The Inside Edge: Advanced Finishing Processes for Aerospace Solutions

New materials and techniques have provided aircraft engineers the ability to create new components that are stronger and lighter than ever before. Staying competitive in the aerospace market, Extrude Hone has developed three advanced finishing processes, Abrasive Flow Machining, Thermal Energy Method, and Electrolytic Machining. These processes allow the engine designer the ability to engineer surface finishes to maximize component performance, integrity and reliability. Extrude Hone is relied upon to produce stress-free edges that can withstand the incredible forces generated in super heated rotating parts, as well as to provide gas and fluid flow passages that optimize combustion and hydraulics operation, and extend component life.

Abrasive Flow Machining (AFM)

The Extrude Hone AFM process defines a new level of quality and manufacturing productivity.

As a result of ongoing advancements, AFM continues to be a leading deburring and polishing process today. AFM significantly improves the overall quality and product performance of cast, forged and machined components at a reasonable and predictable cost.

The AFM process uniformly smoothes and blends in features, automatically and controllably, to a quality level and speed unachievable by hand or other forms of machine finishing. It finishes internal curved and complex surface locations previously unreachable by any other means.

The AFM Process
At the heart of this unique process is Extrude Hone's laden polymer—or media— that changes its apparent viscosity when a shear stress is applied. As the media is forced to flow over or through a restricted flow path, its molecules "cross link", transforming the media from a viscous fluid to an elastic, or even brittle, solid. The media sticks to little other than itself, so it easily slips across edges and surfaces like elastic, abrasive putty with results similar to 3D flowable sandpaper.

AFM media is reusable for extended periods, although life expectancy is dependent on severity of use and application.

There is a wide selection of standard media formulations to service a broad range of customer applications. Custom engineered media formulations for special applications and process optimization are also available.

Electrolytic Machining (ECM)
Extrude Hone's electrolytic technology provides fast, accurate and highly controllable surface finish improvements for your precision workpieces. This process can machine, deburr and polish surface locations previously unreachable by other methods, including manual or hand work. ECM removes metal without direct contact between the tool and workpiece through the dissolution of surface atoms. In adhering to Faraday's law of electrolysis, the metal removal process ensures the amount of material removed is proportional to the time and intensity of an electrical current flowing between the tool and the workpiece.

Extrude Hone's processes uniformly smooth and blend in features to a quality level unachievable by hand or machine finishing.

The Electrolytic Process
Extrude Hone's electrolytic equipment employs a programmed pulse, low-voltage direct current while a conductive electrolyte solution passes between the tool and the workpiece.

This highly controllable process essentially dissolves the workpiece material atom by atom from specific areas. The amount of material removed depends upon the amount of electrical current flowing between the negatively charged tool and the positively charged workpiece.

Since there is no contact between the tool and the workpiece during electrolytic process, your workpiece avoids exposure to mechanical or thermal stress and retains all physical and chemical properties. Typical electrolytic cycle times range from 15 seconds to 45 seconds for most applications.

Because minimal tooling and setup time is required, the ECM process is ideally suited to both short and long production run applications.

Thermal Energy Method (TEM)
Manufacturers are improving workpiece performance with increasingly more complex designs, resulting in greater surface finishing challenges. Extrude Hone's Thermal Energy Method uses intense heat to deburr and deflash workpieces accurately, quickly and cost-effectively.

Invented more than three decades ago, the TEM process is distinctive in that it removes internal and external burrs and flashings simultaneously and without affecting or compromising and adjoining workpiece surfaces. The actual removal of burrs and flashings happens "in a flash" with a mere 20 milliseconds completion time.

Through hundreds of installations and continued refinement of the TEM equipment, one factor remains constant: TEM is a rapid, low-cost, high-production precess that can produce a million or more parts per year by a single machine.

The TEM Process
First, workpieces are securely sealed in a bell-shaped combustion chamber. Depending upon the size of the TEM machine and the containment chamber, several hundreds of workpieces can be processed at a time.

A pressurized mixture of combustible gas—typically natural gas or methane and oxygen—is injected at 5 to 10 atmopheres of pressure, wich is determined by the amount of material to be removed and the volume of parts in the chamber.

A spark plug ignition system ignites the gas mixture, releasing heat energy from oxidation of fuel in a 20 millisecond, highspeed heat wave.

The surface of the combustion chamber absorbs the majority of the heat, harmlessly raising the temperature of the workpieces a few degrees.

With their raised surface areas and thin cross-section features, burrs and flashing burn away instantly. Depending on the heat diffusivity of the workpiece material, most, if not all burrs absorb the heat faster than the core of the workpiece. The burr becomes progressively hotter until it reaches the material's oxidation temperature and ignites.

The ignition process continues until the cross-section of the burr increases in thickness as it intersects the edge of the workpiece, allowing the heat to diffuse into the body of the workpiece faster than it is being generated by the reaction, whereupon the process is completed.

Because the gas mixture engulfs the entire workpiece, all internal and external surfaces are exposed to the rapid oxidation. Internal cross-drilled holes and intersecting edges that are difficult or impossible to reach are instantly processesed.

The manufacturing processes used by the aerospace industry today are continually pushing the envelope of turbine engine design. New techniques, such as AFM, ECM and TEM have given aircraft engine designers the ability to create new components that are lighter and stronger than ever.

Extrude Hone Corporation is a Kennemetal Company. Headquartered in Irwin, PA, Extrude Hone has been in operation for more than 40 years. For more information, visit the Extrude Hone website at www.extrudehone. com, or call 800/367-1109.