Tube shop's success hinges on design for manufacturability
August 1, 2009
A tube laser spurs a shop to think about design and metal fabrication in a new way.
Emerging from the plane at the new terminal of the Indianapolis Intl. Airport earlier this year, Michael Lee looked up and saw a sight: intersecting tubes carrying roof lines, supporting glass walls, opening space.
"For a tube guy, it's an architectural masterpiece," Lee said. "It's a classic example of designing and engineering around a tube platform."
Lee was on his way to a fire industry tradeshow to display one of his company's new products, a tubular stand for fire extinguishers. Lee's company, Winnipeg-based Mercury Specialty Products, bought a tube laser from BLM Group (see Figure 1), and it's done more than help produce a product line for the fire industry. It permanently changed the company's approach to fabrication.
Although the change has been positive, it hasn't been easy. Simply buying a tube laser—a significant investment, to put it mildly—won't magically change a business for the better. According to Lee, the learning curve the tube laser purchase spurred involves selling the technology to customers, garnering design creativity, and fundamentally changing the day-to-day job requirements for shop employees. That's a tall order, but for Lee the benefits outweighed the risks.
Putting a tube laser on the shop floor changes job descriptions, and at MSP this made some personnel changes unavoidable. In 2004 the shop employed 32, today 26. The major change, though, came in the level of skill needed on the floor and in the front office. The shop no longer employs operators dedicated to grinding and deburring, for instance, because the edge quality the laser produces made those jobs obsolete. On the other hand, the company recently expanded its engineering staff dedicated to design for manufacturability (DFM).
It is true that software and control advances have made the technology much easier to learn and integrate into floor operations. As Lee put it, "The equipment is finally catching up to the designer's palette. With the software available, you could be taking parts from a designer's palette and running them on the tube laser within a matter of hours. And with modern CAD/CAM, you can see the design in a virtual state." But software cannot develop design ideas on its own, and no technology, no matter how advanced, can replicate human creativity.
Compared with the flat-cutting laser, the tube laser has just started to penetrate the North American market. Lee, for instance, probably still would be considered an early technology adopter, and he acquired the tube laser only a little more than three years ago. His company was the first among local, independent contract fab shops to do so.
The tube laser reduces the need for certain secondaries. "It reduces the need for sawing, drilling, deburring—the things that we have a hard time putting a price tag on these days," Lee said. For instance, Mercury no longer gang-drills long lengths of tubes. Workers load the tube onto the laser, which cuts all the required holes. More holes cut with the laser means there's less of a need for punching or drilling, and less of a need to manage and catalog tooling associated with these practices. There are simply not that many tools to track.
The tube laser also can process irregular shapes, meaning it can accept stock such as angle iron for operations like mitering, coping, and hole cutting, and perform them with greater precision than cutting with hard tools. These parts make up products like door frames and the structural frame of a tractor cab. Before the tube laser, Mercury had to move parts to various areas of the plant for coping and mitering on the mill, ironworker, and band saws. Today most part ends and holes are cut on the laser, formed on rotary benders, and sent directly to welding—three steps.
To really take advantage of the tube laser's capabilities, said Lee, calls for some creativity and skill—and the learning curve, even with modern controllers and programming, can be steep. Aligning holes perfectly and bringing a cope to bear on adjoining tubes aren't easy feats (see Figure 2). Operators at MSP understand the nuances of tube and the potential for, say, radii variation in the corners of square tube, which they need to compensate for in their programming. (Rectangular tube sometimes arrives from the mill with four slightly different radii. "While the tube falls within the prescribed standard, it's a standard that sometimes you can drive a truck through," Lee said.) Programmers and operators need to understand finish requirements the customer calls for and how they can use the machine to meet them.
A smartly designed tube product either eliminates or reduces the amount of welding a part requires, be it through tab-and-slot geometries, bayonet-style connections, or anything else. Such ideas not only reduce manufacturing costs, but may also change a part design for the better. For instance, a tube can be projected through another tube for added strength (see Figure 3).
Consider a hexagon part that previously consisted of six pieces mitered with a band saw. Now the laser at MSP cuts three sides of the rectangular tube, leaving the remaining side uncut. When the welder receives the part, he simply folds it and welds in one place (see sidebar). Other designs can eliminate brake operations. Consider a part with two up-bent flanges. Why, asked Lee, couldn't this be made simply by cutting the top of the tube away with the laser? This way, the part emerges complete and goes right to assembly, with no welding or bending required.
MSP recently ran an exercise with one of its customers regarding a part that fit into a door handle assembly on a cab for a riding lawn mower. The original design consisted of two elements that were flat-cut on a conventional laser, formed in a press brake, and finally welded together. At MSP the tube laser now cuts the part out of a single piece of 3- by 2-inch tube. This eliminates welding and reduces manufacturing time, overall cost, as well as the part count in the buyer's book from two pieces to one.
For another commercial-grade lawn mower application, the company previously had to cut 3- by 2-in. carbon steel tubes to length; bend the tube to its required shape; then mill holes, slots, and copes. Today the laser cuts the tube to length, as well as those holes, slots, and copes. "We move it to the bender, form the shape, and it's out the door," Lee said.
Yet another example is railings, involving horizontal tube and vertical legs, that go on the deck of agricultural equipment. For decades tube shops have cut the rails to length on a band saw, pressed the ends in an ironworker or hydraulic press, and then butt joint-welded the horizontal tube between the two vertical legs. Now the tube laser can cut in one pass to create, among other things, a cope to give a precisely finished end to weld around.
Coming up with such design alternatives is only half the battle. The other half is selling the technology, not only to current customers and markets, but also to new customers who may never have considered designing with tube.
"It's a very difficult job for a very good salesperson," Lee said.
For this reason, MSP's decision to purchase a tube laser initially was not to bring in more orders, but instead to increase efficiency to make current operations more profitable. The company communicated the technology to its customer base, but didn't aggressively market it.
This has changed. "Now, after having done that for almost four years, we're at a point where we want to take that knowledge and project it out into the marketplace, to illustrate the benefits that we ourselves have experienced.
"The European designers, engineers, and architects, in my opinion, seem to be predisposed to think in tube," Lee added. "They design freely in tube and see the benefit and beauty of it." For instance, that hexagon-tube assembly technique (see sidebar figure) is used quite commonly in the European furniture market. "I asked a contact of mine [in the architecture field] why he thought tube hasn't caught on so much [in North America]. His response was that he didn't see tube as a readily available commodity. So I showed him some photographs [of tubular designs] I took on a recent trip to Europe, and he was astounded at what could be done and what has been done."
To overcome preconceptions takes some communication skills among Lee and his team, who currently are working hard to fill capacity. The shop is pushing what it calls an "Innovations in Tube" marketing strategy to communicate the benefits of the technology, especially to those who might have never considered designing in tube before.
About 80 percent of the company's customers come from agribusiness, little wonder considering the company's location. "Being in Winnipeg, there's lots of farming around us," Lee said. "We've been fortunate during this downturn in that our agriculture business has been buoyant for the past five years—a bit of an understatement, considering the company has enjoyed an average annual growth rate of 30 percent. "We're just starting to see signs of softening now. No one will get through this downturn unscathed. We're just keeping our eyes open and looking for opportunity."