Tom,
You are correct about the G93's, they work good, except they can be time consuming to calculate for every cut. I would prefer to be able to alter the A-Axis feed rate settings using the fixed diameter of the material.

When I'm working on simple fixed diameter pieces, if the X-axis feed rate is 75 IPM, the A-axis feed rate will need to be about 8600 DPM for a 1" diameter piece to reach a 75 IPM surface speed.

If the feed rate is set at 75 for both X ( 75 IPM )and A ( 75 DPM ), the A-Axis turns VERY slow and only reaches a fraction of an inch surface speed per minute.

I am looking for a way to change the " degrees per Unit" setting of the A-axis by using a calculation of the radius of the material.

For example, if the rotary readings were set in degrees per second instead of degrees per minute ( 8600 DPM / 60 seconds in a minute ) = 143.3 IPM A-axis surface speed.

If it was degrees per half second ( 8600 / 120 ) = 71.66, which is getting very close to the 75 IPM A-axis surface speed setting.

Any ideas???
Todd

--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> Hi Todd,
>
> Good question.  The A axis speed is not related to any radius.  It is in degrees per minute.
>
> But my understanding is that when doing a coordinated linear and rotary move "feed rate" really doesn't make sense.  It is necessary for you (or hopefully the CAD system) to specify the feedrate in G93 Inverse Time.  Which is essentially specifying the time for the segment in an inverse form (I guess old computers couldn't divide very well).  So if you or the CAD system can determine how far the tool will actually move through the material for the block then you can determine the necessary time for a desired cutting rate.
>
> HTH
> Regards
> TK
>
>
>
>
> ________________________________
> From: morgtod <todmorg@...>
> To: DynoMotion@yahoogroups.com
> Sent: Thursday, May 23, 2013 5:12 PM
> Subject: [DynoMotion] A Axis speeds
>
>
>
>  
> Is the feed rate of the A axis controlled by the radius of the Z-axis, or is it just straight degrees per minute?
>
> If it is degrees per minute, how do you calculate the federate of coordinated X,A moves?
>
> Todd
>