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Have a 4 cavity part that is being overmolded with 45 Durometer TPE. The part is cashew-gated and cannot be changed to a different gate style. Once in a while a cavity will leave a small amount of material in the tip of the gate. It is suspected that this is causing variation in cavity pressure and worse the inability to meet capability requirements.
Any help on small tweaks to gate to get it to break cleaner would be appreciated.
Hi Joe,
can you place here a picture of the sprue (sprue that gives OK part and case, where the part is NOK).
Also pls add what shore is the "45" (OO, A, D)
J.
Hi Joe,
is hard to say what is wong. Please check the weight of part vs sprue tip diameter. For example for TPE is recommended for 10 grams part diameter 1,1mm. Please check the design. You can try to check also when the tip is frozen and make a holding profile decresing to zero at this time. For better result you can apply delay of plasticizing. Last injection speed (when the material is still flowing through gate) reduce or go up. It is a game with shear in material. My personal feeling is that the design of gate is NOK.
I have also question about Shore value 45, If is it Shore A or Shore 00, the cashew gate is not very good choice, the material is very soft with long elongation. If is it Shore D, you can have a succes .-) Also Jendalf is asking the same...