Mechanism Of Plastic Injection Molding

Use of plastic injection molding

Plastic injection molding is the most common and widely used method for the mass production of plastic products around the world because of its convenience and ease of use. Plastic products made using this method include plastic chairs and tables, electronic product covers, disposable spoons and knives, and other cutlery products.

History of injection molding

Plastic injection molding was started by European and American chemists who were experimenting with plastics. Originally done manually and pushed into the mold using Parkesine, it turned out to be too brittle and flammable. John Wesley Hyatt is the official inventor of plastic injection molding, and this process has a rich history with a brilliant spirit.

Injection molding was originally invented to solve the problems that billiard players face abundantly. The 19th-century billiard balls were made of ivory derived from tusks taken from elephants. Celluloid was one of the first plastics used to make billiard balls.

Instructions for the procedure

The scientific procedure used to produce plastic products by applying injection molding is very simple. Your plastic melts and is put into a huge syringe. It is then placed in a suitably shaped mold depending on the product being manufactured and allowed to cool for a sufficient amount of time to reach the desired shape. However, the actual process of actual injection molding is not so simple and can be broadly divided into three subdivisions: injection unit, molding section and finally clamp. The plastic pellets are gradually liquefied and gradually injected into the injection unit through a tunnel that is completely melted until it reaches the front of the barrel. When it reaches the mold, it cools and hardens to the desired fixed shape. The mold will then return to the original machine position.

Injection molded parts
Injection molded parts

All injection molded parts start with plastic pellets with a diameter of a few millimeters. They can be mixed with certain limited amounts of pigments called “colorants” or up to 15% recycled material. The mixture is then fed into an injection molding machine. Early molding units used a plunger to push down from above. However, the outer area was hot or cold and the melting process did not work properly. The solution to this was a reciprocating screw. This was often seen as the most important contribution that was none other than a revolution in the plastic product manufacturing industry. The screws cause the shear stress necessary to melt the plastic, and the rest of the heat comes from the traditional heater band that surrounds the machine. When molten plastic is injected into the mold, the air is released through the sideways vents. The honey viscosity plastic is so thick that it cannot be released from these vents, which are only a few microns wide.

Engraving witness marks on plastic products is also an important part of marketing. This is because we need to be able to authenticate and verify the authenticity of the product by looking for a line separate from the witness mark. These are created using removable inserts and can prove very helpful in tracking defects.

Why China?

China is well known as a manufacturing center and as an exporter of plastic products. Chinese plastic injection molding manufacturers guarantee high-quality products that are reliable and long-lasting.

How To Buy High Quality Plastic Injection Mold

How To Buy High Quality Plastic Injection Mold

There are plenty of injection Mold Company in China, especially gathered in Guangdong province and Zhejiang province. Then how to customize good quality plastic injection mold? How to choose most suitable mold company?

Mold flow analysis

Before detail mold design, should have mold flow analysis of plastic part. By analyzing material flow direction and path route, check whether injection gate reasonable or not, or there is any flowing imbalance or other problems.

Professional Plastic mold design

Mold design is the basic, also it is the first important item for mold manufacturing. It must be reasonable, based on exact plastic part’s requirement, then to have the most appropriate design. For example, PVC injection molding, if plastic part small, better to use valve gate system or submarine gate. For large PVC part with thick wall, then better to use fan-shaped gate type.

Mold tooling

Good quality injection mold related to precision mold tooling. For example, medical syringe barrel mold, it has strictly requirement of mold core part’s verticality, almost there is no demolding angle, as require sealing the best between barrel and gasket. Here best to use Japanese brand Sodick precision wire cutting machine, mold dimension can be controlled within 0.005mm. Additional, Fidia three axis high speed CNC machine from Italy, Agie Charmilles EDM machine from Switzerland, are most suitable for tooling high precision plastic mold for medical plastic parts, packaging parts and automotive parts. When you hesitate to choose which mold company, to check their tooling equipments first.

Mold installation

After all above items smooth finished, then comes to labor works. Mold assembling and installation should be done carefully, workers should pay attention to this part, make sure every spare part has been assembled and in most suited location without any damage. Also make sure under safety condition.

Mold adjusting and testing

If injection mold have any problem, then it can be directly reflected on plastic parts. Mold testing is important, as custom plastic mold company and client will have fully understand, then know how to fix the mold or next. So at first, all related auxiliary equipments should be well installed, like air blow system, water cooling system, etc. Check its reliability, then add plastic material to test the mold. At the same time, injection molding condition should be suitable.

Mold maintenance

Suitable maintenance of injection mold is important. This will prolong mold life time, also you may have the idea of this injection molds company, how their attitude of the mold manufacturing.