Basic structure of molds for plastic gear molding

 Plastic gears are precision mechanical components used for the transmission and control of rotating shafts. If the gear performance is poor, problems such as poor rotation, noise, and vibration will occur.

Since it is a plastic molding product, shrinkage or deformation may naturally occur, but in order to minimize various defect factors, the mold structure must also be considered during design.


The key points of the design are introduced below.


Point 1: Cavity-Core Positioning


The positioning of the cavity-core should allow cylindrical tapered inserts respectively, so that the centers of the cavity-core are aligned as precisely as possible.


Point 2: Gate location


Be careful to make sure that the gate is a point gate and that it is located close to the center.


Point 3: Number of gates


Improve coaxiality by configuring odd-numbered gates such as 3, 5, and 7.


Point 4: Eject method


When using ejector pins to eject, the ejector pins must be evenly arranged at a distance that can be ejected.

In addition, it is recommended to use a straight push tube at the bearing part.


Point 5: draft angle


When using ejector pins to eject, the ejector pins must be evenly arranged at a distance that can be ejected.


Point 6: Exhaust port


Confirm the final resin fill site to ensure the vent is set correctly.


Point 7: Number of cavities


In common cases, it is 1 cavity, 2 cavities, and 4 cavities. If there are more cavities, it will cause a large deviation in accuracy. Therefore, unless the specifications of the molded product allow it, it is generally considered that the number of cavities should not be too many.

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