Understanding non-woven abrasives

Products are the right choice if you’re seeking a controlled, sustained finish

by Michael Armitage and Julie Meldrum

Non-woven abrasives were introduced to the industrial market in the 1970s by 3M. The concept of non-woven abrasives is sophisticated. The product’s three-dimensional, open structure is achieved by needling nylon filaments to form a web. Abrasive grains — primarily aluminum oxide or silicon carbide — are then bonded throughout the web. This process yields a “hand-pad” type material.

In operations where high-tensile strength is required (for example, belts and discs), a woven polyester or nylon scrim is incorporated into the structure during the needling process. This process delivers a surface-conditioning material.

The result of both processes is a superb finishing product in which the grain is not only embedded on the product’s surface, but throughout the entire abrasive structure.

Non-woven vs. coated: How do they stack up?
Non-woven abrasives offer performance advantages over traditional coated abrasive products.

Coated abrasives are created by bonding abrasive grains to one side of a paper or cloth material. Coated abrasives offer an aggressive means of stock removal or cutting, as the grains immediately come into contact with the surface to be finished. But the cutting power of the coated abrasive constantly (and quickly) declines throughout product use.

Non-woven abrasives, on the other hand, are designed to provide the operator with a controlled, sustained finish. As the nylon fibers of the product wear away, fresh abrasive grain is continuously exposed, providing a consistent finish. The spring-like construction of non-wovens greatly lessens the risk of gouging or severely altering the surface of a work piece.

Typically used near the end of the manufacturing process, non-woven abrasives are primarily used in the metalworking industry for an almost endless variety of surface-conditioning and light deburring applications.

Non-wovens today represent roughly 4 percent of all abrasive products sold in the U.S. market. But as manufacturing advances strive to enable delivery of near-final parts, these percentages will rise substantially. Manufacturers will be faced less with heavy stock-removal issues and more with final finish opportunities.

Understanding how non-wovens work
Non-woven abrasives can be divided into two primary categories:  “surface-conditioning” and “clean and finish.”  How do they differ?

Clean and finish non-wovens are typically hand-operated products that are weaker in nature than surface-conditioning products due to their lack of a scrim. The most commonly used clean and finish products are hand pads, sheets and rolls.

Surface-conditioning non-wovens are designed to run in mechanical operations. As such, they represent the majority of non-woven abrasives consumed in the market. The product’s scrim provides strength and resilience. The most commonly used surface-conditioning products are belts and discs.

Surface-conditioning products are available in three primary material grades:

A/O coarse (brown in color): Designed for aggressive blending, this is the best choice for hardened materials that require imparting a uniform finish with minimum stock removal.

A/O medium (maroon in color): This grade is ideal for general-purpose blending and finishing operations, for use on all grades of aluminum and steel, and is great for imparting a finish on stainless steel.

A/O very fine (blue in color): This grade is suitable for preparing surfaces for paintings or coatings, and is an excellent choice for blending minor surface imperfections with the least amount of stock removal.

Surface-conditioning product applications
Use surface-conditioning products on a large number of materials, including aluminum, stainless steel, brass, chrome, nickel, chrome plate, copper, titanium, waspalloy, fiberglass and wood.

In general, surface conditioning product applications include deburring, cleaning, polishing, blending, scouring and imparting decorative finishes. Some of the most common surface-conditioning applications are featured in the table found below.

It’s all in the finish
Non-woven abrasives are the answer to a huge range of finishing and surface preparation needs. They prevent undercutting and gouging when grinding. They run cooler than coated or bonded abrasives, which lessens the chance of warping or discoloring a work piece. Also, when used properly, non-woven abrasives can reduce the number of grinding steps to obtain a required finish. That’s a benefit to all cost-conscious manufacturers.

This article appeared in the December 2002/January 2003 issue of MRO Today magazine. Copyright 2002.

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