Introduction: An injection molding machine, also called an injection machine or molding machine, is the primary molding equipment that uses plastic molds, or injection molds, to produce plastic products of various shapes from thermoplastics or thermosetting plastics . It’s also the equipment that does the most important job in the modern injection molding process.

Injection molding machines are used all over the place to make plastic parts, from medical equipment to all kinds of tools; from the aerospace industry to the most common automotive industry, as well as everyday things we use and kids’ stuff.

Most of their parts or even the whole thing are made by plastic injection molding. Look around, as long as there is a plastic thing nearby, it’s probably made by an injection molding machine.Since the injection molding machine is so important, how does the injection molding machine work? This article will tell you.

What is the Working Principle of the Injection Molding Machine?

Injection molding machines have two main functions: heating the plastic to make it melt and applying high pressure to the molten plastic to make it eject and fill the mold cavity. Here is how it works .

Using the thermophysical properties of plastics, you add the material from the hopper to the barrel.The barrel is heated by a heating ring to melt the material. You install a screw in the barrel, which is driven to rotate by an external power motor. Under the action of the screw, the material is transported forward and compacted along the screw groove.

The material is melted and mixed by the external heating and the shearing of the screw. When the screw rotates, the material is pushed to the screw head by the friction and shearing force of the screw groove.At the same time, the screw retreats under the reaction of the material, so that the screw head forms a material storage space and completes the plasticization process.

Then, under the action of the injection molding machine pushes of the injection cylinder, the screw injects the molten material in the storage chamber into the mold cavity through the nozzle at high speed and high pressure. After the molten material in the cavity is pressure maintained, cooled, solidified and shaped, the mold is opened, and the shaped product is ejected from the mold.

What are the Structural Components of an Injection Molding Machine?

Injection molding machines typically consist of an injection system, a mold clamping system, a hydraulic transmission system, an electrical control system, a lubrication system, a heating and cooling system, a safety monitoring system, and so on.

Injection System

The injection system is one of the main parts of an injection molding machine.There are generally three main types: plunger type, screw type, and screw pre-plastic plunger injection type. The most widely used one is the screw type.

The function of the injection unit is to heat and melt a certain amount of plastic in a specified time in one cycle of the injection molding machine, and then inject the molten plastic into the mold cavity through the screw at a certain injection pressure and speed.After the injection is completed, the molten material injected into the mold cavity is kept in a fixed shape.

Mold Clamping System

The mold clamping system is responsible for closing and opening the mold, as well as ejecting the product . It also needs to provide enough force to keep the mold closed and resist the pressure from the molten plastic entering the mold cavity. This prevents the mold from opening and ensures the product turns out well.

The mold clamping system is made up of a mold clamping device, a mold adjustment mechanism, an ejection mechanism, front and rear fixed templates, a mobile template, a mold clamping cylinder, and a safety protection mechanism.

Hydraulic System

The hydraulic transmission system is there to give power for all the different things the injection molding machine needs to do, and to make sure that all the different parts of the injection molding machine have the right amount of pressure, speed, temperature, and everything else they need.

It is mainly made up of various hydraulic components and hydraulic auxiliary components, among which the oil pump and the motor are the power source of the injection molding machine.There are a bunch of valves that control the oil pressure and flow rate to meet the different needs of the plastic injection molding process.

Electrical Control System

The electrical control system and the hydraulic system work together to meet the needs of the injection molding machine, like pressure, temperature, speed, time, and different program actions.

It is mainly made up of electrical appliances, electronic components, instruments, heaters, sensors, etc. There are generally four control methods, manual, semi-automatic, fully automatic, and adjustment.

Heating/Cooling System

The heating system is used to heat the barrel and the injection nozzle.The barrel of the injection molding machine usually uses an electric heating coil as a heating device. It is installed on the outside of the barrel and is detected in sections with a thermocouple.Heat is conducted through the barrel wall to provide a heat source for material plasticization.

The cooling system is mainly used to cool the oil temperature. Excessive oil temperature will cause a variety of faults, so the oil temperature must be controlled.Another place that needs cooling is near the discharge port of the material pipe to prevent the raw material from melting at the discharge port, resulting in the raw material not being able to be discharged normally.

Lubrication System

The lube system is a circuit that gives lube to the parts that move against each other on the injection molding machine, like the moving plate, mold adjuster, and hinge on the connecting rod.

To save energy and make parts last longer, you can grease them. You can do it by hand or use a machine.

Safety Protection and Monitoring System

The safety device of the injection molding machine is mainly used to protect the safety of people and machines . It is mainly made up of safety doors, hydraulic valves, limit switches, photoelectric detection elements, etc., to achieve electrical-mechanical-hydraulic interlocking protection.

The monitoring system mainly monitors the oil temperature, material temperature, system overload, and process and equipment failures of the injection molding machine, and indicates or alarms when abnormal conditions are found.

What are the Categories of Injection Molding Machines?

Horizontal Injection Molding Machine

A horizontal injection molding machine is a commonly used type. It has the advantage of having the center line of the injection assembly concentric or consistent with the center line of the clamping assembly and parallel to the installation ground.

It has the advantages of low center of gravity, stable operation, convenient mold installation, operation and maintenance, large mold opening, and small space height; but it occupies a large area, and is widely used in large, medium and small machines.

Vertical Injection Molding Machine

The characteristic of this machine is that the clamping device and the injection device are arranged in a straight line and perpendicular to the ground . It has the advantages of small floor space, easy mold assembly and disassembly, easy installation of inserts, relatively uniform plasticization of materials falling from the hopper, easy automation, and easy automatic line management of multiple machines.

But it’s not easy for the product to fall out automatically after being ejected, and it must be removed by hand, which is not easy to achieve automatic operation .

