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MATERIALS IN DESIGN & PROTOTYPING
PROTOTYPING IN A MATERIAL WORLD
Saleem Shariff, customer engineer manager, Protolabs, guides us
through some of the materials used in different prototyping processes and key points to consider when making your selection
C
hoosing the best material for your design can be complex. With fast prototyping methods offering thermoplastic, thermoset,
elastomeric and metal options, it is possible to create functional models of your part or product with production-grade materials. This means you can test the material to see how it will perform in a real-world environment. But, with the rapid development in material properties and the sheer number of materials commercially available, how do you select the right one for your project? Understanding the conditions that the
end product will function within will help determine which material to use, while the prototyping method you select will depend on the specific product and the project stage. So what should you consider?
RAPID PROTOTYPING PROCESSES The three core manufacturing processes for prototyping – 3D printing, CNC machining and injection moulding – have their own unique features and benefits. They can also be used to produce low volume runs of end-use parts, so that progressing from the iterative design phase to production is seamless and fast. With injection moulding there are over 100
grades of thermoplastic/thermoset resin, as well as liquid silicone rubber, that many widely used products are made from. As a prototyping process it allows you to move from testing to producing mid- to high-volumes efficiently and cost effectively. However, for just prototyping, or production runs in the hundreds or less, it is worth exploring the other manufacturing technologies that avoid the initial set up costs and lead times involved in producing moulds. CNC Machining provides a faster turnaround
on precise parts and, for prototyping, a lower cost per part. The material blocks it uses come in numerous metals and plastics, including aluminium, brass, copper, steel, nylon and polyvinyl chloride (PVC). Some resins are also available in block form, which means that products intended for higher volume end
use production by injection moulding can be tested quickly and more cost-effectively first by the machining process.
SOFT AND SMART MATERIALS IN 3D PRINTING 3D printing, also known as additive manufacturing (AM), is the easiest way to shape highly elaborate components. An excellent technology for producing prototypes and one-off products, it was originally designed only for hard, thermoplastic polymers. In recent years, however, AM has been extended to soft materials such as elastomers and hydrogels, becoming one of the most promising manufacturing approaches for soft robotics, which are increasingly used in industries such as medtech and agriculture. We are also witnessing the development of smart materials, opening up the world of 4D printing. When exposed to specific environmental conditions like heat, light, moisture, electric current, or pressure, 4D-printed components morph into a pre-programmed shape. This is already being trialled in aerospace, where drone wings can bend up to 20 degrees in response to stimuli, significantly improving efficiency; and in medtech, with implants that adapt to a patient’s body over time. Understanding the conditions that the end
product will encounter is the key to choosing the right material, whatever the manufacturing process. Here’s what you need to consider before you embark on your prototype: Environment: will the product need heat and
cold resistance, flame retardance, or UV and chemical tolerance? It might need to be food or medical grade. For example, parts for a medical device may have to tolerate extreme heat or harsh chemicals for sterilisation between uses. Electrical: does the part need to conduct or
insulate, or dissipate static? Mechanical: a part may require tensile
strength or compressive strength, or be able to resist impact or provide flexibility. It may have to resist wear or provide lubricity in
MARCH 2024 DESIGN SOLUTIONS 47
order to function as a bearing. Cosmetic: some plastics can be supplied in a
variety of colours, while metals can be coloured using secondary processes. Certain materials can produce a transparent or translucent part. There might be a requirement for a specific surface texture from non-slip to high polish. Size: prototyping methods can produce parts in a range of sizes, but it might be limited by the maximum available size of a particular stock material. Cost: materials do vary in cost, so this will
need to be factored in, especially if you’re taking it through the full production run.
FROM CONCEPT TO MARKET As new prototyping techniques and materials emerge, designers face a growing challenge in determining which is best for their application. With rapid prototyping, a CAD design can be realised as a physical product within days, in materials similar, if not identical, to those that will be used in the ultimate production process. Producing multiple prototypes simultaneously
in different materials allows comparison and iterative product development, and helps bring the product to market quickly while ensuring it will function in the conditions it is designed to endure.
Protolabs
www.protolabs.com/en-gb/
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