Encoder Installation on PM-25MV Mill

[Dave_C]

I don't see any teeth on the encoder or spindle pulley. Are they just not visible in the pics?

Dave C.

[TCandee]

I used an 1/8 round belt. Very little resistance in the encoder so I tried this “no teeth” friction belt option. This “no teeth” setup works very well and made it much easier to turn the pulleys and incorporate them into parts of the power drawbar.

[martyscncgarage]

Just thought I would share my encoder install on a pm25 and pm833tv. I incorporated it into my power drawbar.

The pm833tv power drawbar didn’t have the air cylinder installed when I took the picture but you get the idea.

Interesting. I hope that o-ring doesn't slip....
Let us know how it works out when rigid tapping. Peck tapping a hole would be a good test.
Marty

[TCandee]

Been using it for quite awhile. Really only using the encoder for rigid tapping which is pretty low rpm. Like I said, the very low resistance along with a high coefficient of friction between the aluminum pulleys and the polyurethane belt is working great.

[martyscncgarage]

Been using it for quite awhile. Really only using the encoder for rigid tapping which is pretty low rpm. Like I said, the very low resistance along with a high coefficient of friction between the aluminum pulleys and the polyurethane belt is working great.

Cool!

[carbuthn]

TCandee » Wed Jun 17, 2020 12:37 am

Just thought I would share my encoder install on a pm25 and pm833tv. I incorporated it into my power drawbar.

I wouldn't have thought that the round belt would track that good. I also wanted to be able to peck tap and to be able to use a thread mill for small holes.

Thanks for sharing your setup, hopefully all that I have left on my encoder is to modify the belt cover.
Chuck

[TCandee]

Looks good. Nice job. Round belt was a risk but it seems to have paid off at least for the functionality of the spindle encoder for acorn. I plan to convert my lathe to the same belt on the encoder to try to quiet it. Hopefully it will work as well.

[martyscncgarage]

My concern with an o-ring is if during the tapping cycle, the motor sops and starts abrubtly, the inertia could shift the belt.

I believe there are timing belts made as narrow as .25, maybe narrower.

[TCandee]

True. I had and have the same concerns. Machining the custom timing belt pulleys was my issue. I’m not really sure how to even design the pulley teeth for machining. Everything I have read suggests that every size pulley has its own tooth dimensions for the same belt. This was much easier and the low resistance seems to make stretching of the belt a non issue. I will update if that changes.

[Dave_C]

Been using it for quite awhile. Really only using the encoder for rigid tapping which is pretty low rpm. Like I said, the very low resistance along with a high coefficient of friction between the aluminum pulleys and the polyurethane belt is working great.

I know most encoder specs say not to side load the encoder bearing and that is why you see most encoders on a mount that has a shaft and some bearings. I can't tell but yours might be a little more robust and can handle the side load. IF not, it won't last very long.

Dave C.