Re: [CAD_CAM_EDM_DRO] STEP-NC

On Saturday 14 September 2002 07:43 am, you wrote:

> Hi:
>
> On StepNC, its seems simply a method of putting the usual CAM functions
> into a library to be called in a different way. I haven't read deeply into
> it, but I fail to see most of the benefits.

I think one of the main goals is to include tolerances in the machining
program. As an example, you are machining a hole in a steel plate. Is it a
bearing bore, or a vent hole? Obviously the two cases require different
actions to produce the required results. A STEP-NC equipped control would
know that the bearing bore should be rough milled undersized and then bored
to the finish I.D. As an added productivity benefit, if the machine is
equipped with inspection capabilities, the tight tolerance bearing bore could
be machined first, then an inspection cycle would be run to check the
finished I.D. If the bearing bore was found to be oversized and out of
tolerance, that part could be shuttled out to the scrap bin without wasting
time on machining the loose tolerance features like vent holes. If it was
undersized it could be bored further and checked again until it was in spec
(or scrap...). If it failed on two successive parts, the control would stop
and signal an error.

Although I expect that a STEP-NC interpreter will be available for the EMC
(and also to those programs that use the NIST interpreter if the authors care
to integrate it), I don't know what, if any, benefit will accrue to us
hobby/small-shop users. I think this is a system mainly designed to help out
folks who make millions of each part, or millions of different parts, or
millions of variations on the same part... I also think that RS-274 "g-code"
will be with us for as long as any of us are alive.

Matt