CNC Milling Machine

PM is famous for non standard key/shaft size. I’ve stacked many shims to make standard broach/bushing combinations work. It sounds like you are on the right track. Just make sure your pulley OD will fit with the motor mount and the PDB. 101.6mm is pretty big. I think that is why I had to go custom. My PDB will not allow that size pulley.

Todd Candee

In the picture above you can see that my PDB fits over the 100mm standard pulley. It can accommodate up to 107mm. Fingers crossed I’m not missing anything.

@TCandee Is your pulley that drives your encoder connected to your drawbar or spline shaft?

Still trying to figure out the best way to incorporate a pulley into the design. Perhaps, if I could find a very low profile pulley, then I could stick it between the spindle pulley and that left-handed nut…

Here is a picture of my drawbar if anyone has any suggestions:

It’s hard to tell what is on top of your spindle on your PDB but my pulley is built into the the “washer” that is on top of the spindle. It is attached the the spindle so it spins with it. It also serves as a base of the spring compression action. The Belleville washers are on top of that with the drawbar through the center.

I don’t think my set up will work with your PDB. I would try to put something on the spindle spline below the top plate of the PDB and mount the encoder to that PDB plate.

Hope I explained it well enough. The size of the spindle complicates things. Especially considering how small the encoder shaft is. Don’t forget to not put too much pressure on the encoder shaft. Best to direct drive the encoder from the slave pulley when using timing belts.

Todd Candee

As always, I appreciate the very timely response! I’m having a hard time picturing this self supported pulley as you described it before. Do you have a diagram or image you could point me to?

One last question, I know that you belt has worked out well for you, but would you recommend a timing belt to drive the encoder?

Thanks again!

I’ll draw something up and get it to you tomorrow. I am going to make a new mount for mine while making the R8 PDB conversion anyway that will be self supporting.

Todd Candee

Here is my lathe encoder mount. the slave pulley in the picture is supported on both sides by a bearing and the encoder is driven directly off that shaft.

Ah yes! I understand what you mean now. Not sure why I was having a problem visualizing that. Makes perfect sense.

Check this out. I’ve used this work holding method a few times and it works really well for flat parts on the mill.

You can do the entire part, including the perimeter, in one setup.

Todd Candee

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I’m not sure if you still have the SLS 3D printer you reviewed but this seems like a no brainer for making timing belt pulleys for special applications like your encoder mount. Most timing belt pulley manufacturers have cad models of the pulleys that could be modified with custom bores, hubs, widths etc. and then printed.

Todd Candee

Still have the printer, so making a pulley out of nylon is definitely an option. My concern is that the SLS prints are a little rough and could ware down the belt. Bt hey if you don’t think its a ridiculous idea then I will definitely start with that. To be honest, I am tired of spending money on belting and pulleys - not very glamorous.

I am seriously considering getting one of those printers. The build volume is kinda small but the price is pretty good considering.

Todd Candee

Hi there. I’m looking at the wiring diagram you have for servo use and note that alarm is being pulled high connected directly to 24V field power, conversely COM is heading off to input pin 20 on TB5.

Are these two backward by chance?


@m3ch not going to lie, I chucked pretty hard at your fork in the road picture.

Regarding your question, the DYN4 Servo drive is a little weird when it comes to the wiring. The alarm on the servo is connected to COM pin 5 through a phototransistor. When the drive enters an alarm state, pin 5 goes from high to low. So really Pin 5 is what LinuxCNC is looking at to see if there is an alarm. Does that make sense?

Check out this wiring schematic I received from DMM:

Ahhh I see, that is similar to my servos drives wiring scheme. Thanks for that, that diagram is quite useful as a cross reference. Cheers David,much appreciated.

Don’t leave us hanging! You will need to post your conversion!

2 posts were split to a new topic: Hare and Forbes 46B (Rong Fu clone)

@TCandee SLS 3D Printed GT2 Pulley that fits over a 28mm spline shaft :sweat_smile:

Its actually working great! Thanks for that idea.

Sweet. Looks good. Can’t wait to see the whole thing put together.

3 posts were split to a new topic: Converting a PM-728VT or PM-833TV - Questions and Discussion