Flexible tool enables robotic finishing: a radially-compliant deburring device makes robotic finishing a reality with its ability to mimic manual finishing techniques with a floating motor and spindle design.

"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," advises Charlie Young, manager, Advanced Automation for Hammond/Roto-Finish (Kalamazoo, MI). "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."

"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," says Young discussing his company's recent application of a patent-pending robotic finishing tool, Flexdeburr[TM], developed by ATI Industrial Automation (Apex, NC).

Automated Finishing Cells

Hammond Roto-Finish is a turnkey solution house for a finishing system that meets a wide variety of finishing requirements as well as production capacity needs. It provides finishing equipment for the automotive, aircraft, aerospace, medical goods, sporting equipment, decorative hardware, jewelry, musical instrument, and household appliance industries. Young explains, "Our systems are very specialized and, while we may use the same technology, i.e. industrial robots, from industry to industry, we consider all of our systems custom made. And, the overall goal is to improve production quality and efficiency.

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"Automating finishing operations is extremely difficult to accomplish with the required degree of quality," adds Young. "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. When we first tried ATI's radially-compliant Flexdeburr device we were pleasantly surprised how closely it mimicked the manual finishing operation. Also, the device is more forgiving, allowing us to change directions quicker and easier. This is especially important during the robot training period,"

"The inherent compliance at the tip saves robot programming time. 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," offers Young, "our programming time has been reduced to a few weeks which is extremely important when you consider a total system from design ... to operator training may take up to six months or longer. Any step in the process that can save time will be investigated."

Robot Programming

Programming the robot path is achieved 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 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.

The cutting force is also adjustable "on-the-fly" allowing the programmer to increase the cutting force in areas having larger burrs or where more material must be removed.

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

High-Speed Air-Turbine

ATI's Flexdeburr, was developed to satisfy a wider range of automated finishing operations. It is a robust, high-speed, air-turbine-driven tool for finishing aluminum, plastic, steel, etc., even in tough to reach places.

While spinning at high speeds, the 2.6 lb. 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" 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, allowing the pneumatic motor to move with the pivot bearing independently of the housing.

Compliance Field

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[degrees]) radially from the tool. Parts finishing can be as fast as 1" - 3" per second on hard materials; 3" - 12" per second (ips) on soft materials. The finishing tool spins at a constant 40,000 rpm when in operation.

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The pneumatically-driven tool has one 90 psi air line to spin the cutting file, and a second 60 psi air line 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 allowing it to hug the workpiece edge at a constant force even as the robot moves as fast as 12 ips 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.

The tool uses standard tungsten-carbide industrial bits that allow for adaptation to changing assembly lines and part requirements. Also, the bits can be easily changed from one operation to the next. ATI Industrial Automation

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