as the controlling geometry, this feature will be a variable in the actual part. It is necessary to set realistic tolerances for these truly variable features. The Involute Shrinkage of a Molded Gear Typical errors in a Molded Part The only way to be certain that a plastic molded gear is within tolerance is by scanning the involute profile and determining the actual physical geometry of the gear. The molded part can be completely out of specification and still give acceptable roll test results. Below is a profile inspection of such a gear. The involute base circle was very far off the defined value. The gear had 64 teeth and a master used to measure the gear had 64 teeth. With such a large number of meshing teeth in roll testing, there was almost no tooth-to-tooth error. The gear simply appeared large, even though the base circle was small. The molder thinned the teeth, brought the gear into
as the controlling geometry, this feature will be a variable in the actual part. It is necessary to set realistic tolerances for these truly variable features. The Involute Shrinkage of a Molded Gear Typical errors in a Molded Part The only way to be certain that a plastic molded gear is within tolerance is by scanning the involute profile and determining the actual physical geometry of the gear. The molded part can be completely out of specification and still give acceptable roll test results. Below is a profile inspection of such a gear. The involute base circle was very far off the defined value. The gear had 64 teeth and a master used to measure the gear had 64 teeth. With such a large number of meshing teeth in roll testing, there was almost no tooth-to-tooth error. The gear simply appeared large, even though the base circle was small. The molder thinned the teeth, brought the gear into
247102386-Fabrication-of-Gear-Type-Injection-Moulding-Achine.docx