Dressers: Advance, high-performance grinding technology is vital to manufacturing industry today. The demands on the grinding process are becoming ever tougher, both in economics and in dimensional and geometrical tolerances and surface quality.

This is where dressing steps in.

Dressing tools for silicon carbide and aluminum oxide wheels must fulfill the following tasks :

1. "True" the wheel to eliminate run-outand correct geometrical shape.
2. Restore the required effective roughness of the wheel.
3. Keep the wheel 'open' for high grinding efficiency.

The dressing process exposes a new sharp cutting layer on the wheel. The dressing tool is clamped and guided by the machine, and relative dresser / wheel movements (infeed and transverse feed) are executed by the dressing tool or the wheel. The path followed by the dressing tool determines the geometry of the grinding wheel.

The diamond's superlative hardness and wear resistance, makes it the ideal material for dressing tools.

The scope of this catalogue is to discuss diamond dressing tools. The catalogue encompasses, in detail, the technology of these tools. It will facilitate in the proper selection and ordering, as well as in the economical application of these tools.

We have the capability of manufacturing custom dressing tools to customer's specifications. Extensive emphasis is placed on "multi point" dressing tools because of their economic and technological superiority, multi point dressing tools in recent years have become increasingly tool of choice.

PCD Tools :

Natural Diamonds
Diamond is the hardest substance nature can offer, and only diamond can process the hardest of all materials. Natural diamond albeit very hard, is also very sensitive to impact, vibrations and heat caused while machining.

Although natural diamond can perform better than conventional tools on certain material, it proves to be economically unviable. This is due to not only the high cost of natural diamonds but also the additional costs involved in investing in new, rigid machinery.

Synthetic (Man-made) Diamonds
The problems posed by natural diamonds have now been eliminated by man's ingenuity through the manufacture of Polycrystalline Diamond (PCD) Cutting Tools. The main characteristics of PCD cutting tools are the amazing economics achievable in terms of cost per component. their repeatability and their predictable long life.

Furthermore, PCD has all the positive properties of natural diamond, thus there are no sacrifices made on the hardness of the tool or the surface finish of the component.

A Brief Overview of the Manufacturing Process of PCD
Man-made diamonds are produced from the purest form of graphite. Under conditions of high pressure and temperature, in the presence of certain catalysts, graphite gets converted to micron-sized diamond crystals. These crystals are then finely graded and sintered together with tungsten carbide to produce different grades of PCD blanks.

Applications of PCD Cutting Tools
PCD Cutting Tools can be easily used to machine non-ferrous and non-metallic components. Diamond, in its purest form, is essentially carbon. Carbon is known to have an affinity towards iron at higher temperatures. These temperatures are quickly reached while machining at certain speeds. For this reason, diamond cannot be conveniently used for ferrous applications.

PCD Tools are most frequently applied in the automobile lndustry -comprising both heavy and light motor vehicles. Some of the materials that have been cost effectively machined with PCD Tools include: Hypo and hypereutectic aluminum alloys, copper, bronze, babbit and abrasive plastic composites.

Although machining ferrous material is not recommended for PCD tools, they can be successfully used for certain cast iron applications where high speed is not attainable and where Cubic Boron Nitride (CBN), which is conventionally recommended for cast iron machining, cannot be used. In such applications, it is seen that PCD wears more slowly at lower speeds. When a critical speed is reached, it starts wearing faster because at this speed, the heat generated while machining is sufficient to cause the chemical reaction between iron and carbon. However, at low speeds, PCD Tools have proved their worth on cast iron material by achieving much better results than conventional tools, maintaining high consistency and accuracy of the work piece for a very long time.

The most significant application of PCD Cutting Tools, in this new generation of aluminium engine manufacturing, is to machine dissimilar materials such as aluminium engines with grey cast iron cylinder liners -either cast or pressed along with the aluminium -which have to be finish machined. along with the aluminium blocks.

CBN Tools :

Cubic Boron Nitride (CBN) is the hardest and most abrasion resistant material known to man, next only to diamond,

The manufacturing process and physical properties of CBN are very similar to those of PCD, except that instead of graphite, boron nitride is the building block for CBN. Like graphite, boron nitride is subjected to high temperature and pressure in the presence of catalysts to form cubic crystals of various micron sizes. These crystals are then graded and sintered together with tungsten carbide as the substrate, to form integral CBN blanks.

Like in PCD, the crystals within a CBN blank are also randomly oriented resulting in uniform hardness and abrasion resistance in all directions. The toughness of cemented tungsten carbide combined with the hardness of the CBN layer enables CBN Cutting Tools to withstand the high cutting forces encountered while taking heavy cuts in tough, hard-to-machine material. It also results in high impact resistance needed to withstand the shocks of severe interruoted cuts.

The CBN layer also has very high thermal conductivity -much higher than carbides and especially higher than ceramics. This allows the cutting tools to dissipate the heat generated at very high speeds of machining applications much more efficiently than seen with either carbide or ceramic tools. Unlike conventional cutting tools, CBN does not weaken or soften at very high temperatures. At machining temperatures up to 1000°C, polycrystalline CBN has the advantage of being completely chemically inert as well as retaining its strength and hardness at the cutting edge.

CBN is available in three different grades, defined by the application for which they are used:

• For rough machining of hard, super alloy or cast iron, CBN tools with approximately 90% by volume of CBN, along with titanium nitride and other binder materials are used.
• For finishing of hard metals and alloys, CBN tools with approximately 65% by volume of CBN, along with titanium nitride and other binder materials are used.
• For heavy material removal rate and heavy interrupted cuts, Solid CBN is used. This type of CBN has no carbide backing; instead, CBN crystals and ceramic phases are sintered together using an advanced high pressure-high temperature process. The Solid CBN has enhanced properties of high fracture toughness, wear resistance and chemical stability making it ideal for this type of heavy machining. The ceramic component provides improved chemical stability, enabling the superior qualities of CBN to be utilised in high-speed finish machining environments.