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fasteddy
03-10-2011, 03:14 PM
Hi all..

One day, in the dim and distant future, I will finally kick all the bugs outa this cnc build, but not today it seems...

When I am jogging the x axis (dual drive nema 34's, slaved together in Mach3) it moves freely, until I try to also move the y axis simultaneously.. Then an awful grinding noise and the x axis completely stalls (no movement)... First picked this up last week when it was cutting a circle and it was rapid moving (G0) to the next cut, it stalled the x axis and therefore did not move to the right place..

I have since redone all the wiring and triple checked all mechanical movement which has made no difference, in fact I would say it has got slightly worse if anything..

I am using a Uniport controller, 2 x PM752 drivers (x-axis) and a PM540 driver for the y.. I have wired it all according to the plan shown here..

4686

Anyone encountered this before? Any ideas? Wanna lend me a really big hammer..?


Steve..

fasteddy
03-10-2011, 03:16 PM
Just to mention, I have reduced the motor tuning speeds and accelerations in mach3 until it now crawls at snail speed, no difference...


Steve..

ptjw7uk
03-10-2011, 04:18 PM
Is the power supply man enough as your simultaneously driveing 3 motors when you move both X and Y.
Just a thought as I assume each drives well on their own.

Peter

mocha
03-10-2011, 06:34 PM
If you'll forgive my ramblings, do you get the same problem with X and Z?

fasteddy
03-10-2011, 07:08 PM
Hi guys..

In order..

PSU has plenty of power, am using a 55v 5amp for the nema 34's, and a separate 24v 2.5amp for the nema 23 (y axis, 3Nm)...
Dont get the same prob with the z and x... Only the x is stalling... And only in rapid, regardless of what I set the motor tuning to...



Steve...

Gary
03-10-2011, 07:33 PM
it could be the psu? can you measure the DC voltage on the driver and see if it drops when you move the other axis? Also are you daisychaining the DC or comming back to a star point?

Web Goblin
03-10-2011, 08:52 PM
Steve,
what current setting do you have the drivers set to?

Ian

fasteddy
03-10-2011, 09:44 PM
Hi again..

Just gonna pop my lad to bed then will check what you guys have asked/suggested..

Steve..

fasteddy
03-10-2011, 11:32 PM
Hi again..

Bit more info on the problem.. It only seems to happen when moving x and y in full rapid, if one or other of the axis is not moving at full speed it does not happen i.e. it happens when rapid at 45 degrees, but not 30 degrees... If that makes sense... Sorta guessing both motors are at full throttle when moving at 45 degrees rapid..

Some more info on my setup..
X axis is a pair of SY855TH80-5504B steppers driven by a pair of PM752 drivers.. The settings on each driver is;
3200 microsteps
5.5amps

Y axis (and z) is a 3Nm nema 23 (from Zapp) on a PM540 driver, settings are;
3200 microsteps
2.5 amps

Got my specs wrong on my PSU's earlier, should be;
X axis run by a single PSU (separate outputs) which delivers 65v 8amps..
y and z share a 24v 4amp PSU..

Will test voltages tomorrow when I can get a new battery for my multimeter...
Am 99.9% sure it is something electronic as I have torn apart and rebuilt every mechanical part and everything is freely moving.. Also, I am a decent engineer and a crap electrician with only slightly more knowledge of electronics than my cat...

Steve..

fasteddy
03-10-2011, 11:50 PM
Just a thought...

Have been roving around all the cnc forums trying to find another with the same probs... I have seen an awful lot of posts about earthing, but I have to say, as a complete burp at electronics, I ended up more confused than when I started... Cant get my head aound the myriad of different advice being handed out, and much of it was american.. Do they use different terms for all that common,starpoint,earth,neutral,-ve supply/rail,0 volt stuff? Damned if I can work out what they are in English without even more varying terminology.. I ramble..

Does seem to be a big cure-all for a lot of electronics issues so I was wandering if there is a good post/guide to earthing for us feeble minded noobs? From what I have read, I ought to do this as a matter of course, if only to eliminate several potential problems...

Steve..

JAZZCNC
04-10-2011, 01:26 AM
Seems to me that you have several issues that could and will be causeing this problem. . . First reduce the microstepping to 2000. Not much to gained above this it will also ease the PP work load. . . . Also good idea to run the driver test in Mach folder to test how well your PP works.
Then re tune your motors and see how it performs.

Next 24V is way too low for these motors and will restrict rapid speeds, this would be the first place I would turn to. . . . You could easily double this figure with these motors (If the drives can handle it)

Regards daisy chaining and grounding etc it's not really rocket science but is important if you want to restrict potential problems.
Basicly when running power from the power supply you want to run a separate wire to each drive not 1 wire to first drive then jump or "daisy chain" from this to next drive.

Think of the PSU as the centre of a star with all single wires running from it out to each component that needs to takes power from it.

The same applies to the ground wires, run each ground back to 1 central ground point. It's a good idea to have single ground connector with multiple connections, basicly you dont want multiple ground points around the machine other wise you can introduce ground loops which can cause noise issue's. Thou I'm pritty sure this is not your problem.

Their is another potential problem that can cause what you are experiencing. . . Mid band resonance.!!
This is caused by resonance from the machine which at a certain point in the accelleration curve interfears with the pulse stream going to the motors causing all sorts of random issue's.! rough sounding motors and poor performance as well has stalling as the speeds increase are just some of them.
Some drives have compensation for this built in some don't.! . . Not sure if yours do or not.?

If I was to place a bet on your problem I'd put money on it being down to 24V supply. . . And possibley too high on the stepping.

Also what Kernal speed are you running Mach at.?

fasteddy
04-10-2011, 01:57 AM
Wow Jazz.. Lots to chew on...

Ought eliminate a couple of potential probs tho... I am not daisy chaining the motors/drivers with power, all have there own separate feeds/wires.. Not sure what the voltage limit is for these motors and I have been frowning a smidge at the 24v power supply as a possible weak point.. But the y axis is not stalling, and my last cnc was driven by just that one 24v psu, and it drove 4 x 3Nm motors then with no probs like this one...

