Doing Origami with Metal
Located in the heart of the Great Plains since 1978, Valley Industries has a proud history of providing field maintenance solutions to meet the needs of industry. Their specialties include custom-designed trucks, trailers (Figure 1) and lube skids (Figure 2) to bring refueling and maintenance to farm equipment and heavy machinery. Their products enable owners to maximize productivity and minimize downtime. What truly makes Valley Industries stand out, however, is their ability to produce individual solutions to unique customer needs, while maintaining the productivity and quality standards of a mass production environment.
The design process is called “mass customization,” in which customers can choose from a wide variety of options to create a specific product configuration. The “build-a-skid” form on the Valley Industries website guides customers through a seven-step process and hundreds of different options to design a lube skid maintenance platform that can include fuel tanks, coolant tanks, waste tanks, pumps, compressors, generators and welders—all exactly specified to a customer’s needs. If a customer needs more mobility, they can offer similar options on a trailer or match them to a truck chassis. There are countless possible variations. Once the Valley Industries team has helped the customer identify the optimal design for their specific requirements, the specifications are passed on to engineer Scott Leacox to prepare the designs for production.
“I call it origami engineering,” said Leacox, explaining how they create tanks, toolboxes and a multitude of other parts by folding sheet metal. “Most people doing sheet metal are doing high volumes . . . we’re setting up the machines for every part, on each order.” It is in this environment that Leacox has developed some unique methods to optimize his productivity with Solid Edge. The results have not only significantly reduced fit up and welding times in the shop, but have also greatly reduced the amount of time he spends manually adjusting drawings. “The first time I set up a model from scratch, it took three days,” he commented, referring to the development of a typical set of drawings. “Today, it takes about four hours for the same level of complexity.” The entire editing process to resize and configure a model can run from 30 minutes to a day, depending on complexity.
Likeable and Parametric
When Leacox joined Valley Industries, he was already an experienced CAD user. Since graduating from Bradley University as a mechanical engineer in 1990, he has been working with CAD on a full-time basis, on projects as diverse as the NASA launch tower, boilers, barges, conveyors and the development of laser-scanning data processing. Valley Industries was already using the free Solid Edge 2D Draftingsoftware, so Leacox thought it would make sense to see how Solid Edge might help bring a parametric approach to their 3D design needs. The experience was a positive one. “Solid Edge has been my first likable parametric software,” he said. “I tried to do this stuff in other packages and maybe you can do it . . . but not the way I’m doing it in Solid Edge.”
The “stuff” that he refers to is extracting critical measurements from the model that allow the fabricators to fold sheet metal parts as precisely as possible in a manner that automatically updates. Two of the critical pieces of information that Leacox needs to generate from his drawings are the back gage and stick out measurements. The back gage refers to how far back in the fold or brake machine one end of the stock is placed and sets the location for the bend. The stick out allows the machine operator to confirm that the part is correctly placed and ready to bend. “Most of our parts have two or four bends—not that complex,” he said. “But some of our parts have nine bends in them. This is when things get interesting.”
Getting Bent Out of Shape
To illustrate the challenge, Leacox created a simple part with two bends (Figure 4). Calculating the back gage for the first bend is trivial, it is simply the distance from the edge of the sheet to the bend line. Once this bend is made, however, the state of the part has changed. When the machine operator goes to make the second bend, the back gage has to be calculated to account for the flange that has been formed by the first bend.
When working with lightweight sheet stock and tight bend radiuses, this makes little difference, but the steel used at Valley Industries is about 1/8-inch thick and the minimum bend radius is also close to 1/8 inch. This can quickly add up to some serious fitting errors if not properly accounted for in the folding process.
It took Leacox a while to develop his solution, and it is one that he continues to perfect. “I figured out how to make the bend tables (the back gage and stick out measurements) using a single-dimensioned flat pattern view and some variables to represent thickness and bend radius,” he explained, adding that for some complex folds, the K-factor, representing the location of the sheet’s neutral axis, also has to be taken into account to get the correct measurements. Figure 5 illustrates the calculations necessary to create the bend table for the second fold in his example. The back gage for the second fold consists of the dimension between the fold lines, plus the bend radius and the thickness of the sheet metal.
Quick and Accurate
As parts become more complex, the thickness and bend radius factors begin to add up. While many of the components that Valley Industries produces are similar in shape, they vary greatly in size and are produced from different materials and thicknesses of material. Leacox has developed his models so that they are defined by planes in an assembly. This way when he needs customized parts, he adjusts the locations of the planes and the drawings update automatically. “This is the definition of parametric modeling,” he explained. When he adjusts a tank or box to suit a customer’s needs, all of the standard fittings and connections automatically update, and through the clever use of Solid Edge’s variables, he has been able to set it up so that the bend tables and working drawings update as well. The final designs can be quite complex, but he can generate them quickly. “I’m mainly concerned with generating drawings that will be used on the shop floor tomorrow,” he stated, explaining the need to generate drawings quickly and accurately.
Joining a Community
Not only has Solid Edge given Leacox the flexibility to create a custom solution to meet his company’s needs, he has also found other positive aspects to working with it as well. He is an active member of the Siemens PLM Community, where he posts as “12Gage,” a reference to the sheet metal that he spends so much time working with. “Siemens is the only company (in the parametric CAD space) that is listening to its users,” he said. “They have a really good feedback system.” This is important to him, as there are still features he would like to see added to Solid Edge.
Scott Leacox clearly has pride in his work and in the products his company produces. “There are many companies similar to us . . . we’re not doing anything unique—we’re just doing it right.” Part of the process of doing it right is using Solid Edge to automate the “origami engineering” of sheet metal folding, resulting in reduced drawing time and faster fit up due to the more accurate dimensions for flat patterns and folding tables. Leacox might claim that their company isn’t unique, but some of their solutions certainly are!
Jason Brett teaches electronics and materials science in the Technology Teacher Education Program at the British Columbia Institute of Technology. He has 17 years of experience in technology education, during which time he founded the first For Inspiration and Recognition of Science and Technology (FIRST) robotics competition team in Western Canada. He is the founding president of the Pacific Youth Robotics Society and remains actively involved in promoting STEM education through competitive robotics. Brett uses CAD to design and simulate a variety of products that he produces using techniques ranging from traditional machine tools through water jet cutting and 3D printing.
Siemens has sponsored this post. They have no editorial input. All opinions are mine. — Jason Brett
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