One thing we did notice, is that using the power supply we had very fine control over the voltage going into the drive. We noticed that the output of the drive goes up or down in steps, we didn't accurately capture this, but it seemed to be around 50 rpm steps at the rpm were we noticed it. So, small changes in the input can have no effect on the output, or, if you happened to be just below or above the the point where the drive steps to the next speed, they can have a significant impact on the output. As I understand it, the output from mach 3 is also in steps, and I'm guessing they are not the same steps as the input to the drive. So you could end up with a harmonic problem here where both the incoming signal to the drive and the internal drive hit steps together. I haven't seen any evidence yet that this is happening, hopefully it wont.

I think these step changes, in conjunction with the noise, is the cause of the change in rpm I see every now and again. Since the initial connection problem has been fixed, the magnitude of the change seems a lot less, and I think if we can get to the source of the problem with the noise these changes will just be a normal part of the drive behaviour where it changes steps.

Next step is to try to locate the source of the noise, or at least try to get an understanding of the circuit producing it. We have experimented with putting various capacitors across the output on the breakout board, but we had no success. Anything that quietened the noise moved the base signal level as well, and basically made it perform worse.

The machine is usable as it is I think, although I still have a fair error between the s value in mach 3 and the set value that gets put on the drive, This seems to be set on the spindle pulley config, the entries there currently are 0 for the lower limit, 6000 for the upper limit, and 1 for the ratio. I have experimented with changing these and found that if I put 300 in the min setting the drive will fault. If I leave it at zero, and drop the max to about 5200 rpm the correlation between the drive setting and the s setting seem closer at some rpm, but nowhere near correct.

I will have to try cutting under load to see if it performs any better than it was.

John