Abrasive flow machining (AFM), also known as abrasive flow

deburring A burr is a raised edge or small piece of material that remains attached to a workpiece after a modification process. It is usually an unwanted piece of material and is removed with a deburring tool in a process called 'deburring'. Burrs are mo ...

or extrude honing, is an interior surface finishing process characterized by flowing an

abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...

-laden fluid through a workpiece. This fluid is typically very

viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

, having the consistency of putty, or dough. AFM smooths and finishes rough surfaces, and is specifically used to remove burrs, polish surfaces, form radii, and even remove material. The nature of AFM makes it ideal for interior surfaces, slots, holes, cavities, and other areas that may be difficult to reach with other polishing or

grinding Grind is the cross-sectional shape of a blade. Grind, grinds, or grinding may also refer to: Grinding action * Grinding (abrasive cutting), a method of crafting * Grinding (dance), suggestive club dancing * Grinding (video gaming), repetitive and ...

processes. Due to its low

material removal rate Material removal rate (MRR) is the amount of material removed per time unit (usually per minute) when performing machining operations such as using a lathe or milling machine Milling is the process of machining using rotary cutters to remove m ...

, AFM is not typically used for large stock-removal operations, although it can be. Abrasive flow machining was first patented by the

Extrude Hone Corporation Kennametal is an American supplier of tooling and industrial materials founded in 1938 by Philip M. McKenna in the Latrobe, Pennsylvania area. Production Kennametal products: *Blades, disks, skins, fuel control systems, and landing gear for the ...

in 1970.

Process

In abrasive flow machining, the abrasive fluid flows through the workpiece, effectively performing

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is di ...

. Abrasive particles in the fluid contact raised features on the surface of the workpiece and remove them. The fluid is forced through the workpiece by a

hydraulic ram A hydraulic ram, or hydram, is a cyclic water pump powered by hydropower. It takes in water at one " hydraulic head" (pressure) and flow rate, and outputs water at a higher hydraulic head and lower flow rate. The device uses the water hammer e ...

, where it acts as a flexible file, or slug, molding itself precisely to the shape of the workpiece. The highest amount of material removal occurs in areas where the flow of the fluid is restricted; according to

Bernoulli's Principle In fluid dynamics, Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluid's potential energy. The principle is named after the Swiss mathematic ...

, the flow speed and pressure of the fluid increase in these areas, facilitating a higher

(MRR). The pressure exerted by the fluid on all contacting surfaces also results in a very uniform finish. AFM may be performed once, as a one-way flow process, or repeatedly as a two-way flow process. In the two-way flow process, a reservoir of medium exists at either end of the workpiece, and the medium flows back and forth through the workpiece from reservoir to reservoir.

Equipment

An abrasive flow machine normally includes two medium chambers equipped with hydraulic rams, a

fixture A fixture can refer to: * Test fixture, used to control and automate testing * Light fixture * Plumbing fixture * Fixture (tool), a tool used in manufacturing * Fixture (property law) * A type of sporting event See also * * * Fixed (disambiguat ...

for holding the workpiece, and a clamping system that holds all the components tightly together. Most machines allow for the loading of different types of abrasive medium, and include the capacity to adjust the pressure used in extruding the medium through the workpiece. They may be manually operated, or automated using

CNC Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining tools (such as drills, lathes, mills, grinders, routers and 3D printers) by means of a computer. A CNC machine processes a pie ...

. For machines designed to accommodate high production volumes, accessories such as part-cleaning stations, unloading and reloading stations, media refeed devices, and media heat exchangers may be included.

References

External links

Video of abrasive flow machining
{{DEFAULTSORT:Abrasive Flow Machining Grinding and lapping Metalworking