Re: [CAD_CAM_EDM_DRO] RE: 5-Axis-EMC

Ray wrote:

> -----Will's post to emc-developers-----
> I just committed a fairly extensive set of changes to the CVS archive.
> Adds some support for programming ABC moves with the new interpreter.
> * See the sections 2.1.2.2 Rotational Axes and 2.1.2.5 Feed Rate in the
> RS274NGC_3 manual.
> http://www.isd.mel.nist.gov/personnel/kramer/pubs/RS274NGC_3.web/RS274NGC_3TOC.html
> * trivkins maps A to joint 3, b to joint 4, c to joint 5, genhexkins
> maps A to roll, B to pitch and C to Yaw, and modifies all the joint
> angles, strut/cable lengths accordingly.
>
> Hi Jon !Why set up the kinematics ? I just want to drive a "simple"

Ah, of course, this now reminds me why this is necessary!

In Rs-274D, you have feed rate, and you have movements, in both
linear and rotary axes. Now, you can specify movement of as many
axes as you like in one block, and you can specify ONE feed rate,
in a linear dimension vs. time. The kinematics needs to know something
about the physical layout of the machine so that linear distance can
be computed. Without that knowledge, movement of a rotary axis
can not be related to linear movement of the tool tip, and therefore,
no velocity of the tool tip vs. workpiece can be determined.

Yes, of course, you just want it simple! But, there's the rub, there is
no clear way, in the RS-274D specification, to just throw in some
extra (rotary) axes, and have them perform in a consistant manner!

So, to avoid messy kludges that could make a real disaster of a simple
task, it really is necessary to properly manage the movements based
on the real physical arrangement of the machine. It looks like at last
this will be properly built into EMC, and the setup should become
pretty formulaic, perhaps just a set of parameters in a file loaded at
run time. I do want to put a single rotary axis on my mill for cutting
gears, busts of people's heads, and maybe even turbine blades.
It might be real nice to have all this set up so that I can normally have
an A axis, but move the (NC) dividing head to become a B axis when
desired, and also put a fixed tilt on it, as if the A axis was stacked on
a B axis set to some fixed value for best turbine blade access.
With a nice little table that could be read in, this would be a very easy
thing to do.

Jon