How Plastic Injection Molding Machine Works?

Injection molding machines are essential in the injection molding method – one of the most used manufacturing processes for creating plastic parts. In this article, we will focus on how a plastic injection molding machine works and its type of machine, which is crucial for a producer with the goal of improving their production procedures.

1. Injection Molding Overview

Injection molding is one of the most effective and adaptable methods for manufacturing plastic products and parts. The most important device of this method is the plastic injection molding machine, which ensures high standards of accuracy and productivity.

Injection molding is widely used across various industries, including automotive, consumer goods, medical devices, and electronics.

2. What Is an Injection Molding Machine?

An injection molding machine is an equipment used for the production of parts which involve the injection molding process. It comprises a number of elements necessary to melt pellets of plastic and then inject the molten material into a mold, where it cools to form end products.

A plastic injection molding machine is important in the injection molding process.

A plastic injection molding machine is important in the injection molding process.

3. How Plastic Injection Molding Machine Works?

The plastic injection molding machine works according to a well-organized mechanical procedure that fabricates different products. Here’s a step-by-step overview of the plastic injection molding working principle:

Step 1: Close the mold

The process begins with the plastic injection molding machine closing the mold halves together. This is an important step since it enables the formation of an enclosed space where the polymer will be injected.

They both exert a large amount of pressure and the clamping unit bears down on the mold to ensure that no material leaks through the mold during the injection phase.

Step 2: Inject polymer into mold cavity

Once the mold is closed, the next step is to inject the molten polymer into the mold cavity. The plastic injection molding machine melts the thermoplastic material to ensure that it is soft and easily moldable.

The molten polymer is then injected from a nozzle into the cavity, till the mold is packed full. This step is very important since it determines the final output of the program.

Step 3: Maintain holding pressure

After the mold cavity is filled, the plastic injection molding machine maintains a holding pressure for a specified time.

This pressure allows the molten polymer to flow into the undercuts of the mold and account for any shrinkage as the material solidifies. Sustaining this pressure is important in ensuring that the parts that are produced are of the right quality and size.

Step 4: Turn the screw

While the holding pressure is maintained, the screw within the injection unit of the plastic injection molding machine begins to turn.

This action serves two primary purposes: It is also used in mixing the polymer material and in transporting the next batch of molten plastic material.

As the screw rotates, it also recedes to take more material from the hopper for the next turning cycle.

Step 5: Open and repeat

Once the cooling period is complete, the mold opens, and the finished part is ejected. The plastic injection molding machine part cycle is then reset for the next molding process.

The entire process can be carried out rapidly, which means many similar components in large quantities can be manufactured at the same time.

The working process of a plastic injection molding machine includes 5 steps.

The working process of a plastic injection molding machine includes 5 steps.

4. Components of an Injection Molding Machine

A plastic injection molding machine consists of several key components that work together to produce high-quality plastic parts efficiently. The overview of the main components is as below:

4.1. Clamping unit

In a plastic injection molding machine, the clamping unit plays an important role in holding the mold halves tightly to avoid movement and production of symmetrical parts.

Types of Clamping Mechanisms:

Hydraulic clamping: It makes use of hydraulic pressure in terms of clamping force applied which maximizes repeatability and mold adaptability.
Mechanical clamping: It fastens molds with mechanical parts, and rates high in ease, dependability, and uniformity for produced parts.
Electric clamping: It uses high-speed motors in controlling clamping force to increase the speed and to address various mold sizes.

4.2. Injection unit

The injection unit in a plastic injection molding machine is used to melt the plastic and then inject it into the mold. Key components include:

Hopper: It supplies the barrel with material in the form of pellets to enhance the material feeding process.
Barrel: It is a cylindrical-shaped space that contains melted plastic to be injected.
Screw: It provides a constant rate of melting and production to avoid interruptions and ensure a smooth process.
Heater bands: They offer the required temperature for melting that is regulated depending on the material.

4.3. Mold

The mold is a hollow block in a plastic injection molding machine where molten material is injected to obtain parts.

Cavity: This is where molten material forms the part. The number of cavities affects production volume and requires careful design for uniform filling.
Cores: They create complex shapes and must align with cavities for accurate dimensions and efficient material flow.

4.4. Cooling channel

Cooling channels in a plastic injection molding machine are passages that circulate coolant to absorb heat and solidify parts. Their strategic positioning is crucial for optimal injection process output.

4.5. The ejector system

The ejector system in a plastic injection molding machine removes finished parts from the mold cavity. Key components include:

Ejector pins: Rods that push molded parts out, preventing defects. Types include through hard, nitride H13, and black ejectors.
Ejector plate: A movable plate that houses the ejector pins and facilitates ejection.
Ejector mechanism: It uses hydraulics to move the ejector plate and pins, ejecting the molded part.

