Most designers focus on one color plastic injection mold, so they don’t to how to design when we met two color plastic injection mold.so we will talk about the theory and important point about two color injection mold.two color mold have another name “two-shot mold”, they inject two resin on the same machine but injection two times, typically consist of 2 sets of mold, the core side will rotate 180 degrees, but cavity side will be fixed.but the molding part is only ejected out one time.we always call it two-color injection molding and need special two-color injection machine.
The characteristics of two color mold:
- Two shape of the cavity is different, forming 1 kinds of products each. But core side has the same shape. (Note: if there are not the same, use sliders)
- After the cavity rotates 180 degrees, the cavity must fit another core, Designer should pay attention to this point.
- Please carefully check the data of color injection molding machine such as maximum mold thickness, the minimum allowable mold thickness, K.O. holes distance etc..
- The gate should be cut automatically in 3 plates two color mold, especially soft resin.
- When we design the second injection cavity, we should leave some space to avoid scratch, but must think about the seal area, the molding part have the possibility of deformation and cause flash
- We can make the first molding part a little bit bigger than spec.it will be pressed tighter when the second injection, reduce the risk of flash.
- Pay attention to in second injection molding if they will make the first molding part deformed by resin flow, If that is possible, we must think of a way to improve them.
- We should make the cooling system plenty, balance and same in two mold
- 99% we injection hard material first, before soft is easy to deform
- In order to make the two plastic stick more tightly, we should consider “sticky” of two resin and the roughness of mold surface