On Saturday 12 September 2020 07:46:05 andy pugh wrote:

> On Sat, 12 Sep 2020 at 05:19, David Berndt <ber...@uberwin.com> wrote:
> > 2) Is there a minimum value for G93 feed rates.
>
> Not as far as I know. I just tried a test move of G93 G0 X100 F0.01
> and it moved 1mm in 1 minute.
>
> > rotating A axis with something like G93 A45000 Z-1 F.2.
>
> I tried this G-code in the axis-9axis sim. It complained that there
> was no movement mode active. Putting in a G1 I got approximately the
> expected result, in that Z moved 0.5mm in 4.5 minutes. So I assume
> that the A axis was maxed out in the simulator.
> Bumping up the A axis max speed from 90 to 360 gave me a system that
> did 25 revolutions in 1 minute.
>
> Had you done a G0 move?
>
> G0 X0 Y0
> G93 A45000 Z-1 F.2
>
> Moves very fast. As G0 is modal. This ought to be an error, I think.
> (G0 X0 Y0 F10 is accepted. It is valid G-code but probably isn't what
> anyone intends. It says "set the feed rate to 10 and then perform a
> rapid move")
>
> G93 with G0 active, however, clearly makes no sense and appears to
> cause confusion.
From this Doc quote:

• G93 - is Inverse Time Mode. In inverse time feed rate mode, an F word 
means the move should be completed in [one divided
by the F number] minutes. For example, if the F number is 2.0, the move 
should be completed in half a minute.
When the inverse time feed rate mode is active, an F word must appear on 
every line which has a G1, G2, or G3 motion, and
an F word on a line that does not have G1, G2, or G3 is ignored. Being in 
inverse time feed rate mode does not affect G0 (rapid
move) motions.

I think it should throw an error for a G0 on that same or previous line 
hat updates the modal to a G0.

And a "G93 A45000 Z-1 F.2" won't run on the G0704 whose A axis is a slow 
worm drive, throwing an instant f error but, it appears to run as 
expected on the 6040 whose A axis is belt driven and capable of several 
rps.

Wall time for that command is exactly 5 minutes, but I preceded it with a 
g1f20x0y0. Rehomed, and xy zeroed with a g0 is not an error but the 
reported z velocity is not .2, but 1.92, crazy fast. I think it would be 
helpfull to issue an "educational" error as its not really a valid 
command for the G0 mode.  As it will quite likely break the tool, it 
shouldn't be allowed to run IMO.

My $0.02.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>


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