I used shielded cable but the twisted pairs weren't shielded between each other, just the outside of the cable...

I also clipped the cable to the outside of the conduit supply the power to the motors, would this cause an issue?

[Muzzer]

Are you using the cncdrive Servoconfigurator3 software to test and debug the servos? https://www.cncdrive.com/downloads.html It sounds like ti from what you say.

The behaviour sounds like classic servo runaway which happens when the encoder signal is the wrong polarity relative to how the motor wants to spin. So in this case the drive tries to reduce the position error by going even further in the wrong direction. It doesn't know any better.

You should be able to talk to the drive without the motor power enabled ie provide the 5V but not the 130V. Then the s/w should see the drive and the encoder without it spinning off into the bushes. You should be able to turn the motor and check the operation and polarity of the encoder signal. It's a good idea to check the encoder signal makes some sort of sense before going any further.

With a DC brushed motor, you can't get the phases mixed up because there aren't any. But you can swap over the motor polarity by simply swapping the wires over. That's the 2 heavy wires from the drive to the motor. You'd think this should stop the runaway by changing the direction of the motor. Try that and see how you get on....

The motor wires don't need to be screened to work properly but it's good practice. Many of the problems people encounter seem to be caused by electrical noise, usually because of poor wiring practice. You don't need to be an expert but the methods are well understood and explained fairly well in places. I'm sure you will be able to find some good pointers if you look for them and we can always help you with suggestions.

You must be getting pretty close now!

[Clive S]

The only other thing I can think of that's different from previously is that I extended the encoder cables. I have double and triple checked the wiring is correct and swapping A and B has no effect.

I would have thought that this SHOULD have some effect as have been mentioned way back in the post like runaway.

I don't know your drives, you mention cat5 do the drives have a RJ45 connector or hard wired ? I have seen many times that using the RJ45 with crappy plugs the pins don't always connect.

Keep at it you will get there.

[Muzzer]

I would have thought that this SHOULD have some effect as have been mentioned way back in the post like runaway.


Indeed - so first check that the encoder is talking sense. Given that the position error stacks up and finally trips the drive, it sounds so. But as as you say, swapping encoder phasing should have done the trick. So start from the beginning, one step at a time......

[JimJam]

I would have thought that this SHOULD have some effect as have been mentioned way back in the post like runaway.

I don't know your drives, you mention cat5 do the drives have a RJ45 connector or hard wired ? I have seen many times that using the RJ45 with crappy plugs the pins don't always connect.

Keep at it you will get there.

Yes, two RJ45. One for the encoder connection and one to the motion controller. Just to add another potential issue, it has a differential line driver, which from what I understand converts single ended to differential signals. The encoder is hard wired to the line driver which then has an RJ45 plug on the other end which then goes to an RJ45 on the motor driver.

I also made up all of the cables with the RJ45 plugs on, I did test them all before installing them but I guess that might not be a bad place to start looking for bad connections as well.

The only major change I made from when it was running was the encoder wiring, so I'm hoping its something silly like a bad connection!

Thanks for the help guys, I'll get stuck into it again tonight and see what I can find.

[Clive S]

I also made up all of the cables with the RJ45 plugs on, I did test them all before installing them but I guess that might not be a bad place to start looking for bad connections as well.

OK. Did you by any chance use the type of RJ45 that has a slot at the front that lets you pass the wires through then crimp then trim off the excess.

If so I have used them and chucked them out. Recently I made a 20Mtr patch cable (not cnc related) checked it with a cat5 tester that showed the errors. I did a continuity test pin to pin and it was fine.

But putting it into place it would not work. It turned out that the pins would not mate into the sockets properly.

[Muzzer]

On mine, I used standard Ethernet network cables and just cut the connectors off one end. I then just wired them into my controller. I believe cncdrive used to sell interfaces to allow everything to use RJ45 connectors and there's a guy in the US trying to do the same. Seemed rather pointless and expensive to me - and hardly industrial practice.

