I just recently received this question from a mold maker…
When would you recommend the use of cashew gates?
note: Cashew gates, or banana gates, are semi-circular gates which tunnel under the parting line to gate on the underside of the part. During ejection, they detach from the part and curl out of the mold. Since these gates cannot be machined directly into the core, they are difficult to machine. As a result, the gate has to be machined into a pair core inserts, each insert contains half of the cashew gate detail. This is done using a CNC milling machine or a die sinker EDM machine.
There are two complications with this gating system which must be overcome before it becomes a viable option.
1) The material must be flexible enough to curl out of the mold during ejection, yet it must be strong enough to not break. Very soft elastomers, for example, will generally break off, leaving pieces of debris inside the gate during the gate removal process. This can either block the gate… or create solids which may act as contaminants for the next shot.
2) The underside of the part must not be cosmetic. Since the gate enters the mold cavity perpendicular, the gate removal process often leaves a large and inconsistent amount of gate vestige behind.
When implemented properly, cashew gates can be a good way to disguise the gate location.