Re: Question about angular and linear feedrates

Dan,
I have been wondering the same thing. I use CNCpro and in your
example, it would take 30 sec. If there is an X (or Y or Z) and A in
the same block, it will set the feedrate based on the X and try to
force the A to complete it's move in the same length of time. If the
A is a large value and the X is small then it will try to run the A
at some astromical speed. However, if there is no X (only an A) then
it uses the F value as Deg/Min, not Deg/Sec,(although you can select
either Deg/Min or Deg/Sec for the display). That is a whole new
problem.
For example, on my Sherline, 5 In/Min will turn the X stepper 100
RPM, but 5 Deg/Min is 1 RPM. That is the equivalent to listening to
your watch tick, not usable.
I ended up writing a little routine to calc a new feedrate for each
block. Deterine the length of the actual vector and then calc the
feedrate based on the X component, if there is one. If not use
Deg/min units for the rotary. It mostly works, but requires that the
origin (0,0) be at the center of the rotary, (to find the radius) and
can't use G02, G03, etc., only G00 and G01. I don't know what effect
this (a feedrate in each block) has on such things as accel,decel,
constant contour, etc.
I am going to hate myself if it turns out that there is an easier way
using some of the software that I already have and don't know how to
use:)

Cheers,
Al Lenz

> "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