Emco servo conversion - compact 5 cnc

I finally got back to the Emco project after a few years. Squirrel! I had thrown it together trying out some pwm drives I had - which seem to work great. When I started pllaying with the spindle I started getting noise. (sporadic estop pulses). (mainly because in my excitement of the servos working well - I didn't pay much attention to grounds..)

So - Taking the time to do it right.. (I want a little lathe to test the polygon turning..)

Currently the servos are tuned with a max following error of .00007", acceleration of 40in/sec^2 and top speed of 150ipm. Very happy with this - and it looks like I could up the acceleration.

addendum... There was a setting in the ini file that was capping the acceleration at 6in/sec^2.. No wonder why it looked so good. So - upping the acceleration to 50in/s^2 I get a peak following error of .0002" (10 encoder counts - which is exactly what I would expect) Now it feels as expected - accelerating to 150ipm is pretty instant.

sam

Hi

I presume you are using service motors fitted with encodes?

What encoder interface have you used?

John

Yes - some Pitmann servos that came with 500 line encoders. I am using Mesa interface hardware that does the high speed pwm and encoder counting. (5i25) which acts like 2 super high speed printer ports. (expandable - you can get daughter boards that do all kinds of cool stuff - analog servos, steppers and such)

I am using it in kinda unconventional way (think cheap a$$) (mesa + cheap bob)

A bit of an update

some machining required...

Getting there

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Great result, but please keep your fingers away from the moving parts even a small machine will take a finger off.

Still nine fingers left then though...

Sam, what CAD/CAM software did you use to generate the cut file? Is the cut file G_Code?

I wonder how practical some live tooling would be on a setup like that? A third axis in Z bolting in place of the tool post with an ER spindle - would make the bolt head a lot easier on the machine!

Very nice setup - servos are certainly well tuned!

Nice job!

Joe

Agreed - I was unprepared for the first run of the program.

more close up action...

Sam, what CAD/CAM software did you use to generate the cut file? Is the cut file G_Code?

That was all by hand gcode. The actual polygon turning is currently done by sending info to hal layer from gcode.. I hope to do a remap but I am not there yet. So something like (this is on the mill - polygon boring)

(polygon radius)
m68e0q.30625
(number of sides)
m68e1q6
(Cutter diameter - probably get from the tool table in the future)
m68e2q.375
(rotate poly 0deg)
m68e3q0

(enable polygon component)
m64p0

(disable polygon component)

m65p0