Can you attach your xml and maybe also the compete code so that I can simulate it here.

Hood

thanks for the effort, really
BTW, Could you tell me what mach does when generating toolpath? Because CPU load is the same as when Mach does nothing. Effect is that i wait for ages when i load file with many arcs.

Can you describe how your machine is set up, first glimpse at the xml  and I see you have an A axis active but no pins or port assigned to it. Also you are sharing Pin6 with spindle and an Output.
 Also 20 steps per mm seems rather low but could well be correct if you have 10mm  pitch screws and your drives are full stepping.
 Hood

I can't tell you how the machine is set up because i am just the programmer of the application which converts plt files into gcode.A axis rotates the knife. I run demo version of mach3 and got xml from machine manufacturer. however, even on my pc which is not connected to anything i see that speed varies( label units/min. ). Meybe it is because of the changing direction of the movement? even if i round the corner and movement should be smooth, i observe dramaticac speed changes.

edit:
i think the reason why A axis is not associated with pins is that my pc is not connected and xml is from my pc, not the one from the plotter.

I think this problem may be related to the A Axis. Brian is currently working on code for that as there has been quite a few issues recently. A new revision with the fixes will hopefully be released in the next few days, if that doesnt clear things up then we can go from there.
Hood

Thanks for the support Hood. I greatly appreciate it

Hi Hood,

Do you have anymore info about the tangentail fixes?? Like a release date?

Jason

Jason,
 afraid I dont, just when Brian gets it done but its probably not tangential fixes as such if you are meaning the tangential knife control. The fixes are going to be for the way the velocity is calculated when doing an A move I think.

Hood

Thanks Hood,

I to have converted all my shapes to arc's to get rid of all the stop/starting i tangentail control. I have done way with all the G0 codes so that the knife will not spin in the bed. The next wil fix for me would be to look ahead to the G2,G3 codeafter my rapid G1 so that the A can orientate itself for the next cut.

I'm awaiting a fix. I have just go a quote in for a commerical cutter at $82K. I have been patient however now that I have staff running the machine all the quirks rear there head which see's me spending a lot of time tweeking it so the bugs do not tear up the material.

Can't wait for a fix.

I may have misunderstood the problem entirely but... why are you programing the A axis rather than using Mach's tangential knife (TK) control? I took your code and removed all the A moves and just let Mach do its thing and movement (feedrate) seemed pretty good to me - definitely not showing the stop starts that the code you posted does.