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Direct Digital Manufacturing Aids Assembly Operations
Direct digital manufacturing's high-tech future has yet to arrive, but Oreck uses the technology right now as a way to produce jigs, fixtures and assembly aids
Joseph Ogando, Senior Editor -- Design News, June 25, 2008
Direct digital manufacturing has a lot of hype swirling about it. And it’s no wonder. The idea of using additive fabrication machines to turn bits-and-bytes into finished goods sounds a lot like the replicator that turned out food and other objects on the Starship Enterprise.
Unlike “Star Trek’s” fictional replicator, however, direct digital manufacturing has started to take off in the here and now. It’s already being used to create medical, dental, aerospace, automotive and consumer goods, usually parts that have low production volumes, complex geometries or both.
Continuous improvements in additive machines and material properties promise to open up even more applications for direct digital manufacturing (DDM) in the coming years. “The part quality from DDM is improving at an exponential rate. I believe it’s fast approaching the capabilities of injection molding for the kinds of part geometries found in aerospace, automotive and consumer goods,” says Scott Crump, CEO of Stratasys, an emerging leader in DDM machines. The same goes for metal parts. And in some very complex geometries, additive fabrication arguably exceeds the capabilities of traditional production methods like injection molding and casting.
Still, there’s lots of work to do before DDM can reach its potential. According to Terry Wohlers, author of the Wohlers Report on the state of the additive fabrication industry, DDM still suffers from a lack of testing standards for parts, material property limitations and additive machines that lack the repeatability and process control required by many manufacturers. These issues have to be resolved before DDM moves widely into regulated, failure-intolerant aerospace, automotive and medical applications. “These applications are the high-hanging fruit,” Wohlers says.
But there’s plenty of low-hanging fruit, too. Wohlers, who believes a growing number of companies are engaged in DDM today, points out that additive systems already work well enough to make a variety of non-structural parts. FigurePrints, for example, uses DDM to make custom figurines based on the “World of Warcraft” game, which has more than 10 million subscribers. Other than figurines, DDM has started to produce custom art, furniture, collectables and corporate gifts, too. “You’re starting to see a lot of activity in non-technical areas,” Wohlers says.
And you’ll see it in one very technical area, too. One of the most promising near-term applications for DDM involves a down-to-earth task many engineers grapple with every day — the design and production of jigs, fixtures and other assembly aids. Stratasys terms this emerging DDM application FAT, which stands for “fabricating and assembly tools.” And by some accounts FAT really is a fat opportunity. Consider that Wohlers puts the size of the global additive fabrication market at $1.1 billion. Compare that to $10 billion for FAT in North America alone, according to research commissioned by Stratasys.
Crump points out the current additive machines are already accurate enough to make the “things that hold things.” And a handful of companies have already started using Stratasys’ fused deposition modeling (FDM) systems for just that purpose.
One of the early adapters is Oreck, the maker of vacuum cleaners and related floor care products. Bill Fish, senior master model maker and rapid prototyping manager for the company, says the company has used its two FDM machines to make more than 300 manufacturing aids, including pallets with fixturing features, nine types of hand tools and assembly guides. On average, Fish builds at least one new tool per week. “If one of them breaks, we can replace it in a couple of hours,” he says. “And we can come up with new tool designs as we need them.”
Oreck started using fixtures and pallets to carry vacuum assemblies down the production line as part of an injury avoidance effort it launched a few years ago. Fish says the pallet-based assembly system produced fewer complaints of repetitive stress injuries. Fixturing components on pallets also eliminated the chance workers would stick themselves with pneumatic screw drivers — an all-too-common occurrence with handheld assemblies.
Likewise, the company found that replacing hand tightening operations with simple wrench-like tools — for example to tighten the collars on the vacuums suction system — cut down on repetitive stress injuries, too. “Our assembly workers suffered far fewer problems with the tools even though the collars could in theory be tightened by hand,” Fish says. As a side benefit, the PC-ABS tools made by the FDM machines are less likely to scratch Oreck’s plastic components the way a metal tool could.
Initially, the company relied on commercial pallets and custom-machined tools, but the FDM machines, which run 24-7 at Oreck, turned out to be a whole lot faster. Fish estimates making the assembly aids in-house saves about 10 to 15 days of engineering work and manufacturing lead time for every new product the company produces.
As for accuracy, Fish says the FDM system has proved itself more than accurate enough to produce Oreck’s tightest fixturing tolerance, which is about 0.010 inches. When Oreck transitioned to FDM-made assembly aids, Fish recalls, the company used to check them on its CMM machine. “Over time, we’ve verified that the accuracy is good enough that we don’t have to do that anymore,” he says.
Oreck isn’t alone in its use of DDM to make assembly aids. Crump estimates dozens of Stratasys’ customers are engaged in direct digital manufacturing of one sort or another, at least some of them using the parts for in-house assembly aids. “We believe many companies are doing this right now. We don’t know how many because they don’t always tell us,” Crump says.
Self-Made Machine
Stratasys has been practicing what it preaches when it comes to direct digital manufacturing. Its newest machine, the 900 MC, has been designed from the ground up for manufacturing purposes and features a large build envelope and upgraded motion control components to boost its accuracy and repeatability. Stratasys, from the beginning, has revealed that 32 of the machines’ components have been produced on its own fused deposition modeling (FDM) machines. Now the company has divulged more details about how these parts are made and the related manufacturing advantages.
For one thing, Stratasys uses freshly made 900 MCs to make components for the units further upstream in the production sequence. Chuck Thompson, the company’s product development manager for FDM, says these machines have a burn-in period before shipping. “We’re using that burn-in process to make production parts, so that each 900 MC coming down the line builds for what comes after it,” he says.
Thompson also revealed the company has saved hundreds of thousands of dollars in tooling costs alone by using FDM to make its own parts. On the machine’s display bezel alone, the savings on tooling came to about $200,000. As Thompson explains, the part has a design with a varying wall thickness and no draft that would have triggered a pricey tool with slides and collapsible cores.
What’s more, that figure doesn’t include the very real costs of waiting up to 16 weeks for the tool itself and another week or two for the first article inspections. “In the past, we often had to modify our design to match the output of the mold because it was faster and less expensive that way,” he says
In fact, without FDM, Stratasys’ engineers probably would have shied away from that bezel design altogether. “In the past, the injection molding process drove our designs,” says Thompson. “Now we just design the parts the way we want to.”
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Direct Digital Manufacturing Aids Assembly Operations
Direct digital manufacturing's high-tech future has yet to arrive, but Oreck uses the technology right now as a way to produce jigs, fixtures and assembly aids
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