Using the s/w to see the encoder should tell you if it's connecting and if it's sending sensible info.

[JimJam]

I just reverted the one axis back to how I had it set up before, I cut the CAT5 extended cable from the encoder back to the factory wiring, and used a premade ethernet cable from line driver to drivers and its working again!

I also tried the premade cable with the extended encoder cable which didn't work. so it would appear it didn't like the cat5 cable I added on.... I checked continuity from the encoder to the end of the extended piece and everything seemed ok. That said I don't know enough about electronics or the workings of an encoder, could I have been getting a false reading due to internal components being linked? ( I didn't unsolder the terminations at the encoder when testing)

I soldered and heat shrinked the individual cables as well as around all of them, so I shouldn't have been getting any kind of short where I joined it....

[Muzzer]

That's progress at least. You can buy cable testers like this https://www.screwfix.com/p/philex-network-cable-tester/93219 although obviously Screwfix isn't the best place for low prices. They simply apply voltage to each wire in turn. A remote display shows you if the sequence is wrong.

Sounds as if you should be cutting chips this weekend, then! Well perhaps not quite but things are on the up.

[Kitwn]

CAT5 plugs can be wired in two different ways T568A and T568B. You will even find 'Null Modem' cables with different wiring at each end. This might contribute to the problem. See disgrams on the link.

https://incentre.net/ethernet-cable-color-coding-diagram/

[JimJam]

Thanks for the heads up, I did have a bit of an idea that they could be different as I had to make a crossover cable to connect the motion controller to the PC.

I hadn't realised there were two different straight through styles though, something to look out for!

It turned out to be the extended encoder cables that were the issue... I have no idea what I done wrong or why it might have caused it!

The software seemed to be receiving what it thought to be a good signal from the encoder but I got that run away on every axis... removing the extended wire from each one has fixed it! well... I have had each one working on its own, time to connect all three and see what issues I get next!

I also now have three exposed line drivers that will potentially get covered in coolant, so I need to sort that out as well.

[JimJam]

I've finally been able to cut some metal last week!

Programmed up some test cuts, just a simple square with a holes in the center. purely just to check dimensions.

Getting a few strange issues and not sure where to start looking ....

The hole in the center is on size and position, but the flats across the square are 0.8mm undersize in the X and 1.8mm under size in the Y.

I've run various cuts with different size squares and its the same amount out every time.

I thought it was a coding issues as I'm using a MACH 3 post processor in OneCNC and running it on UCCNC, which from researching supposedly normally works.

Or is it more likely a motor/encoder issue?

[Muzzer]

You can presumably set the steps per rev in the motor driver to the wrong value. If you have 1:1 ratio in your machine it keeps the numbers simple (do you have a belt drive, I forget). You may also be able to set the pulses per rev or pulses per mm in your controller.

Good to cut metal but now investigate what is causing this issue. Is it (hopefully) a consistent % scaling error or a random (loss of pulses) error?

If it's a consistent scaling error, you should be able to fix it by correcting the settings in the drive via the software. I don't know Mach3 but there may also be some settings in there. If you swap over the X and Y signals, you will see where the scaling error lies - does it stay with the drive or within Mach3?

[JimJam]

Sorry I wasn't very clear, so I am using the UCCNC software as my controller (not MACH 3) but I used a MACH post processor when generating the code on my CAM software.

Within the UCCNC software there is a setup area where you zero the axis position, and you enter a value to move, then it moves what it thinks is that distance, then measure the actual table travel and enter it into the software and it calculates the distance per revolution. I had to repeat this a load of times on each axis to get it to down to where i wanted it. it worked out at something like 885 steps per revolution or something with a load of decimals after..

that is literally the only setup I have done though. So I may have missed some other important settings, but nothing jumped out at me.

all the axis use belts and are geared up/down ( i haven't actually calculated the ratios though)

On another note, the UCCNC software allows you to write some code directly into it and run it. When I enter a rapid or feed movement on any axis and run it, it travels the distance i have entered. So the issue only occurs when running a program, which is why I thought it may be to do with the CAM post processor... but if that was the case I guess I would see the same discrepancy on each axis and not random.

