How Many Parts Make up an Injection Molding Machine?

Injection molding machines are made up of several parts, each of which plays an important role in the overall function of the machine. An injection mold is a device made up of several pieces that enable molten plastic to be shaped and cooled to produce a distinct part shape.

The injection molding machine is divided into two parts; the stationary side and the moving side. The parts of an injection molding machine include a hopper, barrel, screw motion, heaters, nozzle, ejector pins, split molds, clamping unit, injection unit, and hydraulic unit.

Let’s dig deeper and discuss the parts of an injection molding machine in detail.

Parts of an Injection Molding Machine

The following are the most important parts of an Injection Molding Machine:

Hopper of Injection Molding Machine

Before the injection molding process can start, the plastic material is placed into the hopper. To keep moisture away from the plastic material, the hopper typically has a dryer unit. Additionally, it might be equipped with tiny magnets to keep any dangerous metallic particles out of the device. The plastic material is then put into the barrel, the key component that comes after it in the assembly line.


To allow the plastic to move through the barrel, the barrel or the material tube and barrel must be heated until the plastic melts. The clamping unit's inside screw injects plastic into molds or cavities.

To maintain the proper temperature for various types of plastic material, the temperature inside the barrel must be properly controlled. Well before plastic reaches the injection mold, the cylinder transports, compacts, melts, agitates, and presses it.

Screw Motion of Injection Molding Machine

Plastic is fed through the barrel by the screw. Initially, the screw is turned as the pellets are fed from the hopper into the barrel, moving the material ahead as additional pellets are introduced. The flights also offer a constant mixing action that evenly disperses heat throughout the pile. The removal of various materials and any colors left over from prior manufacturing cycles on the same injection molding machine is another benefit of mixing.

The thermoforming plastic receives the majority of its heat from the revolving screw. This is due to the screw's diameter decreasing as it nears the tip. Plastic pellets are then moved by the flights, squeezed into a smaller area, and cut by turning flights as a result.

Heaters of Injection Molding Machine

Different kinds of heaters can be used in an injection molding machine to maintain the temperature in conduits and nozzles as well as to heat molds and plates. The molding material in the hopper can be melted and turned into liquid by attaching a heating element to the barrel.


The machine's ejector system's bottom section houses the nozzle, an injection molding part. It forces the liquid plastic into the mold from the barrel. The sprout bushing and locating ring, a feature on the mold, where the nozzle fits helps position the nozzle on the mold. Nowadays, nozzles may perform several tasks, such as filtering, mixing, and stopping the flow of the melt.

Nozzle filters can reduce the likelihood of foreign particles or pollution in the melt stream obstructing gates and hot runner tips. Mixing nozzles can improve additive dispersal and mixing, which improves the quality of molded parts while lowering additive volu me and cost.

Ejector Pins of Injection Molding Machine

Ejector pins are essential while making components. They are a crucial part of the ejection mechanism in molds, which controls how goods turn out when injection molding is done.

The A and B sides make up the two portions of the metal injection mold. Both sections are separated to extract the solid plastic when the molten material in the mold has cooled. When an injection mold is opened, the A-side half is lifted, leaving the produced portion and the B-side behind.

On the B-side of the injection mold, there are extraction pins that are used to extract the produced part from the mold. The pin mark is frequently visible as a dent on completed goods.

Ejector pins come in a variety of designs. Ejector pins that are through hard are heat-treated to maintain consistency in the hardness throughout the pin's diameter. Case-hardened ejector pins are suitable for die-casting ejection systems because they are substantially more durable able than through-hardened pins. Black surface treatment is applied to a black ejector pin, enabling it to self-lubricate and endure temperatures of up to 1000°C.

Split Molds

When two mold halves are closed together during injection molding, particularly on a split mold, this is known as the parting line. The dividing line, which divides the plastic product made by the injection mold into two pieces, is what gives this term its name.

Split molds are one kind of injection mold in which the mold cavity is formed by the jaws. When the mold opens with a pull tab, the jaws are first injected diagonally on the nozzle side and then transferred diagonally to the outside. The injection-molded component is then let go.

The ejector side can also be used to guide the jaws. Next, either before or after the mold is opened, they are moved, typically using hydraulic cylinders or mechanically with springs or air.

Clamping Unit of Injection Molding Machine

The clamping unit's functions include opening and closing an injection mold and ejecting the items that have been injection molded. The hydraulic and toggle designs are the two primary types of clamping mechanisms. While the toggle clamp system uses several links, the hydraulic clamp system uses one or more hydraulic cylinders.

The Clamping Mechanism Holds The Injection Mold USING TWO SIZABLE CLAMPING PLATES. Two Steel Components are fastened to work. G Unit to Form a Mold. The clamping Device Shuts The Two Separate Plates When The Machine Is Ready to Inject Plastic Into the mold or cavity.

Building the part, allows the plastic to enter the cavity. The plastic part is then solidified by cooling. The clamping unit opens the injection mold when the plastic is cool enough, and the part drops out of the mold halves and is collected in a container.

The clamping unit also includes tie bars, a stationary platen, a moving platen, and machine ejectors.

Injection Unit

The injection unit, which is made up of various pieces, is a crucial part of injection molding equipment. The raw material is to be melted and directed into the mold by the injection equipment. The hopper, barrel, and screw make up the injection unit The coloring pigment or other strengthening ingredients are mixed with the dried and placed in the hopper polymer grains.

The grains are heated, combined, and driven toward the mold by the screw motion as they are fed into the barrel. To help raise the pressure to the proper levels and melt the material, the screw and barrel have the same geometry.

Hydraulic Unit of Injection Molding Machine

For machinery used in plastic injection molding, a hydraulic system or component is essential. The system may run nonstop throughout production cycles. There are a lot of motion-activated sub-circuits needed for the nozzle approach, injection of the plunge screw, rotation of the extruder screw, and mold closure.

When flowing into the mold during the screw rotation and plunge phase, granular plastic material needs to travel through the heated plasticized state smoothly, requiring a very steady motion. Any inconsistencies in the hydraulic motions could affect the quality of the in injection-molded product.

To prevent the mold from opening and to maintain the position of the nozzles along the sprue of the injection mold, force control sub-circuits are also necessary. These processes are essential for injection molding. The mechanical pressure is adjusted and monitored by the hydraulic pressure.

A complex mechanism that calls for accurate hydraulic seals throughout the injection and packing process of the mold is the screw mechanism, which is driven by the hydraulic motor, connected to the cylinder that drives the screw forward.

Modern advancements in seal technology, though, result in leak-free hydraulic machines suited for molding plastic goods that can even be employed in the food and medical sectors.


MING-LI has skilled, educated, and seasoned injection molding specialists who are aware of all the intricacies and specifics of the procedure. They can create and produce a wide range of diverse components needed for various applications across numerous industries because they have a Thorough understanding of the inner workings of the various injection molding components.

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