Was running Mach3 at 25Khz, ramped it up to 45Khz in trying to fix this prob and it made no difference (using a dual P4 board, 2 gig ram with XP in desktop PC mode) so I left it at 45KHz..

Driver test is fine..

By ground, you mean earth right? Connect 0v and or ground to earth? Read this many times but when I look into my box of tricks, there are an awful lotta grounds and 0v points, more if you eyeball the PSU's too.. Pass the aspirin...

Mid band resonance... Is this a resonant frequency of the machines mechanical structure? If so I doubt this is a problem as the motors are very smooth and pretty quiet (apart from that dull thump caused by backlash comp in Mach3) until the very sudden growl from the nema 34's when they stall.. The fact that they both stall, and bearing in mind they are slaved together in Mach3, still suggests something electronic tho... Also as both the y and x are running at full speed simultaneously suggests it might be power, so will get a new battery for my multimeter first thing tomoz...

Will drop the steps as you suggest and check some voltages in the a.m. Starting to get intrigued by earthing, really feeling the need to get that one outa the way..

Steve..

JAZZCNC
04-10-2011, 02:26 AM
By ground, you mean earth right? Connect 0v and or ground to earth?


Yes by ground I mean Earth.
One Earth point which each mains device leads back too or picks up from.

Basicly all roads lead to Rome or in this case one earth point.

Gary
04-10-2011, 09:20 AM
Are your phase cables and signal cables shielded?
If not you may find that noise is being picked up on the signals.
This may be hitting the direction signals and causing one of the x axis to be changing direction?
disconnect the direction signals on the x axis and see if it still happens.

fasteddy
04-10-2011, 10:29 AM
Hi Gary..

Cables are shielded, still troubling me that only the x axis is stalling.. y is unaffected yet is obviously part of the problem... sigh..


As I have got you here, what is the voltage rating for the 3Nm nema 23 motors you sold me? Has been suggested I may need to upgrade my
24v PSU for them...

Steve..

fasteddy
04-10-2011, 02:01 PM
Chicken or egg?

Not sure if the problem caused this, or if this is the problem... On the power supply for the nema 34's (x axis), I have just discovered a 'crispy' component.. Think its a resistor, I can only read '8K' on its blackened surface.. I was about to check voltage outputs from this PSU when I saw a tiny wisp of smoke come from it.. I have switched it all off and will contact the chap that sold it to me to see if he knows what it is..

Steve..

Jonathan
04-10-2011, 02:05 PM
As I have got you here, what is the voltage rating for the 3Nm nema 23 motors you sold me? Has been suggested I may need to upgrade my
24v PSU for them...

I run mine with the same PM752 drivers on 70V, so you can easily increase yours which will make a huge difference to the speeds you get. You can use up to 50V for the motors on the PM542... 48V is common and convenient. Easiest option is probably to get a big toroidial transformer to run both on 48V, but it would be better (faster) if you had two transformers to get 48V and 70V. There used to be someone selling lots cheap power supplies on eBay which were just under that voltage and ideal for this application. They've all suddenly gone now but you can buy them from Zapp for several times the price.

I did have a similar problem to yours at one point...
Since you're saying that X and Y both go at highest speed when moving at 45 you must have their feeds set the same. On my router I started with X a little slower than Y, so to get both to move at highest speed (which makes the actual speed the vector sum of X and Y maximum velocities) I had to move it at a different angle. At that angle or close to it the machine would often stall. The first thing I tried was to reduce the feedrate further on X from about 10m/min to 8m/min then 7m/min which each helped (stalled less often), but that was getting a bit slow...I had a spare transformer, so added that in to power the Y (and A) axis and left both the X's and Z on the bigger transformer. That makes the two axis independent, so from the driver's and power supplies point of view it's no different if one is drawing a lot of current or both. The voltage wont drop.
This didn't make a lot of difference, so I analysed both set-ups with oscilloscope. I can't find where I saved the graphs, otherwise I'd post them ... but it did show there was some ripple (couple of volts I think) with both setups and the ripple was slightly less with them split. Still evidently it was not enough to make much difference anyway.
Since that implies the power supplies were only a small part of the problem I decided to finally get round to swapping the computer to a better one I had (1.4Ghz AMD to a 3Ghz something or other), which made a massive difference. Feedrate on X went up from barely reliable at 7-8m/min to fine at 15m/min! It almost doubled the feedrate ... purely due to the computer's evidently better parallel port as I kept everything else the same. Since then I have increased the kernel frequency to 35kHz as that's sufficient to use 1600step/rev. You only need to use the minimum kernel speed to get the feedrate you require at the chosen microstepping value, so having it at 45kHz versus 25kHz is pointless and unnecessarily unstable if the former is sufficient.

Putting a bigger capacitor on the power supply may help, depending on what the value is currently?
Definately use the driver test in mach3 to check the parallel port. Perhaps try another computer?

Jonathan
04-10-2011, 02:12 PM
Chicken or egg?

Not sure if the problem caused this, or if this is the problem... On the power supply for the nema 34's (x axis), I have just discovered a 'crispy' component.. Think its a resistor, I can only read '8K' on its blackened surface.. I was about to check voltage outputs from this PSU when I saw a tiny wisp of smoke come from it.. I have switched it all off and will contact the chap that sold it to me to see if he knows what it is..

Steve..

Ahh must be a switching power supply, good luck getting that fixed. If something has gone wrong with the regulation circuit that would explain your problem.

I forgot to mention in my previous post that the stalling only occurred with mine at or near full speed, and completely went if I made X really slow (it was always X that stalled). This doesn't seem to be the case with yours... so I'm not sure. Maybe try wiring both X drivers to the same step/direction pins on the parallel port and disable the slaving as that should reduce the 'load' on the parallel port.
Also remember that the average current drawn by the stepper motor is not a simple function of speed...

fasteddy
04-10-2011, 02:16 PM
Hi Jonathan..

I have just emailed you and tried to telephone you.. It is the PSU I bought off you that has the crispy component..! Check your email..

Steve..