I will do a bit more investigating and try what you said about swapping the X and Y signals and see what happens

[Muzzer]

It's a good idea to try to calculate the exact PPR from the belt ratio, ballscrew pitch etc. Trying to do it by trial and error shouldn't be necessary and you could end up including backlash etc. That's my view on it but there's probably no right or wrong.

Bizarre that MDI moves work OK but programmed ones don't, given that they both generate g code. You've got me there but one step at a time perhaps...

[Neale]

Might be a missing steps issue, if you haven't done any other setup? The machine has been told to accelerate or move at speeds beyond its capabilities and the stepper motors can't keep up - could be why it moves correctly in air but not when cutting which puts more load on. Try halving the max speed for each axis and halving the acceleration, and see if that helps. If it does, then you can start winding things up a bit to find the limits.

[Muzzer]

It shouldn't be missing steps in a big way, as it's a closed loop servo drive. It should either recover them or go into an error state and stop.

Also, it appears to work correctly in both rapids and feeds from MDI, although the feeds will presumably be loaded when running a program. Having said that, missing steps wouldn't normally result in a good looking part that has a scaling error.

Let us know how you get on with this.

[Neale]

Sorry - forgotten that bit! Trouble with following multiple threads over a period of time....

Looking back over the current problem, though, it is a bit odd if there is the same absolute error on test pieces of different sizes. That isn't a simple scaling (PPR) error. Sounds more like backlash, but that doesn't fit with the observation that internal cutouts are correctly sized. I think that I would do a backlash check anyway, if only to eliminate it from enquiries. Easy enough to do.

[JAZZCNC]

Sounds more like it's following errors to me, I'd be looking at PID tuning the motor to drives again rather than Steps per, if the servo/Drive tuning isn't right none of that matters.

[Muzzer]

That would be mainly down to the integral "I" term in the PID controller. As Dean says, you could get a good looking response - but with an error if you don't tune it right.

I've got a feeling the cncdrive software actually shows you the response graphically but I may be confusing it with DMM? You want a good response without a noticeable overshoot and no bouncing about afterwards (you want it to be "critically damped").

Tuning a PID is a bit of an art. Here's how I do it:
Start by turning I and D down to zero, then increase P until it's unstable and back off a bit. Then dial in some D until it's unstable and back it off a bit. Then fiddle with both until it feels about as good as you can get. At this point you will have a pretty snappy response - but without the I term, you may end up with a steady state error. So now dial in some I until it's unstable again and back off a bit. You may now need to back off the P and D a little more. Finally, you should check to see what it actually looks like.

Naturally, cncdrive show a slightly different method http://www.cncdrive.com/downloads/help.pdf. It's not a perfect art but you get the general idea.

[JimJam]

Sounds more like it's following errors to me, I'd be looking at PID tuning the motor to drives again rather than Steps per, if the servo/Drive tuning isn't right none of that matters.

AAh Ok, this sounds much more likely to be the issue then. I am fairly happy with my knowledge on setting up with regards to CAM and posts/coding so was fairly happy that was right.

but with the tuning I literally had/have no idea about what I'm doing! I'm away at the moment but when I get back at the weekend I will grab some screen shots of the tuning software and my settings for you guys to have a look at if you wouldn't mind?

[JimJam]

Tuning a PID is a bit of an art. Here's how I do it:
Start by turning I and D down to zero, then increase P until it's unstable and back off a bit. Then dial in some D until it's unstable and back it off a bit. Then fiddle with both until it feels about as good as you can get. At this point you will have a pretty snappy response - but without the I term, you may end up with a steady state error. So now dial in some I until it's unstable again and back off a bit. You may now need to back off the P and D a little more. Finally, you should check to see what it actually looks like.

