Re: [CAD_CAM_EDM_DRO] Contouring and CVV was Re: DeskNC for Windows experience anyone?

chewy8833 wrote:

> --- In CAD_CAM_EDM_DRO@y..., "ballendo" <ballendo@y...> wrote:
> > Chris,
> >
> > I don't know if the MillmasterPro/windows has contouring or not. As
> I
> > said, I have not used it. But the advertising I did see, mentioned
> > improvement of several items which I am aware were problems with
> > their DOS product.
> >
> > Flashcut has had contouring, but by whose definition? And other PC-
> > based cnc controls also beg this question.
> >
>
> >
> > The earliest solution was to begin the next moves' accel at the same
> > point that the current moves' decel began. This is still the most
> > common form of "contouring" in commercial cnc machines. The down
> side
> > is, the "corners" are rounded when using this approach. (corners may
> > also be rounded by servo following errors) Inaccuracies from both
> > following error and the accel/decel contouring algorithm increase
> > with higher feedrates and also with increased toolpath angle change
> > between blocks.
> >
> > True contouring(CVV) requires trajectory planning,
> > We have now come to the place/time in our computer capabilities that
> > this can be done "real-time", allowing feedrates to be changed
> on-the-
> > fly, while still maintaining the most CVV possible, given the limits
> > of the physics acting on the machine. Expensive controls (and
> > Master5) do "real" trajectory planning. I'm not sure where EMC is at
> > this point in time.
> >
> > Does anyone know how EMC handles this? I noticed rounding of corners
> at least on sharp direction changes. If I reduce feedrate most shallow
> direction changes are cut with no problem. I would love to be able to
> tell EMC not to "contour" when the trajectory changes are greater than
> a set amount. I know I can turn it off or on with Gcode but inserting
> these manually ,.. ? Is there a file in Emc with accel/decel
> contouring algorithm numbers that can be changed. Or maybe I'm not
> understanding settings in the ini file?

"Corner rounding" is default behavior. Turn it off (Exact stop mode) with
G61. Go back to "smooth cutting mode" with G64.

I don't know of any good place to insert such code. the trajectory planning

could look ahead to decide whether contouring was appropriate. But,
making such decisions on the fly with some sort of rule sounds like it
could have a bunch of unintended consequences. I'm happy to make the
decision manually.

Jon