Injection moulding is a versatile manufacturing process used to produce complex plastic parts with precision and efficiency.
It is this principal that enables Industrial Designers to push their product designs to new levels, once not thought possible, unleashing freedom of expression for shape and form, fit and function.
Now more un-restrained by the limits of what was feasible of the past.
One of the critical components in this process is the ejector system, which ensures moulded parts are safely removed from the mould.
Among the various types of ejector systems, angle ejectors, also known as angled lifts or lifters for short, are specifically designed to eject parts with intricate geometries, internal undercuts, or side features that are not released parallel to the line of draw (LOD).
Let’s investigate how angle ejectors work, their design, applications, and benefits in injection moulding.
Understanding Angle Ejectors
An angle ejector is a specialised mechanism used in injection moulds to eject parts that have internal geometry at an angle or even perpendicular to the mould’s opening direction or Line of Draw (LOD) that can not be formed by an external side slide.
These features, such as inner side walls or strengthening ribs, internal undercuts, or angled features, can prevent standard ejector pins from effectively removing the part from the mould.
The LOD is defined as the direction of opening of the two halves of the tool, the core and cavity along the tie bars in a plastic injection moulding machine.
Key Components of an Angle Ejector System:
Ejector Pins or Blades:
Elements, moving at angles to the LOD that directly contact the moulded part to press it from the Cavity upon ejection. The ejector usually has the geometry of the desired undercut machined into it.
Cam Mechanism:
Converts vertical motion into lateral or angled motion.
Ejector Plate:
Drives the motion of the ejector pins and is connected to the ejector.
Guide Rails:
Ensure accurate movement along the desired path.
Ejector rod and coupling:
The bar and connector that attaches the mould to the
injection moulding machines hydraulic or mechanical ejector system.
The combination of these components enables the angle ejector to move in a controlled manner, ensuring the part is ejected without damage.
How Angle Ejectors Work
The operation of an angle ejector is based on converting the horizontal motion of the ejector plate into an angled or lateral motion. Here’s a step-by-step breakdown of the process:
Mould Opening:
Once the injection moulding cycle is complete, the mould’s clamping force is released and the mould opens, creating space for the ejector system to activate and the part to be ejected from the moving side of the tool.
The ejector mechanism is primed.
Ejector Plate Activation:
The ejector plate, powered by hydraulic or mechanical systems through the ejector bar and coupling, begins to move forward.
This forward movement pushes the angle ejector pins or blades through the mould base applying force onto the part.
Conversion of Motion:
The cam mechanism or guide rails redirect the vertical motion of the ejector plate into an angled motion.
The angled ejector pins slide along the predetermined path, bearing against the part’s geometry.
Part Ejection:
As the ejector pins apply force, the moulded part is gently lifted or pushed out of the mould cavity.
The force applied to the part is horizontal, but the vector of movement of the contact surface of the ejector is lateral as it slides across the surface of the part.
This lateral vector and ejection stroke continues until the desired undercut feature is free from the tool geometry that forms it.
The precise motion prevents damage to delicate features, ensuring the part retains its integrity.
Reset:
Once the part is ejected, the ejector plate retracts, and the angle ejector pins return to their original position.
The mould closes, and the next cycle begins.
Design Considerations for Angle Ejectors
Effective implementation of angle ejectors requires careful design and planning. Key factors to consider include:
Geometry of the Part:
Analyse the part’s design to identify features that require angled ejection.
Determine the optimal angle and path for the ejector pins.
The surface geometry where the ejector bears against the part and enough clearance to adjacent features for ejector movement will determine effectiveness, and in some cases, viability of use of an angled ejector.
Tool Material Selection:
Use durable tool materials for the ejector components to withstand repeated cycles and high pressures.
Consider wear-resistant coatings to enhance longevity.
Cam Design:
Ensure the cam mechanism provides smooth and precise motion.
Optimise the cam profile to minimise stress on the ejector system.
