spindle settings (servo + Step & Dir via Mesa 7i92 + 7i76)

30 Jan 2021 17:26 #197167 by robertspark
Looking for some suggestions / guidance.... what are your thoughts?

I've got a lathe which has a 750W servo controlling the spindle via a 2:1 ratio HTD belt drive.

It has a 1000ppr encoder on the spindle (directly coupled as a hollow encoder).

The spec of the lathe (originally CNC'd) was 2000 rpm for the spindle, I've checked the bearing specifications from FAG and they are good for a lot more than this, so I've sort of edged it up to 2500 rpm (top speed of the servo 5000rpm), which is still below the rating of the chuck but fast enough for me as I'd hate something flung across the garage at that speed.

I set it up in non LinuxCNC machine controller software as 2880 steps per rev, as I was limited to the motion controller I was using previous .... well sort of and 2880 steps / rev (4steps per deg or 1 step per 1/4 degree) seemed like a nice number (i.e. no real reason why....)

I was wondering if there was any benefit in increasing this in LinuxCNC to say 7200 steps per Rev (at 2500 rpm, which gives a step pulse rate of 300kHz and still well below the capabilities of the Mesa hardware, and still below the capabilities of the fast step and dir input of the ASDA A2 servo motor drives (4Mhz). This I presume would result in smoother motion.

Curious what others would do?

I do at some point want to set the lathe up for indexing as a C-axis, but not yet (I have a 4th axis / converted rotary table for the mill so no "real" need as yet).

all step+direct wiring within the cabinet is done via shielded twisted pair ethernet cable.

Please Log in or Create an account to join the conversation.

31 Jan 2021 01:51 #197192 by andypugh
There is probably no advantage in increasing the resolution for threading. My previous lathe threaded just fine with a 50-slot wheel.

If you want to servo-control the C axis, though, the more encoder counts the better.

Please Log in or Create an account to join the conversation.

Time to create page: 0.067 seconds
Powered by Kunena Forum