Jonathan
04-10-2011, 02:28 PM
I have just emailed you and tried to telephone you.. It is the PSU I bought off you that has the crispy component..! Check your email..

:redface:

That'll be the bridge rectifier then. I put two capacitors and rectifiers on the transformer as it has more than one secondary. Were you using both (one for each motor) as I think that's what I said to do to share the load? Looks like it needed a heatsink, unless something else caused it. I can post you another (this time bigger) bridge rectifier so you can solder it in? I've got to go to a lecture quite soon... I'll give you my mobile number so you can call me after about 5pm.

It's strange as that's the same bridge rectifier as I'm using, and mine has ran 4 of the 3Nm motors just fine for a long time, which adds up to a lot more current than the

I think transformer gives 40VAC, so about 55V DC... can remember exactly. Either way it's a lot more than 24V.

fasteddy
04-10-2011, 02:36 PM
Hi Jonathan..

Just emailed you again;

Just had a real close look at it with a loupe, I can see a single strand of wire from the +ve very close to the –ve.. Reckon it may have been arcing.. Tried to take a pic for you but my camera/phone cant take pictures that close and all I could get is a blur..


Part of me is relieved as this could well be the source of my probs... You set the the PSU for two outputs, 65v 8amps which I am pretty sure is fine for those motors.. Yes please, if you can send me a replacement rectifier, I will solder it on.. The -ve wire is also crispy so will replace that too...

Steve..

Jonathan
04-10-2011, 02:43 PM
You set the the PSU for two outputs, 65v 8amps which I am pretty sure is fine for those motors.. Yes please, if you can send me a replacement rectifier, I will solder it on.. The -ve wire is also crispy so will replace that too..

Ok, I've got a few 35 amp ones lying around which should do the trick.

I'm a bit worried now you appear to be using this power supply with the PM542 drivers? I thought is was PM752. If that's the case it's bad as those drivers are only rated for 50V. I'll check in our emails what voltage the transformer actually is/was.

EDIT: Nevermind, that's me being an idiot...it's the PM752 so not a problem.
I really need to go now.

fasteddy
04-10-2011, 02:49 PM
Hi Jonathan..

No, I am using your PSU for a pair of nema 34's, which are run by a pair of PM752 drivers.. Think these are rated at 70v and have run them well till now.. Have just been reminded that I moved the PSU last week, perhaps I jogged that single strand of wire...?

Steve..

fasteddy
04-10-2011, 07:07 PM
Hi all..

Jonathan gave me a quick fix for the PSU so am up and running again.. But the problem of the x axis remains, so please dont give up on me all you CNC gods out there...

Steve...

audioandy
04-10-2011, 09:00 PM
Steve

I have one of the PSU's that Jonathan is talking about (the ones off eBay).


I have to have a clearout so if its any good to you make me an offer.

I have not used it, just powered it up to make sure all is ok when I first got it.

Regards

Andy

Jonathan
05-10-2011, 12:59 AM
I have one of the PSU's that Jonathan is talking about (the ones off eBay).

I'll buy it if Steve doesn't, but it looks like his needs are greater. I'm guessing as it says you're also in Nottingham there would be no need to post it...

audioandy
05-10-2011, 10:09 AM
Ok Jonathan

No problem, let Steve have first call then it's over to you.

Regards

Andy

ps I'm in Sutton-in-Ashfield just off Junc 28 M1

Karl
05-10-2011, 11:20 AM
Same/very similar problem here. When jogging an X-Y table with MACH3 at full speed (400mm/min) in either the Y+/Y- direction and then, at the same time, attempting to jog either X+/X- at full speed [and completely vice versa] there are a lot of loud horrible mechanical noises and the table clearly stops moving correctly. This is 100% repeatable. Not seen this happen when machining a piece - that said I'm not aware of a situation where the machine is asked to move full speed in, say, the X direction whilst it's already moving full speed in the Y direction. I assumed - for no good reason - that this was a MACH3 jogging thing. So now I'm very interested in the answer.

Setup:
Motors: SY60STH88-3008BF (x3)
Driver: PM542 @ 1,600 pulses per rev, 2.37A(Peak) [1.69A(RMS)]
Supply: 43V
MACH3 motor config': 627 steps per mm, 400mm per min

Jonathan
05-10-2011, 11:36 AM
I'm not aware of a situation where the machine is asked to move full speed in, say, the X direction whilst it's already moving full speed in the Y direction. I assumed - for no good reason - that this was a MACH3 jogging thing. So now I'm very interested in the answer.

Nothing to stop you running a program like this. It's conceivable on a drilling cycle.

G21 G61
G0 X0 Y0
G0 X100 Y100
G0 X0 Y0
G0 X100 Y100
G0 X0 Y0
G0 X100 Y100


Setup:
Motors: SY60STH88-3008BF (x3)
Driver: PM542 @ 1,600 pulses per rev, 2.37A(Peak) [1.69A(RMS)]


You and Steve are both running these motors in Bipolar series, not parallel ... interesting.


No problem, let Steve have first call then it's over to you.

Thanks :)

fasteddy
05-10-2011, 12:02 PM
Hi Karl..

At last! Someone with the same problem.. I ran a piece of code last week with 16000 lines and it was not until near the end that it stalled my x axis.. The code was making a rapid move at 45 degrees for 11mm and then stalled the x axis.. I have now spoken to several people about this problem and between us have eliminated most of the potential problems.. What remains is;

Re-install Mach3 including driver..
Trying a different PC in case it is the parallel port..

I will dive into the workshop and try both these things and report back any success/failure..

Steve..

fasteddy
05-10-2011, 12:03 PM
Hi Jonathan..

I had always thought bipolar series was preferred to get the higher speeds? Is parallel better?

Steve..

Jonathan
05-10-2011, 03:13 PM
I had always thought bipolar series was preferred to get the higher speeds? Is parallel better?

