HOME  > Surface Finishing Tutorial  > #046 Electrolytic Etching - Electrolytic Lapping
Surface Finishing Tutorial

#046 Electrolytic Etching - Electrolytic Lapping

Category : Metal etching
June18, 2010

A type of lapping operation using electrolytes in place of the usual lapping fluids is called Electrolytic Lapping. With this method, the lapping action progresses as the surface layer is removed by electrolytic etching. Instead of the fixed abrasives used in electrolytic grinding and honing, loose abrasives mixed in the electrolytes are used with this method. There are three types of electrolytic lapping, as shown in [Fig.1], depending on the applied method.

[Fig.1] Types of electrolytic lapping

In the method (a), the work piece (anode) and the lap (cathode) is spaced at a certain distance (0.05~0.2mm), and a solution mixture of electrolyte and abrasives (called Electrolytic Slurry) flows in the gap. The slurry flow is created by the lap's rotation and removes the electrolytic byproducts from the surface by abrasion.

With the method (b), the work piece and the lap are pressed against each other with the abrasives in between. To avoid the work piece and the lap from electrically shorting, pressing pressure, abrasive size, and the mixture ratio are carefully adjusted. The lap's shape and slurry injecting method is carefully engineered also.

In the method (c), the lap is made of electrically insulating material (i.e. hard urethane), and the cathode surface is made a slightly concave shape in relation to the lap surface. In this case, there will be no concerns for electrical shorts even when using small abrasive sizes, so fine finish surfaces can be obtained by using fine abrasives in 2,000~3,000 mesh sizes. However, the gap distance will be larger than (a) or (c), and the metal area is relatively small, resulting in slower processing speeds. This type of electrolytic lapping is called Compound Lapping.

The electrolytic lapping can be used for a variety of machining applications depending on the lap shapes and motion patterns. From the industrial application stand point, the electrolytic lapping can be classified into the following categories. One is called "Electrolytic mirror finish lapping" where the work piece may be either too hard and brittle or too soft, but needs to be finished into mirror smooth surface. The other is for grinding hard materials at speeds similar to electrolytic grinding, and is typically called "Electrolytic lapping".

MISUMI USA eCatalog