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