Best speed reducer for a simple project (gearbox design choice)

[awer]

TL;DR

I'm building a pan/tilt mechanism with a small stepper motor, and I need to design a simple 3d printable gearbox with a 20:1 ratio (aprox)

Hi,

As the summary says, I'm trying to design a simple gearbox with an approximate ratio of 20:1. I have two preliminary designs, one using a worm gear and another using a train of 5 spur gears. Both designs give me the desired ratio, but I really don't know which one I should choose.

The application requires an output torque of around 5kg/cm, and a maximum speed of 0.5RPM.

Both designs are pretty much the same in terms of manufacturing cost.

Coud you please suggest which option is better and explain why?

Thanks

 

[jrmichler]

Some things to consider when making this decision:

1) Do a tolerance stackup calculation to make sure that it can be assembled and will work with realistic worst case part dimensions.

2) After #1 above, calculate the total backlash with realistic worst case part dimensions. Compare to the maximum acceptable backlash. You did calculate allowable backlash, didn't you?

3) Does the manufacturing cost include assembly labor?

 

[trurle]

Summary: I'm building a pan/tilt mechanism with a small stepper motor, and I need to design a simple 3d printable gearbox with a 20:1 ratio (aprox)

Hi,

As the summary says, I'm trying to design a simple gearbox with an approximate ratio of 20:1. I have two preliminary designs, one using a worm gear and another using a train of 5 spur gears. Both designs give me the desired ratio, but I really don't know which one I should choose.

The application requires an output torque of around 5kg/cm, and a maximum speed of 0.5RPM.

Both designs are pretty much the same in terms of manufacturing cost.

Coud you please suggest which option is better and explain why?

Thanks

Generally, worm gear is fine for 20:1 ratios. Train of 5 spur gears would have larger loss and will be less reliable.

P.S. If you have a budget for 5 gears, may be better to consider a comparison between worm gear and epicyclic gear. Most of stepper motor reduction gears are epicyclic.

 

[Dr.D]

The packaging constraints also enter into the picture. A worm is typically at right angles to the axis of the gear, whereas either a compound gear train on fixes axes or a compound epicyclic train have parallel input and output axes.