Design for manufacture

Ever since the first caveman knocked the corners off a tablet of stone, to make the ride a little smoother, design for manufacture has been an implicit part of the whole design process. However, most engineers and designers would feel more than a little miffed if you suggested that they needed help with respect to ‘design for manufacture or assembly’. It’s tantamount to questioning their parentage or manhood (or indeed womanhood). Sadly, most designers tend to feel that ‘manufacturability’ and ‘assemblability’ are taken for granted as an intrinsic part of their intuitive creative process. Very few would confess to having done any specific work on DFMA (design for manufacturability and assemblability) or attended any courses. I say this with confidence because so very few engineers and designers have even heard of the definitive DFMA product or methodology. This of course is Boothroyd Dewhurst – any bells ringing? They actually trademarked the acronym DFMA last century. Don’t feel bad – if you check out Boothroyd Dewhurst on the web, sites containing .edu and .ac come up with monotonous regularity – it is well known in academia, but not so well known where it’s needed most. But more on that later. Engineers and designers are happy to embrace technologies that have seemingly obvious manufacturability paybacks. The first of these was probably MoldFlow for simulation of mould filling – you could actually see the effects of changes in mould design on the filling process. When these simulations were confirmed with practical results the place of Moldflow in the DFMA process was assured. More recently the use of ‘Advisor Technology’ for specific processes has become popular; draft angle checkers, sheetmetal advisors, machinability checkers and machining simulation tools all now have a place in modern DFMA. Rather surprisingly, CAD software vendors have helped DFMA by the general acceptance and delivery of advisor technology and machining simulation integrated with their applications. And, as much as real engineers hate them, marketing concepts like concurrent engineering and collaborative engineering have also helped, as they have brought manufacturing engineers into the process at a much earlier stage. There are basically two approaches to DFMA. One is based around geometry and the organisation and dissemination of it. The other is based on processes and methodologies. A good example of geometry based design-for-manufacture strategy comes from Martin-Baker, the ejection seat people. This strategy is based around manufacturing cells and standardised tooling and it is supported by a fully integrated 3D CAD/CAM/CAE/PDM system from EDS’ PLM Solutions. Although Martin-Baker has the lion’s share of the aircraft escape systems market, ‘affordability’ is increasingly becoming a ‘must have’ characteristic. The effort to reduce product development lead times and costs whilst maintaining or increasing product quality led Martin-Baker to adopt its DFM strategy. ‘Integrate’ the key processes This approach required the integration of the design and production engineering processes, so that products could be designed with manufacturability in mind right from the outset. This necessitates a single database used by all departments that generate information on a product’s form, fit and function. Martin-Baker uses Unigraphics and the i-Man PDM system for initial prototype design, through pre-release development and on to production engineering. All CNC toolpaths required in the manufacturing cells are generated in Unigraphics from the 3D master model data, with the tool selection controlled by the system. “The integrated Unigraphics/i-Man system is central to our design-for-manufacture strategy,” says Andy Botwright, who is responsible for the development and support of the system within Martin-Baker. “Our business driver is that we want to do things electronically, not on paper. By doing things electronically we are better able to encourage and support change during the product development process.” Once you adopt an electronic approach to product development, information is captured as a natural consequence of the process. “It also enables the different processes to proceed concurrently,” adds Botwright. “Data is being re-used, not re-invented. Of course you must manage the data in order to make the most of it”. This has lead to a typical reduction of some 30% in the time it takes for a new product to move from design proposal to approval, and final release to production. Boothroyd Dewhurst on the other hand, falls into the ‘processes and methodologies’ category, although geometry forms an intrinsic part. Another way to look at the technology is to consider it as a procedure whereby manufacturing process costs are simulated in software, up front in the design process. Just as F1 designers have turned to complex aerodynamic simulation tools to extract the last grain of performance from a design, so too are enlightened manufacturers turning to cost simulation tools to optimise their designs to the nth degree prior to committing to detailed design, let alone manufacture. Boothroyd Dewhurst DFMA software brings together unique knowledge about design, assembly, materials and manufacturing processes. It also imposes a consistent methodology on the design process. The lone designer can use this information to make sound decisions without having to go through all the original research or employing specialists. The development team can use DFMA to get everyone thinking along the same lines, at the same time. Either way, the result is