Dear people,

Iam trying to mill a large pocket in a piece of wood which need to be the same distance between the upper outside stock and the lower outisde stock. The gcode is correct in fusion360 but when I machined the part the lower dimension is 9,5cm and the upper is 10,5 mm. When I try a smaller part with the same feature it is correct. So looks like mach4 shifts the y coordinates when it starts the program. The x values are the same as my drawing but the Y value is shifted.

It is strange because when I try a smaller part, with the same feature and adjust the feature dimensions to the stock size, the problem does not occure

I use g54 to define my work coordinates. Could someone please help me. Iam really lost what it could be

If your steps per are not right the further you go the worse it gets out. Check you backlash and calibrate your motor tuning. These 3 links will help. They are very short and very relevant.

https://www.machsupport.com/forum/index.php?topic=12513.0

https://www.machsupport.com/forum/index.php?topic=12512.0

https://www.machsupport.com/forum/index.php?topic=16315.0

I don't think that is the problem.  Ok let's say that I have a rectangle(A) which is 200mm x 200mm and I want it on the center of a plate which is 400mm x 400mm(B). So on all sides between rectangle A and B is the distance 100mm if it is correct. But the problem I now have is that the A is 200mm x 200mm and the distance between A and B is in the x direction 100mm on both sides. But the distance between A and B in the Y direction is 99,5mm in the upper part and 100,5mm in the lower part.

So if the counts would be wrong rectangle A would not be 100mm x 100mm am I right? And the strangest thing is that when I try to run a small part the problem never occurs. And then when I enlarge the part with the parameters in fusion360 this problem occurs. I only need to change the stock size, because I have constraint the sketches to the stock so it adapts.

Hope this explanation is clear. Thanks in advance and for the former reply

Jelle