CNC Pulley and Bearing Races

[danielmyers]

Hello,

My company is working on a machine that requires large, non-metalic bearings and timing belt pulleys. There will be two parts. The first is an inner bearing race with timing belt pulley teeth extended from the top of it. This part can either be made as a full ring or as segments that assemble to form a full ring. The second is an outer bearing race. This part needs to be made as segments of a full ring in order to properly assemble the bearing with the balls. The parts will be made from delrin and will have thicknesses of 1.35" (inner race) and 0.8" (outer race).

For the surface the balls will run on, we are thinking that using a convex-radius end mill to create two grooves with a 0.01" vertical separation would be an effective way to make the feature. Does this sound like a reasonable way to do this?

Images of the parts are attached. We are willing to adjust the design to improve production costs. Please contact me if you are interested in quoting these parts and I can send you the prints for them.

Daniel Myers
Associate Mechanical Engineer
Ciholas, Inc
3700 Bell Road
Newburgh, IN 47630
email: daniel.myers@ciholas.com
phone: (812) 962-9438

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[konwey]

Hi Daniel?
We have the ability to produce it. Please provide 3D to kon@plusminusthree.com.

[RCaffin]

Hi Daniel

I gather this is for a retro-fit?

You have not specified the form of the toothed pulley. For the pulley size mentioned, I would suggest something better than the old 'timing belt' design..

You have not specified the ball size. This affects the load capacity. Ball size tolerances are probably not critical if you are using Delrin.

You have not specified what sort of ball cage you want: this will be fairly important. I think it will need to include a slit somewhere, to get it on the shaft.

You have not specified how the balls will be loaded. Are you hoping to 'assemble' the whole bearing on the shaft and to then slide it into position?

Do the parts of the two races have to be so short? Seems to me it might be better to machine each race as a whole, then to cut each race in half with a very thin slitting saw.

You have not specified quantity. Some set-up jigging will be needed, which affects both the style of jigging and the costs.

Cheers
Roger

[danielmyers]

These are for a newly designed machine. It will be a positioning arm for antenna testing.

The tooth profile is mate to match a Gates GT3 belt. We determined this to be the best option due to the high load requirement of our system.

The ball bearings are 0.75" diameter delrin balls.

We are considering not using a cage to simplify machining. On a previous version of this bearing, we found that the bearing performs adequately without a cage. We may still decide to have a slit similar to what I believe you are describing machined to allow for a cage.

The balls will be loaded by first assembling all but one of the outer segments, then loading the balls and adding the final outer segment.

The segments are not required to be as short as they are now (60 degrees). We do, however need to have at least one removable piece on the outer race for assembly. The idea was to make them short in order to be more efficient with material. We are concerned that cutting a full race with a saw would create a sticking point in the bearing, even if the kerf was small.

We are requesting quantities of 1, 5, and 10 bearings for quotes. This would mean 6, 30, and 60 of the segmented pieces as they are designed now. If you are interested in quoting these parts, let me know and I will send you the drawings and step models for them.

[RCaffin]

Hi Daniel

Is there any reason why you can not use an off the shelf bearing and thread it onto the shaft? Really, really consider this seriously. You can buy large plastic bearing for peanuts, off the shelf. To get a few made custom could cost you $1 - 2k easily - or more.

GT3 is the same as GT2: the only difference is a Patent fudge. You can ignore the difference. For the sizes you seem to be talking about, one of the wider belts would be best - wider than the common 6 mm. The common Chinese GT2 belt has a 2 mm pitch, but I am fairly sure you can get larger pitches, which would be worth considering.

Delrin balls: bad idea. Standard plastic bearings come with either SS 316 balls (very good) or ground glass balls. If you need totally non-magnetic then use glass, but otherwise SS would be better.

Cage: this is ESSENTIAL. Without a cage the bearing can slop everywhere and jam. Do not do it! Don't even think about it.

The only thing left then is the GT2/3 pulley and mating it to the bearing. That's soluble. How to do would depend on the engineering details.

Cheers
Roger

[mactec54]

These are for a newly designed machine. It will be a positioning arm for antenna testing.

The tooth profile is mate to match a Gates GT3 belt. We determined this to be the best option due to the high load requirement of our system.

The ball bearings are 0.75" diameter delrin balls.

We are considering not using a cage to simplify machining. On a previous version of this bearing, we found that the bearing performs adequately without a cage. We may still decide to have a slit similar to what I believe you are describing machined to allow for a cage.

The balls will be loaded by first assembling all but one of the outer segments, then loading the balls and adding the final outer segment.

The segments are not required to be as short as they are now (60 degrees). We do, however need to have at least one removable piece on the outer race for assembly. The idea was to make them short in order to be more efficient with material. We are concerned that cutting a full race with a saw would create a sticking point in the bearing, even if the kerf was small.

We are requesting quantities of 1, 5, and 10 bearings for quotes. This would mean 6, 30, and 60 of the segmented pieces as they are designed now. If you are interested in quoting these parts, let me know and I will send you the drawings and step models for them.

I will send you a email for the dimensions Etc I was just in IN the last few days, how much loading will this bearing be seeing, I have experience in making Bearings and GT3 power Grip Timing Pulleys like what you need