Brush deburring brochure
13Pages

D. Mark FultzVice President MarketingAbtex CorporationDresden, NYThe deburring of PM parts is commonly performed in a batch process. This typicallyinvolves loading a quantity of parts into a vibratory bowl filled with abrasive media. The vibration of the bowl causes the abrasive media, and parts, to flowӔ. This interaction between the media and parts gradually abrades all surfaces of the part. Drawbacks to this process include part impingement upon one another, waste generation, lodging of media into the part, deburring of unnecessary areas on the part and the inherent vibration and noise created by the operation of these systems.This paper discusses an abrasive filament medium which is ideal for deburring and edgeradiusing PM parts. When formatted into a brushing tool, it can be applied on machine based systems for semiautomated or fully automated deburring of PM components. Through proper application, it is possible to gain the advantages of productivity, quality, and economics without the negatives associated with alternative methods. FIBER ABRASIVES The term fiber abrasiveӔ is used to describe an abrasive nylon filament. Developedapproximately 25 years ago, they are commonly employed in brush form for a variety of industrial applications. These generally involve deburring, edge radiusing and general surface finishing.The filament is composed of nylon, which has been coextruded with an abrasive grain.The resulting monofilament is a homogeneous structure of nylon and abrasive. Nylon is an ideal material for a brush filament. Compared to other polymers, it excels not only in its durability, but also in its resistance to moisture, abrasion and chemicals (1). Nylon types used in the production of fiber abrasives are Type 6, Type 66 and Type 612. Type 612 is preferred in industrial applications. It offers the greatest heat resistance and least amount of moisture absorbency.The grain, or grit, is impregnated throughout the filament as well as exposed on theexternal surfaces. A magnified example of this filament is shown in figure 1. >

rate. With this feature, burrs and sharp edges are preferentially abraded away. Thisenables the tool to deburr without negatively affecting the size and dimensional tolerances of the part. BRUSHING TOOL FORMATS Fiber abrasives are typically formatted into brushing tools using conventional brushmaking machinery. Abrasive brushing tool formats include: disc, wheel, cup, end and tube as seen in Figure 2. Brushes of this type are applied with portable pneumatic and electric hand tools, manual stationary equipment (drill press, pedestal grinder, buffing lathe), semiautomated (CNC, NC, robotics)...

Figure 3: A radial wheel offers unidirectional brushingaction Figure 4: Disc format offers multidirectional brushing action >

2. DiscThe disc is constructed of a backing into which the filaments are embedded. The fibersextend perpendicularly from the backing. Unlike the unidirectional brushing action of the radial wheel, the disc offers multidirectional brushing action as illustrated in figure 4. As a part traverses across the face of the disc, several surfaces are deburred. Because of this multidirectional brushing action, the disc brush tends to be a more efficient format for deburring PM parts. Disc brushes can be employed when the surface to be deburred is flat with little or no changes in elevation. Disc...

Using a brushing tool with too little density may require prolonged dwell time in order toeffectively deburr. Individual filaments are now required to work harder with less support. This leads to premature filament breakage and reduced brush life.The optimal brush density is shown in figure 5. The filaments are distributed evenlyacross the face of the brush. Filaments are close enough to support one another yet spaced to allow flex and heat dissipation.2. Trim Length The trim length is the length of the visible filament, or the distance from the tip of thefilament to its base. Trim length...

EQUIPMENT leading to accelerated brush wear. As was seen in Table 1, grit size and filament diameterare related. The most commonly applied disc brush for deburring PM parts employs a filament diameter of .022 and a grit size of 120. Radial wheels, with generally longer trim lengths, typically employ filament diameters ranging from .030Ԕ to .040 and grit sizes of 240 to 120. As mentioned earlier, both radial and disc brushes are typically applied on a machinebased system. Either brush is capable of deburring the part. The challenge is to present the part to the brush, or the brush to the...

Since unidirectional rotating radial wheels are used, it is necessary to rotate the part whilebrushing. As the table indexes to present the part to the brushing station, the spindles rotate the part. At each station, the parts dwell under the brushing head for a prescribed length of time or number of rotations. The table then indexes, moving the part to the subsequent station for further deburring, part turnover or loading/unloading.These systems can be either run wetӔ with coolant, or dry. The effect of coolant on thebrushing action reduces the potential for nylon smear. It also acts as a...

Figure 6: Rotary table deburring system >

Figure 7: Close-up view of rotary table station 2.Disc Brush SystemsDisc brushing systems tend to be the most versatile and productive. By taking advantageof the multidirectional brushing action of the disc, it is not necessary to rotate the part during brushing. Part transfer is usually accomplished by means of a magnetic conveyor system. This elimination of tooling for part fixturing expands the use of the system to handle a variety of part shapes and sizes with minimal set up between part changes.Disc brushing systems are designed to present each side of the part to a minimum of...

Figure 8: Automated disc brush deburring system >

fully automated systems. Fully automated disc brush machines attain deburring rates upto 2000 parts per hour. EconomicsFor the purposes of this presentation, cost per part is evaluated strictly from thestandpoint of brush consumption. Brush life is affected by many variables. Severity of burr, degree of edge radius desired, and brush characteristics play a large role in determining brush life. Contributing equally, if not more, is the design and operation of the deburring system. All of these variables have the potential to significantly affect brush longevity, either positively or...