August 29, 2002
If you need to cut production time, you might glean a few tips from a little job shop in Ohio that has made the most of its software.
Tony Thompson and the rest of the crew at Total Tooling Inc. know the importance of quick design time.
Success at the nine-person shop in rural Sabina, Ohio—which specializes in designing and manufacturing bend tooling for the automotive and aerospace markets—rests on moving tooling from design to product as quickly as possible. So anything that can slice minutes or hours off that design time is worth looking into.
That's why Thompson, a manufacturing engineer, and his associates have come up with a couple of key in-house productivity secrets, namely some highly automated programming for the CNC machine tools on which their tooling is cut.
The shop programs its machines with EdgeCAM® software from Pathtrace Systems Inc., Southfield, Mich., primarily with the package's three-axis, multisurfacing module.
At Total Tooling, EdgeCAM programs a Chevalier 3-axis mill with a 20x40 inch table, a 20-tool automatic tool changer, and an older Fanuc CNC.
Most of the work comes in as 2-D AutoCAD plot files, hence the in-house creation of tooling drawings. The big exception is aero customers that use Unigraphics; those files are imported with IGES.
Programming is done on a Dell Computer Corp. Precision 420, recently upgraded from a Dell 4100. The 420 has a 1.5 GHz Intel Corp. Xeon® processor with 512 MB of RAM and a high-end graphics board. The operating system is Microsoft® Windows® 2000.
Cutting tools come to mind in a lot of manufacturers' minds when they talk of perishable tooling. But wiper inserts for tube bending also are notorious for their temporality: In high-production tube bending, wiper inserts usually last about one shift.
"Wiper inserts generally last for 3,000 to 4,000 bends," Thompson explained. "In automotive production volume, that is about one shift. So it is not uncommon to get orders for 100 to 200 inserts at a time from exhaust systems manufacturers. That would take care of one of their production cells, and some of them have a dozen or more cells."
Because Total Tooling's customers go through its products so quickly, speeding up the product process through automation just made sense.
Thompson said he made the jump to automated programming in mid-2001, focusing on the business's two highest-volume wiper inserts. A self-taught programmer, Thompson writes eight to 10 programs a day—70 percent is for automotive applications, and almost all of those are for exhaust systems work. The remaining 30 percent is for aerospace work.
Macro Magic. When the shop was ready to dive in, Automated Technology Solutions Inc. (ATS), a distributor for EdgeCAM, sent an application engineer to Total Tooling for one day of training on the software's PCI custom-macro programming language, Thompson said. ATS reps showed employees how to create programming macros that were customized to their customers' specific tooling.
"Now we have custom macros to draw and program both tooling types whenever we need them," Thompson said.
Asked about payback time on that effort, Thompson said, "the next two jobs."
From a design and machining standpoint, the critical parts of wiper inserts and mandrels are the diameter and sweep radius. With the software's macros, both areas can be addressed parametrically—in other words, changes made from one part to another are made solely within their dimensional parameters. Assuming the basic design does not change, their programs can be generated using spreadsheets as CAM input.
"In designing the compound contour tools, what is important is the parting line," Thompson explained. "We start with a top-down view and once all the bend's geometry is entered into EdgeCAM, the parting line is created with its Split Line command.
"If the parting line isn't right—if it is even a little bit off—a tiny hook or lip may inadvertently form in the finished bend clamp cavity and create a pinch mark on the tube when clamping."
Designing compound contour tooling is all the more difficult, because two bends are rarely in the same plane. Between unclamping from one bend and reclamping for the next, tubing often is rotated 45 degrees or more. Thompson is working on another macro for this.
The macros are needed because the software isn't specifically geared for tube bending.
"But then neither is any other CAM package," Thompson said.
Other macros help with fixturing. A macro for wiper insert fixtures creates them in two setups. With another, "we have cut an hour and a half from the time needed to square up a block of steel before we start to cut into it to make a tool," he said.
In addition, a lot of the aerospace tubing coming off Total Tooling's products is made of hard-to-form metals such as INCONEL®. To ensure that the metal is formed and bent to specifications, the company often must create several iterations of a tool design.
"This repetitive work puts a high premium on the 'associativity' within the CAM system between the design or drawing file in the CAM system and the tool paths it generates," said Thompson.
The first tool the shop put into automated production was a wiper insert used in both automotive and aerospace bending.
"Previously that took 30 to 40 minutes to draw and program," Thompson said. "With the custom macro, this is now completed in 8 to 12 seconds. We enter six values in a dialogue box, [the software] creates the surface and wire frame geometry, and then it automatically programs the parts' tool paths."
Tool No. 2 was a half-round cavity for gripping straight pieces of steel pipe. Those used to take 20 to 30 minutes to draw and program and now take less than 10 seconds, Thompson noted.
Tool No. 3, a compound contour bend clamp, was handled differently, because the tool's two halves have a complex parting line in the bending machine.
"We felt that the geometry and process steps were too complicated to be handled as a straightforward PCI [Pathtrace's term for its particular type of macro programming]," Thompson said. "So we took another macro approach. We created this PCI by duplicating a programming job for a compound contour bend clamp that had been completely optimized."
Instead of spending the several hours it normally would have taken to write out and edit dozens of sequential steps as PCI scripts, an operator highlighted them in the software's browser tree, and the vendor showed him how to create a PCI template from that, Thompson said. All the shop had to do was highlight the sequence of steps, select them, and save them to a macro file.
"To use it, all we have to do is select the surfaces in the tool to be programmed, then shift/click with the right mouse button for each new part," he said. "This saves at least a half-hour every time we do one and we do them all the time."
Wiper inserts operate something like a human hand to shape the inside radius of the bend by rubbing the metal into the bend. Rather than simply wrapping around or bending a tube to a radius, wiper tooling shapes it. The insert wipes across the metal during the bend, supporting it to minimize wrinkling.
Therefore, the geometry of the tubing that is bent by the company's wiper dies is critical. Without wiper inserts to smooth the bend, tubing tends to fold on the inside of the radius and stretch, deform, and weaken around the outside. The stretching and folding also tend to crimp the tubing at the sides of the bend, flattening the cross section and significantly reducing the diameter.
This action in turn constricts the flow of fluid and may lead to blockages inside the bend. It also greatly enhances the likelihood of stress-corrosion cracks, which eventually can cause ruptures in the tubing.
Until recently, all geometry was created right in EdgeCAM, almost all of it by Thompson. To spread that work out and free up the software for more programming, the company recently bought an Autodesk Corp. Mechanical Desktop license. Now most tooling design is done in CAD instead of with ink and paper, then imported through the software's Autodesk integration package.
To sum up, CAM capabilities such as macro programming, parametric inputs for jobs with small dimensional changes, and CAD file associativity can boost output and productivity. To keep up with the demands of production tube bending, at least one shop has found them essential.
Total Tooling, Sabina, Ohio, is a two-year-old, nine-person firm, supplies perishable tooling for the tube bending industry, 256 E. Washington St., P.O. Box 218, Sabina, OH 45169, phone 937-584-5637, fax 937-584-2418, cell 937-205-2598.