PP 2.5.1 Lathe RPM display is acting strange

09 Jul 2020 08:50 #174076 by Stigoe
Hi, all.

I'm running PP v2.5.1 on a converted benchtop lathe with a spindle encoder. I can set the RPM on the display and it will run at more or less the correct spindle speed. The problem is that when I start feeding, the RPM value shown on the display is showing way off actual speed.

If I run with a spindle speed set at 350 RPM, the display will show approx 12200 RPM with a feed of 30/min (I assume 30mm/min, I'm working in metric), approx 12500 RPM with a feed of 71/min and approx 13200 RPM with a feed of 170/min. The display goes back to the set speed when I stop feeding. I've only run the lathe using the ShuttleXpress so far.

My encoder is a 2000/8000CPR and it is counting up the correct amount as I rotate the spindle in the fwd direction. I redid my encoder mount some time ago and I had to swap the A and B signals to get it to count correctly, as inverting scale didn't have any effect on the counting.

Maybe there are some mistakes in my spindle encoder setup.

My hal and ini files are attached. They have not been cleaned up from the original files yet, so there are a lot of commented out parts in there.

Anyone have any ideas as to why the RPM is acting this way.


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09 Jul 2020 18:51 #174122 by Stigoe
Replying to myself...

Looks like I may have found the problem. The encoder scale was set to 240 (don't ask me how I came to that number in the first place) instead of 8000. Now it is showing the correct speed (verified with a handheld tachometer).

Now it's on to the next problems... :-)


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