The electropolishing process is well-suited for deburring. During the process, the transfer of metal ions occurs most rapidly on corners or edges of metal parts. Current density or concentration of electro-chemi¬cal power is greatest at high points, just as lightening is drawn to tall trees and buildings. This helps explain why plating builds metal faster on an edge or burr, while electropolishing (the “reverse” of plating) removes metal fastest at these points.
Properly controlled, the process can remove burrs from incred¬ibly complex or fragile parts that do not lend themselves to conventional tumbling or vibratory finishing techniques. The process is best suited for precision finishing parts having fine blanking, milling, broaching, lapping or grinding burrs. Since electropolishing is non-mechanical, it is important to note that the hardness of a metal part has no bearing on the burr removal. The process works equally well on a fully annealed or hardened part. This is one reason why electropolishing is often specified as a final deburring and precision finishing process after all fabrication and heat treating processes.
The fact that electropolishing is a non-distorting process is often overlooked. Many metal parts produced today have critical microfinishes or are made from lighter, more fragile materials. In those cases, mass finishing techniques such as tumbling or vibra-finishing create distortion or warping, and can nick or scratch fine finishes. Electropolished parts are never subjected to stress from polishing media nor are they impinged or tumbled onto each other.
It is important to note that burr removal is limited based on burr size, compo¬nent configuration and amount of stock removal. Larger burrs produced in rough milling or displaced metal from drilling operations often need pre¬treatment using other methods. In addition, heavy die break burrs caused by improper tooling maintenance are difficult to remove with electropolishing alone.
Case Study 1
The 400 series stainless steel component pictured is the inner portion of a dual drill bit assembly used for surgery on the human brain. Grinding and/or machining burrs prevent the mating parts from freely rotating (one bit within the other), while burrs specifically on cutting edges reduce ease and rate of cutting. Increased pressure on the drill bit due to contaminated cutting edges affects the functionality of the cutting device’s clutching mechanism; the sharpness of the bit is tied directly to the function of the rest of the device. In addition, if not properly removed, burrs may flake or chip off causing a potential bio-hazard for the patient.
By precisely removing .0005″ +/-.0001″ total material off of the drill bit’s O.D., electropolishing preserves edge condition while removing problematic burrs. As in this application, electropolishing is often a superior alternative to hand deburring; the electropolishing process offers greater consistency from part to part or lot to lot and is significantly more cost effective. In eliminating burrs while maintaining sharp, cutting edges electropolishing allows the cutting device to function smoothly, efficiently and safely.
Case Study 2
The part pictured is a 420 stainless blade used on high-end vegetable peelers. After the grinding operation, the blade edges are left sharp, but ragged. Pictured parts on the left side of the page illustrate the burrs post-grinding. The grinding burrs need to be removed in order for the blade to slide and cut smoothly; it is also important for this product to be clean and free of any metal shavings as it comes into direct contact with food. After researching various deburring options, the manufacturer of this high volume product found electropolishing to be the most consistent and cost effective method to finish the blade component of the peeler. As the final operation, electropolishing serves to both deburr and clean the part. In this case, .002″ total material is removed from the thickness of the blade which, after extensive sampling, was proven to be the optimal amount of removal. Once electropolished, the blades are burr-free and sharper than in the “as-ground” condition.