Re: Re: CNCPro

Fred Smith wrote:

> From: "Fred Smith" <imserv@...>
>
> >
> > Myself, I think I can say never. If a tool needs sharpening, I don't
> have
> the equipment to sharpen it, so I would
> > never have the need to compensate.
> >
> never say never ;-)
>
> The main reason for cutter comp is not tool wear & the use of tooling
> that
> is different from that which was used in the program. The primary
> reason is
> to hold tight tolerances. If for instance you had to mill a slot that
> had a
> +/-.002 inch tolerance. You would be able to cut this by programming
> with
> offset curves in a Bobcad or Vector type of application. The usual
> way
> would be to program the offset curve just larger than the tool radius,
>
> measure the resulting size, then *reprogram* the part with the
> difference
> between the desired size & that actually cut. The reprogramming would
>
> involve drawing another offset curve & regenerating the portion of the
>
> program involved with the slot.

Right, you can compensate for tool deflection. I also find that cut
rate
end mills are not exactly on size. Many of them vary up to -.003" or
so. Another reason I use it is to make one program, either manually or
with a CAD/CAM package, and use it both for roughing and finishing
the part. I enter a cutter diameter larger than the actual tool size,
which
causes the CNC control to offset the tool farther from the part than the

radius of the actual tool. This makes the roughing cut, leaving maybe
.010" on the side of the part. Then, I make several passes, stepping
the
depth down each time. Finally, I set the tool table to the actual size
of the tool, and run the program again, milling the sides to the exact
dimensions.

Jon