Automated assembly processes usually make a lot of sense from a cost standpoint-but not always. Some short-run products simply can't justify the upfront costs of creating machined robotics fixturing. CMP Advanced Mechanical Solutions (Chateaguay, Quebec) recently found a way around this automation barrier as it relates to the robotic welding of electronics enclosures.

Instead of machining its welding fixtures, CMP has begun to turn them out with a computer-controlled laser cutting system. Working from the 3D models of the metal enclosures, the company's engineers first create a related model of the welding jigs and fixtures. This model, in turn, drives the company's 4000-Watt Amada laser, which slices out the individual fixture components. These laser-cut components quickly snap together into finished welding fixtures, ready for deployment on the robotic welding line. The time needed to create complex fixturing falls "from weeks to days or even hours," says Steve Zimmermann, CMP's chief executive.

The resulting cost reduction can be significant. Zimmerman estimates that the new laser method reduces fixturing costs by about 50 percent. He attributes the savings to four factors: For one, laser cutting has an inherent advantage in speed. For another, it makes more efficient use of materials and can create fixtures from plate stock. The laser cutting also reduces the hefty labor costs associated with the highly skilled machinists who do fixture work. Finally, laser cutting enables the snap-together fixture designs that need less assembly work and interface with the robots more quickly.

The savings in fixturing costs ultimately translate to an overall enclosure cost reduction in the neighborhood of 30 percent, Zimmermann says. This savings would apply to a variety of jobs whose production volumes once precluded automated welding. With the laser fixturing method, jobs measured in the tens of units rather than hundreds or thousands can take advantage of robotic welding's productivity advantage-not to mention its more consistent weld lines and improved dimensional tolerances. And even jobs that will do have the product volumes to support robotic welding can benefit from the laser cut fixtures. These jobs often start off with machined, manually assembled enclosures until the product's production ramps up, Zimmermann notes. Laser cutting can cut out that middle step. "We can skip the machining and go right to automated production from the beginning," says Zimmerman.

The first job to use CMP's laser-cut fixtures, an enclosure for an automatic teller machine, whose initial production run came to 50 units. And Zimmermann reports the method is currently under consideration for a telecom enclosure that requires just a ten-unit run.
CMP's laser cutting and automated welding lines can accommodate enclosures up to 36 x 36 x 96 inches. For more information, go to www.cmpdifference.com