Re: [CAD_CAM_EDM_DRO] Re: UCMI Interface

Jon:

AHhhhh, I see now. I just took a walk through your segment code. I have
been using the same forward - backward traverse only yours is alot more
complex in its abilities. Thanks for the explaination, it really does
explain alot.

Art

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, August 12, 2001 10:23 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: UCMI Interface


> Art Fenerty wrote:
>
> > >
> > > We demonstrated this capability with EMC and my stepper rate
generators
> > > at the NAMES show near Detroit this April. We got VERY smooth
contouring,
> > > and ran a Sherline with MicroKinetics drivers twice as fast as anyone
> > > had ever seen them go before.
> >
> > Jon:
> > How do you handle the circumstance where a circle is made up of 4
arc's.
> > Do you ramp up and down each line? Does this type of circle move
smoothly
> > around the entire circle without slowing down? How is the decision made
that
> > says when to ramp down and when to ramp up each axis?
>
> No, EMC looks ahead and sees each arc sector can be continued into the
> next without exceeding the machine's acceleration limits (in fact
basically no
> acceleration at the 'joints', only in the rest of the curves). So, there
is no
>
> need to decelerate for this chain of blocks. Now, lets say we have a
bunch of
> short vectors that are nearly all in a straight line, then all of a sudden
> there's
> one the reverses the direction of motion. A surface contouring program
might
> look like that. It looks ahead, and finds the segment with a
discontinuity in
> the
> movement, then works backward in the program to figure out where it needs
> to start decelerating, so that the machine's acceleration limits are not
> exceeded.
>
> You never ramp up and down each axis independently, although you have to
> calculate each axis' acceleration to determine if you are exceeding the
> capacity of the machine. But, if you have to ramp velocity down, you have
to
> ramp them ALL down proportionately.
>
> Anyway, EMC runs totally smoothly around a circle composed of 4 quadrants.
> I also do 'spirals' that are composed of expanding arc quadrants which
meet
> at a point, but have slight dicontinuities in the radius. I use this to
bore
> out
> round pockets and such, and it works real well!
>
> Jon
>
>
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