How do Vertical injection moulding machines work (4/4)

Vertical injection moulding machines are electronically controlled hydraulically operated machines. These machines use complicated electrical components to control the operation process, and the operations are carried out by powerful hydraulic movement.

Rotary Type Vertical Injection Moulding Machine

Vertical injection moulding machines can be understood easily by dividing the machine into 2 parts

1. Injection Unit

2. Clamping unit

   
   

Understanding the Injection Unit

Rotary Vertical Injection Moulding Machine Injection Unit

The injection unit comprises three main parts:

1. Material Feed Zone

2. Injection Barrel

3. Refilling Mechanism

Material Feed Zone

Material is fed into the machine from a bin at the material feed zone. generally, the material used in vertical injection moulding machines is in the form of small beads, these beads are loaded into the material hopper, 10-15kg at a time, and the material hopper is connected to the main injection barrel via the feed pipe, through which the material enters the barrel, there is an opening in the barrel and the material enters the barrel feed zone opening via the feed pipe, and the further processing of material begins inside the barrel.

Injection Barrel

Injection barrel of Vertical Injection Moulding Machine

The Injection barrel is as the name suggests a cylindrical barrel inside which there is a screw and many additional components that help feed the material inside the barrel and heat the barrel and melt the material, there are cylindrical heaters mounted directly to the outside of the barrel, the Screw inside the Barrel is responsible for the injection and refilling of material inside the screw barrel.

The material enters the injection barrel through the feed zone from the material hopper, inside the barrel is where it heats up and melts. The molten material is then injected into the mould cavity by moving the screw inside the barrel downwards pressurizing the material and forcefully injecting it inside the mould cavity. Once the barrel is empty, the refilling process begins. During refilling, the screw rotates to pull new material from the feed zone into the barrel.

All the injection, refilling and suck-back processes are done with the help of hydraulic cylinders, and hydraulic motors.

Refilling Mechanism

Once the injection process is completed, the process of refilling begins. During refilling, the screw rotates to pull new material into the barrel for melting and also simultaneously moves upward to create space for material inside the barrel. The barrel has multiple heaters that heat it in different zones, allowing precise temperature control. The zone closest to the feed zone is kept at a lower temperature, while the zone nearest the mould cavity is maintained at the ideal melting temperature.

As soon as the injection process is completed the screw is at the bottom-most position inside the barrel, and the output signal for refilling is generated, now the screw starts rotating and is pulled upwards with the help of a hydraulic motor and hydraulic cylinders, pulling material beads from the feed zone and pushing it downwards inside the barrel where it is heated and melted, and prepared for the injection process.

Injection Process

The quantity of material injected into the mould cavity is directly proportional to the amount of refilling done inside the screw barrel. This is achieved by adjusting the refilling position. Similar to how a syringe works, the higher the plunger is pulled, the more material is drawn into the syringe. In the same way, the refilling position determines the amount of material in the screw barrel. The higher the refilling position, the more material can be injected inside the mould cavity.

By maintaining precise control over these processes, vertical injection moulding machines ensure efficient and accurate production of plastic components.

To make the injection process happen, there are hydraulic cylinders used to push the screw inside the barrel the screw pressurizes the material, and the pressurised material is injected inside the mould cavity via the injection barrel nozzle. the pressure, speed and position of the complete injection position can be set according to the user's wish.

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Understanding the Clamping unit

The clamping unit is responsible for opening and closing the mould as well as generating the clamping pressure which seals the mould and prevents it from opening during the injection process.

Additionally, the clamping unit also consists of an ejection unit and mould transfer unit in supported models.

The clamping unit has 3 plates, 1) main plate, 2) Injection Plate, and 3) Cylinder plate. The main plate is fixed to the machine's main frame and is stationary, and everything is bolted onto the main frame. the injection and cylinder plates are the ones that carry out all the movement in the clamping unit.

The Cylinder plate is connected to the main hydraulic cylinder known as a hydraulic ram, and two auxiliary cylinders which are responsible for moving the clamping unit and closing and opening the mould, once the mould is closed, the hydraulic ram is responsible for generating the clamping force on the mould.

The cylinders are fed oil through a series of valves (Direction control valves) and pipes(hose pipes), the controller controls the valves to make the movement possible, and the hydraulic oil inside the complete hydraulic circuit is pressurised according to the settings done by the user, the hydraulic system is pressurised and depressurized depending on the need for the movement that needs to happen, at the core of all this is a servo motor and a pump that generates the pressure and makes all the movement possible.

The cylinder plate is connected to the main ram cylinder and auxiliary cylinders. The injection plate is connected to the cylinder plate with the help of tie bars. These are cylindrical high-strength metal rods that connect both plates, making the opening and closing of the mould possible.

The clamping unit is designed specifically to make sure that it can easily handle all the stress/clamping pressure that the machine is generating. the machines can generate a clamping force ranging from 30 Ton to 450 Ton, we utilize multiple simulation software and design principles, as well as our experience to design a rugged and reliable machine structure which is always evolving and improving.

This is the basic operation explanation of vertical injection moulding machines, for more advanced understanding and a deeper dive into the machine stay tuned and subscribe to our newsletter as we plan to post multiple blogs helping you better understand the world of vertical injection moulding machines, as we at Swift Machines believe that knowledge should be shared.

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