First principle:

Determine the viscosity of rigid and flexible plastics when combined. Be mindful that hard plastics have higher melting points than soft ones when molding soft ones – don’t melt hard plastic when molding soft plastic!

1. The first shot: hard plastic: PA66 + the second shot: soft plastic: TPE combined is OK

2. The first shot: hard plastic: PC/ABS + the second shot: soft plastic: PC combination is OK

3. The first shot: hard plastic: PP + the second shot: soft plastic: TPU cannot be combined because PP material and TPU material are incompatible.

The second principle:

confirm that there is no shedding phenomenon after the second soft rubber and the first hard rubber are molded.

1. When sealing the first hard rubber with the second soft rubber, try to use a flat surface for sealing.

2. If the side or inclined top is sealed with hard plastic, try to make a 0.1-0.15mm gap in the hard plastic seal, using a mold steel position to seal the plastic.


The third principle:

design based on the existing two-color machine of the company.

1. The normal type of double-color machine is that the double barrels are arranged side by side.

2. An abnormal two-color machine, where two barrels produce a 90-degree pattern, usually customized or re-engineered.

3. If the insert is placed in the injection molding process, use a vertical injection molding machine for normal use.

First Consideration:

The shrinkage rate of hard and soft rubber is scaled according to the shrinkage rate of hard rubber.

Second note:

The mold guide post and related positioning mechanism require four minutes and a uniform distance, as the male mold side is completely identical during mold design and needs to be rotated 180 degrees during molding.

Third Note:

The first injection molding hard plastic feed point must use a three-plate mold point feed, or use a hot runner, because the male mold side is exactly the same and needs to be ejected.


The fourth note:

1. The waterway on the male mold side should be designed as far as possible on the inside of the mold, as the male mold side needs to rotate 180 degrees. If the waterway is on the outside, the waterway may become loose during the rotation process, causing water leakage.

2. If the male template is connected, the waterway design is on the open side, and the waterway is fixed on the rotating ring of the injection molding machine.

The fifth note:

When the first shot of hard plastic is molded and the second shot of soft plastic is to be molded, the mold steel position on the soft plastic side needs to be sealed with the hard plastic. The mold steel position needs to be over-sized by 0.1-0.2mm. After T0 trial molding, if any hard plastic is found to be crushed, make minor adjustments.

Sixth Consideration:

1. Conduct full inspection with full 3D.

2. Rotate the rear mold by 180 degrees and conduct a full inspection to ensure there is no interference.

3. Create the water pipe of the rear mold and rotate it back and forth by 180 degrees for inspection.