Common problems in plastic injection molding using polypropylene samples as an example.

Text/Polymer

With development of society and development of science, plastic products are used in almost all walks of life, but for various reasons, some of plastic products produced often do not meet requirements of factory, and cost of enterprise has had a great influence. Therefore, discussing common problems of injection molding and solving existing problems will effectively contribute to improving production efficiency of enterprise.

1. Common Problems in Plastic Injection Molding

Injection molding problems and abnormal phenomena finally affect quality of injection molding products. The problems and factors affecting injection molding products are shown in Table 1-1.

Table 1-1 Common Problems in Plastic Injection Molding

Second, countermeasures against plastic injection molding

2.1 Countermeasures for seam lines

Ø First, improve mold, use RHCM high-speed high temperature molding technology to raise temperature of mold cavity, and then pour plastic into mold cavity. When plastic is completely poured, use cold water to cool it, so that bonding line is a problem improved to a certain extent.

Ø When designing a mold, it is necessary to design mold gate intelligently, try not to use multiple gates, and analyze actual injection molding process, deal with parts with serious bonding lines, and increase number of rows of air slots to improve problem.

Ø Strengthen use of appropriate equipment and operate it correctly to ensure heating temperature and injection pressure of equipment.

2.2 Strategies for dealing with traces of stress

When designing, designers must design in full compliance with requirements of use of plastic products and relevant standards. When designing a structure with a thin wall and concave members, designer must make sure that its thickness exceeds 0.6T, and make specific selection according to actual situation of plastic products.

2.3 Countermeasures against pulling a die

1. In plastic injection molding process, operator must strictly follow design to complete work, and select appropriate holding pressure according to design requirements.

2. Add an appropriate restrictive ring to mold punch to prevent product from being pulled out due to temperature difference between die and punch.

Third, causes of common problems in PP injection molding process

3.1 Poor surface gloss like polypropylene

Firstly, poor surface finish of mold and poor polishing, and secondly, molten material cools down prematurely. Table 3-1 is a way to deal with this.

Table 3-1 Solutions to Eliminate Poor Surface Gloss of Polypropylene Samples

3.2 Analysis of causes of burrs and burrs in a polypropylene sample

The reason for this is largely due to fact that clamping force of mold is less than injection pressure and holding pressure.

Table 3-2 Solutions for Deburring and Deburring Polypropylene Specimens

3.3 Analysis of causes of polypropylene surface swelling

After polypropylene pellets are heated, injected, cooled, molded and demoulded, bumps will appear on the sample surface.

Table 3-3 Solutions for Blisters on Surface of Polypropylene Samples

In addition to above common problems, there are also problems such as air bubbles inside sample, whitish surface of sample, uneven surface and slot distortion. The manufacturer needs to pay attention to this in time, and you can also contact us and pay attention to us to analyze together, solve problems and make progress together.

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