Small Plastic Gearbox clearances POM to ABS

[dansoarr]

Hi,
I'm after some guidelines for clearances in a small spur gear plastic gearbox. The spur gears have been moulded with integral shafts. Gear material is POM, average gear size 22mm dia at 0.5mod, shaft diameter 3.2mm dia. Gearbox case is ABS. I'm looking at a gearbox now and it seems to have 0.2mm clearance on diameter shaft to case which seems excessive.
Unfortunatly I have very little info on the motor at the moment so cant ? on load or speed yet.

Any ideas on clearances as a guide?
Many thanks
Arron

 

[plasgears]

Thermal growth should be considered along with clearances and tolerances. And don't ignore load deflections in the integral shafts. This can add to an overly generous centerline separation.