Design engineers wanting to create prototype parts have to face a variety of challenges. For those working for OEMs, be they large or small companies, the problem is always the same: getting the necessary parts made, with the desirable mechanical qualities, without interrupting production. The product design department and the production department are often at loggerheads: the latter intent on hitting a weekly schedule, the former desperate to squeeze in a few prototypes to help validate their latest design. It's an awkward situation and one usually where production, as the revenue generator, gets precedence.
The design engineer working independently or for a small bureau also has his or her challenges when faced with creating usable prototypes. Most will not typically have access to manufacturing facilities and will, therefore, outsource. However, subcontract manufacturers don't always hit delivery dates, and getting a small number of prototypes made is often extremely expensive. In the past, manufacturing economics has always dictated that high volume equals a better price per part.
When designers today think about prototyping they are usually drawn to increasingly popular 3D printing (additive manufacturing, as it sometimes called), believing it to be a panacea for turning design concepts into reality: download the CAD file, load the material, push the button and walk away. Job done, right? Well, not quite.
3D printing is an extremely versatile tool, but it is better suited to pre-prototype analysis. Here it can provide highly beneficial insight into initial shape, scale and fit. The process is also invaluable for producing parts that are simply not possible using other technologies.
While 3D printing has its place in the art-to-part process, for components more suited to the intended end-use application, design engineers want prototypes in design-intent materials that are manufactured using production-intent processes. This is because substitute materials have little if any validity under real operating conditions. Designers want to test parts for form, fit and function, as only this combination can deliver the confidence a product development team needs before moving from prototype into volume production.
It's comes as no surprise then, to find that more and more design engineers are seeking better solutions to the rapid prototyping dilemma. As a result, there now exist third party manufacturers specialising solely in this area, offering an ultra-fast resource for custom injection moulded and CNC machined parts delivered in as little as one business day.
Such services are designed to be accessible to everyone, even those with no prior experience of the manufacturing processes involved. Online quotation services simplify the process for the user. These online tools represent time- and cost-saving systems that are already benefiting design engineers around the world. Using such a service means that designers get real, precision components in real materials. What's more, they will be made using the same processes and technologies deployed in volume production.
The types of parts that can be made using these advanced rapid prototyping methods are many: from smartphone accessories, cable system components and bearings, through to equipment for sports, leisure and outdoor pursuits. There really are no limits.
So, how is it possible to make injection moulded parts, for example, in such a short timeframe? Firstly, the supplier has to have a proven and lean process, from receipt of the CAD model through to parts delivery. Secondly, the issue of the mould tooling has to be addressed. Clearly it is unrealistic, both from a cost and time perspective, to produce fully hardened, tool steel moulds. The alternative, therefore, is to use advanced aluminium alloys.
Aluminium is far easier and quicker to machine, and allows the elimination of costly and time-consuming custom engineering tasks that are normally associated with tooling development. Such moulds can be produced rapidly using a negative of the 3D CAD model to digitally design the two halves. Within a day the mould can be in the polishing process, where extremely high levels of finish can be achieved to ensure the production of high quality components. The mould is then ready for loading to the press, thus facilitating the delivery of parts to the design engineer in ultra-quick time.
Any designers concerned about the longevity of an aluminium mould might be surprised to learn that they are normally suitable for many thousands of parts. In fact, there's little reason they cannot last a lifetime, albeit with the intervention of appropriate maintenance when required. Volumes such as these push this rapid manufacturing service way beyond prototyping. After all, in the grand scheme of things, relatively few products are produced in millions. With this in mind, there's no reason why an aluminium mould cannot service a product's lifetime production run, making it an extremely cost effective option.
Injection moulding with aluminium alloy moulds is no different to conventional injection moulding, in that thousands of engineering grade resins are available that produce strong moulded parts with excellent finishes. As an industry standard process, it's an excellent predictor of manufacturability when moving to volume production, and allows full, functional testing on actual moulded parts. Moreover, because of the speed of such services, many customers are able to develop hard tools in parallel, thus reducing that all-important time to market. Any issues arising from testing can be quickly fed into the hard tooling process. This concurrent engineering strategy is invaluable in expediting many solutions.
The story is similar for rapid prototyping using CNC machining. The machines deployed are the same as regular machine tools operating in subcontract facilities all over the world. However, the process is finely honed to deliver low volume unique parts in very quick time without any compromise in quality.
Rapid prototyping using CNC machining is a subtractive method that delivers components from billets of engineering-grade plastic or metal, giving parts with full functionality and desired cosmetic appearance. Three-axis CNC milling is used for up to six orthogonal sides of the part, to machine as many features as possible in one set-up. Typically, multiple tool sets, including end mills and ballnose cutters, will be available based on a particular material or material type – plastics, soft metal or hard metal. Final parts are nearly indistinguishable from moulded parts, making for high quality prototypes.
Some design engineers opt to use rapid CNC machining services at the outset for initial prototypes and assessment, before turning to moulding services for the production of final material prototype parts that allow the testing of factors such as strength, stress, functionality, performance and ergonomics. If the product uses metal parts these machined versions can be used to substitute for eventual cast or pressed production parts.
The popular press and the general public are fascinated with the idea of 3D printing. But, for design engineers in-the-know, the real revolution in prototyping is happening quietly, with a lot less fanfare. For those who have already discovered online services, getting sophisticated prototype parts in short lead-times has never been so simple, straightforward and cost effective.
John Tumelty is managing director of Proto Labs
