Rapid tooling in plastic injection moulding – Everything you need to know
In the process of plastic injection moulding, rapid tooling plays a crucial role. One of the reasons for its popularity is Its ability to significantly reduce lead times associated with traditional tooling methods. Thanks to rapid tooling, the entire process of plastic injection moulding can be accelerated, promoting efficiency, and innovation in the development of new products.
A beginner's guide to rapid tooling
What is rapid injection mould tooling?
Rapid tooling is the process of creating moulds, or tooling, and tool inserts that are subsequently used to produce small batches of plastic injection moulded parts and components. It plays a key role in streamlining the plastic injection moulding process and increases the speed and versatility of prototyping, short-run production and device manufacturing.
Rapid tooling is a fast process for creating mould tooling inserts and is particularly useful for product development, prototyping and low-volume manufacturing. Rapid tooling’s primary benefits are design flexibility and time reduction in the tooling phase of the product development cycle, making it a valuable process for certain manufacturing scenarios. Thanks to rapid tooling, new tool inserts can take a few days or less to create and mould designs can be produced quickly and efficiently.
Rapid tooling methods include Additive Manufacturing (AM) – otherwise known as 3D printing, CNC Machining, Soft Tooling, Cast Urethane Tooling and Direct Metal Laser Sintering (DMLS). All these processes focus on creating a mould more quickly than is possible using traditional tooling methods.
How rapid tooling is different to conventional tooling
Speed and flexibility are key benefits of rapid tooling, compared to conventional tooling solutions.
Speed of production – rapid tooling involves technologies such as additive manufacturing (e.g 3D printing) and CNC machining. It has shorter lead times than conventional tooling processes such as milling, turning and grinding of metal blocks to create moulds and tooling inserts.
Flexibility – rapid tooling offers more design flexibility and the option of quick design iterations, whereas modifications to conventional tooling designs can require significant time and cost as metal moulds and inserts are reworked or remanufactured.
The rapid injection mould tooling process
- Design – a digital design for the product or part is initially developed using Computer-Aided Design (CAD) software to meet the requirements of the final part’s specifications and dimensions.
- Material selection – intended use, production volume and final part characteristics will all influence the choice of material. These will also dictate to some degree the rapid tooling process chosen.
- Tool path generation – subtractive rapid tooling processes such as CNC machining require the generation of tool paths, based on the digital design. These tool paths act as a guide for the cutting tool, so that the desired form is shaped from the material.
- Tooling production – 3D printing involves the layer-by-layer creation of tooling inserts directly from the digital design. Whereas CNC machining removes excess material from an existing block of material to create the tooling.
- Finishing – after the tool or tool inserts have been produced, additional finishing may be needed to achieve specific surface quality and accuracy.
- Testing and validation – testing is necessary to ensure that the tool meets required specifications. This can involve the production of a small batch of parts, with adjustments made as necessary.
- Production – the finished tool can be used to injection mould prototypes or small batches of plastic parts.
Common applications of plastic injection rapid tooling
Rapid tooling is commonly used in industries that place a priority on quick production turnaround times and cost efficiencies. Applications include:
- Medical – specifically small batches of components for specialised medical devices such as dental equipment or prosthetics.
- Consumer electronics – moulds for buttons, casings, connectors and other components.
- Automotive – interior trim pieces, dashboard components and prototypes.
- Aerospace – low volume, complex components.
Why is rapid tooling a popular choice in plastic injection moulding?
The combination of time, flexibility and suitability for low-volume production all make rapid tooling a popular manufacturing choice in a range of industries.
Time savings – faster than traditional tooling methods, a combination of 3D printing and CNC machining can significantly reduce lead times, facilitating quicker product development cycles and helping bring products to market more quickly. They also help with the faster iteration of designs in the prototyping phase. Rapid tooling can reduce timescales from the usual 8-12 weeks to just 4 weeks, compared to traditional tooling methods.
Customisation – highly complex or customised parts can be produced using rapid tooling and 3D printing processes allow for intricate design creation, without complex tooling setup.
