Re: [CAD_CAM_EDM_DRO] Re: what is POSTPROCESSOR? a fundamental question

Jerry,

When someone says that it depends on the machine as to what post processor
they would use they are really talking about the controller. It's the
different controllers that require some variation in the gcode, hence a
different post processor. If I have a 12 ton machine with servos and a
sherline with steppers and Geckos sitting next to each other, and both are
run from EMC, then I will use the same post for both machines.
As an example, one controller may declare a comment as (This is a comment)
while another may want their comments to read {This is a comment}. If you
feed the first controller some gcode containing the second comment it will
fault with an error message, since it doesn't 'know' that curly brackets are
supposed to be a comment. Also while most of the more common G codes are the
same on all controllers, some manufactures' add their own special G codes,
and only their controllers understand them. If you go to Fanuc's website and
look at the supported G codes, I'll bet it does not match Turbo CNC or Mach1
or EMC exactly. So it's the controller that requires it's own post
processor, the machine has nothing to do with it.

Bill

> "doug98105 " wrote:
>
> > In some cases a post processor can be more than a translator from
> > the CAM program's internal data format to a language that is machine
> > specific.
>
> What are the characteristics of a machine that makes it different
> from any other machine? That is if you have one brand of 5-axis
> machine and another brand of 5-axis machine and both use stepper
> motors and stepper drivers, where are the differences that
> constitute machine specificity with regard to a post processor?
>
> I've been trying for at least 2 years to figure out what a post
> processor does and have had no joy. Fred Smith has come the
> closest, but the explanation is still too generic and ambiguous.
>
> > In case you haven't given it much thought, surfacing with a ball
> > nose cutter can be inefficient.
>
> Inefficient? I'd call it rediculous to suggest doing it,
> although I see your point in choosing this as an example.
>
> So far, no one on this list has explained what a post processor
> actually does; I've asked at least two times in the past 2 years
> about post processors.
>
> So let me ask a specific question starting from the machine end.
> If you have a Sherline and a Taig mill and each are driven with
> size 23 stepper motors of the same brand and lot number, then how
> is a post processor for each different? Probably not different.
> So lets say that both machines have steppers driven via Gecko
> drives. Does that change anything? Probably not. So, say the
> Sherline has Gecko drives and the Taig has Xylotec drives. Does
> that change anything? What I am after is the point at which the
> machines become different and why?
>
> Sorry, Doug, to use your post as a vehicle for these questions.
> But it was handy :-)
>
> JerryK