Plastic Injection Molding Technology and Benefits

Author : HS MOLD | Published On : 23 Jan 2024

Plastic injection molding is a producing plastic products method by injecting a molten polymer into an injection mold and then cooling it. Most of the plastic products in the world are made in injection molding machines. This process by many injection mold companies in China is common in high-volume and small-scale production.

Applications

Plastic injection molding has been used in mass production for over 50 years. Thanks to this, it has become possible to produce various plastic products of different sizes and weights, structures, and thicknesses. From the smallest, weighing up to a few milligrams, to the largest, weighing tens of kilograms.

The main areas of application of plastic products produced by injection molding are:

  1. Electronics (plastic is used to make device housings).
  2. Automotive industry. For cars, plastic parts are also made using this technology.
  3. Medicine (polymers are used to make medical device casings).
  4. Construction and renovation (interior decoration details, tanks, boxes).

What Raw Materials Are Used For Plastic Injection Molding

Various thermoplastics (polymers) can be used for plastic injection molding: polypropylene, polycarbonate, polyurethane, polyamide, polystyrene, and others.

 

All plastics used in production are divided into two types:

  • thermosetting (cannot be remelted, as they are irreversibly changed after solidification);
  • thermoplastic (can be recycled and reshaped).

The material by custom plastic injection molding in China is most often used in granular form. This makes it easier to transport and easier to calculate the dosage.

Plastic Injection Molding Technology

To make plastic products by injection molding, you need special equipment — an injection molding machine (TPA) and molds.

The plastic injection molding process is as follows:

  1. Polymers (polypropylene, polycarbonate, polyurethane, polyamide, or polystyrene) are poured into the feeder.
  2. The mass heats up, melts, and accumulates in a special cylindrical compartment.
  3. The cylinder is connected to the unit where the products are formed.
  4. The plasticizer moves the metered part of the melt into the mold.
  5. The product is molded and cooled.
  6. The plasticizer is pushed back and the mold is opened to remove the finished plastic product.

Injection molding machines are cyclical. Their operation can be partially or fully automated (depending on the type of machine).

Types of Injection Molding Machines and Types of Injection Molding

There are several types of injection molding machines and, accordingly, several methods of plastic injection molding. The choice will depend on what products are planned to be produced.

The main characteristics to consider when choosing an injection molding machine are as follows:

  • Dosage volume (the amount of molten polymer needed to create each product)
  • the closing force of the machine;
  • mold compression force;
  • Geometry of the tooling fixing area

Depending on the selected parameters of the injection molding machine, the technological process also differs.

Horizontal Injection Molding Machine

Usually, the horizontal injection molding machine is used with a standard automatic mold. There are several types of plastic injection molds:

  1. Cold-channeled. This is a simple and cheap system, in which the sprue hardens together with the product.
  2. Hot-channeled. In this case, the material is fed into the mold heated and no sprue is formed.

This type of plastic and injection molding is used in most cases and is suitable for making various kinds of products.

Vertical Injection Moulding Machine

The material is loaded vertically, and the molds for this type of injection molding machine are inexpensive and easy to manufacture.

However such injection molding machines have a disadvantage - products do not fall out of the vertical mold. They need to be taken out manually or a robot can be used to do so. Such a part complicates the technological process and makes it more expensive.

Cascade Casting

The cascade plastic injection molding method can improve the quality of the final products and reduce the number of defects. Its application is only possible with the use of hot runner molds. Also, for cascade molding of plastic parts, it is necessary to have a special hot runner system with shut-off valves.

Injection Molding

This type of casting is characterized by the injection of the raw material into an open mold. Due to this, the polymer is finally compacted and the finished product is formed when the mold is completely closed.

Intrusion

This is the partial filling of the mold in extrusion mode with the rotational movement of the screw. This method is used in the production of heavy and large-sized products.

Bicomponent and multi-component injection

It is a plastic molding technology that differs depending on how many polymers are used in the manufacture of a single product. For this method, a special injection molding machine is required, where two or more plasticization units are installed.

Production Steps

Custom plastic injection molding takes place in several stages:

  1. 3D modeling and prototype preparation.
  2. Mold design.
  3. Making the necessary mold.
  4. Casting of the first copy.
  5. Creation of a series of products.

The stages may vary depending on the specifics of a particular production.

Advantages of the method

Polyurethane injection molding has several advantages:

  • In the process of such manufacturing, a small percentage of defects is obtained;
  • serial production is possible;
  • cheap material;
  • It is possible to reuse the material, which reduces costs;
  • No need for a foundryman.

If you are looking for where to buy plastic injection molding equipment, then contact the best plastic molding China manufacturers!