Getting a good press

When Swiss iron manufacturer LauraStar reached its 25th anniversary, it decided that it needed a new product to celebrate the milestone. Features of the company's highly designed – and highly priced – irons include a separate boiler, which delivers high pressure steam via a connecting tube. LauraStar knew what it wanted when it approached Cambridge Consultants for engineering assistance. “They wanted to turn the steam on for the forward stroke, then turn it off for the reverse stroke,” said Eric Wilkinson, head of the projects and systems business unit at the engineering consultancy. The theory is that the most efficient way to iron clothes is to heat the cloth (with steam) in one pass, then press it (without steam) on the second. But it had to be done seamlessly. “We were told that pressing a button to release the steam would be tiresome,” said Wilkinson. “It had to be automatic.” As a further challenge, the team was given a deadline of four weeks to come up with a design. At that point, it would pitch against two rivals for the contract. The first job was to identify the ideal design for a product that can sense whether it is moving forwards or backwards. “This was new for us – but we are often doing things for the first time,” said Wilkinson. “It's vital when you develop a product that you identify the optimum way of doing it.” The team used 'logic trees' (see box) to identify – and eliminate – potential designs for the new iron. While brainstorming was used to generate ideas, these were further refined so that a single method emerged from the pack. Logic trees are a graphical way of representing all the possible development options – with clear information on why that particular option was chosen. However, Wilkinson points out the logic trees are not a substitute for engineering analysis – but simply a way of capturing it. Using logic trees, the team identified three methods: accelerometers; optical correlators; and strain gauges. Accelerometers seemed the best option, and were very easy to get working -- but there were limitations. Wilkinson said it was hard to define when the iron was picked up; at the same time, there would be a delay – and for long strokes, it might turn itself off half way. “The amount of algorithm development would have been huge,” he added. Assessing the optical correlator was more straightforward: the electronics could not cope with temperatures over 60[degrees]C, so would have been designed to hang out of the back of the iron. “We ended up showing all three and recommended strain gauges – even though accelerometers had seemed obvious,” he said. The exercise shows how each problem is different: had the lead time been longer, or the budget higher, another option may have been more appropriate. The final design incorporated two strain gauges into the handle – one at the front, one at the back. This meant that the iron could distinguish between forward and reverse motion – even when this was not in an exact straight line. The other challenge was that LauraStar did not want any more wires, as this would have made the cable stiffer. The alternative was to use thinner wires, but these might snap. The problem was that a feedback signal from the strain gauges had to turn the steam on and off. The answer was to transfer this data down the power cable: by overlaying a 'fingerprint' on the mains power, the iron 'knew' when it was moving – so could control the steam. At the end of the day, he says, his team was able to help LauraStar turn a concept into an engineering reality. “They had an idea but did not know how to make it work – but we did,” he said. “It's now a very successful product, and half of all irons they sell now have this feature.” Logic trees are a graphical way of representing development options for a product or system. Simple rules are applied, allowing engineers to focus on those options with the greatest chance of success – which is vital if a product is to be brought successfully to market quickly. NoteCambridge Consultants is the sponsor of the Design Collaboration Award of iDEA 2007