Page 17 - MetalForming December 2019

Carbon-fiber end effectors reduce cycle time while lengthening the lives of robots.
ble, increasing its weight even more, yet still not achieving a comparable stiffness to the carbon fiber.
“Conforming to stan- dard, interchangeable sizes, carbon fiber was rel- atively simple to integrate into the existing end effec- tors by simply replacing the tubing, based upon a stan- dard 2.5-in.-dia. main- frame 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 han- dle additional part weight, achieving a 10 to 15-per- cent increase in production weight. Another advantage was a 6-second reduction in cycle time, representing an overall improvement of 15 percent And, part con- sistency 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, espe- cially when changing tools. “With alu- minum, 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 recover- ing 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
increased equipment life results in an attractive return on investment, says Zdenek Posvar, Bilsing’s account man- ager 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 man- ufacturing scenarios?
Garant points to a Tier One auto- motive 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 compo- nent 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 oper- ators during changeover.”
Garant says that a switch to carbon fiber addressed these problems by pro- viding a lighter, stiffer alternative to the aluminum tooling. In order to achieve the same strength of carbon fiber, the wall thickness of the alu- minum tubing would have had to dou-
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