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Wiper CBN Inserts |
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CBN- introduction
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In the mid 1980’s, Iscar introduced into the cutting tool market, the wiper concept on its unique multifunctional Grip tools, causing a revolution in the metal cutting industry. In 1991, Iscar introduced the unique WG, Wiper Geometry, as an integral part of its standard ISO turning inserts. In recent years, the introduction of CBN and ceramic inserts and its standard positive ISO inserts together with the unique wiper concept, offered a new dimension for turning and a much wider range of applications. During this last 10 years, the wiper geometries and the chipformer configurations of turning inserts as well as the application range were optimized. The wipers’ design resulted in excellent surface quality with high removal rates and clear cost savings, mainly in finish turning operations. An example of a mirror like surface produced by machining a hardened shaft with a CBN wiper insert is shown in Figure 1.
CBN and Ceramic Wiper inserts
The use of Iscar’s standard ISO turning inserts and multi-function Grip tools with wiper type CBN tips facilitates the machining of hardened steel and cast iron, giving an excellent surface quality and at the same time, a significant machining cost reduction. These wiper type inserts replace or eliminate many grinding operations. Successful implementation of the wiper designs for hard cutting is demonstrated by their use in the automotive industry, in turning of bearing and hydraulic parts as well as in the milling or turning of dies and molds.
The results of turning of a D2 tool steel shaft with a hardness of more than 60HRc using a wiper type CNMA 120408T-WG-IB50 insert is shown in Figure 2. A surface roughness better than 0.5µm is achieved in dry machining at a 0.2mm/rev feed rate and a 100m/min cutting speed. Even after 16 minutes of longitudinal turning, the surface roughness Ra is better than or 1µm. When reducing the feed to 0.15mm/rev with the same wiper insert (WG), the achieved Ra values reached as high as 0.3µm.
Comparing these results with the use of standard CNMA 120408T-IB50 inserts with the same 0.8mm corner radius, a surface roughness Ra of only 2µm was achieved. After 16 minutes machining time the roughness quality was even poorer than 2.5µm. In many cases, especially in the automotive industry, new CBN or coated wiper inserts replace or eliminate additional grinding operations. This saves machining time and reduces production costs.
Iscar’s new double-sided wiper inserts, made from IS8 (Silicon Nitride), are used for turning cast iron. The combination of the new ceramic material with the WG design improves performance and economy in many cast iron turning applications.
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