Taking the CNC Plunge

[TomS]

I had the spline rattle and fixed by greasing it.

I don't use electronic breaking with spindle controlled from Mach3. There is enough drag with the belt drive to slow it down quickly enough. I do like it on the lathe though.

Thanks for the tip on greasing the spline. I'll give it a try.

I was thinking along the same lines as you on electronic braking. I've looked through the parameter list and there are several that address overvoltage fault error. I'm going to change them one at a time and see what effect they have on decel time and if I still get the dreaded overvoltage fault.

Tom S.

 

[TomS]

If you install an external braking resistor ($20-30 on eBay), it will help the rapid deceleration. You would be able to stop the spindle in less than a second.

Thought about a resistor but this project has stretched my electrical skills to the max. For the moment I'm going to play with the deceleration features and see if I can get around the overvoltage fault by increasing the decel time. Phase 2 will be an upgraded BoB, ESS, and spindle control board. I'll look at it again when I do Phase 2.

Thanks,


Tom S.

 

[TomS]

This is my first time uploading a video. It is a clip of my mill running at 6400 rpm (90 hz) after completing the VFD/belt drive conversion. Sure beats a top speed of 1970. Not sure why it turned 90 deg. or how to correct it. File size started out at 63 mb. Got it down to 4 mb. Still have some fine tuning to do and a few details to finish up. If you listen closely you can hear the spindle spline/drive sleeve rattle I mentioned in my post above.

Tom S.

 

[Davd Flowers]

Maybe I missed it, but how is the driven pulley attached to the spindle? Awesome thread BTW....

 

[TomS]

Maybe I missed it, but how is the driven pulley attached to the spindle? Awesome thread BTW....

Thanks for the kinds words. As most others have done when converting their mills to belt drive I modified the splined sleeve (part 57) on the attached drawing by machining off the gear and cutting a snap ring groove to retain the pulley. Some have threaded the end of the sleeve for a retaining nut. The sleeve is then assembled inverted from it's original orientation. See the picture below of the finished sleeve.

Tom S.

 

[Davd Flowers]

OK, I think I see.
The pulley is pressed and keyed to the splined coupler, but then does it just sit over the spindle shaft or is there any type of bearing support on it?

 

[TomS]

OK, I think I see.
The pulley is pressed and keyed to the splined coupler, but then does it just sit over the spindle shaft or is there any type of bearing support on it?

There are two ball bearings and a spacer that support the sleeve. These pictures are not of my assembly but illustrate how it's done. You will see that this assembly has inner and outer bearing race spacers. That's because a retaining nut is used to compress the bearings against the lower snap ring. Here are a few pictures of the sleeve assembly and installation.

Let me know if you need more info.

Tom S.

Individual components that make up the assembly. Note that this picture shows a retaining nut at the top. My assembly uses a snap ring and no inner bearing race spacer. See the snap ring between the two bearings? That fits into a groove in the bearing bore of the cover plate and retains the sleeve assembly in the cover plate.


Here are the components assembled on the sleeve for illustration only. To assemble the parts in the cover plate you first install the snap ring in the bearing bore, then press in the bearings. Drop in the bearing spacer(s), slip the sleeve into the bearings, install the key and pulley and tighten the nut or in my case install the upper snap ring.


The sleeve assembly, minus the pulley installed in the cover plate.


Bottom view of the cover plate.

 

[Davd Flowers]

OK, I got it now
Thanks for taking the time to show me.

 

[TomS]

OK, I got it now
Thanks for taking the time to show me.

Glad to help.

Tom S.

 

[Davd Flowers]

Im thinking that this is a mod I want to do sooner than later Now if only my ball screws would hurry up and get here!