HobbyCNC microstepping problem

[ZeptoBit]

Edit due to me not seing your latest post
Have you got an osciloscope so you can view the coil voltages and shape?

I have a two channel DSO. A bit tricky measuring 4 voltages with 2ch, but I did not see the waveform I would have expected. When I get around to fixing this board I will check again, hopefully I can get hold of a 4 channel scope.

 

[ZeptoBit]

What is the kernel speed? I don't have LinuxCNC up in front of me right now and don't remember how it's calculated.

I've been pleasantly surprised with the Taig. It has a lot more capability than I was expecting. I have access to it as part of a high school robotics team I mentor and it has really helped me understand how the hobby-grade CNC systems work and has helped put a boot in my rear to finish my conversion (at least once it gets above 45 degrees in the garage).

I had all sorts of issues with the eBay TB6560 board. I eventually traced them to the pulse per inch being incorrect. For some reason one axis was set at 1/8 microstepping and the rest at 1/16. The 1/8 axis was also set with 64000 pulses per inch (as opposed to 16000) and somehow worked properly for a year or so. Granted, this machine was also set up with Mach at 4ipm rapids. Needless to say, I did some tweaking and the board works well now.

Does your current board work well without microstepping? You may not need it. I've been running a Taig that initially was set up for 1/16 microstepping and had all sorts of speed and torque issues (1/16 microstepping could result in the motors with as little as 10% of rated torque). I turned off microstepping and have had good results. Here is with 2D adaptive clearing in a plastic sheet with a 2 flute HSS, 10k rpm, 0.125" DoC, 36 ipm. 2D adaptive clearing wasn't the best strategy timewise for this (all of those jogs were painful), but I'm still new at this.

Also, one thing to note: how is the grounding of the machine? I noticed any large static charge on the machine will trip the "Reset (E-stop)" on Mach. This can cause all sort of issues. I am going to investigate bonding all of the electrical system grounds together (power supply, control board, mill) to see if this is a potential issue.

I was surprised too, I can take larger cuts than I was expecting and the surface finish is excellent. So far I'v milled aluminum, steel and styrofoam. All looks great.

I see no advantage to more than 4 microsteps on this machine. I'm using 1/4 step now, I was considering 1/2 step which I think would be fine too. I'm a bit worried about using fullsteps for a few reasons: Surface finish. Breaking very small drill bits if Z-axis feed is jerky. Some loss of resolution compared to 1/2 steps. Possibly more resonance/vibration/noise compared to 1/2 steping.

Not sure about the kernel speed, I'm at work now, but I can check it when I get home. The maximum jitter was 36000ns. I don't think the problem is related to this as it runs fine with the MA860H drivers and the problem with the HobbyCNC board was the same even when moving one microstep at a time with several seconds between each microstep.

The HobbyCNC board worked with full stepping in the sense that it steped and the steps where the correct size. But it was a lot more noisy and the full steps seemed very rough. Half stepping did not work.

The case for the electronics is connected to earth ground directly form the power cable. The power supply negative terminal is also connected to earth ground. The gnd pins of the parallel cable are connected to earth ground trough the PC. The case of the spindle motor is connected to ground as well, so the structure of the mill should be grounded, but I have not measured the resistance. I should have a look at how I connected the ground to make sure I don't have any ground loops.