Diamond tool machining

Machineable Ceramics. All ceramics can be machined in the green state, and in the fired state with diamond tooling. Machineable ceramics are those which can be shaped when fired, to engineering tolerances with ordinary high speed metal cutting tools. See machining, and... 

A second option is to machine the rib structure from a massive disc by water-jet cutting, ultrasonic cutting, or conventional diamond tool machining for subsequent fusion to a front plate and possibly a back plate. Especially water-jet cutting is a very flexible process with respect to cavity shape because the tool - a high-pressure water jet mixed with an abrasive - is always the same. 

The modern material Ebonex is a mixture of substoichiometric titanium oxides Ti40y, TisOg. .. Tin02n-i ( Magneli phases [32]). It offers a unique combination of electrical conductivity and corrosion resistance. Primarily, Ebonex is produced as a powder. As is usual for ceramics, the ready-formed material is hard and brittle, the possibilities of machining are restricted (diamond tools). 

Glassy carbon can only be machined with diamond tools or with ultrasonic techniques. The shape must therefore be defined as exactly as possible during the forming of the polymer... 

The solid SisN4 forms as a smoke. It is captured as a powder, mixed with a carefully controlled amount of MgO additive, placed in an enclosed mold, and sintered at 1850°C under a pressure of 230 atm. The resulting ceramic shrinks to nearly full density (no pores). Because the material does not flow well (to fill a complex mold completely), only simple shapes are possible. Hot-pressed silicon nitride is impressively tough and can be machined only with great difficulty and with diamond tools. 

Machining flred ceramics can be expensive and can represent a significant fraction of the total fabrication costs. Ceramic materials are difficult to machine because they are hard and brittle. The tooling costs are high because diamond tools are likely to be required or if conventional tools are used the tool life is very short. Also the time required to machine ceramics is long because if high tensile loads are applied to the ceramic part it might fracture. 

Following the successful commercial synthesis of diamond in the 1950s, the second hardest material known, cubic boron nitride, cBN, was introduced to the market in the 1960s and is complementary to diamond. The iron, and its alloying elements, in ferrous materials has a tendency to react chemically with diamond under machining conditions and this can reduce the efficiency of the tool. cBN, however, although not as hard as diamond, does not react chemically with iron and is therefore particularly well suited to machining hard ferrous materials. 

Figure 4. Natural diamond cutting tool machining a contact lens.

Test Results Figure 40 shows, for each test, the average linear length machined by the diamond tools, before the tools were taken out on the basis of visible edge chipping of the floor panels. 

For ultra-precision machining of ceramic fiber-reinforced aluminum, single point diamond tools are the best suited. While processing, very low surface roughness can be achieved. The surface quality depends on the orientation of the fibers from the cutting direction (Yuan et al. 1993). 

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