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First, I looked at the interpolated and raw signals in HalScope. As expected, one had jaggies and one didn't. In my INI file, I changed:
net spindle-position encoder.0.position => spindle.0.revs
To:
net spindle-position encoder.0.position-interpolated => spindle.0.revs

I ran the threading program at 200 RPM:
 

Jaggies gone, plus initial slope change before threading now a straight line. However, there's a break in the velocity midway on the line that was not there before. Still have the odd saw-tooth velocity while threading. (Note: I was running the program without a tool, so no actual threading took place)

I thought this might have fixed the problem. So I made another 8TPI thread at 100 and 200 RPM. Alas, they did not overlay. Same problem. In case you're wondering, I could not find another piece of 1" stock, so I used a 1/2" rod.
 

PS. Looks like I need to resharpen the cutter! Easy to see in the closeup.

 

HelloI have a plasma cutter runing on mesa 7i76e / thcad10 / linuxcnc 2.8.My Problem:As you can see on the attached picture (left cut) it starts really good but after about 100mm the THC starts to move up and down the Z Axis. The move distance of the Z Axis gets more and more up to 10mm at the end. Is there an another setting as in the Config Penel Arc - Height Per Volt? (currently set to 0.05mm)So I really don't know how to fix this and which settings could be responsible for this behaveHope that you know the reason for that and I would really appreciate a hint how to fix that.Thanks in advance for you replay.The settings:Config Panel THCDelay:1Threshold(V):1PID P GAIN(Speed):10VAD Threshold(%):90Void Sense Override(%):100PID I Gain: 0PID D Gain:0Run Panel THCAutoUse Auto Volts: (ticked)Velovity Anti Sive Enable (VAD): (ticked)Void Sense Enable: (ticked) 

The freq pin is 0 and the valid pin is false.  So it appears that there is an issue with the PWM measuring. 

PCW,

Okay, lets hope nothing is fried.  I will go try the outputs of PWM freq and valid now and report back.

I got a chance to spend some time with the oscilloscope today am getting interesting behavior out of the EDM supply.  What I am seeing is a sine wave that has an amplitude of about .5v. This entire sine wave moves up and down depending on the intensity of the EDM cut.  At no cut it is at 0 volts and at short it is at 3.3v.  In other words it seems to be behaving like an analog signal. It seems to me that will not work with the periodm func in mesa.  I have contacted the creator of the Powercore EDM to see if this is the correct behavior or if something was damaged. 

My alternative plan is to use an arduino that I have here to take the analog input and send it to the computer via USB to monitor cut duty cycle. Hopefully the python script that I am writing can accommodate communication with the arduino.