Above: Relief slots punched into Grand Rock’s 16 gauge and 14 gauge exhaust components facilitate effective clamping for good joints.

Fabricator’s truck exhaust systems rely on a small detail added by a simple, robust punch

September 2013 - Compared to all the parts and pieces that go into a diesel engine, an exhaust system is fairly simple. But unlike engines, which are preassembled, exhaust systems come in pieces that have to be connected to a
muffler and to each other. How easily and how well the pieces fit together is one good indicator of system quality.

To address that issue, Painesville, Ohio-based Grand Rock Exhaust Systems developed a variety of band-type clamps. The company has been fabricating an extensive range of exhaust systems for more than 30 years and has always prided itself on its high quality. Today it manufactures and distributes more than 3,000 exhaust products for heavy- and medium-duty trucks as well as school buses and pickups. To ensure its clamps create an effective seal at each
joint, Grand Rock also puts four relief slots on the flared end of its pipes.

The nitty gritty

Grand Rock begins with 20 ft. and 24 ft. lengths of steel tube, ranging from 1 1⁄2-in. diameter to 10-in. diameter. Most of the material is 16 gauge or 14 gauge, but the company also works with 14 gauge, grade 304 stainless steel.

Production is organized around nine cells, each with its own band saws, deburring and bending equipment and a punch, among other things.

“We cut blanks in two different ways,” says Bill Stoneman, Grand Rock’s vice president of sales and marketing. “Often we use a high-speed tube cutter and cut a whole bunch of blanks.” For short runs or custom work, blanks are cut as needed.

Each pipe is bent, then trimmed to length as needed and deburred. Some of the components are then welded together, but for others, that is the point at which one end is expanded to form the larger part of a pipe-to-pipe push fit connection. For ease of assembly, the expanded end is made slightly larger than the pipe it slips over. Relief slots are then punched into the expanded end to allow the clamp to make a tight, effective seal.

For about a decade the company has been using Multicyl punches to make the slots. “We have the Multicyl air-over-hydraulic cylinder, with their tooling and their punches, hooked up to one of their C-frames,” Stoneman says.

One feature Stoneman particularly appreciates is the system’s simplicity. “Air runs to the cylinder and into the regulator, then down to the foot pedal,” he says. “When you push the pedal, it releases the air which goes back to the cylinder and it works. How much simpler can you get?”

The punching hardware

Multicyl Inc. is based in Bolton, Ontario, and offers fast-operating, high-power cylinders. The cylinder stroke has two stages, an air portion and a hydraulic portion.  The air portion drives the cylinder quickly down into position. Then the hydraulics are engaged for the power portion. For example, out of a 2-in. overall stroke the air portion may be 1 1⁄2 in. and the other 1⁄2 in.  would be the hydraulic, or power, stroke.  The resulting cylinder runs quickly and simply, like an air cylinder, but provides the power of a hydraulic cylinder.

The cylinder’s hydraulic portion, which acts like an intensifier in delivering the power stroke, is self-contained and so avoids the messiness often associated with hydraulic systems. Additionally, the punching force is much greater than what a similarly sized air cylinder delivers. These versatile cylinders also are relatively inexpensive.

Multicyl’s standard cylinders range from 2 1⁄2 ton to 40 ton capacity and have overall strokes from 5⁄8 in. to 4 in. Both single-acting and double-acting models are available, but it’s the different configuration possibilities that make this such a handy tool. The company’s standard C-frame is typically bench mounted, but often multiple units are positioned to simultaneously punch a single workpiece. For many installations Multicyl develops, or assists in developing, appropriate configurations based on customer needs.

Safety is another attractive aspect of air-over-hydraulic cylinder technology. For example, because the stroke self-
adjusts, operators punching flat material, like sheet metal, can position a cylinder such that no guards are required for OSHA compliance.

Low maintenance, too

After using Multicyl punches for years, Stoneman observes, “We’re sold on these things. They’re brutally reliable, ridiculously simple to operate, and they last forever.” And especially because he’s been with Grand Rock since 1976, he would be the one to know.

“We’re doing a lot more lean manufacturing now,” Stoneman says, “so we don’t stock as much, but we build a lot more quickly.” The cell setup for production has been beneficial in that regard. In times past the company would do large batches, producing hundreds of the same thing then holding it in inventory until it was needed. But now, Stoneman says, “we’re making 10s and 20s and doing it three times a day.” Having an economical and reliable punch in each cell helps prevent production bottlenecks.

“We make a lot of parts, so these things cycle quite a bit,” Stoneman says. “We bought a replacement die for one of them, years ago, and it’s still sitting in the maintenance shed. They just don’t wear out.” FFJ

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