better quality products produced at less cost and in less time than products produced using more ‘organic’ development methods. Boothroyd Dewhurst DFMA software usually pays for itself on the first project. Boothroyd Dewhurst customers claim that the software and methodology reduces design-to-product-launch cycles by as much as 50%; it reduces part count by 30–70%; and it reduces assembly time by 50–80%. Bottom line benefits Dr Geoffrey Boothroyd and Dr Peter Dewhurst invented and developed the concept of DFMA. They were awarded the 1991 National Medal of Technology by President George Bush (senior) for their contribution to improving American competitiveness. Ironically, both are British and much of the early work was done at Salford University. Boothroyd took his ideas to the US in search of commercial funding, where he met Dewhurst. They founded Boothroyd Dewhurst in 1981. DFMA software addresses design and manufacturing issues systematically and with measurable results, so engineers can consider how things are made and at what cost while they are designing. In very simplistic terms, design features and manufacturing and assembly operations are scored and weighted so that designs can be ‘scientifically’ assessed and compared for DFMA to reach a quantifiable optimum solution. For management, the benefits begin at the bottom line. The benefits of DFMA start at the design stage and follow through sales, service and support. Since products have fewer parts, companies can save direct labour, inventory and supplier costs. They can also reduce their need for documentation and administration. Often, the indirect cost savings are more significant than the direct savings in material and assembly. To date, more than 500 companies both large and small and in many different industries, have used Boothroyd Dewhurst software to save billions of dollars. They include automobile and aircraft manufacturers, computer companies, machine tool producers, communications products companies, agricultural equipment producers, toy manufacturers, instrument companies and more. One of my particular favourites is Harley Davidson Motorcycles. It’s using DFM Concurrent Costing software from Boothroyd Dewhurst to meet costing targets, whilst fulfilling customers’ performance expectations. DFM Concurrent Costing builds on the firm’s DFMA methodology and software, to allow fast and accurate cost estimating at the design concept stage, where, according to some estimates, at least 70% of the final cost of a product is typically fixed. Drawing on the DFMA database, the software isolates major cost drivers and guides users as they investigate the cost implications of changes in design, materials and manufacturing processes. In a sneaky benchmark, Harley gave Boothroyd Dewhurst design and manufacturing information for a bike that was already in production, so they knew exactly how much it cost to build. “After the Boothroyd Dewhurst people had run their analysis, they came back with a figure that was within one percent of what it was costing us to build this bike,” says Dantar Oosterwal, Harley’s director of product costs. “We knew we could quickly and accurately project costs early in the development cycle, and then use those projections in evaluating design and manufacturing alternatives,” adds Dan O’Callaghan, Harley’s other joint director. “The balancing act between quality, cost, time and function only works if you can accurately estimate the cost impact of various choices.” Using the software, Harley was able to identify some errors in the cost targets that had been established for the new design. “This was a crucial discovery, because if you can identify these extra costs well in advance of vehicle launch, then you have a chance to make some modifications to the design in order to meet your cost objectives while still maintaining a balance with the other key elements,” says O’Callaghan. “If you don’t identify these extra costs until after your tooling is cut and your manufacturing processes are in place, then any design changes will entail major expense.” Oosterwal and O’Callaghan also foresee other advantages in the use of the new tool. Design engineers, for instance, tend to design for familiar manufacturing processes. The software’s DFM methodology encourages them to investigate other processes and materials to develop more cost-effective designs. Leaner design works A little closer to home, Linx Printing Technologies of St Ives, Cambridgeshire, develops and makes continuous ink jet printers and inks. Linx’s ongoing growth has been maintained by developing an operational environment that encompasses effective new product development practices and lean manufacturing principles. In helping to create this environment, Linx has turned to Smallpeice Enterprises to provide much of the training in the specialised DFMA tools and techniques that needed to be brought into the business. The benefit of building DFMA into the culture – along with the adoption of cross functional teams with manufacturing input – has been a dramatic evolution of the internal design of its products. “From what was admittedly a somewhat over-engineered system, new products now have a much more structured layout, reduced part count and simplified assembly. All of which means lower manufacturing costs, a more robust and reliable product and lower operating and maintenance costs,” says Malcolm Ryman, Linx’s production director. Boothroyd Dewhurst has demonstrated that DFMA is a serious scientific endeavour that is available to everyone and not just the preserve of naturally gifted engineers.