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Technology of injection moldingxpj8.com
Author:admin  From:Letian Plastics   Hits:2016  Update:2008-12-9

Temperature of charging barrel

To prevent the oxidation stain of material, the temperature should not be too high. It is right to just providing the flow ability to filling-in the mould. The temperature of charging barrel is always 310-340. The lower temperature is applied for bigger product and the higher temperature for that of smaller.

Temperature of feed port

It is all right to keep the good flow ability of material without extension.

Temperature of mould

It is always 140-170.

Injection pressure

For PPS product, it is better to applied high temperature and high Injection pressure, especially for parts with complex shape and thin wall. The Injection pressure is always 80-150 Mpa.

Injection speed

The faster the injection speeds, the brighter of product surface. At the same time, the problems of distortion, overflow edge and burned are appeared. So it is always applied moderate injection speed.

Pressure maintaining

To prevent the internal stress arise, the pressure maintaining should keep as low as possible. It depends on that there is no shortage such as voids, sinks and short of resin.

Backing pressure

In order to obtain product with stable quality, a certain backing pressure is needed. It is always 0.3-0.8 Mpa.

The rotational speed of screw rod

The rotational speed of screw rod is always 40-110 rPM for injection molding of PPS. The speed can be above 220 rPM for high cycles molding. But the temperature of charging barrel is needed to reduce for the heat of resin sheared. In addition, high shear rate lead to increase of fracture of filled fiber, and it is harm to the product performance.

Molding period

In order to increase crystallinity and obtain good mechanic properties, it is needed to properly extend the cooling time when the thick wall is molding. The molding period is always 20-30 s.

Product demoulding

It often need none or little demolding agent because PPS has the release property. If agent is used, it is better to employ zinc stearate or fluorine and silicone demolding agent.

Cleaning after molding

It is economical to use polyethylene with low melt index for cleaning.

Use of recovered resin

The usage content of recovered resin depends on the performance of molding product. In general, it is not above 30%.

Anneal treatment of product

For product molded at low temperature, the anneal treatment could remove internal stress and keep the performance and dimensional stability of product. The condition is always 200-240 for 2-4 hours. Pay attention to that the anneal treatment may introduce re-shrinkage by crystallization and lead the change of product dimension.

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