Design complex parts with more freedom and creativity

Times are changing fast. Up to now, design engineers have been restricted in the freedom and creativity of their designs by the manufacturing process. Questions designers have to constantly ask themselves such as 'How do I get the plastic part out of the mould tool without making the injection mould tool complex and expensive?' inevitably restrict the designer to follow the path of least complexity, which is usually not the optimum design. However, advances in rapid manufacturing techniques are now breaking down these barriers and removing the need for design teams to work to such rigid 'design for manufacture' (DFM) techniques. Dr Richard Hague, head of the world's largest rapid manufacturing research centre at Loughborough University's Wolfson School of Mechanical and Manufacturing Engineering, is passionate about the subject. He manages a staff of 40 people dedicated to researching rapid manufacturing on behalf of a consortium of major manufacturing companies, including Airbus, Martin-Baker Aircraft, Siemens, Boeing, BAE Systems, JCB and Redbull Racing. He told Eureka: "There is a general lack of awareness amongst design engineers and the manufacturing world just what rapid manufacturing can offer. Designers are so educated in DFM techniques that when they train for rapid manufacturing, they still actually come up with fairly non-complex designs. "One of our PhD students found that through studies with groups of design engineers and students on rapid manufacturing training courses, that the students were quite 'free' with their designs but the design engineers, despite the training still had fairly constrained designs." Although rapid manufacturing (RM) isn't right for all manufacturers, Dr Hague pointed out that for low to medium volume, high value added components, particularly customised product, RM is the way forward. He explained that there are still certain barriers that are holding rapid manufacturing back. "The cost and unstable mechanical properties of certain materials used for rapid manufacturing are holding things back, but even here, a good designer can work around these issues." The speed and repeatability of rapid manufacturing machines are other concerns, especially the problems caused by thermal variations in different areas of the machine chamber. But top of Hague's list of concerns is the cultural barriers to adopting RM techniques. He explained further: "Some designers will always resist change by saying things like 'We've always done it like this, why change?' or 'We used this material last time so we'll use it again'. Manufacturing is generally a risk averse industry." Dr Hague suggested that the first step to getting your designers to think differently is putting them on a training course or join an RM research group. Getting designers to optimise their designs without being constrained by DFM is the key, according to Hague. Although the consortium members at Loughborough are all large manufacturing companies, Dr Hague said he did hope that the education would filter down through the supply chains to smaller firms. "The new wave of RM techniques can be viewed in two different ways by SMEs. Either as deadly to these companies because if they don't adopt them they won't survive, or alternatively as an opportunity." Loughborough is not the only University involved in rapid product development and rapid manufacturing. Desmond Burns, a Masters Degree student from De Montfort University (DMU) in Leicester, recently developed a rapid manufacturing system that won a top regional engineering prize. His system has already been used at Glenborough Engineering and the Lear Corporation, an automotive interior systems supplier. Professor David Wimpenny, head of Rapid Prototyping and Manufacturing at DMU told Eureka: "Desmond's system offers the potential to produce plastic parts of almost unlimited complexity without the need for any tooling and could revolutionise manufacturing in the UK." Burns is currently trying to attract partners to take his concept forward. Using RM methods, Burns worked with Glenborough Engineering on the company's Mark 3 connector plug for Lear. The plug was complex to design for manufacture; the company had limited R&D capability; a large number of plugs were required (between 60 and 100); and there was a limited timescale and budget for the project. Burns helped re-design the connector plug for rapid manufacture and eventually, after a couple of ergonomic design iterations, the 60 parts were produced by 3TRPD at a fraction of the cost of injection moulding. These parts were used directly in Lear's production process. "The potential of rapid manufacturing is phenomenal," commented ??? MD at Glenborough. "We can make more design iterations and the whole process is more flexible and parts can be turned around faster for our clients." Dr Wimpenny offered a word of caution though. He told Eureka: "Despite the obvious benefits of rapid manufacturing, there is still a long way to go before it is a mainstream production route. The existing rapid prototyping techniques are still too slow to support medium to high volume applications [100,000 to 1 million parts per year]. The limited range and high cost of RP materials is still hampering the adoption of the process. The accuracy and surface finish of RP parts falls below the standard required for some, but not all, applications." He added that the ideal applications for RM are small complex parts that are produced in low volumes (1-1,000 off) where the surface finish required is "negotiable" and the accuracy required is not too demanding (±0.1%). However, he did say that there were many successful examples of RM which do not meet this precise specification. "The aerospace, medical, jewellery and automotive industries have been quick to grasp the benefits of RM," said Wimpenny, "but more mainstream engineering applications include the manufacture of small components for specialised machines. Renishaw, for example, often makes batches of its metrology products (up to 200 at a time) using RM parts produced using stereolithography. According to figures compiled by the rapid prototyping guru Terry Wohlers (Wohlers Report 2004) over the last 12 months, 6.6% of RP models (around 320,000 parts) were used in direct production, compared to 3.9% in the previous year. Moreover, this figure may be a significant underestimate since it does not include models used to produce investment castings, many of which are used to support production not prototyping. So RM is clearly on the up. This year's Wohlers Report stated that MG Rover in the UK has manufactured many parts by laser sintering for its cars. The company was facing a delay of six weeks for the manufacture of a plastic clip due to the time needed for tooling and injection moulding. The company instead used laser sintering to produce 1,800 parts (two per vehicle) in 48 hours. The work required six builds of 300 pieces each and saved the company weeks of time and around £50,000. Loughborough and DMU are also both involved in a European Framework project, the "Custom-Fit" project, led by CAD/CAM software company Delcam. Other partners include TNO Industrial Technology, Materialise, AIJU, Democenter, bike maker Ducati, Fraunhofer Insttitute in Germany, Zimmer and Human Solutions. The objective of the project is to create a fully integrated system for the production of, and supply of, individualised custom products or components for the medical and consumer goods sectors, utilising developed RM techniques and affiliated systems. Automotive, aerospace and defence will be covered in parallel. The work encompasses all areas from geometry capture through to the design of the product, simulation of performance, production of parts and even the distribution of fully customised products. Chris Jones, project coordinator at Delcam told Eureka: "It's a four and a half year project with 32 European partners involved. The idea is to link research with industrial partners and end users. A fund of 15.9 million euros was provided of which 9.25 million euros is an EU grant. "The work involves customised products for the body such as facial, hip and knee surgical implants; prostheses; custom grips for sports equipment; individualised cycle helmets. The idea is that an individual could walk into a shop and have their heads scanned to create CAD files, which could then be interpreted by the machines to print bespoke crash helmets on site.