News | July 6, 2006

Robotics Deburring: Taking The Edge Off The Manufacturing Process

Intro
In today's aerospace industry, manufacturing engineers are always looking for new ways to produce high quality parts and components in a more cost-effective manner. In recent decades, quantum leaps have been made in machining, and yet the ancillary process of deburring has received relatively little attention. In some manufacturing processes, precision-machined components are still shuttled from state-of-the-art CNC (computer numerical control) machining centers to special departments that manually deburr with hand files and power-tool-driven abrasive products.

Automated deburring methods, including robotic cells utilizing specially-designed nylon abrasive filament brushes, are being integrated into the manufacturing processes. These methods are replacing repetitive and potentially harmful hand operations, providing consistent quality, improving productivity, shortening cycle times, generating precise edge radii, and lowering finishing costs.

Robotic deburring achieves these benefits for three reasons:

  • Automation versus manual processes
  • Nylon Abrasive Filaments brushes versus less compliant media
  • Integration into manufacturing processes versus separate "batch-and-queue" processing

Deburring is a critical step in the aerospace manufacturing. For example, the components that make up a turbine engine are subjected to extremely high temperatures and cycles.

Consequently, all the edges must be completely defect-free, with a generous radius, to reduce fatigue and prevent any type of crack nucleation. The machining operation or CNC grounding process that shapes the component produces burrs and sharp edges. The deburring process is intended to remove these imperfections and produce specific edge radii.

"For aerospace applications, the deburring and edge finishing process must be performed within very stringent dimensional tolerances. For a turbine blade, for example, it is necessary to generate an edge radius of between fifteen and thirty thousands of an inch," said Rick Morgan, of Applied Control Technology, of Bristol, CT, a manufacturer of automated deburring equipment. "For each new application, we rely on the test lab at Weiler Corporation to assist us in developing the optimal process for automated deburring of the particular part. We must demonstrate the ability to not only meet the dimensional tolerances but also the cycle time specified for the manufacturing process. Working with Weiler Corp, we have been able to prove again and again that automated deburring is superior to manual deburring in consistently meeting the exacting quality specifications of the aerospace industry."

Manual deburring can degrade the quality of parts that had been successfully created by upstream machining and grinding processes. Since manual deburring is at the end of the manufacturing process, part-destroying errors in deburring can be extremely expensive. Scrapping a raw casting due to dimensional problems is not nearly as costly as scrapping a machined part that has been subjected to "Friday afternoon deburring."

In a robotic cell, there are two different ways to accomplish the deburring process: by manipulating the brush or by manipulating the piece, typically depending on the size of the part. Turbine blades and vanes, for example, are often picked up by a robot and moved to the brushing media. Because of their larger size, turbine disks are usually fixed in space, with the robot taking the brushing media to the part. A robotic cell can reproduce the exact movements of a human being, and can do it consistently all day long, without interruption. This ability to precisely repeat processes for extended periods of time translates into a faster, more efficient deburring process.

Ergonomic problems associated with repetitive work, such as carpal-tunnel syndrome, are also driving users away from manual deburring. Further justification is created by the difficulty of attracting and retaining competent manufacturing personnel who will reliably perform manual deburring, a job that can be perceived as dirty and demeaning.

Nylon Abrasive Filament Brushes
Nylon Abrasive Filament (NAF) brushes are ideally suited to robotic deburring and offer significant advantages over alternative abrasive media. NAF brushes provide superior compliancy, that is, the ability to absorb different part shapes into the face of the wheel, an important characteristic of aerospace manufacturing which typically involves parts with unusual geometry.

The compliance of NAF brushes accommodates small errors in part positioning and slight variations in part or burr sizes, making them good candidates for robotic and automated workstations. Typically, positioning within 0.020" of the ideal location will produce acceptable results. Although this window of acceptability varies with brush size and application, most operating windows are large and do not require significant robotic programming time to achieve.

Another advantage of NAF brushes is that part dimensions are not changed. The compliant quality of NAF brushes provides selective aggression focused toward part edges. Although the filaments in a nylon abrasive brush act aggressively when applied to an edge, their aggression diminishes on flat surfaces. As a result, they refine surface finishes without measurably changing part dimensions, making them preferable to many aggressive abrasive products.

Because NAF brushes are filamentary in nature, they do not function like grinding wheels or coated abrasive products. The abrasive grits are contained within the nylon carrier. Therefore, during use, sharp new abrasive grits are constantly being exposed as nylon wears against the work surface. This provides consistent brushing action throughout the unit's life.

Integration
Manual deburring typically involves "batch-and-queue" production processes. The drive toward "lean manufacturing" and "single-part flow" has highlighted the expense and inefficiency of such processes. The existence of secondary and tertiary processes is a major contributor to manufacturing costs relating to lead time and WIP (work in progress). Eliminating these operations can improve customer responsiveness and help reduce the financial burdens created by long manufacturing cycles.

Robotic deburring can be fully integrated with upstream processes in single part flow cells. This creates single point accountability for the combined process and encourages overall optimization of quality and productivity.

Summary
The compliance of nylon abrasive filament brushes makes them ideal for robotic applications for manufacturers of aerospace components. It is essentially impossible to damage a part through inaccurate programming or part fixturing. As lean manufacturing philosophies continue to demonstrate their merit, manufacturers are looking for opportunities to implement these ideas. The consolidation of machining and deburring operations is typically easy to implement and generates immediate financial results. Implementation assistance is readily available from the producers of nylon abrasive filament brushes.

SOURCE: Weiler Corporation