What is the reason why helical gears are harder to machine than spur gears

According to the current processing method, helical gear machining needs to consider two factors: the shrinkage of the plastic itself and the discharge gap. Due to the difficulty in accurately quantifying the inaccuracies of plastic shrinkage and discharge gaps, it is difficult to manufacture precise electrodes. When using electrode discharge machining to machine the gear ring, it is necessary to add spiral motion so that the electrode can machine the gear ring according to the spiral motion. The existence of this motion directly leads to the accuracy of the machine tool being added to the machining accuracy of the gear ring.

The reason why helical gears are more difficult to machine than spur gears is:

1. Injection molding factor: Straight tooth ejection can be directly ejected by the enterprise at the same time, but oblique teeth must be rotated out. Due to the force factor, the plastic gear problem has a significant impact on the force during the oblique tooth rotation of the mold, so there may be a relatively large deformation in the control work of the oblique tooth mold process. These deformation factors result in lower tooth profile accuracy and radial runout index injected from plastic gears compared to spur gears.

2. Factors in mold processing: The straight tooth core gear ring can be cut with high-precision slow wire cutting, which has high quality, especially surface roughness and cutting accuracy. However, due to the presence of helical angles, the core gear ring of the helical gear must be machined using discharge machining, which requires electrodes and is usually processed using customized hobs.

That is to say, the precision of the precision gear ring gear will be affected by the precision of the spark machine. These factors together determine that the machining of helical teeth is more difficult than straight teeth.