Prototyping provides value and feedback that is otherwise hard to measure such as proof of concept, technical feasibility, ergonomics, and human factors information.

Take ergonomics for example; although a hand can be theoretically placed in a CAD model, it cannot provide user experience, insight, analysis, and feedback that handling a 3D prototype would. Although a CAD model provides great insight into a design, ultimately it is theoretical so needs to be physically proven at some point. It is vital that designs are tested with prototypes before expensive tooling is manufactured.

Prototyping from an early stage of the design process is extremely valuable to the evolution of a design. Using both CAD simulation and prototypes will significantly reduce risk as a project evolves. Recognising a mistake in a 3D print is much less costly than recognising a mistake once tooling has been manufactured!

It is common to think in terms of one high fidelity or ‘final’ prototype however, prototyping is usually a non-linear process. It is iterative and helps solve technical challenges across various phases of a project. If you take our WorkFlow process, for example, we utilise many different types of prototypes and materials. The prototypes across these phases are usually vastly different in sophistication yet are all important in providing us with a breadth of information at key stages of the design process.

The level of prototype sophistication is dependent upon the scale of a project and the stage of development. As a rule of thumb, sophisticated prototyping is unlikely to be used in the early immersion stage of a project. Immersion concentrates on understanding a project brief. This exploratory phase enhances a designer’s understanding before ideating. Although it can be tempting, it is worth withholding sophisticated prototyping until ideas are more mature. It can be useful in this phase to replicate a design idea or gain feedback by utilising a similar device, perhaps with simple adaptation, or even a crude mock-up using cardboard and balsa wood. We have been known to use bits of an old auto-injector together with plasticine, elastic bands, and the odd 3D printed part for a basic proof of principle prototype. If it portrays design intent and proves a concept, then that is adequate.

Moving into the concept stage, you might make some basic prototypes to experiment with ergonomics or aesthetics, these will typically be to improve understanding by exploring form or how a user perceives an idea. Frequently our concepts are quite novel, so we typically need to make quite sophisticated mechanism prototypes to check a design will work in principle. At this stage, the aim of prototypes is to convey design intent for a chosen concept and include some basic functionality. This will allow stakeholders to understand how a design will work, how it is likely to look and its size etc. It’s a good point to gain input and feedback from potential manufacturers of the product too.

It is in the feasibility stage, where the objective is to determine if the concept is both commercially and technically feasible, a functional and more technical prototype needs to be assessed. Prototypes at this stage need to be sufficiently close to the final product, to provide assurance to all stakeholders that the project can reach completion, and be a profitable project for all stakeholders. A feasible prototype may comprise of cannibalised parts, and frequently contains 3D printed or CNC machined components. 3D printing and rapid prototyping has been a fantastic development for our industry, but the materials and surface finishes are not true mimics of the final production material, so there are limitations to prototypes at this stage. Material properties for some designs are crucial, so it may be necessary to cut soft tooling to provide sufficient evidence that a design is truly feasible.

At the feasibility stage, you might have two separate prototypes. One that demonstrates a rough mechanism and how it works (technical demonstrator) plus another that shows how it might look (styling prototype) as the final product. The technical demonstrator may be significantly larger and rather clunky, but its purpose is purely to prove the feasibility of the design intent.

Check back next week to understand how prototypes bring value in the detailed design stages of the process.

Jack Dunkley CEng 10 February 2021

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Get in Touch with Jack Dunkley CEng

Lead Design Engineer

Jack is a chartered engineer who holds a Master’s degree in Mechanical Engineering from Cardiff University. He has experience working with design for injection moulding, machining and sheet metal as well as design for assembly and serviceability. Prior to HD, he worked at metrology company Renishaw for 6 years where he led several complex mechanical projects from initial concepts through to production. He has also worked at electrosurgical medical device manufacturer Olympus Surgical Technologies Europe (Gyrus ACMI).

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