One of the more noteworthy advances in tools for in-line machine-deburring, edge radiusing, cleaning and other surface finishing applications is the abrasive nylon brush. With new advances in abrasive technology, machining-centre operators can complete surface-finishing requirements at the same time as other machining operations, thereby shortening production times, improving quality and saving on off-line finishing time and costs.

For automated applications, these brushes are densely bristled brushes and comprise abrasive yet flexible nylon filaments attached to a machine-mountable base. Each filament contains grit particles that provide deburring, cleaning, edge blending, polishing and other surface-finishing functions; and although brushes of various sizes and shapes are available, when configured for CNC or robotic applications, typically thousands of nylon filaments containing the appropriate grit are affixed in clusters to a single base. Indeed, these tools commonly replace grinders, polishing heads, chamfering tools, hand deburring and other equipment.

Eric Sun, the founder of Orange Vise Co — a machine shop and machine tool manufacturer in Union City, California — says: “The abrasive filaments work like ‘flexible files,’ conforming to workpiece contours, wiping and filing across part edges and surfaces to deliver maximum burr removal rates plus an ideal surface finish.”

High-quality abrasive nylon brushes are very durable and self-sharpening, providing excellent performance and wear life. They feature a ‘linear filament construction’; as the brushes come into contact with work surfaces during use, the abrasive wears off, exposing new cutting particles, thereby ensuring that the brushes stay sharp. Moreover, unlike the bristles of metal brushes, the nylon fibres are not prone to deforming or break-off; they also offer improved compliancy to the contours of even very complex workpieces, preventing damage while ensuring consistent finishing quality.

Mr Sun adds that abrasive nylon brushes can also eliminate the need to use other tools in automated applications, such as chamfer tools for deburring and face mills for surface polishing. “This tool is also applicable when tumbling would be required to achieve extensive deburring. While tumbling can certainly produce a nice surface finish, it can also create minor defects on parts because they come into contact with one another. Although it may take an extra minute or two to completely finish workpieces in the machine using an abrasive nylon brush, in my experience it is usually worth it in terms of quality and cost.”

Options available

Among the variety of abrasive nylon brush tools available, Mr Sun uses the NamPower range available from Brush Research Manufacturing, which is based in Los Angeles and is represented in the UK by Hertfordshire-based Pacehigh Ltd (www.pacehigh.co.uk).

Mr Sun says: “We have two different patterns for these brushes; one is called Dot, while the other is called Turbine. We use Dot brushes for deburring highly contoured workpieces with a lot of peaks and valleys, because it is particularly economical for light deburring operations when short cycle times are important. The Turbine brush has a more-aggressive pattern and is used mainly for medium and heavy deburring applications. This style of brush is better suited to flatter workpieces with fewer contours; it can be used to simulate a milled finish without actually removing any material.”

Both these abrasive nylon brushes are available with a variety of abrasive types and grit selections that allow them to work with a wide range of materials; these include metals, super-alloys, plastics, advanced composites, metal matrix and ceramics. Both brush styles are available in three different diameters and two different trim lengths to suit most applications. Moreover, they can be used to automate processes on VMCs, HMCs and robotic applications, producing a consistent finish from part to part.

Brush composition

NamPower abrasive disc brushes contain a combination of both ceramic and silicon carbide abrasives. Although there are other abrasive nylon filament products that use silicon carbide or ceramic, it is the combination of both in one tool that makes this type of abrasive nylon brushes most effective.

The ceramic abrasive is for material removal but tends to cut a bit coarse, while the silicon carbide acts as a buffer to the cutting action. The end result is deburring and surface finishing in a single operation. Moreover, these brushes are said to work well withnon-ferrous, cast iron, mild steel, ductile iron, stainless and alloy steels, titanium and high nickel alloys.

“We weren’t expecting to use brushes so much, but we’re finding more and more uses for them,” says Mr Sun. “We use the same brushes for aluminium, steel, cast iron and stainless steel, without having to replace them very often. For many operations, it’s more efficient to let the machine do everything, so that parts come out ready to be washed and boxed for delivery to the customer. That can really make a big difference — plus you are producing parts with a consistently high quality.”

New developments are also on the horizon. Brush Research is set to release several new products featuring diamond- and ceramic-impregnated filaments. Furthermore, a new series of diamond-filament wheel brushes has been designed to finish harder materials, like ceramic and carbide. Moreover, several new end-brush designs featuring ceramic filament will be available in smaller diameters to provide the benefits of abrasive nylon finishing for small parts and recesses.