Re: Re: What does Tool Radius Compensation do ?

Andrew Werby wrote:

> [Yes- "exactly" and "accurately" are words I've never been too comfortable
> with (I'm an artist, right?) , but I suppose I could get closer.. But I
> have been trying to zero to the rotary (A) axis line- if this is going to
> work, that would have to be the axis of symmetry. Thanks for your help with
> this, Jon- I'll let you know how it goes.]

Oh oh! For this to work, exactly needs to be taken seriously. What you need
is to mount a hardened and ground rod (maybe 10 mm or so) in the chuck,
and then mount a dial indicator on the spindle, and wipe the dial indicator
along the rod by moving the X axis. Adjust the position of the rotary table's
mounting to the table until the dial indicator doesn't move as you move X
back and forth. If the rotary table has a method for tilting it so the rod would
not be parallel to the table's surface, sweep along the top of the rod and adjust
until that is parallel, too. Finally, set the Y offset. With a 5mm cutter in the
spindle, say, and a 10 mm rod in the rotary table's chuck, you bring them
together until a thin piece of paper gets stuck between the two. Say the
cutter is in front of the rod. You would then set the Y axis to
Y = - (2.5+5+.1)mm (2.5mm for the radius of the cutter, 5 mm for radius
of 10mm rod, and .1mm for thickness of paper). The command would
be something like G92 Y7.6 in MDI, or whatever your CNC uses.

Raise the tool, and then go to Y=0 and see if the tool looks centered over
the rod. If you work out the trig, you will see that even small errors will
cause pretty large gaps under some circumstances.

Jon