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lerman
03-27-2005, 01:49 PM
I'm trying to write some general code for milling pockets, and could use some advice on how to ramp the depth.

Two general approaches I've seen are to do a straight line ramp and a helical ramp. For general purpose code, it seems that a helical ramp would have more use.

So, for a helical ramp, using a 1/2 inch mill (for instance), I could imagine cutting a helix 3/8 in diameter (I'm describing the cutter center). The feedrate (F) would depend on the material, the desired chip loading, and the RPM. The questions I have relate to the Z axis motion. How much should I increase the depth per cycle around the helix? Is there any way to set this independently of the feedrate? The total path is about 0.6 inches per trip around the 3/8 circle. So, if F is 6 ipm (to pick a number) it will take .1 minutes per cycle. If I set the Z increment to -.100 inches, the vertical feed rate will be 1 inch per minute.

That sounds reasonable to me. It says that the vertical feed rate is 1/6 the horizontal feed rate (that's a ramp angle of about 9-1/2 degrees). For a ramp of 1 degree, we need about one tenth the feed. So, set the Z increment to -.010 inches (per cycle around the helix) and the vertical feed would be .1 inch per minute.

I've looked in Machinery's Handbook and on the net, but haven't found any guidelines for ramp angles. I assume it would vary with cutter type, material, and other things.

Can any one provide some guidelines?

Thanks,

Ken