Wednesday, December 9, 2015

Milling Question

I fear I know the answer.  I am trying to remove quite a bit of aluminum with a 1/2" finishing end mill.  (0.01" per cut; 0.5 ipm)  Part-way dowm, typically at .04", it often seizes the material and drags it out of the vise, with predictable results.  Should I be using my 3/4" roughing end mill instead?

UPDATE: LinuxCNC has a feed 9override you can use to override the feed rate of your program.  Now I have the mill cutting at .4 inches/min instead of 1, and the problem has cleared itself.  I will still try the the roughing end mill at some point.


Mauser said...

If you're roughing something out, use the appropriate cutter. I would also look at your clamping, since that seems to be the weak point in the forces you're unleashing. And check your spindle speeds. you may be taking too big a bite too slowly.

Will said...

It appears that as you deepen the slot, the cutter is dragging on the wall(s), which really shouldn't be happening. This indicates that something in the structure is loose, or very weak. At some point, the clamp/table/head/tower/chuck assy, or multiple items, provides enough wobble to cause the cutter to bite into the part with sufficient grip to move it relative to the vise.

Chuck up a rod with an indicator against it, and start pushing or pulling on the end of the rod. Determine if it deflects more easily in X or Y. Repeat this with something in the vise.

Check the walls of the slot it was cutting. They should be flat. I expect a close exam will show waviness or chatter.