How Much Microfinishing is Enough?

Posted by Able Electropolishing on October 29, 2013

The electropolishing process is renowned for its ability to improve a metal part's microfinish, reducing the surface irregularities and imperfections to create a smoother, better-performing part. Because electropolishing is more precise than other metal polishing methods, it can be used to remove a small amount of surface material, reducing the microfinish value as much as necessary without altering the size and shape of the part more than its tolerances allow.

Determining Microinch Value

The first step is to determine the microinch value of a part. This value is a quantification of the irregularities in the surface of a part—the higher the number, the more irregular the surface. This value is determined using a profilometer, which measures the part's microscopic peaks and valleys.

Electropolishing to Reduce Microinch Value

Typically, electropolishing reduces microinch values by 50 percent, by removing .0005" material per surface-(recommended to achieve the maximum benefit). Removing the necessary amount of surface material requires precision that mechanical and manual metal polishing methods can't achieve.

Remaining Within Tolerances

Not all metal parts can have as much as .0005" removed from each surface, because it would size them out of their unique tolerances. This makes electropolishing well-suited for reducing their surface irregularities without dramatically altering their size—it is a controlled process that can remove a pre-determined, predictable amount of material.

This precision also helps make electropolishing well-suited for treating fragile or complex parts. Because this process treats parts in an electrochemical bath, it is able to affect the entire surface area of a part equally without bending or distorting it. Other microfinishing processes, like grinding, are not as appropriate for parts like this.

By carefully measuring microinch values with a profilometer and experimenting with various levels of surface material removal, an electropolisher can significantly improve the surface of a metal part, and in turn, improve its performance.