Abrasives Lesson 9: Belt Problems and Solutions

Solving Belt Problems (Loading, Glazing, Stripping)

Introduction:

The continuing increased use of coated abrasive belts for metal removal and finishing operations has placed greater demands on high quality and uniformity of the products used for these purposes. Carborundum Abrasives Company employs state of the art quality control measures to assure that these demands are met.

The applications and operations using abrasive belts are very diverse and range from heavy stock removal using high grinding pressures to fine polishing and finishing. A broad range of abrasive products is available to meet these current requirements, and ongoing research and development provide continuing product improvement and introduction of new products to maintain a competitive edge.

The overall efficiency of an abrasive operation is affected by a number of interrelated factors. These are abrasive commodity selection and grit size; flex requirements; grinding pressure; belt speed; lubricants; contact wheels; and operating procedures and techniques. The full performance life of an abrasive belt is obtained by correctly meshing these factors to best fit the application requirements.

All belts at terminal use show a condition of loading, glazing, or stripping. The purpose of this lesson is to identify the used belt condition so that appropriate corrective action can be taken to improve performance.

Loaded Abrasive Belt:

A loaded belt shows metal adhered to the abrasive tips and/or packed in between the abrasive grains. In severe cases, the abrasive grain is almost completely covered. Loading substantially reduces both rates of cut and belt life and is most commonly encountered when grinding or finishing non-ferrous materials.

By eliminating the loading, belt life increases of 50 to 200% or more are possible.

Glazed Abrasive Belt

Glazing is dulling of the abrasive grain tips from contact with the workpiece and is usually encountered when grinding or finishing ferrous metals. Some metals will weld metal particles to the tips of the abrasive after the belt has had some use. The rate of cut decreases and more heat is generated in the workpiece as glazing progresses.

Glazing is identified by a smooth glossy surface on the face of the belt. There is minimal grain breakdown or loss and little if any, metal lodged between the grains. Reducing or eliminating glazing can increase belt life from 10% to 150%.

Stripped Abrasive Belt

In stripping, particles of grain, or of the grain and bond, have been pulled away in the grinding process. The cloth or fabric backing of the belt may be exposed - a result of too rapid a breakdown of grain and bond.

Stripping is most often encountered with coarser grit sizes used for heavy stock removal. It can be produced by both ferrous and non-ferrous metals.. Reduction or elimination of stripping can yield belt life increases from 20 to 200%.

Steps to Solving Problems

There are three distinct steps which must be taken to minimize or eliminate these problems:

1. Define the problem:

a. Examine the used belt to determine if the belt was discarded because of loading, glazing, or stripping.
b. Determine the degree of loading, glazing, or stripping - i.e. light, medium, heavy.
c. Determine the full specification of the belt being used - product, grit size, and flex.

2. Determine the cause of the problem.

3. Recommend corrective action by referring to the charts which follow.

General

The abrasive product or commodity, contact wheel, and lubricant can all have a major impact on loading, glazing, and stripping problems. Other factors may be important, but are less common and are treated later in the section.

For each of the problems listed below, the factors of abrasive product, contact wheel, and lubricant are numbered in typical order of importance for minimizing or correcting the problem.

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Courtesy Carborundum Abrasives