Re: [CAD_CAM_EDM_DRO] part holding

Hello Rick,

> The hardest part about cnc is not the electronics, the servos, the
> ballscrews. The hardest part is holding down the friggen part!

<snip>

> How do you guys hold down a part when
> you want to machine 5 surfaces on it?

I make fixtures for the parts. I use dowel pins (usually 1/8 inch
diameter) to securely and accurately locate the parts on the fixture. I
can remove parts, inspect, reorient, and replace within a fraction of
0.001 inch.

I often make a "standard" that can be installed on the fixture. The
standard allows me to use an edge finder to locate sides for X and Y
referencing. Then parts can be dropped into the fixture without any
change of X or Y reference.

Sometimes I reference Z to a standard top surface too. That is handy if
I want to flycut several parts to a particular thickness.

Minimum of 2 dowel pins to locate and orient a part. I often use 4 or 5,
especally if that many dowel pins will be used to mate pieces in a
complex but precise opto-mechanical assembly.

The fixture itself may be secured directly to the XY table or it may
just be replacement pieces for jaws in my vise.

Tom Hubin
thubin@...