Steppers Stalling During Multi-Axis Rapid on Taig/Microproto Mill (w/ video)

Hey Guys, sorry to make my first post a "help me solve this" but I have done quite a bit of troubleshooting and reading and haven't been able to solve this problem.

Setup:
Microproto Micromill 2000
Gecko G540 Driver
1/2 - 20 lead screws
XP PC running Mach3
PSU: 48v 7.3a
200oz-in steppers
Velocity 30ipm
Accel 5

Issue:

Video

I am having issues with the steppers stalling during a multi axis rapid. The issue first presented itself on a ZXY rapid from home to a location above the part. It does not happen while using any single axis. It seems to happen only when engaging a second axis rapid about a half a second after the first. The problem does get mitigated at lower speeds (10-15 IPM) but is present with most acceleration values above 1. When it occurs I loose steps and the part will be off by that value. In general at cutting speeds of 10IPM or so I never see the issue.

Troubleshooting:

-I measured voltage and amperage from the PSU to the Gecko and got 2amps at full rapid on all three axis. When the issue occurs there is no change in voltage from the PSU to the Gecko. This leads me to believe that the PSU is not the issue and that the driver is getting enough power.

-I tore down the ways and lead screw nuts and adjusted everything. XYZ all move smoothly by hand. I don't think it's mechanically binding causing the steppers to skip.

-I changed the parallel port mode to EPP per Gecko's instructions. The computer has no network connection or any programs running aside from Mach3. I ran the communications test in Mach3 and the computer gets good results. I have turned on the sherline mode as well with no change. So it looks like the PC is not the issue and the Gecko drive isn't suffering from the Xilinx CPLD issue.

Conclusion:

I can run the machine as is with settings at 15ipm and 5 accel but I am loosing a ton of capability from the machine. The only thing I can think of to check is measuring voltage from the individual steppers to see what happens when the skipping occurs. The issue there is that it happens on all three steppers; I doubt they are all cooked.

Anyone have any ideas or things to further troubleshoot? Let me know if I forgot any details.

Thanks!

30ipm is 600rpm for the stepper motors. What's your power supply voltage??

The gecko should be able to spin the stepper motors that fast if the motors inductance is reasonable. I run my 270oz-in motors over 1000rpm with a 48volt PS. Gecko 201.

The PSU is 48v 7.3a. The steppers are 200oz-in.

48volt is good. My best guess right now is poor/ragged step pulse from the parallel port. Im using uc300eth/uccnc to output a very stable step pulse to my drives. Any number of windows PC problems can cause step pulse issues. It's can be difficult to diagnose what that could be. Using a external pulse generator solve those problems for me.

200oz-in is a bit low but that depends on the motors torque curve at 600rpm. If you can look up the motor datasheet, and see how much torque you have left at that speed.

Thanks for the replies jfong, I appreciate it.

I found the datasheet for the steppers here.

Here is some questionable math:
30IPM = 600 RPM
/60 seconds = 10 RPS
*200 (steps/pulses)/rev = 20,000PPS

If this is true, I am just off the chat at something like .1Nm torque. This could be the answer (if the unit conversion is correct).

*The gecko driver is micro-stepping so is it actually *2000 (steps/pulses)/rev? or does that make it 2000 (microsteps/pulses) / rev?

I am running Mach3 at 25,000 Hz, is that enough to drive 12,000 PPS?

Step pulse calculation is slightly off

600rpm/60sec=10rev/sec

10microstep x 200full steps=2000steps/rev

10rev/sec x 2000steps/rev = 20,000 steps/second (PPS)

Mach kernel speed set at 25k should handle 20k PPS. I'm no mach3 expert but I'm sure someone will say if that is ok.

The graph is for a half step drive, so you have to do a bit of conversion

600rpm is 4000 PPS for a half step drive. So about .6NM or about 85oz-in. However that's if the graph is correct for your motor.

Also the graph is at 30volts. You will get little bit more torque at 48volts.

I am probably blind, but I did not see a current rating for the motors.

200 oz-in is certainly not overkill .

Don

So the motors seem reasonable, the mechanical setup is reasonable, the PSU is reasonable, no reason to believe the stepper driver is cooked. I'm led to believe that the computer is responsible for the issue? I just find that a little hard to swallow because the issue happens at such a specific point in the machine's operating range. It would be different if it were hiccuping doing some code-intensive 3d contouring but these are simple 2 axis rapid movements. Can you guys think of any simple checks to rule out any of the the larger component culprits? To me the noise sounds very mechanical; perhaps tomorrow I will reassemble the drive linkages and see if there are some glaring issues. Perhaps the set-screw on a motor spindle flat was loose...

I just realized that can't be the correct torque curve for your 200oz-in stepper motors. It starts off at 1.8Nm, which is 254oz-in.

Hey werksmini:

I experienced similar issues when I was using an old and slow computer. It turns out that it was a wireless network card that would periodically push the CPU to 100% utilization. I upgraded to a faster computer and the problem went away.

Run Task Manager and keep an eye on the performance graph to see if the stalling coincides with maxing out the processor.

Alan

i was having the exact same problem...ir it looks the same
https://www.youtube.com/watch?v=DRZSAqznXzA

if your using backlash compensation... look in config/general config at the shuttle accel setting if it is set to fast youll get that stalling...i actually stopped using backlash comp..
but when i got it to stop doing that i had to use a value of about .04 or so... if its set around .004 it will be too fast and cause that stalling..
try using a slower shuttle accel setting im sure yo already know this bt by slower i mean ... if its at .004 go to a slower setting which would be .005 ... .009........01 so on and so forth
less zeros is a slower setting.....
for a quick fix check just disable backlash comp..if it stops stalling you need a slower shuttle accel setting
hope that helps

Quote:

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Originally Posted by 1hander

i was having the exact same problem...ir it looks the same
if your using backlash compensation... look in config/general config at the shuttle accel setting if it is set to fast youll get that stalling...i actually stopped using backlash comp..
but when i got it to stop doing that i had to use a value of about .04 or so... if its set around .004 it will be too fast and cause that stalling..
try using a slower shuttle accel setting im sure yo already know this bt by slower i mean ... if its at .004 go to a slower setting which would be .005 ... .009........01 so on and so forth
less zeros is a slower setting.....
for a quick fix check just disable backlash comp..if it stops stalling you need a slower shuttle accel setting
hope that helps

---

Solved!

It was the backlash comp accel setting. I turned it off and the problem went away. Huzzah. This makes total sense because the issue only arose with axis directional changes or starts.

Thank you SSG Gonzazles; you're my hero of the day!

Woo-hoo... I got one.. I forgot to mention that turning the backlash comp setting down will help... The backlash comp and shuttle accel setting seemed to be inversely proportional.. Glad you got it fixed
Rick