Insights to the Process of Grinding
Norstone Inc (http://www.norstoneinc.com/) has been providing mill operators and owners of all kinds with a wide range of proppants, industrial media supplies and grinding media. Art Gib is a freelance writer.
Grinding practice is a large and diverse area of manufacturing and tool making. It can produce very fine finishes and very accurate dimensions, or in large production volume it can also roughen the surface of metal quite rapidly. It is usually better suited to the machining of very hard materials than is “regular” machining in the past was the only practical way to machine such materials as hardened steels.
There are several types of grinding media available. The most appropriate type will vary from one application to another. Common media include ceramic, glass, still and plastic.
One of the first considerations, when determining the best grinding media to use is whether or not the media will introduce any unwanted chemicals to the product being ground. Or will the media cause discoloration, as steel will often do to lighter colored product.
The next consideration is the specifications involved in the grinding process. What diameter of media will be used? What size chamber will be most appropriate? What density is appropriate, and what is the most cost effective media for this application. When determining the budget, there are multiple things to consider. Different media may be less expensive for one project, however, if it causes more wear and tear on other equipment, it will me more expensive in the long run. If the media itself last longer, it may be worth the higher cost up front because it will cost less in the long run. Other factors include wear-resistance, erosion-resistance, magnetism-resistance, high-temperature-resistance, high mechanical strength, high hardness and strong shock resistance.
Often it is necessary to run grinding trials with different media. Glass is typically a good place to start because the cost is low, typically has good wear properties, can be manufactured to be round, and can be purchased in a variety of grades.
Plastic media comes in just about any shape, size, density, texture imaginable. Depending on the application, you might select spherical, cube shaped, cone shaped, or pyramid shaped, just to name a few. The sizes range from sand and powder consistency to each particle being several inches each. Extensive studies have been done understand the effects of many media shapes on load behavior and mill power draw at various mill speeds and load filling.
The next category is polishing media. These, for obvious reasons, are most commonly less abrasive. Some media is even available in a paste form. Media in this arena are commonly made of materials, including carbon steel, stainless steel, inconel, etc. and can produce a mirror finish on all types of products.
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