Flexible Tool Completes Automated Finishing Cell

April 4, 2006
Programmable robotic deburring brings flexibility and consistency, for more efficient automated finishing processes

Automating finishing processes is extremely difficult to accomplish with the required degree of quality," according to Charlie Young, manager for advanced automation at Hammond/Roto-Finish, in Kalamazoo, MI. Hammond Roto-Finish designs turnkey finishing system for customers in a range of industries, with a wide variety of finishing requirements and production capacity needs. "Often, the complexity of the part, and the robot's limitation to generate a path exactly equivalent to the part edge, make it difficult for the finishing operations to meet overall quality goals," Young continued.

"We develop totally automated, self-contained metals finishing cells for a wide variety of industries, and we are constantly looking for new systems and components that will improve efficiency," Young says, by way of explaining Hammond/Roto-Finish's adoption of the newly patented robotic deburring tool, Flexdeburr, developed by ATI Industrial Automation. "We feel we have found the ultimate solution for automating the finishing process. Using an extremely flexible finishing tool allows us to solve several design and robotic training challenges in the work cell."

Hammond Roto-Finish offers different types of automatic systems, robotic systems, cylindrical systems, flat finishers, and a wide assortment of heads that can be customized to suit a specific finishing process. The company has provided finishing equipment to automotive, aircraft, aerospace, medical goods, sporting equipment, decorative hardware, jewelry, musical instrument, and household appliance manufacturers.

The systems are developed with some common technologies, but each one is specialized for its installation. Young explains that the "flexibility and consistency of the finishing tool will allow us to design more efficient cells with a smaller footprint. Also, the system's robot is quicker and easier to train (program) with a more forgiving finishing tool."

He says that the radially compliant Flexdebur device mimics a manual finishing process, but is more forgiving - allowing directional changes quickly and easily. "The inherent compliance at the tip saves robot programming time," says Young. "Our programmers can program fewer path points since the tool compliance will accommodate deviations between the robot path and the part edge, i.e. the robot path does not have to precisely follow the part edge. Programming savings are multiplied in applications where multiple passes are necessary in order to achieve a desired finish."

"For example," Young continues, "our programming time has been reduced to a few weeks, which is extremely important when you consider a total system - from design to manufacture, to run-off, to installation, to run-off, to operator training - may take up to six months or longer. Any step in the process that can save time will be investigated."

Programming the robot path is done by mounting either a dowel pin of the same diameter as the cutting tool, or a pointed teaching tool, in place of the actual cutting tool. The robot is manually moved to a point where the dowel or pointed tool is touching the edge of a finished part, and the point is recorded. This is repeated at intervals along the edge of the part and the robot controller uses these recorded points to define the path to be followed. Also, the cutting force is adjustable "on-the-fly," so the programmer may increase the cutting force in areas having larger burrs or where more material must be removed.

Also, programming robot movements depends on the complexity of the part, and complex parts require significant programming time to achieve acceptable robot paths.

ATI developed Flexdeburr to satisfy a wider range of automated finishing operations. It is a rugged, high-speed, air-turbine-driven tool for finishing aluminum, steel, etc., even in tough-to-reach places. While spinning at high speeds, the lightweight, rotary tool has radial compliance supported by air pressure applied to the shaft, allowing the tool to perform consistently on irregular part patterns. The "floating" motor and spindle arrangement provides +/-0.31-inch (8 mm) of radial compliance, and maintains a constant finishing force.

The tool has a rigid outer housing and an internal motor/spindle assembly that provides the compliance. The pneumatic motor/spindle assembly is mounted on a pivot bearing mounted to the tool housing. This allows the pneumatic motor to move with the pivot bearing independently of the housing. The radial "compliance field" is created by a ring of small pneumatic pistons located near the front of the tool housing. The compliance force can be exerted on the spindle/tool in any direction (360°) radially from the tool. Parts finishing can be as fast as 1 to 3 in./sec. on hard materials; 3 to 12 in./sec. on soft materials. The finishing tool spins at a constant 40,000 rpm when in operation.

The pneumatically-driven tool has one air line to spin the cutting file, and a second to apply force radially to the motor/spindle assembly. Regulated air pressure on the floating head provides the constant force needed to produce a good quality chamfer. The tool is extremely light in order to "hug" the workpiece edge at a constant force - even as the robot moves as fast as 12 in./sec. along the edge of the part. Additionally, the long, thin envelope of the "working" end of Flexdeburr allows finishing in tight, deep, and generally hard-to-reach places.

Flexdeburr satisfies nearly all robotic and automated finishing applications. Its "floating" motor and spindle arrangement provides the finishing tip's radial compliance to perform consistently on irregular part patterns.

The Flexdeburr, mounted to a robot or CNC machine, has a quiet air turbine motor that requires clean, dry, filtered, non-lubricated air that can be directly vented into the workplace. The finishing tool uses two air connections; one at 90 psi to spin the cutting file, and a second at 60 psi to apply the radial force.

The motor's internal governor maintains a high spindle speed of 40,000 rpm and the compliance force is 1.5-9.5 lb at air supply pressure of 5-60 psi. The entire tool weighs only 2.6 lb and has an operating temperature of 41° to 95°F. The tool uses standard tungsten-carbide industrial bits that allow for adaptation to changing assembly lines and part requirements. Also, the bits can be changed easily from one operation to the next.