RUSH TO BRUSH

Small parts that require deburring, edge blending or other surface finishing operations can present particular production challenges to manufacturers. Production is often taken off-stream, where hand-held tools are necessary to perform the intricate secondary finishing operations many of these components require.

This action frequently results in reduced productivity and inconsistent product quality. Even in instances where the process is fully automated, specifying the appropriate finishing brush for the application plays an integral role in improving the tool?s overall performance and life span.

A miniature deburring brush can solve both the productivity and quality challenges involved when manufacturing parts of various small sizes, contours and materials. These tools are generally best suited to address tight tolerances, edge blending, deburring and other finishing requirements that have a direct impact on overall functionality.

Precision Planting, Inc. (Tremont, IL), an industry leader in agricultural seed planting equipment, manufactures a variety of systems that are designed to solve exact seed spacing and placement issues. Because the accuracy of seed placement is heavily reliant on precise timing, it is critical that the surface finish of the seed ejection component be void of even the slightest variations and irregularities.

"One of our newest systems has tubes that are injection molded, and we had great concern about removing the residual flashing that was created by the molding process," notes Precision Planting engineer Derek Sauder. "It may only be only .002 in to .005 in thick. While not very long, the ridge of the flashing is rough and would cause problems in the performance of our part."

Sauder explains that the component is used in planting seed for corn, beans and other crops. In operation, the part has a vacuum applied to one side, and the other side contains the seed. "The seed is held by vacuum against a hole in the part," he says. "If we didn?t remove the flashing, it may grab onto the seed and cause it not to release properly.

In the initial phase of development, the part would not perform without the flashing being removed. Getting the seeds to accurately release was only achieved when an abrasive nylon brush from Brush Research Manufacturing (Los Angeles, CA) was incorporated into the manufacturing process. "We knew the miniature nylon brush was necessary," remarks Sauder. "It worked quite well, so I was confident that we had a good solution. We had tried the injection molded piece without the nylon brush, and it didn?t work as well."

Sauder adds that while the nylon clean-out brush does not speed up part production, it is automated and therefore highly efficient. "It has allowed our products to become the most accurate planting equipment in the market," he says. "Our product is well-known and has a fine reputation in the marketplace. And this process helps us attain that. It is economical and gives us good results."

The application will certainly affect the choice of miniature brushes and includes variables such as contours required, the type of material, and the amount of material to be removed. Other factors that apply to brushes used in automated applications include rpm of the machine tool, feed rates, and optimum wear-life of the brushes.

There are several types of miniature brushes available today that vary not just in size, but also in filament type. Carbon steel, stainless steel, brass, nylon and abrasive filled nylon are commonly used. Abrasive-filled nylon can contain silicon carbide, aluminum oxide or diamond abrasive.

GENERAL PARAMETERS

"Overall, the specification of a brush involves the task at hand (e.g., deburring or surface finishing), the speed at which it must be accomplished, the size of the feature being worked, and the material the brush is working on," states Mike Miller of Brush Research Manufacturing.

Miller explains that there are miniature brushes for bores ranging in size from as small as 0.024 in and varying in lengths and tip styles. Filaments options include nylon, carbon steel, stainless steel, brass and abrasive filled nylon. One new brush is filled with diamond abrasive nylon and will cut harder materials, deburr faster and last longer, providing a unique level of flexibility and longer tool life.

Another brush, the Flex-Hone®, is available in miniature sizes as small as 4 mm (0.156 in). Sometimes referred to as the "dingleberry hone," this ball-style hone features globules or balls of abrasive grit permanently laminated to the end of nylon filaments.

"For any application with a bore size of 4 mm or greater, this is almost always the preferred tool," says Miller. "One reason is that it is more abrasive at the point of attack, whereas an abrasive nylon brush will have abrasive grit particles interspersed throughout the filament. The ball-style hone is about 95 percent pure grain abrasive right at the point of need, so it really does an effective job."

Miller adds that the ball-style hone is not recommended for working on threads, whereas abrasive nylon is very effective for removing burrs and polishing thread peaks and flank angles, particularly in tapped aluminum holes. "This type of operation can be automated," Miller says, "although sizes 1/16 in and smaller may best be cleaned up by hand with an abrasive nylon or stainless steel brush. Small diameter brushes are not usually rotated under power because the brush stem wires are very fine and may bend. However, there is a series of holders and pin vises that is commercially available to grip the small diameter brushes."

Abrasive nylon brushes have gained in popularity. To begin with, nylon is not reactive, Miller explains, so the brush will not impart carbon impurities onto the surface of the product. Nylon doesn?t oxidize, and therefore doesn?t rust or cause rust. Safety is another issue because metal filaments can develop wire fatigue over a period of time. If you are using a wire brush incorrectly, that could happen in a short period of time.

ON THE OTHER HAND

Sizes that are 1/16 in and smaller clean up best by hand, using an abrasive nylon or stainless steel brush. Small diameter brushes are not usually rotated under power because the brush stem wires are very fine and may bend, though there are holders and pin vises available to grip small diameter brushes.

Grit selection is another important variable that may require supplier technical support. For example, products that have very fine finish requirements may benefit from brushes with finer grit material. Hard materials such as ceramics and glass may require diamond grit.

"That is not to discount the effectiveness of metal brush filaments," Miller adds. "One popular miniature all-stainless steel brush features stainless steel filaments and a stainless steel stem. It is available in diameters down to 0.024 in and is ideal for clearing chips out of holes or clearing protruding and break-through burrs."

"It depends on the surface finish spec or whether they have an issue where they need a little more aggressive brush for more deburring power," Miller advises. "Sometimes you have a combination of needs such as cross-hole deburring and achieving a fine surface finish. It is not always best to try to accomplish both with the same brush. You may want to use a coarser brush first to remove the burr and a second, finer brush to achieve the required finish or contour."

GETTING HELP WITH SPECS

According to Miller, customers may have several concerns about specifying brushes. Whether to automate the brush operation is a primary concern, although it quickly becomes obvious to most users that automating a process and avoiding secondary operations are significant benefits in terms of both productivity and consistency.

"With a very broad selection of miniature brushes available, there are customers who have a lot of questions about the operating parameters, especially the first time," he says. "So we encourage them to get assistance. For example, we have a surface-finishing laboratory that we encourage customers to send their parts in question to. We analyze the parts and then select the tools we think will provide the best solution. Then we run tests and return the parts to them with our best recommendations regarding the selection of the tool, the operating parameters, and surface finishing measurements, if required."

Precision Planting, Inc. 23207 Townline Road, Tremont, IL 61568, 309-925-5050, Fax: 309-925-5029, www.precisionplanting.com.

Brush Research Manufacturing Company, Inc., 4642 East Floral Drive, Los Angeles, CA 90022, 323-261-2193, Fax: 323-268-6587, www.brushresearch.com.