Re: What does Tool Radius Compensation do ?

hansw wrote:

> My MAXNC software claims to have
>
> "TOOL RADIUS COMPENSATION "G" codes (G40, G41, G42)"
>
> and the Program by Doug Yeager "CNCPRO.EXE" does not have this. I
> prefer the Yeager program, it's much more logical in it's user
> interface.
>
> What is "TOOL RADIUS COMPENSATION " how can I see the difference
> between the results of with and without it...

Your program (toolpath) must activate it, and you must have already entered
a radius (or diameter, usually) for a specific tool into the CNC's tool table.
It allows tools of somewhat different diameter to be used without changing the
program. The CNC has to know which side of the specified line to cut on.
The toolpath is specified as the actual dimension of the part, and is not offset
by the tool radius, as you would usually do when writing G-code by hand
or with a CAD/CAM program. Then, when the program is run, the CNC
control uses the tool's radius to offset its movements to one side or the
other from the specified coordinates. See my desciption of this at
http://206.19.206.56/diacomp.htm Also, you might find a lot of interesting
info in the CAD_CAM faq, at http://206.19.206.56/cadfaq.htm

> The kind of things I do, I have not seen any difference... Dumb Fat and
> Happy... but would like to understand this, what am I missing...

The big advantage here is that you can use re-sharpened cutters, which are
usually a little under-size, if the side cutting flutes have been re-ground.

A cute trick I use is to run the program several times, first with the cutter
diameter entered into the tool table larger than the real size, and then reducing
the entry in the tool table. This allows one program to be used to make
roughing passes, and then a final cut. As the offset is made smaller, the
tool will cut closer to the line specified in the toolpath program.

Jon