Re: [CAD_CAM_EDM_DRO] Re: Up and Down; Is Z- away from the part or into the part?

Smoke wrote:

> I have personally found that the SAFEST way to set up and use the Z axis

is

> to ALWAYS set the "0" reference point at the bottom of the part. <

Hi Smoke and others:
NO, NO, NO, NO, NO, NO, NO, NO, NO, NO!
BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD, BAD!!!!!

The customary way, and I (obviously) believe the safest way, is to set Z=0
at the TOP of the stock.
That way a glance at the code will immediately tell you if your move is
above the part or into the part, just by looking if there is a + or a - in
the Z destination.
If you have a 1" tall clamp sticking up, you know you will be safe with Z=
+1.10 without any calculation whatsoever.

In addition, a lot of commercial post processors set the return point for
tool changes and program end statements with a G28 or G29 command which can,
under certain circumstances result in a rapid move to Z=0, thereby pounding
the cutter into the bottom of the stock at 700 IPM if Z=0 is set at the
bottom of the stock.

I've seen it done, and it's not a pretty sight!
Cheers

Marcus