Thieves are shameless in their pursuit catalytic converters (they're after the precious metal contents, especially platinum), which has resulted in the development of a number of defensive devices aimed at preventing efforts to cut the “cats” away from a vehicle's exhaust system.

The emissions control devices use platinum and palladium as oxidizing catalysts to remove several pollutants from a gasoline engine's exhaust stream. Platinum, the more expensive metal, sold for $600/ounce five years ago. In 2008 the price was over $2,000/ounce — far more valuable than gold.

The crime is simple, and too common: a thief slips under a vehicle, often a SUV or truck with ample clearance and, with a reciprocating saw, slices through the exhaust pipe on either end of the catalytic converter, freeing it for removal. The operation takes about 10 seconds, and may yield the criminal $50 to $250, or more, from a scrap yard or recycler.

One of the most affordable and foolproof designs to combat catcon theft is a stainless steel device known as the CatClamp^™ (www.catclamp.com), an innovation manufactured by American Welding Inc. (www.americanweldinginc.com) — a welding and fabricating operation in Toledo, OH.

“Thieves simply find that it's too hard to cut through the CatClamp's 300-series stainless steel,” explains American Welding president Jim Dusa. “This grade of metal is often cut by industrial lasers, so using a reciprocating saw would take too long and be too noisy. When a thief sees our device, they know they had better move on.”

Although the losses from cat thefts and related exhaust system damage often range into the thousands of dollars, Dusa says he realized early on that his theft deterrent needed to be very high in quality, yet still affordable.

“I felt that the product should sell for a starting price as low as $250,” he explains, “and should be sold in a kit that could be installed by the purchaser. Yet the 300-Series stainless was a key material, so we had to be very careful with manufacturing costs.”

Investment casting provided the ideal process for making a high-quality clamp that was not only very hard and durable, but was also affordable, even in smaller quantities.

When launched in 2007, the CatClamp was fabricated from laser-cut stainless steel that was welded and machined. Because Dusa's firm had many years of metal fabrication and finishing experience, the finished product looked very professional and certainly worth the money it cost.

Still, Dusa was not satisfied that he was using the most efficient manufacturing technology and it was a seemingly impossible challenge to make the product available for $250, due especially to the high costs of welding and machining.

In order to contain costs and yet produce the highest quality, Dusa decided to consider investment casting the CatClamp.

Investment casting produces specialty shapes, beginning with a custom-designed die. Into this die, wax is injected to create the patterns needed for the final casting. The patterns are attached to a central wax tree (“sprue”), creating an assembly, or mold. The sprue is topped by a fill cup, into which molten metal is poured.

The wax assembly is dipped into a ceramic slurry as many times as necessary to create a shell of a desired thickness, with a layer of zircon (or other fine sand) on top of each ceramic layer.

After the shell is created to specification, the wax is removed by autoclaving (which gives the process its common name, “lost wax casting”), leaving an impression of the casting to be filled with metal. The ceramic shells are heated (to temper them for casting), and the metal is poured to fill each part of the assembly up to the sprue cup. After cooling, the mold and shell are removed (for example, by water blasting) and the castings are later removed from the sprue assembly.

Dusa says he knew the reputation of Rimer Enterprises (www.rimerinc.com), a nearby investment casting specialist that produces castings for a range of applications — railroad equipment to food processing — mostly in carbon or stainless steels, bronze, brass or aluminum.

“I was very confident that Rimer could do a great job investment casting our product,” Dusa explains. “Equally important, they were known for advanced design and engineering capabilities, which meant I could work with them to see if investment casting was the best way to make the CatClamp, and then fine-tune it from there.”

The device is designed to envelop a catalytic converter in a cage-like system. Two alloy collars lock at both ends of the converter, and a special aircraft cable runs between the collars, forming the cage. That same cable locks the whole unit to the vehicle frame. The CatClamp can be installed with one specially designed tool in 20-30 minutes without drilling, cutting, or welding.

Dusa explains that the design process was easier than he anticipated, with Rimer's engineers using CAD illustrations of how they thought the pieces should be made, in collaboration with his own design work. “That all went smoothly and very efficiently,” he says. “I believe that we had our first finished products in about three weeks.”

Dusa adds that this process proved to be faster and much less expensive than other metal casting technologies, and the finished components were virtually perfect, requiring little if any machining.

Investment casting can achieve remarkable detail and tolerances, but the challenge in making the CatClamp was to keep the unit affordable. Dusa and Rimer claim they achieved the price point they hoped to match.

Also, using investment casting allows the design to include alloys that make the part much stronger than it otherwise would be; the unitary design is stronger than a fabrication would be, and more economical to produce. More recently, American Welding and Rimer Enterprises have simplified the design even further, so fewer models are needed to fit most vehicles. Today there are seven variations of the CatClamp, three of which will fit about 80% of all vehicles.