graph in Fig. 2-3-9 shows the Machine Power while the graph in Fig. 2-3-10 shows the Static Stiffness of the sample part ground in this example.
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Over the past three to four decades industry in the United States has been affected by intense global competition from industries using the latest technologies in their manufacturing methods. Superabrasive tooling, designed to increase productivity, produce better quality products, and reduce manufacturing costs, can cut and grind the hardest materials known.
The fundamental cutting processes in machining - those of bringing the work into contact with the cutting tool - should remain mainstays of the industry. One of the most important components in the machining process is the cutting tool and its performance determines the efficiency of the operation. Modern tooling systems that can accommodate increased spindle speeds, higher feed rates, increased radial loads, modular adaptability, and profitable short part runs are required by manufacturers to stay competitive.
(Michael Flaman – Portland Community Colllege)
Over the past three to four decades, industry in the United States has been greatly affected by intense global competition from offshore industries that are using the latest technologies in their manufacturing methods. Even though the United States continues to lead in the development of new technologies, other countries research, test, and implement them far sooner. Improved productivity and quality result in a larger share of the world market. Products that were previously produced in the United States are now being produced offshore; this has reduced employment opportunities in this country. U.S. industry must take advantage of the benefits of new technology as quickly as possible in order to maintain its leadership in manufacturing.
The superabrasives, Diamond and Cubic Boron Nitride, possess properties unmatched by conventional grinding wheels and cutting tools for grinders, lathes, and machining centers. The hardness, abrasion resistance, compressive strength, and thermal conductivity of superabrasives makes them the logical choice for many difficult grinding, sawing, lapping, machining, drilling, wheel dressing, and wire drawing applications. Superabrasives can cut and grind the hardest materials known, making difficult material-removal applications routine operations. Superabrasive cutting tools are designed to meet the challenge of today by increasing productivity, producing better quality products, and reducing manufacturing costs.
BACKGROUND
In 1954, The General Electric Company (GE), after years of research, produced Man-Made® Diamond in the laboratory. Carbon and a catalyst, such as iron, chromium, cobalt, and nickel, were subjected to tremendous heat and pressure to form diamond crystals, Fig. 3-1-1. Because the temperature, pressure, and catalyst solvent can be varied, it is possible to produce diamond abrasive of various sizes, shapes, and crystal structure to suit a range of grinding applications on nonferrous and nonmetallic materials.
In 1969, GE introduced an entirely new material, BORAZON® cubic boron nitride (CBN). Cubic boron nitride is synthesized in crystal form from hexagonal boron nitride and a catalyst using the same high pressure, high temperature technology perfected to produce diamond, Fig. 3-1-2. CBN, second only to diamond in hardness, is used for the grinding of hard alloy steels and other difficult to grind ferrous materials.
MANUFACTURED DIAMOND
Diamond is used for truing and dressing grinding wheels and for the manufacture of diamond wheels. The need for a reliable source of diamond during World War II was realized when natural diamond was not readily available.
Fig. 3-1-1 A combination of high pressure and high temperature plus carbon and a catalyst are necessary for diamond growth. (GE Superabrasives)
Fig. 3-1-2 The process for manufacturing CBN and the crystals produced. (GE Superabrasives)
To produce diamond by a manufacturing process, the conditions of pressure and temperature found far below the earth’s surface had to be duplicated. This required a high-pressure, high-temperature belt apparatus capable of reproducing the conditions necessary for diamond growth. Graphite (a form of carbon) and a catalyst (such as iron, chromium, cobalt, and nickel) were subjected to high temperatures (2550° to 4260°F, or 1400° to 2350°C) and high pressures (800,000 to 1,900,000 lbs./sq. in. of 55,000 to 130,000 atmospheres) to form diamond crystals, Fig. 3-1-3. Under these conditions, the graphite is transformed into diamond and remains that way when it is cooled and the pressure is removed.
Types of Manufactured Diamond
There are many different types of manufactured diamond to suit various grinding applications. Manufactured diamond is available for grinding cemented carbides, carbide/steel combinations, nonferrous and nonmetallic materials, and many products such as natural stone, concrete, and masonry. The four main manufactured diamonds are:
▪TYPE RVG DIAMOND is an elongated, friable crystal with rough edges, Fig. 3-1-4A, and consists of thousands of tightly bonded small crystals that make up each abrasive grain. Type RVG (resin and vitrified) wheels are used to grind ultra-hard materials, such as tungsten carbide, and tough, abrasive nonmetallic and nonferrous materials.
▪TYPE CSG 11 DIAMOND, Fig. 3-1-4B, is designed to grind cemented carbide brazed tools where it may be necessary to grind both the carbide and some of the steel shank supporting the carbide insert.
▪TYPE MBG-11 DIAMOND, Fig. 3-1-4C, is used for grinding glass, ceramics, and carbides. The wheels with MBG (metal-bond grinding) abrasive have a metal bond to hold the tough diamond crystals in the wheel.
▪TYPE MBS DIAMOND - The Type MBS (metal-bond sawing) diamond, Fig. 3-1-4D, is used in metal-bond saws to cut granite, concrete, marble, and a variety of masonry and refractory materials.
Fig. 3-1-3 The high-pressure, high-temperature belt apparatus used for manufacturing diamonds. (GE Superabrasives)
Metal Coatings
The RVG diamond abrasive can be coated to prevent the diamond crystals from being pulled out from the resin bond. Coatings,
