Need Help!- How to offset VMC

[Maxz]

Dear all,

I would like to contour the profile shape like "8" (outside shape only). But my blank size is quite big. I have to rough the size of my workpiece.
- first time, I just lie the machine that I use tool diameter 25 mm (in fact, I use dia 5mm)
- second time, I use the real big tool diameter 20 mm. The result is the same.

The result is machine is alarm. I notice that I cannot lie the D tool's value bigger than workpiece's R.
Please anybody tell me how can I offset the (real) current cutting path at the machine, instead of offset it in the desktop. I would like to use only 1 program from rough to finish machining.
My control is Fanuc 18M,
I use I J with G41 (G2 and G3)
Thank you in advance.
Maxz

[punchpressman]

Maxz,
try this I run a 6M Fanuc .When using cutter comp. G41 ,G42 a total of 5 lines at least of G1,G2 or G3 with feed no rapids so machine can calculate the offset path. Also remember you cannot cut a radius with a D offset that is larger than the radius you want to cut. example ( if D31 is cutter radius of
.500 inches) program radius has to be .500 or larger.

Hope this helps
Punchpressman

[guru]

You can lie to the machine by program for largest dia. that will fit inside corner rad on work piece, when run finishing pass just put in negative cutter comp.