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View Full Version : Accelerations in Mach



mcphill
12-06-2011, 10:22 PM
I was having a lot of VERY jerky movement on the machine when cutting at and above 50 ipm. Just doing simple cuts on a 2 inch radius resulted in huge steps in the cut (like .250 jerks, not a smooth radius AT ALL!). I improved it significantly by lowering my X and Y acceleration to 30 (they were set to 40) and the Z to 15 (was 20).

I went from horrible jerky movement that lead to broken tools and many lost step incidents to buttery smooth motion even with short rapid movements in all three axes.

I doubt this change will affect any actual overall cutting times (other than making it WAY better since I won't scrap jobs when cutting fast), so I suggest you all make the change as well...

ihavenofish
12-14-2011, 05:40 PM
I was having a lot of VERY jerky movement on the machine when cutting at and above 50 ipm. Just doing simple cuts on a 2 inch radius resulted in huge steps in the cut (like .250 jerks, not a smooth radius AT ALL!). I improved it significantly by lowering my X and Y acceleration to 30 (they were set to 40) and the Z to 15 (was 20).

I went from horrible jerky movement that lead to broken tools and many lost step incidents to buttery smooth motion even with short rapid movements in all three axes.

I doubt this change will affect any actual overall cutting times (other than making it WAY better since I won't scrap jobs when cutting fast), so I suggest you all make the change as well...

40-60 should be more the area to aim for on a machine like the mikini with steppers.

what your jerky motion sounds like its a program that has made an arc of many right angle steps. when you slow the acceleration down, you are basically just slowing the machine down. its likely still jerky, just less apparent. there are some cam programs that can create downright horrendous code.

you also want to check that mach is using g64 for contouring, otherwise the axis will start and stop for ever line of code. this can yield an extremely jerky motion. sometimes controuring (CV mode) is disabled in the mach3 xml, so if g64 doest help, you might need to check that.

its somewhat important to deal with this correctly, because the machine wont actually be travelling at the intended cutting speed when it has to stop and start every mm.