Re: [CAD_CAM_EDM_DRO] Motors too weak or bad ball screws or software issues?? pictures of odd cuts

Mike Mueller wrote:

> BP Series 1, stock Sigma steppers, Gecko 201s, running 72vdc to each
> 201
>

In second pic, left hand part (worst) looks like it was burned.
What does your end mill look like after this cut? It looks like
the cutter was eroded badly, or was driven back into the collet,
as the cut doesn't go to full depth of the stock.

How were you programming this? Did you do the entire part
outline to full depth in one cut? (I kinda see some steps on
the middle part, so maybe you did it in several passes at
successive Z depth.) You don't give the cutter size, but I'm
taking a guess at 1/2". At 900 RPM, that would be
120 SFPM, which sounds very reasonable. If the cutter is much
larger than 1/2", then 900 RPM is too much for HSS. The feed of
10 IPM would give a chip load of .0055" per tooth on a 2-flute
mill, which also sounds reasonable. Are you sure this stuff is
mild steel? What about your cutters? Are they the no-name
Chinese end mills that come in the blue plastic tubes? These
are quite awful, and I only bought them once! I now use M-42 or
M-57 cobalt HSS tools, and some solid carbide in the smaller sizes.
Ordinary HSS doesn't hold up, and the M-42 only costs cents
extra, but extends cutter life 3-5 times.

Were you using a bull-nose or ball end mill? I see what looks
like a curved edge at the bottom of the cuts. If it wasn't at
least bull-nosed when you started, it sure is now.

Your backlash is probably too much, but cutting in the
"climb-milling" direction gives better tool life and surface
finish. This is where the work is feeding into the tool in the
same direction as the tool rotates. Why backlash is important
is the cutting forces will pull the table and work toward the
cutter, ahead of the backlash. .001" is no problem, .005" could
cause jumping of the table.

Jon