Tool automates deburring in a flash

Feb. 12, 2009
Flashing on die cast parts must be removed for operational, safety and aesthetic reasons, but how the chore is competed often comes under considerable scrutiny by manufacturing engineers and more importantly Occupational Safety and Health ...

Flashing on die cast parts must be removed for operational, safety and aesthetic reasons, but how the chore is competed often comes under considerable scrutiny by manufacturing engineers and more importantly Occupational Safety and Health Administration regulators.

TPi Arcade’s first automated deburring installation using the Flexdeburr reduced deburring operations by 90 percent and overall bench time by 60 percent.

For TPi Arcade Inc., a shop that provides a multitude of casting services and one that specializes in aluminum V-process manufacturing in Arcade, N.Y., overcoming the deburring hurdle involved a special automated tool. That tool allowed the shop to robotically remove flashing quickly and efficiently while virtually eliminating operator exposure to casting dust from manual deburring operations. The tool also slashes deburring time by half and minimizes employee involvement in the process.

TPi Arcade uses the Flexdeburr RC-660 provided by ATI Industrial Automation. The patented robotic deburring tool was designed to satisfy automated deburring applications that ATI’s Speedeburr could not perform.

Robust, high-speed, air-turbine-driven, the Flexdeburr easily deburrs aluminum, plastic, steel and more, even in tough to reach places. While spinning at high speeds, the lightweight, rotary tool has radial compliance supported by air pressure applied to its shaft, allowing the tool to perform consistently on irregular part patterns. The tool’s “pivoting” motor and spindle arrangement provides radial compliance to +/- 0.31 in. and maintains a constant deburring force.

A rigid outer housing and an internal motor/spindle assembly deliver the compliance. A pivoting bearing secured to the tool’s rear housing supports its pneumatic spindle, which allows the spindle and cutting file to articulate freely and follow a part’s profile independent of the housing.

A circular array of small pistons at the front of the tool housing creates the compliance field and makes for free spindle motion radially in any direction (360 degrees) around the tool.

Pneumatically adjustable compliance force delivers high tool stiffness, a feature that minimizes chattering, which is a common problem with robotic deburring. The tool deburrs as fast as 1 in. to 3 in. per second on hard materials and 3 in. to 12 in. per second on soft materials.

One air line spins the cutting file, and a second air line applies radial force to the motor/spindle assembly. Good quality part finishes come from constant force from regulated air pressure on the pivoting spindle.

The extremely light tool hugs workpiece edges at a constant force even as the robot moves as fast as 12 ipm along the part profile. Also, the long thin envelope of the working end of the Flexdeburr allows for deburring in tight, deep and generally hard-to-reach places.

“We have always looked for ways to implement robots to perform routine and repetitive deburring tasks,” said Tom Wittmeyer, process technician for TPi Arcade. “However, we were somewhat restricted when programming the robot. Typically, robotic programming moves the deburring tool along a path defined by discrete points, and that path may not exactly coincide with the shape or contour of the surface to be deburred due to variations in the part itself or to differences between the part edge and the exact path the robot has interpolated.”

Implementing the Flexdeburr has solved this problem, and Wittmeyer said that the tool’s pivoting motor and spindle arrangement gives radial compliance for accommodating differences between the part edge and the actual tool path.

In addition, the inherent compliance at the deburring tip saves robotprogramming time. Programmers can program fewer path points since the tool compliance will accommodate deviations between the robot path and the part profile. The robot path does not have to precisely follow the part edge. Savings in programming are gained in applications where multiple passes are necessary to achieve a desired finish.

By temporarily mounting a dowel pin the same diameter as the desired cutting tool in the spindle, shops can easily program robot paths by moving the robot to a point where the dowel touches the edge of a finished workpiece, then recording that point. This process is repeated at intervals along the part, and a small tool offset is then programmed into the robot controller to account for part profile variations.

At TPi Arcade, the aluminum V-process provides quick turnaround, high-quality castings that are ideally suited for prototyping and lowvolume applications. The process generates zero-degree drafts to reduce weight, and it minimizes post cast machining. It also generates thin wall thicknesses of 0.125 in. over large areas and 0.09 in. in small areas; tight tolerances as much as twice as accurate as sand casting; unlimited pattern life lasting as long as the part’s life; 150 Rms finishes as compared with a sand cast and 200 to 500 Rms for permanent mold; and excellent molding integrity maintaining repeatability of all casting dimensions.

Some of TPi Arcade’s jobs include engine cases, primary cases and tranny covers for Harley Davidson, alternator housings for Delphi Automotive, snow mobile drive covers for Polaris and engine oil pans for John Deere.

Wittmeyer explained that when aluminum castings come out of the V-process, there is minor flashing that needs to be removed. The shop uses the Flexdeburr RC-660 mounted in a stationary position, and a robot maneuvers the part for deburring.

“Our first installation of the Flexdeburr resulted in a 90 percent reduction in deburring operations and an overall bench time reduction of 60 percent. Also, the reduced deburring time significantly lowers employee exposure to aluminum dust and other contaminants. This initial success convinced us to look at other applications that can benefit from robotic finishing operations,” Wittmeyer said.

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