Re: [CAD_CAM_EDM_DRO] RE: Why can't I re-run this program?

Alan Marconett KM6VV wrote:

> Hi Jon, Ray, Tim et. al.,
>
> That's what I figured (after I searched a considerable time trying to
> find subroutines). Is it because the Gcode is pre-compiled, or because
> of the "contouring" (?) process that smoothes the flow of the blocks?

It is not "pre compiled". The interpreter DOES look ahead, and they didn't
do the extra work to have the interpreter follow through a subroutine
to keep track of any reasons it might need to slow down there. That is
the whole reason for the problem, that it has to look ahead at least as
far as it would take to slow down. For instance, if there was a long
string of very small, almost parallel moves, and then a sudden right turn
or reversal of an axis. This is a common situation in contouring. The
machine might have to slow down hundreds or even thousands of blocks
of G-code before the actual discontinuity in the motion, or it would
exceed the machine's acceleration limits, and gouge the work.

> I'm also curious about the G98/G99 "canned cycle return level", is that
> widely used? I understand that canned cycles can vary a lot.

Canned cycles are very irregular, and are generally specified by the machine
tool BUILDER. The CNC maker then programs these required functions
into the CNC control as requested. that's why you can have the bizarre
situation of two apparently identical machines side by side in a plant
(bought at different times) with different canned cycles!

Jon