I've been using Mach3 Turn for many months on a converted bench lathe and everything has worked as I expected so far. Most of my problems have been easily solved by reading the forum posts.
I recently added a C6 speed control board from cnc4pc so I could use spindle control (I use the C10 breakout board, and C3 index pulse card). I thought I configured it pretty well and get close to the requested spindle speed, both in the Mach3 DRO and against a laser tach.
BUT, I'm experiencing some really odd behavior with regards to G95 and can't figure out what's going on. On an intermittent basis Mach3 will reduce the feedrate, while executing a program, to some unusually low number like 0.0002"/rev. It will often be on like the first couple of roughing passes, but then Mach begins to execute the feedrate specified in the program on later passes. It usually fixes itself as the program goes on. Sometimes it doesn't, and I have to restart the Mach software.
If I stop the program and enter a feedrate in the MDI, it executes fine. It only occurs while executing a program. At no time do I see a drop in RPM in the Mach 'True spindle speed' DRO
What could possibly be causing Mach to ignore a feedrate as specified in a program, but do so on an intermittent basis, and then execute the feedrate later in the same program?
In general I use the following syntax for example:
G97 S800 M3
G95 F0.004
G01 Z X whatever...
Under 'ports & pins' -> 'spindle setup' both 'spindle speed averaging' and 'use spindle feedback in sync mode' are checked.
What am I missing here?
Thanks for any help!