TPE/TPR/TPU/TPV Material Sticking Problem Improvement

TPE/TPR/TPU/TPV Material Sticking Problem Improvement

Date:Aug 09, 2019

TPE/TPR/TPU/TPV thermoplastic elastomer soft rubber materials are more common in the injection molding process, especially in the case of low hardness, TPE/TPR/TPU hardness is lower than 60A, TPV hardness is lower than 40A, the sticking problem is quite common, and the main sticking modes take two forms:

1. Thermoplastic elastomer in the mainstream mold

Since the main flow path is the closest position to the injection nozzle, the pressure applied by the screw injection is the largest, resulting in a minimum material shrinkage in this area, whereby the material slides against the inner wall of the gate to generate greater friction.

The specific solution is as follows:

1.1. Because of the particularity of the thermoplastic elastomer material, the smoother the surface of the mold, the greater the adsorption force, which is exactly the opposite of the hard plastic. Therefore, the gate bushing can be subjected to electrical discharge machining to retain a certain thickness of the discharge pattern and reduce The adsorption force of the flow channel;

1.2. The ejector pin of the flow cell adopts the shape of the inverted pin of the flow groove pin to increase the force of pulling the flow channel. Do not worry about the reverse buckle, the flow channel will not be taken out, because this is soft rubber, of course, the angle of the inverted buckle can be small Start, slowly experiment, if you use a general Z-shaped needle, there may be insufficient pulling force, resulting in a flow channel sticking master.


2. Thermoplastic elastomer injection molding products

Compared with the main gate sticking mold, the probability of the product sticking mold is low, usually the product sticking mold occurs in the product structure design, such as the male mold drawing angle is too large, the male mold needs the skin texture treatment and so on.

The specific solution is as follows:

2.1. The male mold is polished to a mirror surface as much as possible to increase the adsorption force, which is also contrary to the hard plastic;

2.2. The draft angle of the male mold can be made small in size, or simply not drafted, and if allowed, can even be reversed;

2.3. The thimble head can be added with a cross rib;

2.4. Considering the molding process, the master mold can be connected to the high mold temperature, and the male mold can be connected to the low mold;

2.5. Adjust the formulation of the thermoplastic elastomer material to lower the injection molding temperature;

2.6. Reduce the pressure of holding pressure;

2.7. Before molding, release the release agent in the cavity.

Under normal circumstances, the thermoplastic elastomer is molded on the back mold, which is the first mainstream mold and the second case described above.

However, sometimes due to materials, process parameter settings or mold design reasons, the product will stick to the front mold (such as the front mold has a large adsorption force), it is difficult to demould, and even the product is deformed or pulled, and may be because of the main casting. The problem of sticking to the mouth is generally caused by too much pressure on the pressure. This will also create a gate problem.

For thermoplastic elastomers with a medium hardness or higher, the depth of the dermatoglyphics is increased, and on the contrary, it is easy to form a sticking mold, which requires attention.


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