RE: [CAD_CAM_EDM_DRO] Re: CNC Newbie

No I made stub shaft ends and bored them to .615. The ballscrew ends are
secured to the stub shafts by 5/16D set screws(2).
I did not like the stock end plates so I bored them out for a 17MM
radial ball bearing so that the side loads of the timing belt pulley
wouldn't drag on the end plates. I reused the existing thrust bearings.
Itwas easy to do with a 4 jaw chuck on a lathe.
I bought my belts and pulleys from Besco but they changed their name.
Call 1-206-762-3800 they do mail order. I would recommend the 42XL037
timing pulley for the XY ballscrews and the 21XL037 pulley for a .625D
servo motor. That will give you a 2/1 ratio. If you use smaller
diameter shaft motors I would use the smallest diameter pulley that you
can fit and still have a good set screw thread.
I'll send some pictures of the ballscrew installation that I made using
two standard ballnuts, my motor mounts and a few other pictures. I'll
also email the .doc file on how I solved the mill/drill backlash
problem.
Ethe encoders must go on the PMDC motors.
Dan

>

Dan, yes the ballscrews were only .615. .631 was the ball cicle
diameter from the data sheet. Did you machine the the ball screws
down to the root diameter of .4800"? I bought some taper bearings
with an 1/2" ID. I was thinking machining to the root diameter and
placing a shaft collar there. It looks like the collar should be able
to take the axial load. The rest of the shaft will be 1/2" OD. I had
some stub shafts that came with the nuts that I have been practing
on. Dam hard shafts. I do not want to anneal with heat, so I have
been using carbide inserts with slow feeds. It looks like it will
work.

I would love to see the pics. You can zip them to me. Where ia a good
place to get the belts and pulleys from? I thought about making my
pulleys using my 8" rotary table, but thought that the accuracy would
not be there. I am still debating servo or stepper.

Who has the best control gear for the PMDC servo's? I am still
debating the Z axis. As we all know of the large backlash in the
quill on these mill/drills. I have another set of NTN, 1/2"
ballscrews that I bought before the Thomson's came along. I was
thinking about slapping one in the dovetail column? As for encoders.
Do I try to get some as part of the motor, or just put one on the
shafts directly?

Jason


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