Clearance and Alignment:
Maintain accurate alignment of all components to prevent jamming or uneven ejection.
Provide sufficient clearance for the ejector pins to move freely.
Ensuring the is enough run out space for lifter head movement across the part.
Ejection Force:
Calculate the required ejection force based on the material, part geometry, and mould design.
Ensure the system is capable of delivering consistent force without deformation.
Applications of Angle Ejectors
Angle ejectors are widely used in the Automotive, Consumer Goods, Medical Devices, Electronics & Aerospace industries that require intricate or complex moulded parts.
Common applications include:
Producing components with undercuts, such as dashboard panels or air vent housings.
Ejecting parts with angled ribs or side features.
Manufacturing plastic cases, handles, and containers with side openings or angled surfaces.
Creating precision parts with internal features or lateral openings.
Ejecting housings, connectors, or components with complex geometries.
Producing lightweight and intricate parts with undercuts or angled features.
Benefits of Angle Ejectors
The use of angle ejectors offers several advantages in the injection moulding process:
Improved Part Quality:
Ensures smooth ejection without damaging delicate or intricate features.
Maintains dimensional accuracy and surface finish.
Versatility:
Handles a wide range of part geometries, including undercuts and angled surfaces.
Enables more complex part designs, expanding the possibilities for product innovation.
Reduced Manual Intervention:
Automates the ejection process, reducing the need for manual trimming or secondary operations.
Improves production efficiency and reduces labour costs.
Enhanced Mould Longevity:
Distributes ejection forces evenly, reducing wear and tear on the mould.
Extends the lifespan of mould components.
Consistency and Reliability:
Delivers consistent performance across multiple cycles, ensuring high-quality parts every time.
Challenges and Solutions
While angle ejectors offer numerous benefits, they also come with challenges that need to be addressed:
Complex Design:
Challenge:
Designing and manufacturing an angle ejector system requires expertise and precision.
Solution:
Collaborate with experienced mould designers in early phase DFM (Design for Manufacture) and use advanced simulation tools to optimise the design. Early engagement will enhance and optimise your design whilst ensuring it is still achievable and produce the desired results.
Maintenance Requirements:
Challenge:
Regular maintenance is essential to prevent wear and ensure smooth operation.
Solution:
.Implement a maintenance schedule and use durable materials for components.
Higher Initial Cost:
Challenge:
The addition of angle ejectors increases the complexity and cost of the mould.
Solution:
Evaluate the long-term benefits, such as reduced scrap and improved productivity, to justify the investment.
Angle ejectors are an indispensable tool in injection moulding, enabling the production of parts with complex geometries and side features. By converting vertical motion into angled ejection, they ensure smooth and efficient removal of moulded parts, maintaining quality and consistency.
With careful design, regular maintenance, and proper implementation, angle ejectors can significantly enhance the capabilities of injection moulds, opening the door to innovative and intricate product designs.
As the demand for complex and high-precision plastic parts continues to grow, angle ejectors will remain a vital component in the evolution of injection moulding technology. By understanding their operation and benefits, Industrial Designers can leverage this technology to achieve superior results and stay ahead in a competitive market.
For an enhanced and optimised design that pushes to the edge of capability but not over it, there is one key element I have found over the course of my career that will provide success.
That is early phase engagement with your chosen tool maker and moulder.
It may be a challenge considering many companies purchasing polices. But if you can lock in your chosen supplier early in the design phase, have them buy into the process and leverage their experience and work in partnership with them as your design evolves, the results will be truly outstanding.
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équipe design & consulting is a Product Design Consultant in Sydney
with 20 years experience in design and manufacture of Medical grade moulded parts and product, including 5 years at the coal face as Operations Manager at a world class medical grade moulding facility; we are specialist in Design for Manufacture (DFM).
Please reach out if you feel you need assistance with your part design for plastic injection moulding.
We offer Design Coaching and Guidance to Full Service Design Consulting.
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References: ChatGPT, Google Images, custompartnet.com
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