1. Lower the cost: can use two kinds of material or color to molding, so then can reduce the secondary processing required

    2. Expand the space for part design: combine two kinds of material or color when molding, can reduce the use of inner space; and also can be more different application, expand the space and variety for part design, such as design the I I I I molding, reduce the assembling process, which can make the part be waterproof effect, and operational texture also is nice.

    3. Beautify the appearance: use the different colors and different material can improve the sense of worth and the sense of touch when using.

    1. Compatibility between two kinds of resin: as they are different resin, the chemical property is different, the compatibility will immediate impact the bonding strength and bonding effect, so should note the compatibility between the resin.

    2. The shrinkage difference between resin should be small: if the shrinkage difference is too large, which will effect the bonding strength , and may be make the part warp .

    3. The shape of part not suitable be too complex.

    1. The common double injection mold

The general use method for double mold injection, the double injection machine has two kinds of plasticizing system and gearing, one common locked mold system, also should have two pieces of male mold and female mold. please see the operational theory as below, the cavity of B mold is bigger than A, and first molding in the A mold, cooling and molding , opening mold after finishing , leave the semi-product on the mold , stub bar drop off automatic , then use the system 5 turning mechanism , make the mold turn 180 degree around centre line, and do the second injection. Finish the second injection mold, then finishing the mould.

    The cost will higher than general injection mold

    Forming machine must have the turning system or ancillary installation of slide core, must be special forming machine, so the cost is higher than common forming machine

    Forming time should include drop the core or turn the mold, so the forming time will be longer than the time for single color forming

Use the plastic temperature of secondary injection to melt with the plastic at first injection, so the strength of adjoining plane is worse.

    2. Injecting molding by putting two kinds of resin into one inlet orifice in turn

(1). Can apply to the thicker part, use the low price plastic , can lower the cost of material , and keep surface tactility but do not affect the whole strength.

(2). Use the good conductance plastic, can be EML control.

(3). Do not need two many mold, then saving the mold cost.

(4). The injection process is rip into different resin in turn, the injection time will be limited.