Re: software questions

--- In CAD_CAM_EDM_DRO@y..., Ray Henry <rehenry@u...> wrote:

>
> Starcast
>
> I gotta say that there has been a lot of talk about drawing parts

to the path

> size rather than real size. This surely does rub me the wrong

way. I draw

> the part to the size that I want and then use my CNC's (EMC's) tool

diameter

> offset commands to make the cuts.

Now hold on a minute... this is only applicable for simple 2D part
contours. You cannot do this as easily with pocketing as there is no
pocketing function in G-code. Cutter compensation G41/G42 is most
useful when there is a tight size tolerance, small tweaks in the tool
offset allow you to tweak the resulting part to hold a tight
tolerance.

There is a also a school of thought that the "best" way to implement
cutter comp is to create the offset for the size tool you plan to
have and then tweak the offset curve with a G41/G42 to adjust for
actual tool size. The compensation register would have a value like -
.010 to indicate the difference between the planned tool size and the
actual reground (resharpened) size.

One of the benefits of drawing the toolpath to the size needed is
that the offset function smooths internal radii to a size that the
cutter can cut. This means that you will not get a condition in
which you have specified an internal corner and the cutter is too big
to fit(since regrinds are always smaller than nominal). In many CNC
controllers this is a program abort error when using cutter comp.
There is also the issue of approach and departure control,which is
automated in a CAM program.

Then there is 3D cutter compensation. Surely we are not going to
attempt to do this with a tool offset in the control?

Best Regards,

Fred Smith
IMService