Cutting trouble

[frever]

I`m trying to cut many 70*70 milimeters squares (aprox. 2.5 sqr. Inches) in mdf with a 1/8¨ bit. My shopbot is an prs standandart and the problem is that one side is 2 milimeters grater than the other.
I don`t know if this theme was treated before, if is so, i appologize
thanks in advance

[gc3]

bit deflection

[jerry_stanek]

did you check your values to be sure they are set right. Have you checked to see if your machine moves the correct distance in each direction. Is your machine cutting square? 2 mm is a lot.

[paul_z]

I'd also check that your router/spindle is rock solid attached to your Z axis. 2mm is a lot of deflection.
If you are cutting in steps, are there ridges on the sides for each step?

[bleeth]

Seems like deflection would be more of an issue if the parts were out by the same distance in both directions. I'm betting on pinions needing tightening and/or replacement. 1/8 is a pretty small bit though unless you are cutting 1/4" mdf. Even then that's pretty small as a cutout tool. Are you leaving any nest between them? You may be better off cutting your first path for all the parts in climb leaving a skin and then cutting out in conventional. Try a 3/16 bit (again-assuming it is 1/4" mdf)

[frever]

Wich values?

[bleeth]

I believe he was speaking of unit values.

[jerry_stanek]

Yes I was talking unit values. check to see if you tell the machine to move 96 inches that it moves 96 inches.