Naturally, cncdrive show a slightly different method http://www.cncdrive.com/downloads/help.pdf. It's not a perfect art but you get the general idea.

Sounds good, I will give this a go a the weekend. I did have a bit of vibration develop on one of the axis when it was trying to hold it's position, so that's probably a pretty good indication something isn't right in the settings!!

[Muzzer]

Most likely too much P or D. Start off with I and D at zero and go from there. The steady state error is taken care of by the I term, so if PID tuning is indeed the issue, that's most likely where your solution will be found.

[JimJam]

I finally got another chance to play with the mill, with no success at all so far!

The more I mess with tuning the more I realise I have no idea what I'm doing!

When you say unstable, I assume you are referring to the visual display on the servoconfig software displaying any line that is not a straight one?

I am a bit unsure of the actual shape of the plot I should be looking for as well, from what I've researched on the subject it should be a square up and back down kind of thing?

I have attached a screenshot of the settings I have currently, which I believe are not correct at all but this is the only combination I got to that doesn't result in the motor oscillating back and forward.

[Muzzer]

I always note the settings when i do stuff like this. Having said that, I also find no trace of said records when I need them. It might be helpful to be able to show you my final values but I can't find jack shit when I look.

The response doesn't look too daft. Ideally you wouldn't get any overshoot or oscillation on this kind of step change. You aren't far off, although the numbers do seem a bit odd. The P value seems very low and the D seems high. The I seems way OTT. You also seem to have a bit of an offset left when the system has settled down. The I would take care of this normally but perhaps your very low P is an issue.

Did you start with P, then dial in some D, then finally some I? It will start to wobble, oscillate, tremble etc if you overdo it and it can get a bit exciting on occasion. Back off about 20% or so to give yourself some margin before trying to dial in the next term. It's a bit of a black art!

[JimJam]

I started with everything at zero ( Ap, Ad, Ai, Li) then started with the Ap but anything past 200 made it oscillate like mad. Whereas on the other two motors I think they were around 1000-1500 figure.

I ended up taking the motor off the machine in the end, I got a bit carried away with the settings at one stage and the machine got a bit of a jig on. Hopefully it didn't do any lasting mechanical damage! Having it off the machine shouldn't effect setting it up too much should it?


I guess I will just have to keep at it, try increasing P and backing off the D and I?

When you say it has a bit of an offset, I should be aiming to get the green line back down to zero (red line) and have as little oscillation before that as possible? I think I was getting confused by what I should be looking for. Researching PID tuning for the 100th time seems to be making it a little bit clearer now

[m_c]

Tuning really needs to be done with the motor attached to the machine, as the weight/inertia of the machine essentially acts as a big damper.

What Muzzer said about the basic PID tuning is the basic process.
Increase P until things go unstable, and back it off a bit.
Add some D which should then allow you to increase P.
Then once you find the limits of P and D, if needed you then add some I to reduce position error, but it will make everything unstable, so you then probably have to reduce P and D to get things stable again.

I'm not sure what other settings CNCdrive gives you, but once you've done the above on some controllers, you can then apply Feed Forward / filters to help further reduce any following errors.

[JimJam]

Ok nice one, I might get it somewhere near off the machine so it doesn't shake itself to bits, then mount it up again and start adjusting the tuning again.

Thanks for the info on the tuning Muzzer and m_c, I watched a few videos on the process earlier as well and I now at least have a better understanding of what each value does to the tuning and how they relate to each other.

I think the screenshot I previously attached of the settings is the only values you can change for the drives. There may be some other settings in UCCNC control software but I haven't delved into that too far yet.

[Muzzer]

Odd that one motor goes unstable with Ap = 200 or so while the others manage 1000 or so. Perhaps you could swap a couple of them over to see if the problem stays with the motor.

