In a hurry to get a new mobile phone design from concept to production in just 10 days, a US phone manufacturer insisted that its design engineers produce a new prototype of the evolving design each day for the customer to feel and comment on. The logic was simple. It wanted instant feedback from the customer and from its design and marketing teams at every stage in the design process in order to speed things along and ensure that the new design was right first time.
Two or three years ago, a prototype-a-day regime like this would have been virtually impossible. Traditional model-making techniques take far too long. Even conventional stereolithographic prototyping systems, which use lasers to cure liquid resins, are expensive and slow. Now, however, low-cost and easy-to-use rapid prototyping technology is beginning to appear. Coupled with the falling price of 3D CAD systems, this technology is changing the way products and components are designed.
The US phone company mentioned above used a machine developed by Z-Corp of Massachusetts that does away with lasers and slow-curing resins. Instead, it relies on ink-jet technology to print a programmed pattern of glue on to a layer of cellulose powder. As the glue sets, the loose powder is vacuumed off and another layer is deposited on top and then glued to build up the model, layer by layer. Z-Corp says models only take a few hours to build and cost a few tens of pounds each, or a few hundred pounds for a fully finished model awaiting final approval.
More and more companies are finding that they can afford to buy the new prototyping systems and are using them to produce prototypes much earlier in the design stage, a process that has been dubbed `concept prototyping’. The effect of concept prototyping is to break down the traditional design sequence into a number of short incremental steps, so keeping the cost of redesign work to a minimum. In the past, design departments would have waited until a design was almost complete before going to the expense of making a prototype.
Concept prototyping allows everyone involved in a new product, from the production manager to the marketing department, to have a model to evaluate at each stage of the design process. This makes it much easier for non-engineers to contribute to the process, as they have a tangible object in front of them to refer to. Mistakes and problems can be spotted early on, well before money is committed to tooling and manufacturing systems. But perhaps the biggest benefit of concept modelling is at the concept stage itself when half-a-dozen possible ideas can be quickly and cheaply prototyped. Early on, clients can gain a clear idea of something the CAD screen can never demonstrate – the weight, feel, texture, comfort and ease of use, even the sheer sexiness of a new design.
Simon Graham, rapid prototyping manager for Umak, the Birmingham-based agent for Z-Corp machines, believes concept prototyping is a way of eliminating scrap from the design process. `The last thing you want is to go through a lot of design work feeling fairly confident that you’ve got to the final design, and then make a prototype only to start finding mistakes. The best prototype you can make is the one that’s in the bin in five minutes. That’s because you’ve found the mistake, you know where the problem is, and you’ve moved on,’ he explains.
Because conventional prototyping is relatively expensive, designers worry about justifying the cost of having umpteen models made during the design process, believes Graham. `Most departments don’t have the budget for this, so they want to be 99% sure of their design before they spend money on a prototype. The aim of rapid prototyping is to be able to produce models as and when you want and not worry about the cost. You want to be able to design a part in the morning, leave the machine to produce a prototype over lunch, and come back and have a look at your part in the afternoon,’ he says.
Rapid prototyping should be viewed as a strategic investment, not a capital cost, argues Lee Styger, international projects director for ARRK Styles RPD, the Teesside rapid prototyping company. There are plenty of studies, he says, that show how the cost of rectifying a design error in a product multiplies exponentially by the time a product comes off the production line. If the cost of making good an error at the design stage is equivalent to the cost of one unit of a product, for example, then changing the design at the final prototype stage might cost the equivalent of 10 units, explains Styger. But by the time the product is in production, recalling it for modification could cost the equivalent of one million units. `In relative terms, the cost of using rapid prototyping to ensure that every new product is right is peanuts,’ he argues.