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Smoothing edges

By Lauren Duensing

From tough burrs to automated equipment, Greg Nykiel, product development specialist at Timesavers LLC, Maple Grove, Minnesota, talks flat part deburring.

FFJ 1217 face leadDecember 2017 - Q: Please define a burr and explain how burrs are formed.

Greg Nykiel: A burr is a raised edge or small piece of material that’s still attached to a workpiece after a modification process. A burr can be vertical (above the surface of the material), horizontal (even/below the surface but protruding from an edge) or both. Common burrs come from cutting material with processes such as oxy-fuel, plasma, laser, waterjet, punch and saw.

Q: Why does the definition of a deburred part vary?

Nykiel: Unfortunately, there are no all-encompassing industry standards for deburred parts. Tests help to accept or reject a part—like the surgical glove and nylon tests—but usually the procedure and criteria are developed internally. Historically, a flat part was considered deburred after it was run through a wide belt sander, which removed the vertical burr but created a horizontal burr that left edges quite sharp. Requirements have been trending toward the “soften edges” level of deburring to address this. But who determines what level of sharp is acceptable, and how can you communicate that to internal or external customers?

Q: I want to automate my deburring process. How can I justify the investment?

Nykiel: First, operator safety is greatly improved by keeping employees out of the work zone, and they also can avoid repetitive motion injuries common with hand processing. Part rejections will diminish and part flow will be more predictable as parts are deburred at a constant, repeatable rate. Abrasives cost more but last much longer than hand tools; most customers see a steep decrease in total abrasive spending. Overall value rises through higher capacity, lower cost per part and less rework.

Q: How do I choose a machine to automate my deburring process?

Nykiel: Many factors affect machine selection: duty cycle, throughput, deburring quality, part geometry/size, material type, part constraints (surface finish, timesaverheat restrictions, warping), and, obviously, budget. After reviewing these parameters, machine configuration can be dialed in to meet these needs: manual processing, vibratory, abrasive belt, straight/rotary/cup brush, disc, cross-belt, wet/dry processing, abrasive selection and head/feed speeds. Have equipment manufacturers propose a machine for your specific needs and ask them to process your samples. This allows the manufacturer some trial-and-error testing to dial in a process/configuration, as well as showing exactly how that machine will perform. Samples can then be presented to your internal and external customers for feedback on which ones meet their standards.

Q: Can machines process small parts?

Nykiel: Processing small parts is commonly performed by a vibratory tub or centrifugal barrel finishing machine. These processes are slow, loud, dirty and overall quite inefficient, but they often are the only options that can meet customer requirements. Feed-through machines can process small parts, but capabilities vary greatly from machine to machine. Typically, the smallest part that can be processed is the distance between hold-down rolls (between 4 in. and 12 in.). To run parts smaller than this, some machines can be equipped with vacuum hold-down, a magnetic bed or a special conveyor belt. Other solutions to handle small parts can be as simple as leaving the parts tabbed/nested and running the entire sheet or designing a custom fixture.

Q: What are the toughest burrs and how do you handle them?

Nykiel: The two types of burrs that I find most challenging are from worn-out punching dies and laser-cut stainless steel with heavy dross. When a die/shear is worn out or uses improper tolerances for the material being cut, the cut edges tend to be drawn or stretched until the material breaks—instead of a clean break. Stretching leaves a burr that is thick at the surface and tapers off into a sharp peak. The entire burr needs to be ground flush with the surrounding surface. Laser cutting creates burr formed when  melted metal solidifies and welds itself to the edge of the material, becoming heat treated in the process. These burrs can be in the shape of little round beads or long jagged serrations and require heavy grinding.  FFJ

Greg Nykiel specializes in application knowledge, product management and strategies to help customers solve problems and achieve an optimal finished part.

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