Re: Newbie - Z-axis slipping

Sounds to me like your using a pretty small bit into metal (guess
aluminum or brass) and you're holding it in a tiny chuck or collet.

I'm guessing you went through all the steps to make sure your work
surface is level and all, by checking the height at all 4 corners of
the work.

Bit Slippage:

To prevent bit slippage in those situations put a collet around the
bit shaft. You can get pretty small ones at a RC model shop for a
buck or two each. If the bit is even too small for a shaft collar,
get a tiny piece of brass rod and drill a hole in it using the bit,
then solder (plain solder will work) it onto the bit where the flutes
end. That way you have a ready-made permanent collar. You'll need
to remove any coating on the bit where you plan to solder.

Loosing steps.
You could always check the height before and after a run to make sure
you didn't loose a step. You could always slow your
acceleration/feed rate a pinch to see if that helps.

Soft Metal:
Soft metal is a pain to drill if you do it dry. The bit doesn't dull
it just gets clogged at the tip and won't drill any more. Oil down
the surface or at least the bit every hole or two. This can be
easily done with a toothbrush and a pause OR put a small container of
oil on the cutting surface at a known spot. In between peck drills
put in a small piece of code that will pick up the bit and go over
and put it in the oil, just a dip (don't drill through the bottom).
The next peck drill will automatically go to the proper location
before drilling begins. That will keep the bit as cool as it was on
the first hole and will keep the metal from sticking. Cutting oil is
best, light machine oil will do, new motor oil in a pinch. Clean the
part in Dawn dish soap when you're done.


Thanks
Aaron Moss
www.IndustrialHobbies.com


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Janice" <bigforkshop@y...>
wrote:

> I'm brand new, self taught on my CNC router/engraver. I am
> currently using a single drill point function where I am drilling

30-

> 90 holes per part, at a precise depth of 0.043. I am losing depth
> starting at about hole 25, and losing up to .030 worth of depth

over

> the course of the remaining holes. Am I expecting an unreasonable
> level of precision, or are there some explanations for why a Z-axis
> would lose depth? Thanks in advance!