Unless you are shifting a massive (large mass and / or large force) load on one of them, they shouldn't be significantly different. Have you got similar encoder PPRs in the drive and similar steps per pulse in the controller? It's possible that could change the system gain enough to cause this issue - not sure how that would work without actually thinking it through.

There are also a few parameters in there that I don't recall or understand immediately. At the very least you should ensure they are consistent for all the drives if you want to eliminate this strange behaviour. Perhaps a parameter reset would help.

[JimJam]

I've been playing with this again today with the motor off the machine still and got what looks to be a pretty decent (not perfect) tune.

So I loaded up UCCNC just to jog the motor and see what it was like. When I jog the motor it will happily rotate in one direction but when I try the other way it is fighting itself and just judders a bit and doesn't really rotate at all....

Does this indicate it may be a hardware issue rather than the tune?

I will try the motor on another drive tomorrow and see what results I get to start ruling some stuff out.

But could this be down to an issue with the motor or encoder? or does it still seem likely to be my lack of skills with the tuning software?

[m_c]

Sounds more like some kind of hardware issue.

I'd try swapping motors, then drives, to see if the problem moves or stays.

[Muzzer]

Yes, I'd start swapping over the motor / encoder etc. Sounds like a buggered component or a wiring fault, crossed over wiring etc. Time to go for a process of elimination etc.

IIRC, you fitted your own encoders. Getting those wired up correctly would be helpful. That must be a fairly likely candidate.

[JimJam]

I've attached a photo of the encoder just so you can verify it's even suitable for this application..

So the encoder wiring is labelled up as:

Brown: 5 - 24VDC
Blue: 0V Common
Shield: GND
Black: OUT A
White: OUT B
Orange: OUT Z

This is wired to the line driver module to convert to differential signals. I have attached a photo of the wiring info for this, but all it is is ground, A, 5 Volts, and B. so I have this wired up as:

Ground: Blue: 0V Common
A: Black: OUT A
5 Volt: Brown: 5 - 24VDC
B: White: OUT B

From there it is just a standard RJ45 cable that plugs into the drive unit. I have also tested the cables I'm using with the proper tool to verify the wiring is correct.

I have also attached the pin outs for the RJ45 side of the line driver and the servo drive encoder input.

[JimJam]

Just noticed after I posted that, looks like I may have the + and - the wrong way around on the A and B inputs from the line driver to the servo drive!

EDIT: Would this actually cause any issues though? or just result in opposite rotation?

[m_c]

Just noticed after I posted that, looks like I may have the + and - the wrong way around on the A and B inputs from the line driver to the servo drive!

EDIT: Would this actually cause any issues though? or just result in opposite rotation?

As long as you've still got the A/B paired correctly, direction is the only thing that could be affected.

[Muzzer]

And as noted before, you need to be sure the cables don't cross over any of the conductors.

[JimJam]

Progress! You may remember a while ago I tried extending the encoder cables with some CAT5 cable I bought which turned out to be the cause of an earlier issue. I used the same cable to make up the RJ45 cables that link the encoders to the drives.

I have no idea why I didn't replace these earlier when I had the other issue, but swapping them out for some bought patch cables has stopped the motor juddering..

I stripped back the outer insulation of a piece of the cable from the reel and every now and then there is a break in the conductor but the insulation remains in tact! which I can only assume was enough to make a contact when I tested the cables but mounting it on the machine must have given it an intermittent connection.

Now back to the tuning!

[Muzzer]

Well I suppose a smart arse would point out that network cables aren't exactly industrial grade flexible cables, being single core etc. In my own defence, I only used it in my own system within the cabinet for the short distance between the line driver and the DG4S drive.

Good you found the issue in the end. It could have been even more intermittent which would have been even more frustrating. With intermittent faults you can never be 100% certain you've found and fixed the issue.

That cable sounds surprisingly crap if it has multiple breaks straight off the reel. You need to get the whole thing out of the building and into a skip where it belongs before you use any more of it now or in the future.

That video of swarf can only be hours away now - looking forward to seeing it in action!