4.6. The hydraulic system

The hydraulic system in a plastic injection molding machine uses pressurized fluid to generate the force needed for clamping molds and injecting molten plastic. It is ideal for large-volume production due to its high clamping force and efficiency.

Key components include:

Hydraulic pumps: They generate pressure and deliver fluid to system components, controlled for required flow and pressure.
Hydraulic valves: They regulate fluid flow and direction, with pressure control valves managing pressure and flow valves adjusting fluid rates.
Hydraulic actuators: They convert hydraulic pressure into mechanical motion, controlling clamping cylinders, injection units, and ejector systems.

4.7. The control system

The control system in a plastic injection molding machine regulates parameters like pressure, temperature, and flow rate, optimizing performance for consistent production of high-quality parts.

Advanced control algorithms enable fault detection and closed-loop mechanisms, allowing manufacturers to produce superior products. Control types include:

Manual controls: They require direct input to adjust injection speed, temperature, and pressure using knobs and levers.
Semi-automatic controls: They combine manual input with automated functions for parameter adjustments.
Fully automated controls: They use automated systems for real-time adjustments, offering the highest precision.

4.8. Ancillary equipment

Ancillary equipment supports the plastic injection molding machine in producing final products, including:

Material dryers: They remove moisture from plastic pellets before injection to ensure product quality.
Material feeders: They automatically convey plastic pellets to the hopper, streamlining material handling and reducing downtime.
Part removal robots: They automate the removal of molded parts, enhancing speed and accuracy, which improves lead times and increases throughput.

A plastic injection molding machine is made up of multiple essential components that work together.

A plastic injection molding machine is made up of multiple essential components that work together.

5. Types of Injection Molding Machines

The common types of plastic injection molding machines include hydraulic, electric, and hybrid machines. Here’s an overview of their features, along with the pros and cons:

	Hydraulic Injection Molding Machines	Electric Injection Molding Machines	Hybrid Injection Molding Machines
Features	These plastic injection molding machines utilize hydraulic systems to generate the force needed for injecting plastic.	These plastic injection molding machines use electric motors to operate the injection and clamping processes.	These plastic injection molding machines combine the benefits of both hydraulic and electric systems.
Pros	High force capability: Hydraulic machines are capable of producing high clamp forces, which are particularly useful for large and intricate molds. Versatility: They can process various materials and different dimensions of parts, from minuscule to vast industrial parts Robustness: Such machines are usually very sturdy and efficient for use in large-scale production processes.	Energy efficiency: Electric machines are more energy efficient since they only draw power during the injection cycle, hence they cost less to run. Precision and control: They provide better control of injection speed, pressure, as well as position, hence improving precision and productivity. Reduced noise: Compared to hydraulic machines, electric machines are comparatively quieter in functionality.	Best of both worlds: Hybrid machines have both hydraulic and electric systems and are advantageous because they incorporate the best features of both systems. Energy efficiency: They employ electric drives for the injection process, which involves low power consumption when compared to conventional solutions, but high clamping force. Versatility: Used in many operations, they are ideal for all types of materials and different sizes of parts.
Cons	Energy inefficiency: They are less efficient than electric machines and they use more energy when they are in operation which makes their cost high. Maintenance: Hydraulic systems contain fluids that need to be checked frequently for leaks or any signs that will affect their performance. Noise: These machines can be more noisy because of the hydraulic pumps and systems used in the machine.	Higher initial cost: Electric machines are generally more expensive to purchase than hydraulic machines when one is making the initial purchase. Limited clamping force: They may also have less clamping force than hydraulic machines and this may not allow them to be used on large molds. Complexity: Electric systems are relatively more complicated than other types of systems and might need some expert knowledge to work on them for repairs.	Cost: Some of the hybrid machines might be pricey because of their technology and many parts. Maintenance complexity: Hydraulic and electric system integration can also make maintenance even more difficult. Potential for compromise: While they aim to optimize both technologies, they may not achieve the full advantages of either system in certain applications.

Three common types of plastic injection molding machines: Hydraulic, electric, and hybrid machines.

Three common types of plastic injection molding machines: Hydraulic, electric, and hybrid machines.

6. Conclusion

Understanding how a plastic injection molding machine works is crucial for manufacturers seeking to produce high-quality plastic parts efficiently. By mastering the plastic injection molding working principle and familiarizing themselves with the machine’s components and types, manufacturers can optimize their production processes and enhance product quality.

In addition, if you’re seeking plastic products for injection molding, look no further than EuP Egypt. We pride ourselves on supplying high-quality plastic raw materials that help enterprises optimize production costs and enhance their competitiveness in the market.