Knowledge Hub

03/06/2024

Hydraulic Cores in Injection Moulding

What are Hydraulic Cores in Injection Moulding?

Hydraulic cores, also known as hydraulic coring systems, are components used in injection moulding machines which help to create complex shapes, interior cavities, and undercuts in moulded plastic parts.

When manufacturing plastic parts with complex designs, it can sometimes be challenging to create undercuts or internal features with conventional injection moulding techniques. These features may include holes, threads, or even intricate shapes.

And that’s where hydraulic cores come in.

Hydraulic Cylinder

Hydraulic cores use a hydraulic mechanism to extend or retract pins, slides, or other components within the mould cavity during the injection moulding process. These components are designed to move in synchronized motion with the mould opening and closing mechanism.

By precisely controlling the movement of hydraulic cores, the injection moulding machine can create cavities, undercuts, or internal features in the moulded parts. The hydraulic cores move within the mould to create voids, slide actions, or ejector pins to shape the part according to the design requirements.

Why Are Hydraulic Cores Used in Injection Moulding?

Hydraulic cores are commonly used in injection moulding for several reasons:

Precision control: Hydraulic cores allow for precise control over the movement and positioning of the core in the mould. This is crucial for applications that require high accuracy and dimensional consistency.

Complex geometries: By using hydraulic pressure, the core can move in multiple directions, enabling the production of parts with complex shapes and geometries. These components are difficult to produce with traditional mechanical systems.

High force application: In some cases, injection moulding requires the use of high force to hold the core in place or to retract it from the mould cavity. Hydraulic cores can generate and withstand higher forces compared to mechanical systems, ensuring efficient and effective operation.

Durability and reliability: Hydraulic cores are known for their durability and reliability, especially in the long term. They can withstand repetitive movements and high-pressure applications without significant wear and tear, resulting in increased productivity and reduced downtime for maintenance.

Versatility: Hydraulic cores can be utilized in various types of injection moulding processes, whether it’s for single-shot injection, multi-component injection, or insert moulding. They offer flexibility and adaptability, making them suitable for a wide range of applications and materials.

Hydraulic Core

How do Hydraulic Cores Function During the Injection Moulding Process?

Here’s how hydraulic cores function and operate during the injection moulding process:

  1. Core insertion: Before the injection moulding process begins, hydraulic cores are inserted into the mould cavity. These cores have a complex shape and are typically hollow to allow for the ejection of the moulded parts.
  1. Mould closing: Once the hydraulic cores are properly placed, the mould closes to prepare for injection. The mould consists of two halves: the stationary half and the moving half. The hydraulic cores are attached to the moving half of the mould.
  1. Plastic injection: Molten plastic material is injected into the mould at high pressure. The plastic flows around the hydraulic cores, filling the mould cavity. The hydraulic cores have channels and pathways that allow the plastic to flow into the desired shape and create features such as holes, threads, or complex geometries.
  1. Cooling: After the plastic material is injected, the mould remains closed for a cooling period. The cooling process ensures that the plastic solidifies and takes the shape of the mould cavity.
  1. Ejection: Once the plastic has cooled and solidified, the mould opens, and the hydraulic cores are moved by the hydraulic cylinders. The movement of the hydraulic cores helps release the moulded part from its core, allowing easy ejection without damage.
  1. Repeat: The process is then repeated for the next injection cycle. The hydraulic cores are reset to their initial position, and the mould closes again for the next plastic injection.

Throughout the entire injection moulding process, hydraulic cores rely on hydraulic cylinders and actuators to provide the necessary force and movement. Hydraulic oil under high pressure is directed to these cylinders, which then drive the movement of the hydraulic cores. Hydraulic valves and controls regulate the flow and pressure of the hydraulic oil, ensuring precise and controlled core movement.

Benefits of Using Hydraulic Cores in Injection Moulding

Hydraulic core systems offer several benefits to the injection moulding process:

Increased productivity: Hydraulic core systems allow for faster and more efficient moulding cycles. They provide swift and accurate movements, resulting in reduced cycle times and increased production rates. This efficiency is crucial for meeting high-volume manufacturing demands.

Precision and accuracy: Hydraulic cores enable precise and repeatable movements. This accuracy is essential when producing complex and intricate parts with tight tolerances. Hydraulic systems ensure consistent and reliable core movement, ensuring the quality and dimensional accuracy of the moulded parts.

Flexibility: Hydraulic core systems offer flexibility in design and functionality. They can be easily integrated into existing injection moulding machines and accommodate various core shapes, sizes, and configurations. This adaptability allows for greater versatility in mould design and the manufacturing of a wide range of parts.

Enhanced part quality: The precise control provided by hydraulic systems helps achieve consistent and high-quality moulded parts. Hydraulic cores ensure uniform cooling and proper filling of the mould cavities, minimizing defects such as warping, sink marks, and voids. This results in improved part aesthetics, structural integrity, and dimensional accuracy.

Reduced maintenance and downtime: Hydraulic core systems are highly reliable and require minimal maintenance. They are designed to withstand demanding production environments and extended operational periods without significant wear or breakdowns. This results in decreased downtime and increased equipment effectiveness.

Cost-effective: While hydraulic core systems may have a higher initial cost compared to other alternatives, their efficiency, accuracy, and productivity can lead to long-term cost savings. Reduced cycle times, improved part quality, and increased production rates contribute to lower production costs per part, making hydraulic cores a cost-effective choice for high-volume injection moulding operations.

Hydraulic Cylinder on Tool
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