Cut size problem

[Plasmalex]

Hi everyone , i have question ,I spend many hours to find my problem without result , my machine cut over of .0125 in for every inch cut (ex : 2"= 2 1/4 , 1"=1 1/8) , i double check mach 3 and also check if each displament are exacly the same in mach3 and on the machine . I also check on sheetcam if the dimention are the same of draws and its ok . I verifie them by putting the material size at the same size of draw suposed to do . Do you think its can cause by sheetcam when posting code ? I double check to set the proper post processor ( mach 3 plasma )

[Les Newell]

If the drawing dimensions are correct in SheetCam the issue is almost undoubtedly your motor steps per unit.

Put a tape measure parallel to the X axis and line up the torch with a convenient point on the tape. Zero the X axis DRO them jog exactly 10". Does the axis move exactly 10"? If not you need to adjust your steps per unit for that axis. Repeat for the other axes.

[Plasmalex]

Thanks for reply, yes Ive do the test and the machine move exacly 10 inch on jog for alll axis , but when I open g code ,cut larger than draw😯

[Les Newell]

Draw a simple 10" square and run it through SheetCam using a 'no offset' operation. Take a look at the g-code. Do the numbers look correct? You don't need to understand much of what the g-code is doing. Just look at the X and Y numbers. Coordinates in that post are 'modal' which means that if a coordinate is not specified the last number is used. For example

G0 X1 Y1 Rapid move to X1, Y1[/1]
G1 X10 Cutting move to X10 Y1. The Y1 is taken from the last move

Now try an inside offset. The g-code numbers will be offset by half the diameter of the tool.

[Plasmalex]

I do the test off 10x10 square and I think mach 3 doesnt read the offset of the tool , i've try to change the tool diameter and its same size , i think the problem is on mach3 setting , the g code is ok .