Re: [CAD_CAM_EDM_DRO] Re: Question about angular and linear feedrates

Rab,

Thanks for your reply. I have picked the feedrate based on the diameter of
my parts and how fast the cutter can move through the material without
breaking. I generally pick a conservative value. Since each move of a
linear and rotary axis together produces the equivalent move of the
hypotenuse of a right triangle, the worst case scenario would be for a 45
degree hypotenuse, or a move that would be 1.414 times the set feedrate of
the slowest individual axis. Therefore, if I pick a feedrate that is
1/1.414 times my maximum speed I can allow then I would be safe.

This obviously assumes that the controller would limit the move to the speed
of the SLOWER axis. Are different control program setup to do this
differently? Why would you ever want the angular axis to move faster than
the feedrate setting, which it seems to do "some of the time." Is this a
bug in the software, or do most people not care about this.

It seems to work fine if I set the maximum speed of my rotary axis to the
maximum cutting speed. The program realizes this limiting value and then
adjusts the linear feedrate to match for the geometry of the move. The
serious downside of this is that there are then no rapid moves for the
rotational axis.

I know most people do not use angular axes in their work, but I need to.
Another option would be to setup the angular axis so that instead of 360
degrees around the circle, I could make it 3.6000 inches and divide all of
my angular moves by 100. But then I lose the ability to go fully around the
circle and end up back at zero degrees without then unwinding all of the way
back around.

Thanks for your help.

Dan.

----- Original Message -----
From: "rainnea" <rainnea@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, August 03, 2002 7:50 PM
Subject: [CAD_CAM_EDM_DRO] Re: Question about angular and linear feedrates


> Hi Dan,
>
> In your example, you need the move to complete in the time of the
> slowest axis, but it dosn't always happen that way. It gets worse if
> you have
> G01 A180 X0.005 F1.0
> where the interpreter can lose the plot by trying to complete the
> angular move in the timespan of the linear move and you get the A
> axis trying to move faster than it's able to.
>
> You really want to work out the actual distance that the tool moves
> through the workpiece and then re-calculate the appropriate feedrate
> based on that. For 4-axis work you'd first need to know the distance
> of the tooltip from the centre of rotation in order to work out the
> distance it moves. This could be done on the interpreter level, in
> the CAM software or as a post-processor.
>
> In theory EMC should be able to do this if the feed_reference mode is
> set to "CANON_WORKPIECE" but I don't know if the algorithms for this
> are there in the EMC sources or have been implemented, a google
> search on "CANON_WORKPIECE" and EMC should explain what it should do.
>
> Good luck,
>
> Rab
>
>
>
> --- In CAD_CAM_EDM_DRO@y..., "Dan Statman" <dan.statman@r...> wrote:
> > I would like to know how most (all) control programs will handle the
> > feedrate for the following moves:
> >
> > A-axis is angular with feedrate expressed in degrees/sec
> > X-axis is linear with feedrate expressed in inches/min
> >
> > Assume that I am always starting at X0 and A0 for these moves.
> >
> > If I command: G01 A180 F1.0 it should take 180 seconds to make the
> move.
> > If I command: G01 X0.5 F1.0 it should take 30 seconds to make the
> move.
> >
> > My question is how long should the following move take starting at
> A0 X0:
> >
> > G01 A180 X0.5 F1.0
> >
> > Does it take 30 seconds or 180 seconds?
> >
> > Thank youf or your help.
> >
> > Daniel J. Statman, Statman Designs
> > www.statmandesigns.com
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this as a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
>
> Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Mom
> List Owner
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>