Stepper motors not running smooth MACH3 LPT

[burnley1]

Hi,
it very tempting to believe that increasing the number of microsteps also increases the resolution, but the practical reality is that it does not. The effective best
resolution for a two phase stepper occurs at half-stepping, ie 400 pulses per revolution.

The real reason we use microstepping is smoothness of motion. The idea was first invented by astronomers who wanted much smoother motion from the steppers they use on their
telescopes. The higher the microstepping the smoother the motion, however the higher the microstepping requires ever faster signalling to the driver to cause the stepper to spin at
maximum speed, and you may find the parallel port is just too slow.

For instance lets assume you want the stepper to spin at 600rpm (10 revs/sec) to make the machine go as fast as you want:

4 microsteps per fullstep =800 pulses /rev and at 10 revs/sec requires a pulse rate of 8000 pulses/sec.
32 microsteps per fullstep=6400 pulse/rev and at 10 revs/sec requires a pulse rate of 64000 pulse/sec

So you can see that a parallel port would have almost no chance of driving the stepper to full speed at 32 micro step per full step but have no trouble
driving it to full speed at 4 microsteps per full step.

For this reason most people use 4, 5, 8 or 10 microsteps pert full step, corresponding to 800, 1000, 1600, 2000 pulses per rev. It s good balance to get smooth motion
without requiring blindly fast pulses from your controller.

craig

Interesting, you've got the point. I will then just test microstep setting at 4, 5, 8, 10 and see how motors run then.
Thank Craig!

[dazp1976]

Interesting, you've got the point. I will then just test microstep setting at 4, 5, 8, 10 and see how motors run then.
Thank Craig!

As you change the microstepping and sters per unit, you will see the maximum velocity you can achieve get lower on the axis graphs. Microstepping and kHz are relative to each other.
If you're set at 25khz in Mach, using 1600/400 for a 4mm screw but still need more velocity available (unlikely at these settings). The best way is to put microsteps and steps per on the next lower setting. You'll notice the velocity graph change.

I did have very good reliability from the 5axis type breakout board (one with the on-board relay) when set at 35khz. Those boards use buffers for the axis though.

The 6axis type aren't as good because of the slowish optocouplers they have fitted.

I was running 35khz, 2000/400 with 5mm pitch screws on a mill at the time without problem using the 5axis board.

[joeavaerage]

Hi,

I will then just test microstep setting at 4, 5, 8, 10 and see how motors run then.

I doubt you'll notice much difference. Sure the 10 microstep per full step (2000 pulse/rev) is supposedly better than 5 microsteps per full step (1000 pulses/rev) but you may not notice any
difference. Settle on one that is a good match (speed wise) to your parallel port and leave it there. Its not worth wasting your time on.

Craig

[burnley1]

As you change the microstepping and sters per unit, you will see the maximum velocity you can achieve get lower on the axis graphs. Microstepping and kHz are relative to each other.
If you're set at 25khz in Mach, using 1600/400 for a 4mm screw but still need more velocity available (unlikely at these settings). The best way is to put microsteps and steps per on the next lower setting. You'll notice the velocity graph change.

I did have very good reliability from the 5axis type breakout board (one with the on-board relay) when set at 35khz. Those boards use buffers for the axis though.

The 6axis type aren't as good because of the slowish optocouplers they have fitted.

I was running 35khz, 2000/400 with 5mm pitch screws on a mill at the time without problem using the 5axis board.

Thanks dazp, I will try 35khz setting and see how it rolls. About previous posts, should I limit the amperage on driver by peak or RMS? For 5A motor I should set to 4,9A peak and 3.5A RMS or should I go by RMS?

[burnley1]

Hi,



I doubt you'll notice much difference. Sure the 10 microstep per full step (2000 pulse/rev) is supposedly better than 5 microsteps per full step (1000 pulses/rev) but you may not notice any
difference. Settle on one that is a good match (speed wise) to your parallel port and leave it there. Its not worth wasting your time on.

Craig

So I wont waste my time for those settings, I will just set to 2000pulse/rev, test it if its good and leave it like that. Thank you!

[dazp1976]

Thanks dazp, I will try 35khz setting and see how it rolls. About previous posts, should I limit the amperage on driver by peak or RMS? For 5A motor I should set to 4,9A peak and 3.5A RMS or should I go by RMS?

I start with the closest peak setting so 4.9A in this case.
Once its been running for a bit, check motor heat. If it's fairly cool you can go to next highest. If hot go to next lowest.
It's all about finding a balance of best performance without any step loss or burnout.
Leadscrews tend to make them work a bit harder.

Mine run almost cold on a mid-size benchmill with ballscrews.
Almost identical to your sets. They're still set to peak A I started at. Performance was spot on so left it as is.

[burnley1]

I start with the closest peak setting so 4.9A in this case.
Once its been running for a bit, check motor heat. If it's fairly cool you can go to next highest. If hot go to next lowest.
It's all about finding a balance of best performance without any step loss or burnout.
Leadscrews tend to make them work a bit harder.

Mine run almost cold on a mid-size benchmill with ballscrews.
Almost identical to your sets. They're still set to peak A I started at. Performance was spot on so left it as is.

Dazp thank you!
Very nice explanation. I will try all of that this weekend, cant wait. Sure I will report back here!
Have a nice weekend!

[dajanasa1]

I have had this problem in the past and when I changed PC's to a different one it disappeared.
It was a problem inside the old PC.
Hope this helps.

[burnley1]

I have had this problem in the past and when I changed PC's to a different one it disappeared.
It was a problem inside the old PC.
Hope this helps.

Good man, I also changed my PC and problem was fixed