Injection molded part quality is highly dependent on gate designs, sizes, and location. Because cashew gates, also called banana gates, can be placed in areas that are not visible, they are an option for molded parts that require perfect surface quality.
Cashew gates, or banana gates, are sub-gates that are automatically de-gated and can be placed in hidden areas that do not interfere with a part’s surface appearance requirements. It’s important to consider certain factors when using cashew gates such as achieving proper filling and packing, avoiding over-shearing of the polymer material, breaking cleanly at the part intersection, and proper ejection functionality. The gate size and design, overall radius, sprue and sprue puller design must all be considered for optimal functionality.
Some things to note about cashew gates:
- Generally, cashew gates are prefabricated by specialized companies and then inserted into the tool.
- Sprue and puller designs for cashew gates will vary based on the polymer material used for molding.
- Cashew gate diameters can vary from 0.8 to 3.5 millimeters and can be round or D-shaped, depending on their location to the part.
- Because cashew gates are used for parts that need to maintain a blemish-free surface appearance, avoiding gate blush or a dull halo is important.
Here are a few examples of cashew gate inserts and how they function.
Gate size influences overall flow to warp behavior. Smaller gates will break off more cleanly than larger gates, but they will have higher injection pressures, shear rates, and potentially cause gate blush. The positioning of cashew gates and their length will influence gate seal time and temperatures inside the gate and runner systems which will impact ejection functionality.
High quality molded parts can be achieved by implementing the most appropriate cashew gate insert for the material and optimizing the gate location and sizing.
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