What is blow molding?

Blow molding: It is a method of clamping molten thermoplastic raw materials extruded from an extruder into a mold, and then blowing air into the raw materials. The molten raw materials expand under the action of air pressure, adhere to the wall of the mold cavity, and finally cool and solidify into the desired product shape.

Blow molding can be divided into two types: thin film blow molding and hollow blow molding:

1. Film blow molding

Thin film blow molding is the process of extruding molten plastic into a cylindrical thin tube from the annular gap of the extruder head mold. At the same time, compressed air is blown into the inner cavity of the thin tube from the center hole of the head, and the thin tube is blown and expanded into a larger diameter tubular thin film (commonly known as a bubble tube). After cooling, it is rolled up.

2. Hollow blow molding

Hollow blow molding is a secondary molding technology that uses gas pressure to blow and expand the rubber like blank closed in the mold cavity into hollow products. It is a method for producing hollow plastic products. Hollow blow molding has different manufacturing methods according to the blank, including extrusion blow molding, injection blow molding, and stretch blow molding.

1) Extrusion blow molding: Extrusion blow molding is the process of using an extruder to extrude a tubular billet, clamp it in the mold cavity while it is hot, seal it, and then blow compressed air into the inner cavity of the billet to form it.

2) Injection blow molding: The blank used is obtained by injection molding. The blank is left on the core mold of the mold, closed with a blow molding mold, and compressed air is introduced from the core mold to blow and cool the blank. After demolding, the product is obtained.

Advantages:

The product has uniform wall thickness, small weight tolerance, less post-processing, and small waste corners; Suitable for producing small precision products in large quantities.

3) Stretch blow molding: Place the billet that has been heated to the stretching temperature in the blow molding mold, use a stretching rod for longitudinal stretching, and use compressed air blown in for transverse stretching and blowing to obtain the product.

Application:

1. Film blow molding is mainly used to manufacture plastic films;

2. Hollow blow molding is mainly used to make hollow plastic products (bottles, packaging barrels, spray cans, fuel tanks, cans, toys, etc.).

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Compression injection molding

Compression injection molding is a relatively traditional injection molding method

Principle:

First, inject the molten material into the mold cavity, and when the molten material enters the mold lung. The mold opens slightly under its pressure blade; After the molten material fills the mold cavity, use a high-pressure locking mold to obtain the required product. The second step is compression molding. Due to the fact that the molten material enters the mold cavity when the mold has been slightly opened, the required allowable mold labor is relatively small.

During the molding process, the screw no longer injects material into the mold cavity, but relies on high-pressure locking of the mold to force Lf against the plastic, resulting in a smaller product orientation and lower internal stress. This method is particularly suitable for products with high transparency requirements that are formed and have a small volume;

Advantages:

It can increase the flow length ratio of injection molded parts; Adopting smaller locking force and injection pressure; Reduce internal stress of materials; And improve processing productivity.

Injection compression molding is suitable for products made of various thermoplastic engineering plastics; Such as large-sized curved parts, thin-walled, miniaturized parts, optical lenses, and parts with good impact resistance requirements

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Low pressure injection molding

Low pressure molding is a process that injects packaging materials into molds at very low injection pressures and rapidly solidifies them into shape.

Low pressure molding process is a packaging process that injects packaging materials into molds at a very low injection pressure (2-20 bar) and rapidly solidifies (5-50 seconds) to achieve insulation, temperature resistance, impact resistance, vibration reduction, moisture resistance, waterproof, dustproof, and chemical corrosion resistance.

This process is currently mainly applied to the packaging and protection of precision and sensitive electronic components, including printed circuit boards (PCBs), automotive electronic products, mobile phone batteries, wire harnesses, waterproof connectors, sensors, microswitches, inductors, antennas, and so on.

Low pressure molding is a process method that falls between high-pressure injection molding and sealing.

Features and advantages

The traditional injection molding process has defects due to high pressure, as low-pressure molding only requires a small amount of pressure to allow the melt to flow into a small mold space, thus not damaging the fragile components that need to be packaged, greatly reducing the scrap rate.

The low-pressure forming process can effectively seal, moisture-proof, waterproof, dust-proof, and chemically resistant the encapsulated components. In addition, it can also balance performance including high and low temperature resistance, impact resistance, insulation, and flame retardancy.

Shorten product development cycle

Low pressure forming molds can use cast aluminum molds instead of steel, making them very easy to design, develop, and manufacture, which can shorten the development cycle. In addition, compared to the time-consuming two-component sealing process, the process cycle of low-pressure hot melt injection molding can be reduced to a few seconds to tens of seconds, greatly promoting production efficiency.