Yes parallel is generally faster. Bear in mind the current the drivers is set to also makes a difference as the torque is roughly proportional to the current (until you go much above the rated current and the rotor saturates). If the nearest current setting to the current in series is greater than the parallel setting then it may not make much difference. Karl has the motors on 2.37A, and the rating is 2.1A so it's already 13% over. The PM542 maximum is 4.2A, so the same as the motors ... so if putting in parallel gains less than 13% then you may not gain anything though it would be nicer. There's more to it than that though... in the end it's easiest to just try it and see. Keep an eye on the motor temperature too.

JAZZCNC
05-10-2011, 03:29 PM
You and Steve are both running these motors in Bipolar series, not parallel ... interesting.


If so then it's very likely your way under voltage and just simply running out of torque, the torque drops off very quickly when wired series.!#

Jonathan
05-10-2011, 03:39 PM
If so then it's very likely your way under voltage and just simply running out of torque, the torque drops off very quickly when wired series.!#

However, for completeness, the torque when wired in bipolar series is greater at low speed than the same motor wired in parallel.

It looks like in Steve's case it's the Y/Z axis motors that are in series, and they're not at fault. Still worth trying, as long as the power supply can take it.

JAZZCNC
05-10-2011, 03:53 PM
However, for completeness, the torque when wired in bipolar series is greater at low speed than the same motor wired in parallel.

It looks like in Steve's case it's the Y/Z axis motors that are in series, and they're not at fault. Still worth trying, as long as the power supply can take it.

Yep exactly, thou as the speed rises the torque drops away very quick in series and because the X axis needs the most torque due to it's mass and it's happening when rapiding I'd be changing to parallel.

Edit: That said I still don't think this is Steves problem due to him having the problem at lower speeds.?????

Karl
05-10-2011, 05:38 PM
Just taken some motor current measurements on my machine - measured at the output of the star-wired PSU:

- Powered up but stationary the 3 drivers and motors together pull 0.87A (DC) total. Motors bipolar series. Driver PM542 settings now 2A (RMS) limited.
- MACH3 jogging X,Y or Z axis individually pulls 1.36A during acceleration levelling at 1.25A - this is the machine's full MACH3 limited speed of 400mm/min.

Jogging in, say, X and then also jogging Y - ie causing the horrible mechanical noises and poor movement - pulls 1.6A to 1.9A total.

Jogging the Z full speed and then - at the same time - jogging either the X or Y in any direction does not cause any problem (likewise moving either X or Y and then engaging Z causes no problem).

My PSU is rated at (43V) 5+ amps so, given the figures above, current does not seemed to be an issue.

I'm wondering if this problem is due to inertia/momentum/twisting forces in the, not very expensive, X-Y table?

fasteddy
05-10-2011, 06:55 PM
Hi Jazz..

Just a quick mention that I am only getting this problem when the X and y are at maximum speed...

Steve..

fasteddy
06-10-2011, 08:58 AM
Have now re-installed Mach - no difference..
Also tried another PC, although it is a pretty low spec laptop (setup as a standard PC) - no difference..
Going to rewire my nema 23's (3Nm) in bipolar parallel today, not sure if I will be able to do the same with my Nema 34's as they are 4 wire motors, just waiting on a bit of advice on that, unless someone out there knows how to do it?

Just want to say that although I have not got to the bottom of this problem yet (and neither has Karl, my sympathies dude), I am very grateful for all the advice given.. Checking so many aspects of my machine is a real confidence booster with the level of scrutiny it has had this week, I feel like several engineers have checked my work and so far, most of what I have done seems right and a couple of things I have been able to improve..

Steve..

Gary
06-10-2011, 09:34 AM
you cant connect a 4 wire motor in parallel, it is similar performance wise as if you had an 8 wire motor connected in parallel.
Out of interest does this problem happen if you disconnect the ballnuts from their mounts?
Also does the X axis stall when the Y axis is in a specific position or is it random?
My thinking is that is may be a mechanical problem with the stiffness of your machine?

fasteddy
06-10-2011, 10:03 AM
Still happens with the ballnuts disconnected, I had removed the ballnuts last week and cleaned them out, then tested that principle as I was originally thinking along the same lines.. The problem can happen at any position on the bed (2mt x 1.4mt) although it seems to happen much more on moving the x axis +, rather than -..
Mechanically, the machine is sound and I have torn apart and rebuilt it twice in the last week, everything is freely moving..

If I get a chance, I will make a little video of it happening later today..

Steve..

Gary
06-10-2011, 10:10 AM
at what RPM on the motors does it stall? is it at the same speed all the time? Do both motors on the X stall even if they are not linked mechanically?

fasteddy
06-10-2011, 10:15 AM
Both motors stall simultaneously, they are using separate drivers and slaved together in Mach3.. I have tried varying the speeds and accelerations in Mach3 but that makes no difference. It only does this on full rapid, when the x and y are being moved simultaneously.. I can repeat this every time by jogging both axis at full speed, it also does it if I run code that rapids (G0) at 45 degrees...

Steve..

Gary
06-10-2011, 10:22 AM
What speed are you stalling at?
What happens if you are moving X at maximum speed and then just move Z?

fasteddy
06-10-2011, 10:37 AM
It is stalling at all speeds.. Had it as low as 500mm/min up to 2500mm/min.. Acceleration from 10 - 120.. Stalls at any speed.. The x axis is completely unaffected by the z axis.. It only happens when the Y and x is both moving at full speed..

fasteddy
06-10-2011, 02:23 PM
Have wired my nema 23 (3Nm) in parallel.. Wow, whizzes along now at nearly double the speed...!
Was re-checking this fault and had the y axis stall as well as the x..! Hmm.. seems the problem is getting worse now.. Spent a good chunk of the morning frowning hard at my PC, its a quick computer but have had some comments about the parallel port that are starting to sound ominous...!

Steve..

JAZZCNC
06-10-2011, 04:48 PM
Steve, Smooth stepper on it's way this will eliminate the PP completely. . . Remember thou I want the bugger back.:confused:

fasteddy
06-10-2011, 06:59 PM
Thanks Jazz..!

Will pop the bugger back as soon as I have tried it..!

Steve..

