Cut size problem

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 )

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.

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😯

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.

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 .