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Design for Manufacture and Assembly is reported to improve CNC performance, modularity, durability, and serviceability
When Hypertherm (www.hypertherm.com) was getting ready to design its next generation of metal cutting CNCs, the engineering team’s goal was to make improvements. But the controllers, which automate the Lebanon, New Hampshire-based company’s advanced cutting tools and systems, were already well-accepted in the marketplace and highly regarded in the industry. So why redesign? And how would they go about it?
In the world of high-temperature plasma cutting systems, working conditions are less than perfect. Factories and machine shops—for shipbuilding, automotive, construction, metal fabrication, and sign-making—expose tools to the harshest of conditions. Moisture, dust, dirt, gases, and extremes of temperature, as well as physical impacts and vibration, all need to be taken into account. The bottom line is that designs need to be nearly indestructible and easily serviceable. They also need to meet stringent performance standards.
Hypertherm says that its controllers get high marks on all fronts. Returns and repairs are low; they can interface with a variety of systems where repeatability is essential; and they are flexible enough to manage the typical two-cutting head operation, as well as stations with up to six heads. And they can guide both intricate cutting for artwork and high-speed ripping for heavy industrial manufacturing.
As the maker of a reliable, versatile, and high-performance product, Hypertherm understands the need for continuous product evolution to stay competitive. That’s why they redesign. How they do it is with Design for Manufacture and Assembly (DFMA)—a unique design analysis methodology pioneered by Boothroyd Dewhurst (www.dfma.com), of Wakefield, Rhode Island.
Benchmark, listen, and then design
John Sobr, design engineer in Hypertherm’s Automation Group, started the controller redesign project by benchmarking the existing EDGE® II CNC’s design and assembly. “The software prompts you to evaluate the product part by part, and document the assembly step by step,” said Sobr. “Following this, it yields a compelling Pareto chart that not only establishes a baseline from which you can measure success, but also quickly illuminates the parts and processes where there is the greatest opportunity for improvement.”
In general, the DFMA suite of software solutions helps engineers ask critical questions about their product designs early in the development process. The goal is to reduce part count and improve assembly, both of which contribute to lower costs and increased reliability. Such an evaluation can have major impacts downstream on the manufacturing, assembly, and organizational cost of those products. Companies of all sizes, including big players in the aerospace and automotive industries, have put DFMA to work with dramatic results.
At Hypertherm, where DFMA is enthusiastically embraced, a number of other best manufacturing practices, such as Continuous Improvement, Lean Manufacturing, and Voice of the Customer (VOC), are also used to push for superior product designs. In the redesign of the controller, VOC—a market research technique designed to identify customer wants and needs—complemented DFMA by surveying all of Hypertherm’s customers, including end-users, integrator partners, and their own assembly-line workers. At stake were performance and reliability for the operators, serviceability and modularity for the integrators, and manufacturability for the assemblers.
From the VOC process, Sobr’s engineering team learned a number of key things. Regarding reliability, they identified the LCD display and the power supplies as the most vulnerable components. Related to serviceability, they decided that the interior of the controller needed to be even more accessible. And as for manufacturability, they watched their own assemblers twist, turn, lift, and rotate the controller as it moved down the assembly line. All of this input pointed to room for improvement and guided the creation of design goals for the new EDGE® Pro CNC line.
“The VOC process tells us what the product has to do—its functions and features, for example,” said Mike Shipulski, engineering director at Hypertherm. “How you get there—that’s DFMA. And DFMA is the biggest lever in lean.” (see sidebar)
Pulling the lean lever with DFMA
Having set the design goals in the concept stage—function first, robustness, modularity, reliability, and serviceability—the DFMA team next reviewed the virtual CAD model. Meticulously dissecting the model, they examined the product’s modularity scheme and looked at all the service issues, such as how to open the doors or reach into the unit without disturbing wires or cable connections. All the while, they collected data that suggested further refinements. Then they went to work creating the first functional prototype.