Karl
06-10-2011, 08:07 PM
Disconnected the X and Y motors from their X-Y table. Unable to reproduce the problem of horrible sounds and missed steps described above when MACH3 jogging the motors at full speed. I'm becoming convinced that, since the X and Y-axis move very smoothly on their own, that the issue - in my case - is related to some resultant force vector in the heavy X-Y table causing table twisting and thereby increased friction and too high loading on one or both of the the motors (even though motor currents seem low). I can't tell by sound or feel whether it's the X or Y motor generating the noise. A mystery that's annoying and puzzling.

JAZZCNC
06-10-2011, 08:21 PM
Disconnected the X and Y motors from their X-Y table. Unable to reproduce the problem of horrible sounds and missed steps described above when MACH3 jogging the motors at full speed. I'm becoming convinced that, since the X and Y-axis move very smoothly on their own, that the issue - in my case - is related to some resultant force vector in the heavy X-Y table causing table twisting and thereby increased friction and too high loading on one or both of the the motors (even though motor currents seem low). I can't tell by sound or feel whether it's the X or Y motor generating the noise. A mystery that's annoying and puzzling.

Sounds very much like you have some binding then or if it's X-Y table that uses dovetail ways with jib strips then you could have some slop enabling the table to twist and jam.?
If so then I would strip down the table and check for any chips that have got lodged or stuck, clean all surfaces carefully checking for damage or high spots.
Re-lube the ways and rebuild being carefull not to over tighten but still enough take out any slop then try again.

Good luck.!

JAZZCNC
06-10-2011, 08:38 PM
Steve I'm clutching straws for you here but it may be worth trying another PP cable.?? Will at least be another part of the elimination process.!

I'm pritty sure you have a pulse issue and this where I'd be concentrating my main focus.!

fasteddy
07-10-2011, 02:24 AM
Think you are right Jazz.. Having revved up my y axis by re-wiring it as parallel, I am guessing that there are more pulses/second now and this may be why I am experiencing even more stalling, the y axis did not stall before and it is now... Your smooth stepper will surely prove this one way or another and I will do as you suggest and get another cable..
As we discussed before, I should probably think about a PCI PP but I remember your thoughts on this.. So, anyone out there know a tried a trusted PCI parallel port that they use on their CNC?

Steve..

Swarfing
07-10-2011, 09:10 AM
Look fr cards that contain the 'NetMos' chip on it,a lot of the cheap ones on Ebay do, just fire odd a mail asking them. There has been good feedback on these.

fasteddy
07-10-2011, 08:48 PM
Alrighty..!!!

Finally getting somewhere...! Changed my parallel lead, big difference and stalling was reduced immediately, but not gone... Then dropped micro stepping down to 800 for each axis and then re-sited every wire.. Bingo...! No stalling.. Had it whizzing around the limits of each axis in 45 degree moves for about an hour.. Not one stall.. Gradually ramped up the speed and acceleration of each drive and would have got it up to around 4500mm/min except one of my ballscrews is bent, nearly shook the frame apart..! Just got to remove the dodgy ballscrew as I think the machined (motor) end might by eccentric...

Thanks all so much for your help, wish I had done everything step by step now as I am not certain if reducing micro steps or rewiring it was the cure.. From what I have read on many posts, 800 micro steps should be within easy reach of my PC, so I still think I have a weak parallel port.. Will get a PCI one from ebay (with a NetMos chip, thanks 2eUpoz) and will still try Jazz's smooth stepper (mucho thanks Jazz) as that sounds like a cure all for this type of pulsing problem..

Once I've checked the ballscrew I have a 6 hour job to do so am going to see how it goes with the new settings..

Karl, guess you have tried reducing the micro-stepping on your drivers, if not, got to be worth trying and definitely try a new PP lead as Jazz suggested.. If that does not work, then good luck and please continue the post until you have it working properly..!

Steve...

Swarfing
07-10-2011, 09:07 PM
Good to hear it's work Steve :-)

by the way the last PP card i bought was from this guy. Had to search quite hard but found him.

http://myworld.ebay.co.uk/fullspeedit

JAZZCNC
07-10-2011, 10:29 PM
Great news Steve. . I've known a few case's of failing or poor quality cables giving troubles, thou I still think it's your PP causing the problem. Thats why dropping the microstepping works.
Bet if you dropped the kernel speed to 25K you will be able to micro step higher.? . . . Give it a try and I think you'll find you can get 2000 M/S.!

Edit: The only reason to run higher Kernel speeds is if you can get higher speeds from your motor/screws than the kernel allows and your if PP is upto the job.
Other wise Mach works best or should say most stable at 25K. . . . If your happy to run at around 5mtr/min then I would leave it at 25K for best stabilty.

mocha
07-10-2011, 10:37 PM
good result Steve!


...and then re-sited every wire.. Bingo...!What did you change with ther wiring??

JAZZCNC
07-10-2011, 10:52 PM
Ok heres a post from the Yahoo forum By Art fennerty the genius who invented Mach3 that may may explain something of what I mean and also clear up why Mach likes 25K best.

It's part of a reply over along running issue a guy had and so some of it may not make sense but it's interesting reading and should shed some light.!

Here's the deal with kernal speed.

Lets say you select 25Khz, and then tune your motors. While tuning, you find you have the velocity slider up all the way, but would like to go faster than you can tune.. you then must select the next higher kernal speed, and retune all motors. If while tuning, you find you cannot go fast enough, repeat till the kernal speed is such that you CAN select the speed you need.

The reason is this..

In 25Khz mode, the computer interrupts every 40us.. in 35Khz, every 28.5us , in 65Khz, every 15us , and for 100khz, every 10us.

Now, the time-in-int is the amount of time spent servicing that interrupt. One of the secrets of the printer port driver, one Ive never discussed , is that
all drivers in windows are told to do their thing fast, and get out. My driver breaks that rule..heck it breaks most rules. :) . SO it takes the time it needs to
do 1 step pulse, read input, set outputs, unset the step pulse, jog if necessary, etc.. and then exits to wait for the next interrupt. The time-in-int is the time it takes to do all that.

So lets say your in 25khz, every 40us an interrupt will come along, and your machin has a time-in-int of 15, that means your cpu has 40-15=25us to do its
normal windows activity. Your computer is now 37% a pulse driver, and 63% a windows OS..

