Prototyping enables more complex designs

A British company has taken rapid prototyping to the next level by developing an advanced manufacturing technology that is already cutting costs and lead times for OEM customers. Dean Palmer reports The need to dramatically reduce new product development lead times is forcing design engineers to look at alternative production techniques in order to bring new products to market ahead of the competition. A UK-based company, KV Automation based in Milton Keynes, has developed an 'advanced manufacturing technology' (AMT) based on selective laser sintering, that is cutting lead times and giving manufacturers the design flexibility they need to produce complex shapes quickly. The process also offers excellent surface finishes and machineability. KV Automation is better known for designing and manufacturing pneumatic and fluid control products, including custom design solutions. Applications for these products range from sliding pneumatic modules for train doors, through to automatic milking systems and customised manifold assemblies for the pressing and coating of pharmaceutical tablets. Although KV receives most of its revenue from the sale of pneumatic and fluid control products, a new line of business has emerged over the last couple of years which, as well as saving the company internally more than £20k in manufacturing costs, could also, according to sales and marketing director Neil Winterbottom, "represent as much as 10% of our total revenue in five years' time." He continued: "Take our own rodless cylinder range. Our tooling costs for this were around £140 to £150k. With AMT we've now reduced this figure to £20k and our engineers can also do far more design iterations than previously. The lead time was 16 weeks and that has dropped to 2 weeks." Hence, KV began to offer its AMT service to clients. And manufacturing customers are already benefiting from outsourcing the production of critical components to KV. As Winterbottom explained: "A major manufacturer of medical equipment in Italy has used our technology, as have test equipment and automotive manufacturers. We've used AMT to produce aerodynamic parts for wind tunnel testing for Williams Formula One; injection moulded parts for aircraft ejector seats at Martin Baker; and injection mouldings on jigs for Airbus wings." Now AMT manager at KV Automation, Paul Gray joined the company six years ago. He recalled: "The firm needed a fresh set of eyes back then as it was still manufacturing the pneumatic modules conventionally, using two or three-axis machining. The modules were manufactured by gluing steel or aluminium to a machined plastic plate. There was a pneumatic printed circuit board with airways or channels and tracking underneath. The problem though centred around its reliability. The glue, for example, might block a channel if it wasn't applied correctly, resulting in poor airflow through the device and leaks can also occur." Gray, previously a design consultant before joining KV, realised that 3D modelling software could help KV and he also advised the MD and operations manager at the time to consider using different resins in the manufacturing process. With the help of Warwick University and its 3D printer machine supplied by Z Corporation, Gray managed to produce the pneumatic module in one piece with no adhesive. "This convinced KV to invest more heavily in the new technology," explained Gray. "The goal was to develop the rapid prototyping technology to a point where we could manufacture the modules in a single piece." Gray's method of using 3D printing to produce a single piece module was first patented in 1999. "This proved the principle but not the production items," said Gray. "The next stage of the development involved going down a slightly different route." This route involved using stereolithography, a known technology at the time that creates prototype models by building layer upon layer thin strips of resin, to produce a silicone mould. The bond would be molecular rather than by an adhesive. As Gray told Eureka: "Alongside all of this, KV was developing new resins as the current ones available at the time simply weren't strong enough. The materials were good for producing prototype models but not for production items. So we blended our own resins using our own formulae. This then enabled us to produce our own master models for production." But, according to Gray, serious investment was now required: "In 2001, KV spent around £250,000 on a selective laser sintering machine [from 3D Systems]. We're currently producing a respirator product for a customer using CAD data [Solidworks] taken directly into Magix mould tooling software and then the 'Sinterstation 2500' machine. A master model is produced using glass-filled nylon. This is then used to produce around 50 or 60 vacuum cast silicone moulds used directly in production." Gray claimed the new process has led to a zero leak rate within the block itself for the pneumatic modules. But, just as important, KV can now produce more complex shapes, virtually any shape a customer requires using 3D CAD. "For some clients, we've cut lead manufacturing lead times from months to 2 or 3 days. All because we've taken the whole concept-to-prototype process and taken it into our manufacturing process to produce parts in hours." Andrew Rea, senior engineer at KV, regularly uses the laser sintering machine and 3D CAD software to produce prototype models and production moulds. He told Eureka: "We download stl files from Solidworks and the machine then slices the 3D model from bottom to top. Rather than using a print head a laser is used to melt the powder or resin in those positions where the computer programme has told it that there is a solid layer. It gives very high accuracy and we can use steel, nylon or glass-filled nylon as the laser is powerful enough to fuse these materials. It means we can produce one-off injection mould tools or production parts in a couple of hours." Parts produced have an excellent surface finish ranging from 5 to 10 (m Ra and require little or no additional post processing depending on the application. Highly complex geometries and features can be created that are normally difficult to produce using conventional technologies. KV simply converts the 3D CAD design into appropriate top and bottom mould tools allowing for appropriate draft angles and integrate complex, conformal cooling channels - which would normally take weeks to produce - in hours. KV has become so proficient in using the technology that, according to Rea, 3D Systems regards the company as a world leader in the use of rapid prototyping technology. The unique, patented part of KV's 'advanced manufacturing technique' (AMT) is in the silicon mould and how the company puts the backing plate on this without blocking the airflow channels. It uses an ablative material, polyethylene glycol (or wax) which melts at different temperatures. It melts well below the melting point of plastics so KV fills in the airflow channels with the wax. The modules are then placed in an ultrasonic bath, which melts off the wax to produce the channels for the pneumatic modules."