Shopbot PRS 48x96 Acorn / Clearpath Conversion

[paulwall]

I knew they'd be pricey, but this I wasn't expecting.



Would it be the end of the world if I ran 3/8" face-width spurs on my 0.50" width racks?

[Gary Campbell]

You can always give it a try, but the reality is that SB found they wouldn't hold up to the torque of their old PK series motors. Your ClearPath motors have 10 times the torque

[tblough]

https://www.ebay.com/itm/InvolGearCuttr ... ect=mobile

Image shows #7, but the description says #6 which is what you need.

[carbuthn]

Tom,
Would he need a #6 (with a range of 17 to 20 teeth) or a #5 (with a range of 21 to 25 teeth)?
The only gears I have made was with a home-made fly cutter.
Just checking (and hoping to learn something).
Chuck

[tblough]

Chuck, you are correct. For some reason I was thinking he needed a 20 tooth gear!

[paulwall]

I think I'm going to pursue the pinion gear stock option and have it machined into hopefully what I need and a few extras.

To keep costs down, is there any harm in running a the same 25 or 30 tooth gear on all axis's? SB used a 20 gear on Z, but I've got the bigger 3421S motor there so torque shouldn't be a problem.

I assume larger gears = longer gear service life, is that about right?

[tblough]

Larger gears = load spread over more teeth but also higher torque.

[Gary Campbell]

Paul...

I assume larger gears = longer gear service life, is that about right?

To an extent that is correct. The hardness of the gears and rack, and lubrication will also play a factor. The larger the gear the less torque is available from a given motor.

The real answer is that you need to adjust your belt/gear reduction and pinion pitch diameter to achieve the desired resolution and keep the motor in its desired RPM/torque range. Use that combo to determine which torque/RPM range motor that best fits the overall design.

It would be my opinion that, yes, the Z axis would benefit from a smaller pinion (more reduction) as it always fights both gravity and inertia and operates at slower speeds than X and Y.

[paulwall]

The real answer is that you need to adjust your belt/gear reduction and pinion pitch diameter to achieve the desired resolution and keep the motor in its desired RPM/torque range. Use that combo to determine which torque/RPM range motor that best fits the overall design.

I suppose that's the trouble with lack of 0.5" face spur gear availability.

Gary - Can I ask how you handle this recommendation for customers of yours who upgrade to your conversion kits?

[Gary Campbell]

Paul...
Depending on the application & model, I use a combination of 3 ClearPath models, 5:1 or 10:1 gearboxes, and 18,20, 24, 25 & 30T pinions to get the output to match the machine's weight, desired speed and have more than adequate torque. I try not to provide upgrades for the old PRT's with the 14.5* PA rack, only the 1/2" wide 20* PA. Even then its hard not to over torque the frame as they use a spring loaded spur to rack engagement.

I have conceded to only putting NEMA23's on PRT models