Time-in-int doesnt vary from kernal speed to kernal speed, only computer to computer. Lets say yours is 11us. ( a bit high ), if your in 65Khz mode, your now interrupting every 15us.. , so Windows now has 3us every 15 to do its thing, its now a cpu that is 20%windows, and 80% pulse engine.

The windows component runs Mach3, so you now have 20%Mach3 ( plus windows fucntions) , and 80% pulse engine. As the pulse engine % goes higher, the chance of lockup goes higher.

So higher kernal speeds give you higher criticality, which can be defined as your sensitivity to random bad events affecting the computer. The lower the kernal speed, the higher your immunity. As youve noticed, your 45Khz machine doesnt lock up as much as your 65Khz machine. That follows the logic Im explaining. (Im almost willing to bet your machine at 25Khz will never lock up , or would be very very rare, (Im assuming this from your statement about the two machines correlated to hundreds of very similar conversations over the years with lockup victims. Fully 80% of them didnt realize the connection, and tuning lower in kernal speed stopped the problem.

Now sometimes you NEED higher kernal speeds, ( high step count machines typically), but fully 90% of people who have set high kernal speeds
dont really need them, they do so simply as a result of the very human instinct to have the highest possible speed selected. ( "Yeah boys, my engine has triple hedenstock carbs with dual-hemi semi-octagonal rebuf cyclinder hose accessory packs!".. :)

You may wonder..why the heck dont I tell people this more forcefully, since it will stop most lockups. Fact is, higher kernal speeds DO have a smoother
motion just as a result of granularity, and Ive found the vast majority CAN use higher speeds with no problem. ( I am limited here to 65K ), I use 25K though for reliability. With over 25 thousand machines out there, the number of overall lockups is extremely small, and thats including the tendancy people have to select the higher speeds,so as a result, I try to keep my nose out of their selections, unless they have trouble.

The final question you should be thinking about now is.. "Why didnt you ask me this when I complained about lockups.. :) ), the answer is that the
subject comes up so infrequenctly now that even I forgot to ask this basic question about the kernal speed. I used to post it periodically on this group,
but stopped quite a while back. In retirement I guess Im getting forgetful is my only excuse. Hopefully, youll find 25K never locks up.. Im suspecting this is true in your case. I hope so.

For those that want maximum reliability, I suggest this, use as low a kernal frequency as you can live with. On many machines maximum cutting speed is easily achievable in 25Khz, the only sacrifice in using 25Khz is perhaps a slower rapid speed. Rapids are nice, but not as nice as perfect stability, so I tend to give up some rapids to put their power into stability. Look at kernal speed as a trade-off, you can go real fast, or real stable.. (This is only if you have a lockup problem, many can have both and use higher kernal speeds. )

My own suspicion, again based on time and numbers, is that many people would have lockups, but most leave the kernal at the install speed of 25Khz.. I rarely hear form them. I hear most from 65Khz, and Ive heard quite a bit from 100Khz.. this is because those that can run 100khz are a rare breed, very fast clean machines with extremely stable operating system installs. For 65Khz, you better have a nice fast computer. 45Khz isnt bad, lockups on those indicate a computer suffering some periodic problem that slows the time-in-int too much..

None of this incidentally explains a random move. The driver is pretty much incapable of it, it canot move unless commanded, and it takes quite a sequence normally to command it. Youd have a better chance of winning a lottery than getting uncommanded motion.....unexpected..yes. :), that happens to all of us.. usually at our unknown request, but uncommanded...near impossible in the drivers context.

Let us know how 25Khz works.. do you have to sacrifice much speed ( or any ) to use it? And what IS your time-in-int number?

My average time-in-int is 5-7us by the way, which is pretty normal for a 2Ghz machines, by dual core is only 3-4us, meaning it will take much higher
kernal speeds without reaching any high level of criticality. My 1.2Ghz was around 15us.. ( pretty bad, but ran fine..)

Sorry for the ramble, I guess it was time for one anyway, for some reason there are some that actually like my rambles. lol

Thanks,
Art

Jonathan
08-10-2011, 12:42 AM
Steve has hopefully already reduced the kernel speed as I mentioned it early in this thread (#17). Perhaps not I was not forceful enough.

If it's 800step/rev then on 25kHz with 10mm pitch screw and direct drive the maximum feed is 25000/800*10*60=18750mm/min ... so plenty. Clearly half that with 1600, which it sounds like is still a lot more than your machine will currently do.

The only time I've used more than 25kHz is experimenting ... when I got 1m/s feed on Y-axis that was with a higher kernel speed. I've also monitored the port at 100kHz with oscilloscope and interestingly it seemed fine.

JAZZCNC
08-10-2011, 03:58 AM
Steve has hopefully already reduced the kernel speed as I mentioned it early in this thread (#17). Perhaps not I was not forceful enough.

Seem to remember Steve saying he was running 35K thats why mentioned running 25K.! . . . Obviously it's the bent screw thats now Screwing him..:cry:



If it's 800step/rev then on 25kHz with 10mm pitch screw and direct drive the maximum feed is 25000/800*10*60=18750mm/min ... so plenty. Clearly half that with 1600, which it sounds like is still a lot more than your machine will currently do.

Well yes those figures are right in Theory regards what Mach could actually put out in pulse's but in actual practice 1/1 direct drive on 10mm pitch then a realistic usable figure is 8000mm/min 10,000mm/min Max due to running nema 34's which 800rpm is about the norm and 1000rpm would be about max.
Steve was getting close to half this lower figure with bent screws so when every things running straight and true I'm sure he will reach these figures. . . . I'd also wager at higher M/S as well if he was indeed running 35K not 25K.?

Jonathan
08-10-2011, 12:47 PM
Seem to remember Steve saying he was running 35K thats why mentioned running 25K.! . . . Obviously it's the bent screw thats now Screwing him..:cry:

He said 45kHz, so even worse.




