Rapid prototyping moves onto manufacturing simulation

Techniques originally developed for rapid prototyping of single items are increasingly being extended to enable greatly accelerated production runs of up to even 20,000 components – simple and complex. Advanced digital manufacturing (ADM) systems are also improving firms’ ability to make one offs and devices that can perform properly in service, resulting in reduced manufacturing costs as well as better real world visualisation. Graham Lindsay, European director of the 3D Systems thermoJet business told MCS, “We see advanced digital manufacturing as the future.” Lost wax casting processes, based on casting wax into silicone moulds made from rapid prototypes, have been with us for some time. The prototypes are usually made by stereolithography. But companies like Phonak and Siemens, for example, are working together to develop a process for the direct mass manufacture of hearing aid shells each shaped to meet the needs of individual users. With their system, 200 nylon shells can be made at the same time in four hours using SLS (selective laser sintering). A crucial part of their process is tagging each component as it is made to ensure that the right hearing aid shell is delivered to the right person. Also based on SLS is the making of ‘Duraform’ PA (polyamide) components for hockey puck sized flying magnetometer satellites for NASA/JPL. Cost of each component made this way is $300, as opposed to 10 times that using conventional processes. Military and civilian aircraft companies too are turning to ADM to produce parts, especially to supply spares in order to reduce inventory. 3D Systems cites On Demand Manufacturing, a subsidiary of Boeing, which has purchased two SLS machines to make environmental control system ducts for military aircraft. SLS of Duraform PA has even been used by designers Olive Vogt and Hermann Wiezenegger in Berlin to make one-off designer furniture. 3D’s advance stems from its purchase of Optoform, a French joint venture with DSM Somos. Its process is called direct composite manufacturing (DCM) and involves the laying down of paste-based material through a print head. The machine rolls the paste across a platform, where it can be hit by a laser to solidify it. SLS, however, can be used directly to manufacture mould tools in metal. Lindsay says his company now has a stronger LaserFom ST-200 base material, with an enhanced ‘green’ strength and has improved both accuracy and repeatability. The latest version of the process is now undergoing beta tests with 10 users, which in this case means that it is, “pretty close to market, but adjustments to material composition can still be made.” When finally launched, it may also come with the option of automatic powder handling. Andrew Mitchell, sales manager of the Centre for Rapid Design and Manufacture says it has one of two direct metal SLS machines in the UK (the other is at Ford). The EOS M250 machines can directly manufacture plastic injection mould tools without a separate metal infiltration stage. Tool lives are similar to those achieved by conventionally manufactured aluminium tools.