Save total production costs

Firstly, the equipment cost of low-pressure injection molding process is low. Traditional injection molding equipment systems generally have higher costs, including purchasing high-pressure injection molding machines, as well as having a water-cooling system and expensive steel molds. The low-pressure injection molding process equipment system is generally relatively simple, consisting only of three parts: a hot melt glue machine, a work console, and a mold.

Secondly, due to the extremely low injection pressure, aluminum molds can be used for mold design, development, and manufacturing, which can save material costs and development cycles. If low-pressure injection molding technology is used to replace traditional sealing technology, it can also save the cost of sealing the shell and post heating curing.

Finally, due to low pressure and low temperature, the scrap rate of finished products can be greatly reduced, avoiding unnecessary waste.

Therefore, choosing low-pressure injection molding technology can not only significantly improve production efficiency and reduce the defect rate of finished products, but also help production enterprises establish cost advantages overall

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Gas assisted injection molding

Gas assisted injection molding, also known as gas injection molding, is a new injection molding process. It is one of the most important developments in the injection molding industry since the introduction of reciprocating screw injection machines.

Gas assisted injection molding is an extension of injection molding, which is developed on the basis of injection molding technology and structural foam injection molding; It can also be considered as a combination of injection molding and hollow molding, in this sense, it can also be called "hollow injection molding". The principle is to use relatively low pressure gas to replace the resin in the mold cavity during the pressure holding stage of the original injection molding. 

Gas assisted injection molding can be achieved by adding a gas supply device to the existing injection molding machine. The gas supply device consists of an air pump, a high-pressure gas generation device, a gas control device, and a gas nozzle. The gas control device uses a special compressor for continuous gas supply, and is controlled by an electric control valve to maintain a constant pressure. Pressure usually has three levels. A gas control device can be equipped with multiple injection molding machines.

The gas commonly used in gas assisted injection molding is nitrogen. The gas pressure and gas purity are determined by the shape of the molding material and the product. The pressure is generally between 5~32MPa, with a maximum of 40MPa. High pressure gas is injected from the gas nozzle at a set pressure timing during each injection. One or more gas nozzles, located on the injection molding machine nozzle, mold runner or cavity.

Advantages:

Gas assisted injection molding technology has many incomparable advantages. It not only reduces the manufacturing cost of plastic products, but also improves certain properties; When the parts can meet the same usage requirements, using gas assisted injection molding can greatly save plastic raw materials, with a savings rate of up to 50%. On the one hand, the reduction in plastic raw material consumption leads to a reduction in the time of each link in the entire molding cycle

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Water-assisted injection molding

Water-assisted injection molding technology is an advanced injection molding process that injects part of the melt into the mold cavity, then injects high-pressure water into the melt through equipment to finally shape the workpiece.

Advantages:

Due to the incompressibility of water, the front end of the water forms a solid interface, squeezing the inner wall of the product into a cavity. The front end of the water also plays a role in rapid cooling. Therefore, water-assisted has many advantages that gas-assisted cannot match. Research and application show that water-assisted can generate thinner and more uniform cavity walls, and the inner wall surface of the flow channel is very smooth. Especially for thick-walled workpieces, the cooling time of water-assisted can be greatly reduced compared with gas-assisted.

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What is LSR injection molding?

 LSR injection molding as liquid silicone rubber injection molding. LSR, also known as liquid silicone rubber, is fluid, colorless, odorless, safe and environmentally friendly compared to solid silicone.

LSR injection molding: Liquid silicone (Liquid silicone rubber) is divided into two components, A and B. The quantitative device is used to control the two to a 1:1 ratio, and then fully mixed through a static mixer and injected into the barrel of the liquid silicone injection molding machine, and then accurately injected into the heated mold for molding.

The process of LSR injection molding is very simple: it does not require the manual requirements of ingredients, rubber refining, cutting, etc. in the solid silicone process, does not require manual intervention, and even fully automated production throughout the process. It has many advantages such as high product precision, high output, labor saving, material saving, and electricity saving, and can produce all products produced by high-temperature solid silicone.

As people's requirements for the environment become higher and higher, the liquid silicone injection molding process will be more widely used, mainly because of environmental protection, and no harmful substances will be produced during the production process. And it is safe for human contact.

In the maternal and infant industry, liquid silicone materials are more widely used. Babies are relatively fragile, so the products used should be more assured. Products made of food-grade liquid silicone are soft and comfortable, can better protect babies, and mothers can use them with more confidence.

Liquid silicone rubber is used by manufacturers in many industries and applications due to its own characteristics: colorless and odorless, safe and environmentally friendly, biocompatible and safe for contact with the human body, including medical products, electronic 3C products, baby products, auto parts, kitchen and bathroom, and daily necessities.

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