Part-Handling Choices for Advancing Automation

December 1, 2019

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This comparison of steel, aluminium and carbon fiber automotive cross bars (photo) shows carbon fiber as having a slightly higher stiffness profile (lower deflection) than steel and significantly higher stiffness than aluminium.

When talking of automation advancements in manufacturing circles, software, controls and robotics often take center stage. However, how about the tooling necessary for transferring parts to and from forming presses?

The material from which such tooling is made can be a game-changer when it comes to automating part flow, say Tom Garant, general manager of Bilsing North America, a Roseville, MI-based provider of carbon fiber tooling solutions. Garant says such options as carbon fiber crossbar beams, loading and unloading beams, destacking beams, panel loading t-booms, and tooling supports are lighter, stiffer and vibrate less than tooling made of steel and aluminum, resulting in improved production rates and longer life for the robot “with lighter end effectors saving on overall wear and tear.”

While automotive companies such as Jaguar and Chrysler accept that the carbon fiber design is more expensive than aluminum and steel, they recognize that more parts/min. and increased equipment life results in an attractive return on investment, says Zdenek Posvar, Bilsing’s account manager at Compotech (Czech Republic), the company’s technology partner in carbon fiber solutions. “Customers require faster run times and with the carbon fiber they achieve that because of the material’s greater stiffness and lower deflection, resulting in less part vibration,” he says.

Why is that important? “Imagine a welding fixture,” explains Garant. “When the robot comes into the station with the parts, typically there’s some wait time due to waiting on the tool to settle and stop vibrating. With carbon fiber, settling is much faster.” (See Crossbar Profiles.)

So how does greater stiffness and lower deflection affect common manufacturing scenarios?

Garant points to a Tier One automotive supplier that manufactures a tubular part weighing about 20 lb. for an engine cradle. The production line features a hydraulic preform press, hydroforming press, five integrated robots and baseline tooling constructed of aluminum with a rotation device mounted on the leading end of the end effector. Two blanks were handled by a common tool; the first was picked and placed for cleaning and lubrication and the second was placed into the die cavity following lubrication.

“Although it was a two-cavity die, the robot could only load one component at a time due to the combined weight of the parts and end effector,” says Garant. “While one part was set in a nesting station, the robot would select the second part for lube using a separate gripper. The weight of the tooling also affected robot efficiency and became cumbersome for the operators during changeover.”

Carbon-fiber end effectors reduce cycle time while lengthening the lives of robots.

Garant says that a switch to carbon fiber addressed these problems by providing a lighter, stiffer alternative to the aluminum tooling. In order to achieve the same strength of carbon fiber, the wall thickness of the aluminum tubing would have had to double, increasing its weight even more, yet still not achieving a comparable stiffness to the carbon fiber.

“Conforming to standard, interchangeable sizes, carbon fiber was relatively simple to integrate into the existing end effectors by simply replacing the tubing, based upon a standard 2.5-in.-dia. mainframe with 0.30-in. wall and 1 in. for extensions or cross booms,” Garant says. “Because carbon fiber made the overall tooling lighter, the robot can handle additional part weight, achieving a 10 to 15-percent increase in production weight. Another advantage was a 6-second reduction in cycle time, representing an overall improvement of 15 percent And, part consistency and process repeatability improved due to the harmonic stability of the carbon fiber tooling, creating less bounce on the robotics.”

Further process improvements included increased ergonomics, especially when changing tools. “With aluminum, changing one end effector was a two-person job,” says Garant. “With carbon fiber, two workers help to guide the end effector to its nest, but it’s light enough for one person to carry. Carbon fiber is easier to guide into place because of its rigidity, and it’s less likely to damage magnets and other parts during changeover.”

Another benefit, says Garant, was a reduction in downtime when recovering from a robot crash. Aluminum is prone to breakage, so in the event of a crash, it would break or bend the tool, not only affecting the main part, but also other parts. “Should carbon fiber break, there are no bend issues and little clean up,” he says. “Typically, one half snaps off while the other half is still held in the clamp and there is no dust as with aluminum.” MF

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See also: Bilsing Automation North America