The vertical injection molding machine sealing machine is suitable for small injection molding machines, generally more for injection molding machines below 60 tons (60 tons refers to the clamping force), and not suitable for large and medium-sized machines.

Angle Injection Molding Machine

The injection direction and mold interface are on the same plane. It is particularly suitable for flat products where gate marks are not allowed to remain in the machining center. It occupies a smaller area than a horizontal injection molding machine, but the inserts placed in the mold are prone to tilt and fall.

Multi-Mode Turntable Injection Molding Machine

It’s a special injection molding machine with multi-station operation. Its features are that the mold clamping device of the manual packing machine adopts a turntable structure, and the mold rotates around the rotating shaft .

This type of injection molding machine fully utilizes the plasticizing ability of the injection device, which can shorten the production cycle and improve the production capacity of the machine . So, it is especially good for making a lot of stuff that takes a long time to cool and shape or needs more time for extra stuff to be put in.

But because the mold is big and has a lot of parts, the thing that holds the mold together isn’t very strong, so this kind of machine is used a lot for making things like plastic shoe soles.

What are the Working Steps of the Injection Molding Machine?

Feeding

The injection molding machine starts with the feeding link. Before feeding the injection molding machine, you need to put the pre-cut plastic particles into the hopper, and then use the button on the hopper to start the feeder and add the particles to the barrel of the injection molding machine.

Melting

After the feeding is done, the injection molding machine starts the melting stage. The heater of the injection molding machine gradually melts the plastic particles in the barrel and pushes the molten plastic to the nozzle.

Injection

The melted plastic comes out of the nozzle, goes into the injection mold, and fills the mold cavity. When filling the mold, you need to control the injection speed, pressure and time parameters to make sure the injection is even and stable.

Holding Pressure

Once the mold is filled, you have to hold the pressure to keep the plastic injection molds for a while to let the plastic fully solidify. How long you have to hold it depends on things like the properties of the plastic and the process parameters.

Mold opening

After the holding pressure stage is done, the injection molding machine goes into the mold opening stage, opens the mold, and takes out the finished product.

When you open the mold, you need to adjust the mold opening force and mold opening stroke correctly to avoid affecting the quality of the finished product and the life of the mold.

What is the Main Function of the Injection Molding Machine?

Melting and Injection

The main job of an injection molding machine is to heat and melt plastic particles and then inject them into a mold. When the injection molding machine is working, it feeds the plastic into the injection cylinder and then pushes the melted plastic into the mold by air pressure.

There are many kinds of plastic pellets that can be made by injection molding machines, and some new injection methods also increase the ability to make plastic products.

Cooling and Separation

Once the plastic is in the mold, the injection molding machine cools the plastic in the mold. This is done by putting the mold in a pool of water or blowing air on it.

The cooling process of the injection molding machine is directly related to the quality and look of the product. After the cooling process is done, the injection molding machine will take the mold off and cut it into the final plastic product.

Automatic Production Can be Achieved

The injection molding machine is computer-controlled and can achieve intelligent and automated production. It is easy to operate, reduces the investment in labor costs, and improves production efficiency and output.

Production of Various Plastic Products

The injection molding machine can produce plastic products of various specifications and materials, such as furniture, toys, parts, containers, and so on.

It has high production efficiency and can produce hundreds or even thousands of products per hour, and the quality can also be effectively guaranteed.

Improve Production Efficiency and Product Quality

Injection molding machines are capable of producing products with high speed and precision. A single injection molding machine can produce hundreds of products.

The injection molding machine adopts an integrated design, which is easy to operate and has high production efficiency. The mold molding is precise, the product size is accurate, and it has high quality characteristics.

The products made by the injection molding machine have a short production cycle, can quickly make a lot of products, and improve production efficiency. The injection molding machine can be automated and has very high efficiency.

The injection molding machine has a large output, strong consistency, and high efficiency, which can meet the production requirements of large-scale batch production. Thereby improving production efficiency . The injection molding machine has a stable production process, and the product weight, size, and appearance are relatively accurate, and the product quality is high.

Reduce Production Costs

Injection molding machines are great at making plastic stuff. They’re fast and make good stuff, so it’s cheap to make things.

Compared to other production methods, the cost of products made by injection molding machines is relatively low, and the production cost of injection molding machines is much lower than other manufacturing processes.

What are the Application Areas of Injection Molding Machines?

Home Appliance Industry

Home appliance manufacturing is one of the main application areas of injection molding machines. Household appliances like TVs, refrigerators, washing machines, etc. often need a lot of plastic parts, and injection molding machines can make these parts by injecting plastic through molds.

Also, injection molding machines can be used to make micro plastic products like disposable plastic tableware.

Automobile Industry

Another big area for injection molding machines is the car manufacturing industry. Lots of car parts are made by injection molding machines.

For example, plastic parts like car glass rings, glass frames, and dashboards all need injection molding. Car parts made by electric injection molding machines need to be really precise, have good quality, and last a long time.

Medical Devices

Medical device manufacturing also relies heavily on injection molding machines. Medical devices require plastic material that meet strict environmental and biological standards.

Using plastic injection molding machines can produce medical device plastic products that meet environmental protection standards and do not produce secondary pollution.

Daily Necessities

Injection molding machines can also make all kinds of daily necessities, such as household items, children’s toys, etc. Injection molding machines can make daily necessities with high quality and long life, making it more convenient and safer for consumers to use in daily life.

Conclusion

In short, the injection molding machine is the main tool for making plastic products. It heats up the plastic, melts it, and then squirts it into a mold. After it cools down, you have a finished product . It’s used in lots of industries, like making stuff for your house, cars, and medical things. It makes things faster and better, and it’s cheaper too. It’s also automatic. The plastic injection molding machine is a big deal.