TOS-KURIM CNC Upgrade

[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-m...mer-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-pr...ule/dp/SC15622

https://cpc.farnell.com/panasonic/ec...dc%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-m...mer-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.


For the caps, I used a couple of these in parallel https://cpc.farnell.com/vishay/mal21...P=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.

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.