Manufacturing reliable, high-performing parts and components that have extended lifecycles is crucial for the pneumatics and hydraulics industry. From springs to fittings, the performance of each these manufactured parts and components is essential to the operation of machinery used in a variety of disciplines in the pneumatics and hydraulics industry. When reliability, functionality, performance, and life of metal parts are paramount, electropolishing is a single-process metal finishing method that effectively meets the challenges.

Springs before and after electropolishing.
Often referred to as a “reverse plating” process, electropolishing is an effective metal finishing process. Electrochemical in nature, electropolishing uses a combination of rectified current and a blended chemical electrolyte bath to remove flaws from the surface of a metal part. Unlike mechanical or hand-polishing, electropolishing is a precise electrochemical process that dissolves an even layer of surface metal across a metal part. This saves both time and resources by creating a uniform finish when manufacturing parts with complicated or delicate shapes.

Many parts manufactured for use in the pneumatics and hydraulics industry require a precise surface finish to ensure proper operation — neither too rough nor too smooth. Since friction is involved in hydraulic applications, oil retention is crucial. Too smooth a finish can lessen a surface’s ability to hold onto lubricant. At the same time, too rough a finish can cause added friction and wear, which eventually will lead to a breakdown in function. To create this ideal finish, parts must be uniformly treated to achieve a consistent surface. Electropolishing removes a uniform layer from the part’s surface to a precision of ±.0001.

Parts used in pneumatics and hydraulics applications are often required to bend, rotate, twist, or cycle. Examples include springs, cylinders, regulators, pumps, valves, compressors, and actuators. Because the manufacturing process often leaves behind micro-cracks on the surface of these components, premature part failure is a big concern for the industry. Although not visible to the naked eye, these micro-defects often become initiation sites for crack propagation or corrosion that can threaten the part’s function, ultimately reducing its anticipated lifecycle. Electropolishing removes these imperfections on the surface of metal parts, leading to significant fatigue life improvement.

Scanning electron microscope (SEM) images of the springs before (left) and after electropolishing.
A variety of hydraulic and pneumatic assemblies, such as robotics and heavy machinery, require an impeccable, contaminant-free surface finish to ensure proper function, reliable performance, and extended lifecycles. In many cases, particulates or contaminants left on the part’s surface can lessen the surface’s ability to hold onto lubricants or other fluids, or cause added friction and interfere with the function of the assembly. Premature failure due to contamination can lead to equipment being idle and lost production time. In order to prevent this, components must be free of any flecks of metal, residual dust, oils, grinding compounds, imbedded scale, foreign debris, and other impurities. With the ability to remove even the most marginal amount of metal from parts and adhere to precise specifications — such as keeping corners sharp or preserving grooves and spooling — electropolishing is an effective solution for deburring while maintaining part integrity. Grinding, honing, and mechanical polishing are all processes used for surface finish improvement that may also be critical steps in finishing parts for this industry. These processes come with the risk of leaving particulate or contaminants behind, and often work best in tandem with electropolishing.

Because many pneumatics and hydraulics components are constantly exposed to fluids, corrosion resistance is often a challenge for manufacturers. Corrosion may begin at welded areas or initiation sites, and create an unsightly look, but most importantly, oxidation can disturb the function and performance of the component and assembly. With many moving parts critical to the function or operation of a single machine, failure from internal components is not an option. While many parts and components are made from stainless steel, manufacturers in the hydraulics and pneumatics industry also utilize carbon steels, aluminum, brass, and core iron. Often, these alloys are harder to treat to achieve a uniform, clean surface finish. Unlike other methods, electropolishing can be employed for virtually any metal alloy.

Typically the last operation in the metal finishing process, electropolishing eliminates peeling or abrading as with platings and coatings, prevents surface distortion or weakening of the part, improves weldability, and resists staining.

This work was done by Able Electropolishing. For more information, Click Here .


NASA Tech Briefs Magazine

This article first appeared in the October, 2015 issue of NASA Tech Briefs Magazine.

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