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Author Topic: CV better with arcs, but still a bug with 'CV disable for angles greater than'  (Read 2334 times)

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I bumped up to the latest development release (3.043.062) because my cam tool produces a lot of short helical arcs during lead in moves.  The lockdown version (3.043.022) would produce bursts of pulses at the max frequency in these cases.  Very nasty with a stepper setup. The dev release doesn't do this anymore, but still has something not quite right.

If you try and use the 'CV disable for angles > x' in the general settings tab you get erratic results.  In particular when going from a line to an arc sometimes CV will slow down for the entry of the arc.  Within a simple program it will do it for some arcs and not for others, but repeats which ones it does it on exactly.  It seems like it may be a round off error where it sees a tiny transition between the line and the arc and says it is a tight turn?  For example  see the attached code for a very simple 3 pass face mill operation.  Set the CV disable on angles> = 88 deg and on the first 2 retract arcs I get a max decel, accel at the entry to the arc, but the last pass is fine.   

CV disable on angle would be a really useful feature if it worked right.

I'm new to the forum, so is this the right way/place to post a bug report?
Anyone have any thoughts on this?  Are people having success using the CV disable angle setting or is it a 'pick your poison' kind of thing.

Offline ger21

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Bugs of this type (complex to fix) aren't going to be addressed in the current version of Mach3. The new version, Mach4, should hopefully be much better at CV. It may get an entirely new trajectory planner.

I occasionally see Mach3 stop on Tangent moves, from a straight line into an arc, with the "Stop on Angles" turned on, even though it shouldn't. There are probably hundreds of little things like this lurking in Mach3. Unfortunately, the code has gotten so complex over the years that it's almost impossible to fix some bugs without creating new ones.

My recommendation is to find out what works best for you and use it until Mach4 becomes available.

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