“Physical prototypes are important,” said Sobr. “You can model things like wire harnesses, but how you actually install them—how you put the tie-wraps in, how the wires dress—the model can’t tell you that.” But a physical prototype can and, with one in hand, the team met again and totally dismantled it down to the nut, bolt, and screw level. Throughout, DFMA was used to look for further parts consolidation and assembly efficiencies, all of which were then rolled into the final prototype, or Alpha units. From here there was exhaustive testing—HALT, Environmental, ESD, and drop testing—a Beta round of units, and shipment to customers for feedback.
When the design dust settled, DFMA had guided Sobr’s team to a number of significant design improvements for the EDGE® Pro CNCs. Regarding reliability and robustness, the team designed better mounting for the main power supply and consolidated the unit’s electronics onto a printed circuit board. To achieve modularity, they created a standard front panel with multiple back panels—resulting in 10 unique product configurations—as well as other opportunities for customization. To improve serviceability, they made the interior of the product accessible from three sides, rather than just through the back-door, as had previously been the case. And to enhance manufacturability, the lower part count and better-fitting components eliminated the previous twisting and turning of the assembly-line workers and reduced the number of product lifts on the assembly line from seven to zero.
Often, when engineers think about performance, it’s assumed that part count will increase with the addition of features. “For a lot of engineers, the idea of more performance for less cost is contradictory, but it’s not,” said Sobr. “When DFMA is the lens through which you look at product design, you see it differently. Functionality can go up, while parts and costs go down.”
And that’s just what happened. When the final tallying was done, the design engineering team had achieved an overall reduction in part count of 27 percent, while adding features and performance capability. “We were able to hold the price of the new product,” said Sobr. “At the same time, the value of the controller improved dramatically. That’s hard to do when the price of components continues to rise.”
On the manufacturing side, the team saw even bigger gains, with a 50 percent decrease in build and test time. In addition—with the improvements in reliability, durability, and serviceability—the team projected warranty cost-savings of 50 percent per unit and, as a result, recommended that the new EDGE® Pro CNC have a two-year warranty. In manufacturing environments, where conditions are tough and machine downtime can freeze your assembly line, improved durability can provide customers with a huge competitive edge.
Lean from the Start
Mike Shipulski, the engineering director at Hypertherm, is on a crusade for improving the American factory when he talks about DFMA and Lean Manufacturing. “Think about what it means to your factory when you introduce a product with half or a third less parts. That’s where your lean folks should start!”
Manufacturing companies have enthusiastically embraced Lean and Six Sigma, but Shipulski thinks that, from a product quality standpoint, if you are not also using DFMA, you are missing out on big benefits. “With DFMA, you can eliminate a significant amount of design and assembly time and labor,” says Shipulski. “You can also reduce the number of opportunities for people to make defects.” It’s formulaic, he says, because if you reduce the number of opportunities, your yield goes up.
But DFMA goes a step further, Shipulski says. “DFMA helps redesign parts so you can’t make mistakes. You can’t break the parts when you put them in. You can’t put them in backwards. You can reach everything. You can see everything.” In other words, DFMA not only reduces the opportunities for failure by lowering part count, it also increases the likelihood of success by improving part design with ease-of-assembly in mind.
While Shipulski clearly acknowledges that American businesses have seen success with the lean factory, with things like value stream mapping, he firmly believes that the lean folks need to bring product design into the lean equation through the DFMA process. “Lean and DFMA complement each other nicely—DFMA eliminates parts and lean reduces the waste of the ones that remain,” Shipulski says. Beyond that, he sees DFMA as the key to reinventing product lines from a cost-per-unit performance standpoint. “It’s bigger than any other element that’s been used thus far,” Shipulski adds. “If you’re not doing DFMA, you’re really not doing all you can with lean. DFMA takes lean to the next level.” |
—Edited by D2P
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