Machine not travelling correct distance

[RAD]

Hello, I have set my steps per inch in Mach3 over the longest travel of my table (4ft.) I have done this a few times and it is spot on, however when I run a job that is 48" the machine travels 48.3125" (using no offset in sheetcam) this error is the same all the time. The error seems accumalative because it is worst the longer the run is. Any ideas what can be causing this? Thanks

[WyoGreen]

By my quick calculations, you are off .007" per inch. Have you tried changing your steps per inch slightly to adjust for this?

That's my best thoughts for now, Steve

[Bigdogbro1]

I wanted my travel distance as good as I could get it but by measuring only a short 1" distance of travel you will not get the accuracy over four feet.

That's why I made a long precision measuring tool.

http://www.plasmaspider.com/viewtopic.php?f=87&t=19526

[Larry83301]

Hello, I have set my steps per inch in Mach3 over the longest travel of my table (4ft.) I have done this a few times and it is spot on, however when I run a job that is 48" the machine travels 48.3125" (using no offset in sheetcam) this error is the same all the time. The error seems accumalative because it is worst the longer the run is. Any ideas what can be causing this? Thanks

I would suggest slowing your feed and rapid travel down and see if perhaps you are exceeding what your motors can handle. it sounds like the motors are being turned by the weight of the axis being driven. Do you have two motors on your long axis or just one driving both sides? That can make a difference.

Also check and see if you have the kerf size set to the wrong decimal point ( example 0.032 or 0.320)



Larry

[RAD]

thanks guys for the ideas. Yes two motors driving gantry and rapids are already slow, but bear in mind that my steps per inch is spot on when I set it in Mach and measure it, it is only when I run a file that it goes beyond where it should cut, last cut I had to alter the drawing so that it would cut to the right dimensions. Dosn't matter if I use Inkscape or AutoCAD same problem (so that rules out CAD software). Think if when Mach ask how far did x/y axis move I should put in 48.3125"?? (48.3125" is how far it would move when it should move to 48" when running a file)