Design changes – design changes can be made, and multiple iterations tested, in a shorter time frame than using traditional tooling methods. Also, design changes during the production process can be accommodated, making rapid tooling ideal for industries where product designs evolve rapidly.
Hybrid machines for rapid tooling
The development of hybrid rapid tooling machines, that print and machine within the same unit, has enabled even more efficiencies and flexibility to be built into the production of tool components. Additive manufacturing processes (such as 3D printing) can be combined with subtractive methods such as CNC machining.
Rapid tooling hybrid machine benefits include:
- Surface finishing – tool inserts can be built up layer-by-layer using the additive method and then machined or finished precisely using the subtractive process.
- Reduced lead times – machine setups and transfers between different manufacturing systems are reduced, leading to faster production cycles and reduced lead times for creating tooling components.
- Tool and die manufacturing – hybrid machines deliver moulds with complex geometries and critical tolerances, making them popular for injection moulding applications.
- Flexible design – complex geometries can be created using additive techniques that can be difficult to achieve using subtractive methods on their own.
- Prototyping – the speed of quick iterations is possible with additive manufacturing as well as achieving a high-quality finish via the subtractive method.
How rapid tooling benefits rapid prototyping
The primary focus of rapid tooling is to quickly manufacture moulds, dies or tooling inserts needed for mass production processes. However, rapid prototyping, as the name says, is for the quick development of physical prototypes or models of the final product.
Rapid tooling facilitates prototyping in a range of ways. Moulds can be created quickly and with less material than traditional tooling methods. Designs can be fine-tuned, customised and optimised and an iterative design process supported, allowing for fast adjustments to be made based on testing and feedback. This ability to adjust during the prototype phase reduces the financial implications of design changes further down the line. The validation process for prototypes is also accelerated as any issues are identified and adjusted promptly, to ensure performance is optimised.
Validation
A key step in the production of prototypes, particularly for the medical sector, is a stringent validation process. This includes:
Functionality testing – relevant tests and simulations are carried out that enable the part’s performance to be evaluated. These can include stress and mechanical testing and fluid flow analysis.
Accuracy testing – the dimensions and features of the part are compared with intended specifications using coordinate measuring machines (CMMs), micrometers or calipers.
Material compatibility – the material used in the rapid prototyping process is checked for compatibility with the final product requirements. This can include evaluating material properties, heat resistance, chemical resistance and durability.
Surface quality and finish – any rough surfaces, warping or other inaccuracies that may affect functionality are checked.
Iterative testing – based on the validation results, modifications and iterations can be quickly developed to overcome any issues. This process can be repeated until the desired quality and performance levels are achieved.
Rapid production of tool inserts
Cavity and core tool inserts, produced by OGM on its hybrid metal additive manufacturing machine, are fitted into a plastic mould tool bolster which creates a fully functional mould tool. This is a much quicker and more cost-effective option for prototyping or if you need to be in production fast.
In addition, complex geometries and intricate features can be created that would be costly to produce using more traditional methods. The more complex the design, the greater the risk of potential defects during the injection moulding process. However, with metal additive manufacturing, cooling channels that follow the contours of the part can be created so that more efficient and uniform cooling can be achieved. Unlike straight-line cooling channels, this conformal cooling technique reduces distortion and improves overall cooling efficiency.
Materials used for cavity and core tool inserts
The intended use of the tool and its required temperature resistance, production volume and type of moulding process will all impact the choice of material used in the creation of the tool insert. Thanks to rapid tooling, different materials can be tested quickly and efficiently to obtain the optimum end tool insert result. However common materials for the creation of tool inserts are:
- Tool steels (P20, H13 and S7) that are hard wearing, have wear resistance and deliver thermal stability and are ideal for demanding moulding processes and larger volumes.
- Aluminium offers machinability, is lightweight and a good thermal conductor, making ideal for injection moulding.
Getting started with rapid injection moulding and tooling
When looking for a plastic injection moulding company to produce components, it is important to assess if rapid injection moulding and tooling are being used. Afterall, plastic injection moulders that use these processes offer highly responsive and cost-effective services. OGM’s rapid tooling services enable the production of technical parts quickly and efficiently, whether its complex electrical connectors, electronic casings or components for medical devices.