Well yes those figures are right in Theory regards what Mach could actually put out in pulse's but in actual practice 1/1 direct drive on 10mm pitch then a realistic usable figure is 8000mm/min 10,000mm/min Max due to running nema 34's which 800rpm is about the norm and 1000rpm would be about max.

Yes obviously I was just stating the limit...clearly those motors are not going to get anywhere near that with the current setup.

Tension the screw + rotating ballnut = no whipping ? Since that requires a timing belt could gear it up to go even faster anyway. As this is (I think) an 8x4' machine it would help...

JAZZCNC
08-10-2011, 01:50 PM
He said 45kHz, so even worse.

Sorry Jonathan should made it clearer.!..I was refering to a telephone conversasion I had with Steve.







Tension the screw + rotating ballnut = no whipping ? Since that requires a timing belt could gear it up to go even faster anyway. As this is (I think) an 8x4' machine it would help...

Seriously don't get your fasination with speed jonathan.?. . . The ONLY thing it's usefull for is Rapids and seen as 85% + of the time a machine spends is cutting why go to all the trouble of rotating nut, esp on a machine with twin screws .? . . . I see the bennifit of rotating nut to allow long screws but not extra speed and 10mtr/min rapids is good enough for most machines even an 8 x 4.!

Let me ask you this.? What do you CUT above 10mtr/min.?? . . .Not much if anything I bet.! . . Also out of the last job (other than mass drilling, which high rapids can help) you cut how much of the overall job cycle time consisted time wise of rapid moves.? . . bet it was easily less than 10% of total cycle time.?

Thats an awfull lot of extra work and expense incorparating 2 rotating ballnuts into a DIY machine just to gain a few percent saving on cycle times, the Key word being DIY machine where cycle times are usually not an issue. . . .Yes in industry every little bit helps but in DIY it's not worth the expense and trouble just for a few percent.!! . . IF . . normal screw setup can be used.

Said this before .!!. . .It takes a substancial machine with a powerfull spindle using high quality tooling to cut at high feed rates. . . . High rapids are only usefull on very small percentage of jobs other than that they are just used for bragging.!!
Also seen as most DIY builders use modified routers usually of the cheaper quality range or spindles like Kress then high cutting feeds with any reasonable depth are simply not achievable anyway.

John S
08-10-2011, 02:10 PM
Jazz,

At last a man after my own heart. All this 10,000mm / sec is just dick slapping. Think about it your part is programmed to run at say 600mm / min the only time this high speed comes into effect is on rapid moves and unless you are belting 4 holes into the corner of an 8 x 4 board any long rapids usually means you are not cutting / programming efficiently.

Even when you ar look at the sceen and see if the actual speed ever gets close to what's' allowed for rapids given that it has to accelerate to speed then slow.
Most time it never gets close to max rapid given the short distance it has to travel.

All insane rapids do is wear a machine out, put undue stress on parts probably not capable of handling them and more chances of loosing steps.

I say dick slapping because a beginners reads all this on here, CNCZone etc and thinks that's what he has to do, most are on small machines that can never, ever reach these speeds and even if they get close how fast can someone get to an Estop ?

When we were first doing the X3 CNC conversions we tried to see what the max they would run at before loosing steps and it was nearly 5 1/2m /min.
We then dropped this back to 4 m/min but it was still scary on such a small machine so finished up at 2m /min.

As a test the machines were sent out with a Sieg Logo badge so the punter could engrave a plate to cover the defunct Z axis handwheel hole as a first job.
There was 4 seconds difference in running at 4m /min and 2m /min

JAZZCNC
08-10-2011, 03:17 PM
I say dick slapping because a beginners reads all this on here, CNCZone etc and thinks that's what he has to do, most are on small machines that can never, ever reach these speeds and even if they get close how fast can someone get to an Estop ?

Exactly John and just the reason why I ALWAYS jump on this, It's false and miss leading to new comers and can be very costly and wastefull in both time and money.
Unfortunatly like you probably do, I see too much of this miss guided route being taken.!!

John S
08-10-2011, 03:27 PM
Jazz,

The same with over rating components because of bad advise. Following a conversion at the moment on another form of a Taiwanese 636 milling machine.
The guy is using 25mm ballscrews and 1640 oz in type 34 motors, unless he can hit that with 10,000 volts it will crawl but bigger is better - yes ?

End of the day he'll get as much 'useable' power as a 600 oz/in motor and probably twice the speed.

Jonathan
08-10-2011, 03:40 PM
I agree entirely that 10m/min is more than enough and that the difference in machining time between 10m/min and greater is often negligeble. My machine will do at least 15m/min on X and 60m/min on Y, but I leave it at 10-12m/min as it's less likely to go wrong and more time to react should something go wrong. I think the most I've actually cut at is 8m/min.

The reason I tested the Y-axis up to 60m/min was an experiment to verify my modifications to Irving's motor calculation spreadsheet to include pulleys. I was ascertaining how accurate the calculation was by trying different ratios and comparing the limit to the calculated value.

I meant that comment to be just pointing out it is probably possible to get round the vibration problem and the feedrate gain is a bonus.

JAZZCNC
08-10-2011, 05:04 PM
Jazz,

The same with over rating components because of bad advise. Following a conversion at the moment on another form of a Taiwanese 636 milling machine.
The guy is using 25mm ballscrews and 1640 oz in type 34 motors, unless he can hit that with 10,000 volts it will crawl but bigger is better - yes ?

End of the day he'll get as much 'useable' power as a 600 oz/in motor and probably twice the speed.

Ah ha ye and it was probably the supplier who told him he needed that.!! . . .. . . . The same someone who sold a guy I know 12.5Nm for his Z axis.:whistling:

JAZZCNC
08-10-2011, 05:10 PM
I meant that comment to be just pointing out it is probably possible to get round the vibration problem and the feedrate gain is a bonus.

Nah much better to replace the bent screw IMO because after you have gone to all that trouble and expense for what amounts to a very costly and mostly un-usable bonus the screw is still bent.:exclaim:

RE 60M/min Y axis out of interest how much pulley ratio did you have to use and what sort of accelleration did you achieve.? . . . If you don't mind me asking.!

fasteddy
10-10-2011, 11:37 AM
Hi All..

