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Flowable Cutting Tools

AFM Media is the primary cutting tool for the Abrasive Flow Machining (AFM) process. All Extrude Hone Medias are comprised of a Media base material (viscoelastic polymer) plus an abrasive. The viscosity of the Media base along with the size, type, and quantity of abrasive particles determines the basic properties of a given Media. These abrasive-laden Medias are cold flowable, yet firm-bodied to keep the abrasive particles uniformly suspended in the less-dense, Media base material. Although the abrasive does the actual cutting, it is the physical properties of the AFM Media that cause the abrasive to cut. AFM Media is often referred to as “liquid sandpaper”.

The key adjective in describing AFM Media is viscoelastic. That is, the Media is viscous and thus flows when a force is applied. It also is elastic, or rubber-like. This “rubber-like” property acts as the "backbone" of the Media, holding the abrasive cutting particles against the surface being machined.

To classify AFM Media, Extrude Hone developed the Media base numbering system. Prior to receiving the abrasive particles, AFM Medias are typically manufactured in batch or bulk quantities to a specific viscosity level. These known viscosity levels are numbered from 10 (less stiff – low viscosity) through 70 (very stiff – high viscosity) and form the basis for classifying all Extrude Hone Medias.

At the top end of the range, base 70 has the highest viscosity (stiffness) because it is rich in polymer and contains little diluent. Base 10 however, which is rich in diluent, is sufficiently fluid to easily pass through very small diameter holes.

In addition to over 250 standard Medias, Extrude Hone also works closely with customers to develop special or custom-engineered Media’s for unique applications or process and productivity optimization.

Material Removal Process
Extrude Hone’s Abrasive Flow Machining is a pure mechanical process. Workpiece material is removed by a non-abusive grinding action caused by the Media’s abrasive particles moving across the workpiece surface. Cutting forces at the workpiece surface are extremely low and as a result, the workpiece surface remains stress-free or with only minimal values of compressive residual stress.

Unlike some mass-finishing and vibratory techniques, surface defects are not peened over with the resultant entrapment of foreign particles or impurities. AFM processing removes material cleanly and workpiece burrs are accurately ground away rather than smeared or broken off.

Extrude Hone offers a comprehensive selection of abrasive materials for inclusion in all AFM Medias. Each abrasive provides its own unique set of properties and application performance.

• Aluminum Oxide (2100 HK) is the preferred choice when a metallurgical inert abrasive is required, such as the finishing of high-nickel, super-alloy aircraft engine blades and vanes, semicon valves and tubing, and numerous medial implant applications.
  
  
• Silicon Carbide (2700 HK) is our most widely used abrasives because it is very hard, durable and a consistent performer over a wide spectrum of applications.
  
  
• Boron Carbide (3580 HK) is the second hardest known material next to diamond. It produces a faster material removal rate than Silicon Carbide under ideal cutting conditions. Boron Carbide is also lighter than Silicon Carbide and as a result, up to 25% more Media by volume will be found in a 10 kg. container of Boron Carbide Media than the same weighted container of Silicon Carbide Media. Boron Carbide is applied on low-machineability materials, such as hardened tool steel, cobalt steels, nickel-based super-alloys, titanium, and tungsten carbide applications.
  
  
• Diamond Powders (7000 HK) are used for special applications, such as workpieces that require a very high-quality surface finish or are made from extremely hard materials like tungsten carbide. Typical examples are extrusion, drawing and heading dies or where a high-gloss finish is required.

Extrude Hone offers it’s abrasive Media in a wide selection of particle sizes ranging from coarse 8 grit with an average particle size of 4620 microns (0.181 inch) to 800 grit with an average size of 12.0 microns (.0005 inch). Very fine 1200 grit with an average size of 6.5 microns (0.0003 inch) is available for our MicroFlow AFM process.

In addition to standard and custom-engineered AFM Medias, Extrude Hone offers several Media Maintenance and Replenishment programs that extend the Media’s usable working life. These programs provide customers with significant cost savings, improved productivity, and assure a consistent, reliable process. Contact your Extrude Hone representative for complete details on our Full Circle^SM maintenance programs.