ABC axis stuff was Re: EMC, ISA and other Questions...

Well there is a method industial controllers
use.
For all moves that include a rotary axes,
G93 "Invers Feedrate timing" should be used.
What this dose is the value given by the F feedrate
parameter is interpreted as a invers timing code wich
the controller uses to establish the speed of the move.

The benefit is that this is a established procedure and
it dose work well.
It is also easier for the controller since no computation
is required to calculate the distances traveled and
compute the speed of the move.

The downside is that a cam program with a specificly setup
Post Processor for the Machinetool is required to compute
the Feed codes.
The Numbers would be difficult to interpret manually and editing
by hand is pretty much out of the question.

Zero Positions do not have to be in any specific location, this
may only be helpful for operators to understand the resulting
code easier but a cam Processor dose not care either way.

As I mentioned before the Post Processor needs to be setup
with the specific kinematics of the Machinetool in order to
compute this properly.
May require a more expensive cam program that is capable of
incorporating each Axes location and direction.

As far as Axses rollover is concerned I have seen this implemented
both ways.
It worked in some strange kind of way.
I personaly prefer not to allow for more then one rotation within
a Block.
Gota keep it simple somewhere.
Good Luck


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo <ballendo@y...>"
<ballendo@y...> wrote:

> Matt,
>
> That last one is a GREAT question! (Snips, inserts below)
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Matt Shaver <mshaver@e...>
>
> >Is it assumed that if you're using an A axis, that Y0.000 is the
> >centerline of the rotary axis (or if it's the B axis, that X0.000

is

> where the tool is directly over the centerline)?
>
> Yes.
>
> > Do you have to also tell Mach1 what axis you're using?
>
> Art is still working on the implementation of rotary axes, so it's
> prob'ly best to let him answer. At the rate he works, my "current"
> knowledge is prob'ly out of date<G>...
>
> >How about the C axis, do you specify the X,Y coodinates of the
> >rotary table's center?
>
> Again, great question. I s'pose you could? Every setup I've ever

seen

> or done puts the rotary at the XY origin. Using G92, or fixture
> offsets, or... But always putting the center of the table on the
> spindle centerline.
> So no spec'ing is necessary, as it is taken care of during the part
> setup.
>
> >Sorry for asking so many questions, but this is going to be worked
> >on in the next few weeks and we can use all the good ideas we can
> >get...
>
> You'll want/need to consider the vaious effects of "stacked" axes,

if

> you're headed to 5 axis capability. And have "constraints of
> movement" variables so that the cables dont get ripped apart! Also,

a

> topic much discussed recently at the Master5 list, you'll have to
> make some decisions about whether to "roll over" when passing zero,
> or just go for large allowable angular moves(multiple revolutions).
> Don't forget those physical constraint consids...
>
> And of course, the "radius" var(s).
>
> Hope this helps,
>
> Ballendo
>
> >
> > Thanks,
> > Matt