Nonwoven Abrasives

Nonwoven products fill a growing market of abrasive finishing. Typically nonwovens are less aggressive than coated abrasives but there is overlap, as seen in the diagram below.

Features and Benefits of Nonwoven

Highly Conformable - Less likely to gouge the work piece, which makes the product more forgiving.
Conforms to contoured surfaces which gives a uniform finish and does not disturb critical tolerances.
Requires less finishing steps than coated materials.

Abrasive Grain is Dispersed Through 3D Structure - Uniform scratch pattern throughout the life of the product.

Open Structure - Resistant to loading.

Synthetic Components - Fully waterproof, also resistant to cutting fluids and metalworking chemicals.

 

Nonwoven Construction

To understand the cutting action of nonwovens, imagine the grit particle held by a helical spring rather than a solid block. The force applied to the nonwoven product is not transferred directly to the workpiece. Some of the force is absorbed in the compressing spring. Nonwovens are less aggressive than coated products and tend to give a finer finish.

As a nonwoven product runs over a contoured surface the “springs” compress and expand allowing the grain to constantly be in contact with the entire surface. A coated product would skip over the valleys and remove excess metal on the peaks as the force of application would be concentrated on the smaller area of the peaks. The nonwoven finishes more uniformly contoured surfaces without compromising critical tolerances obtained in earlier machine or molding operations.

This feature is especially important during a finishing process. The conventional method for removing deep scratches is to use a progression of coated abrasives, e.g. 80, 120 and 180 grit, each giving a progressively finer finish while removing the previous deeper scratch. The conforming nature of nonwovens allows deeper scratches to be removed while providing a fine finish. This reduces the number of steps in the process - A major cost saving given today's labor costs.

The wear characteristics of nonwoven abrasives are different from coated abrasives. This is due to the 3D structure of nonwoven abrasives compared to the flat structure of coated abrasives. In use, the abrasive grain within coated abrasives wears down and changes shape which results in different scratch patterns. With nonwoven abrasives, as the product wears away, the substrate breaks down and the grain is lost which reveals a new sharp grain. This process leads to uniform finishing, defined by a more consistent Ra throughout the life of the product.

Other features of nonwovens are the fibers and chemicals used in the construction. Like coated abrasives, nonwovens have a substrate base (nylon fiber), a resin bond (phenolic or polyurethane) and abrasive grain. In nonwoven abrasives the fiber and resin are fully waterproof so the product can be used wet or dry. The structure of a nonwoven abrasive is extremely open so that the product resists loading and is cool running.

Surface Conditioning (Scrim Reinforced) products have the basic nonwoven structure but are scrim reinforced and are one sided. The scrim adds strength for use in high speed belt and disc operations. Surface conditioning products are used flat as they are one sided. The product is available in three grades: Coarse – equivalent to 120 grit finish; Medium – equivalent to 180 grit finish; Very Fine – equivalent to 320 grit finish.

For airfiles, the base nonwoven is modified to give increased flexibility as the belt has to run around a small diameter contact wheel (less than 1”) without cracking. For longer belts the base has been modified to resist stretch in the length direction. Discs and Quick-Lok Discs use a regular scrim product.

Non-reinforced Products are made of the nonwoven base and have not been reinforced with a woven scrim. They can be broken down into three categories: Handpads - best suited for hand applications; Heavy Duty - best for flap wheels, mops; Super Duty - best for discs where extreme durability is required.

The materials are generally color coded by the abrasive mineral as follows:

Aluminum Oxide		Maroon/Brown
Silicon Carbide		Gray/Black
Alumino Silicate		Green
Non Abrasive		White

The products are coded by finish description rather than grit size. This is because nonwovens give a finer finish than coated abrasive products and therefore quoting a grit size would be misleading. The AO and SiC ranges are available in the following grades with the corresponding equivalent grit size:

Grade		Equivalent Finish to Coated
Ultra Fine		600 to 800 Grit (only SiC)
Very Fine		320 Grit
Fine		180 Grit
Medium		120 Grit
Coarse		80 Grit