Been out the loop for a couple of days but I note some fascinating posts from you cnc guru's.. Love the one about Mach and kernal speeds, have popped mine back down to 25KHz and it seems fine..

The sort of speeds you guys are talking about seem more than fanciful to me at the moment.. Have been running my machine at 1.8mts/min max during all these other problems, now that I can achieve more, I still dont dare go above 2.5mts/min due to the bent ballscrew shaking the machine so much.. I did try 4mts/min which the motors seem to easily achieve, but shaking was so severe I thought something was going to rattle off the machine.. Am going to try straightening the ballscrew today, will let you know how I get on..

Steve..

Jonathan
10-10-2011, 09:47 PM
Nah much better to replace the bent screw IMO because after you have gone to all that trouble and expense for what amounts to a very costly and mostly un-usable bonus the screw is still bent.:exclaim:

True it is quite costly having already bought the bearings etc for rotating the screw. If the nut is rotating and the screw is tensioned (ideally a lot) then the bend should not matter much. As long as the ballnut is precisely on centre (which admittedly is tricky) then there's no radial force on the screw. If the screw is bent and spinning there is a large cyclical radial force which causes it to vibrate... No doubt there's more to it than that but I bet it would be a lot better.
I'm guessing it's a 25mm screw, what length is it?


RE 60M/min Y axis out of interest how much pulley ratio did you have to use and what sort of accelleration did you achieve.? . . . If you don't mind me asking.!

It was 42:14, but I accidently put 42:12 on the video. See here, post #136:

http://www.mycncuk.com/forums/showthread.php/2288-1.7*0.74*0.4m-Mill-Router-building...

I can't remember what the acceleration was... think it was 2m/s^2, might have been 3. Either way it only hits 60m/min for about 200mm... except if you smash it into the side :whistling:

michael
11-10-2011, 08:34 PM
Just a thought...

Have been roving around all the cnc forums trying to find another with the same probs... I have seen an awful lot of posts about earthing, but I have to say, as a complete burp at electronics, I ended up more confused than when I started... Cant get my head aound the myriad of different advice being handed out, and much of it was american.. Do they use different terms for all that common,starpoint,earth,neutral,-ve supply/rail,0 volt stuff? Damned if I can work out what they are in English without even more varying terminology.. I ramble..

Does seem to be a big cure-all for a lot of electronics issues so I was wandering if there is a good post/guide to earthing for us feeble minded noobs? From what I have read, I ought to do this as a matter of course, if only to eliminate several potential problems...

Steve..

Hi Mate, are you using Mach3 with a parallel port? If so what kernel speed are you using and what is the maximum velocity for the X and Y axis.

Mike.

fasteddy
20-10-2011, 09:19 PM
Ok...

Seems my run of bad luck is continuing..! Got an EP002G1 psu from a fellow forum member, but I have measured 58.8v output unregulated..! I know this is much higher than it should be (42-46v on the spec sheet).
This is too much for the drivers I am using which are limited at 50v (already blown one of them).. I know there are many out there that have these psu's and am wondering if there is anything I can do to 'dial' down the voltage? Will pop the cover off a bit later and see if there are any pots but this is like letting a road digger perform brain surgery and I would prefer some advice before rummaging around in it..

Steve..

John S
20-10-2011, 11:13 PM
Are you just putting mains in and taking pos and neg out ?

Reason I ask is I have used quite a few and done it this way and they have put 42 volts out, rock solid.

If you feed a voltage into some of the pins you can vary the voltage but only higher. I just use 4 wires, two in, two out.

Jonathan
21-10-2011, 12:48 AM
http://www.mycncuk.com/forums/showthread.php/985-ebay-power-supply

fasteddy
21-10-2011, 01:56 PM
See that red glow on the southern horizon? Thats me blushing with embarrassment.. Turns out the 'budget' pp3 battery in my multimeter is only kicking out 6v so it was making all the readings out... Sigh... New battery and voila, all the voltages measure as they should do..

Sorry for flapping, will get on and bugger summat else up now...

Steve..

Swarfing
21-10-2011, 02:02 PM
I wondered why the sun was out in Swindon? LOL

John S
21-10-2011, 02:14 PM
Clumsy bugger

mocha
21-10-2011, 08:10 PM
did you actually blow one of the motors??

fasteddy
22-10-2011, 01:03 PM
Hi Mocha..

Did not blow a motor, just an old driver that was only rated at 35v, and I put 43 into it.. Bought a Gecko g250x to replace it, but seems my luck is running consistently and this driver is dead.. Just waiting for a replacement now...

Steve..

m_c
22-10-2011, 09:41 PM
Bought a Gecko g250x to replace it, but seems my luck is running consistently and this driver is dead.. Just waiting for a replacement now...


Why a 250?
Surely a 251 with terminals/heatsink would be a better choice with less risk of it dying due to not installing it correctly?

fasteddy
24-10-2011, 11:27 AM
How do you install one icorrectly?

Steve..

m_c
24-10-2011, 12:00 PM
The G250 needs to be isolated from whatever you bolt it to, and comes with a pin header for cable connections.
The G251 comes bolted to an annodized heatsink which isolates it (hard annodizing is a good insulator), along with screw terminals to make wiring it up easier.

Gecko sell the heatsink seperately for those who want to use the plug and play benefit of the G250, without having to worry about how they're going to isolate the driver.

fasteddy
24-10-2011, 01:13 PM
Hi m_c

I am using a Pentium heatsink and have it isolated with heatsink tape.. The pins are the same gauge as those found in PC's... I have made up a terminal block with shielded cable, heatshrink and the correct connectors (robbed from an old PC).. Its all good..! But I do agree that for an extra few quid, the G251x is a better bet, especially if you dont want to prat around with all those bits and bobs..

Steve..

luke11cnc
24-10-2011, 01:16 PM
could we have a image of what you have done please steve

James & Luke

fasteddy
24-10-2011, 01:19 PM
Sure..

Will receive the replacement tomorrow and will taken a pic or two then..

Steve..