[JimJam]

Yeah, I’ve learnt my lesson there! Out of interest what would have been the best cable choice for this application?

Is there flexible cable available that would work with the RJ45 plugs?

[m_c]

Igus supply pretty much any kind of flexible cable you can think off, however you may want to be sat down when looking at some of the prices.

[Muzzer]

I suspect it's a bit of a contradiction in terms. As far as I know, the std RJ45 shells for ethernet expect to see single core wires which by definition are not good for flexing. You may be able to buy braided, very flexible cable but how good it is I have no idea.

I managed to get some surplus drag cable for my machine. It typically has multiple bundles of shielded wires of varying sizes, so you can run sensors, encoders, motors, PSUs etc up one cable without risk of interference, in an oil resistant cover. But as m_c says, the price might interfere with your underwear.

Rapid Electronics "stock" Lapp drag chain cable (https://www.rapidonline.com/drag-chain-cable), although that's "stock" as in they will order it for you from Germany. Possibly worth getting the real deal if you want to make a really pukka job, otherwise use multicore shielded PVC cable inside a conduit etc and use the ethernet / RJ45 for the last few inches in the cabinet where there is no flex required.

[JimJam]

You weren't kidding, pricey stuff this flexible cable! If I ask nicely the electrical guys at my work might have an offcut of something suitable kicking around.. worth a try!

The motor didn't seem to be the issue in the end, I don't think anyway.

I was still getting the dimensional inaccuracy's when running a program so I went through the setup process again within UCCNC to define the steps/rev. This time I done it over a larger distance where as previously I just used the max travel of my DTI (only about 15mm), this time I just used the closest accurate thing I had at home (50mm slip gauge).

Running the program again, the dimensions were pretty good, 0.15mm of what was programmed, which is most likely backlash to be honest.

A few more test cuts and see what happens over larger/smaller lengths!

[Kitwn]

Ethernet patch cables which are intended to be flexible SHOULD be made from stranded conductors rather than the single core of fixed cabling. Sounds like you got some that were not. A search on eBay for 'Cat 5 stranded' will find you plenty. Not recommended for repeated movement but it might last until Santa can bring you the real stuff!

Kit

[Hood]

I run Mach3 on most of my machines (Chiron FZ12, Beaver NC5 and Plasma) but recently fitted an SZGH CNC1000 control to the lathe.
I love it for a lathe but not so sure for a mill. Having said that around the same time as I put the SZGH on the lathe a friend bought one for his Mill and he loves it, so might be worth looking at.

EDIT
Ignore my post, for some reason I only saw the first page of this thread but now see it has progressed a long way since then :D

[zoookii]

Hi Jim,

I also have a TOS Mill the same as yours apart from mine does have the CNC parts installed.

I’m looking at the feasibility of installing ball screws and servos and wondered if you have any more photos of the conversion?

TIA

[dazp1976]

I suspect it's a bit of a contradiction in terms. As far as I know, the std RJ45 shells for ethernet expect to see single core wires which by definition are not good for flexing. You may be able to buy braided, very flexible cable but how good it is I have no idea.

I managed to get some surplus drag cable for my machine. It typically has multiple bundles of shielded wires of varying sizes, so you can run sensors, encoders, motors, PSUs etc up one cable without risk of interference, in an oil resistant cover. But as m_c says, the price might interfere with your underwear.

Rapid Electronics "stock" Lapp drag chain cable (https://www.rapidonline.com/drag-chain-cable), although that's "stock" as in they will order it for you from Germany. Possibly worth getting the real deal if you want to make a really pukka job, otherwise use multicore shielded PVC cable inside a conduit etc and use the ethernet / RJ45 for the last few inches in the cabinet where there is no flex required.

I'm going Cat7 solid core from the control box all the way to the base of the machine. Terminated with custom RJ45 modules either end with 2.54 pins out or jst.
Then short stranded cables for sensors into jst connectors plugged into the modules.
Or something like that.