Z-axis Pulse Unit Setting Not Adjusting Z distance correctly

[Patrick34]

I have a 2012 version DSP controller that I have finally taken the time to get powered up and working. I am 98% complete on my custom laser machine, and currently trying to correct the Z table distance.

I am running 4 Nema23 steppers off of two MD882ES drivers. Each pair of steppers are wired in parallel. The two drivers are also in parallel. I have confirmed that the movement is synchronized nicely as long as I use a low speed and stay over 2500 steps/rev resolution. I encounter synchronization problems if I try to run less steps per rev, and over-amp the circuit and stall the steppers at higher speeds.

I can only achieve a large difference in the z-axis distance by changing the step/rev resolution on the drivers. The pulse unit setting will adjust the z-axis to a point, but then the setting number becomes so low that the distance stop changing all together.

What is the assumed default setting for steps/rev?

Here is what I am doing in order to figure out the correct setting: (I am driving a 3/8-12 ACME screw to lift the table)

1 rev / 2500 steps * 1 inch / 12 revs * 25400 um / inch = 0.84667 um/rev

This pulse unit input does not move 10mm in inching mode. So I started at the lowest pulse unit the software will take (0.01) and progressed the number up until I finally got a significant change in the z-axis move distance. Here are the results:

Pulse Unit Distance Moved
0.01 8.39mm
0.05 8.39mm
0.1 8.40mm
0.5 8.46mm
1.0 8.50mm
5.0 1.68mm

So by this trend, I need to set the Pulse unit to a number less than 0.01 to get the full 10mm at 2500 steps/rev resolution. The ideal case would be for me to run over 5000 steps/rev in order to keep the movement nice and smooth.

What am I missing? What am I doing wrong? Does the pulse unit work differently than I have assumed?

I do not have my laser tube installed (or ordered yet for that matter) so I am not sure if this is happening with my x or y axis as well. They appear to be moving the correct amount. I do not have the power/ synchronization problem with these axis as the are just normal Nema17 steppers on single drivers.

[Greolt]

I don't know about the 2012 controller but;

The AWC608 will not allow value less than one in the um/step setting.

An annoying restriction. Fairly common thing for the Z axis to be geared such that a value less than one is correct.

Though I have never used the 2012 controller, I am not surprised if it is the same bug.

[Telrad]

Maybe you should try lowering the acceleration and jerk settings along with the micro stepping settings on the drive. Stepper drivers loose torque fairly quickly when driven to quickly.

[lbug7575]

I need to set the Pulse unit to a number less than 0.01 to get the full 10mm at 2500 steps/rev resolution. The ideal case would be for me to run over 5000 steps/rev in order to keep the movement nice and smooth.






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[Patrick34]

I don't know about the 2012 controller but;

The AWC608 will not allow value less than one in the um/step setting.

An annoying restriction. Fairly common thing for the Z axis to be geared such that a value less than one is correct.

Though I have never used the 2012 controller, I am not surprised if it is the same bug.

... So who do we have to get a hold of to try to get an update to address this issue? This seems like it works great for belt drive systems, but will almost never work with screw drives or to get high resolution cutting/engraving.

[Greolt]

... So who do we have to get a hold of to try to get an update to address this issue?

Good luck with that.