Cutting of composite materials by diamond coated tools

Guide: The manufacturing industry is vigorously promoting product development based on multi-functionality and high performance; in recent years, the development of environmentally-friendly products has become increasingly necessary; at the same time, the materials used in the products are changing year by year...

At present, the manufacturing industry is vigorously promoting product development based on multi-functionality and high performance; in recent years, the development of environmentally-friendly products has become increasingly necessary; at the same time, the materials used in products are changing year by year. In the automobile industry, the aerospace industry, and the semiconductor industry, which represent the manufacturing industry, although iron-based materials have been mainly used as component materials of products in the past, the use of high-strength and lightweight non-ferrous composite materials has shown an increasing trend. The biggest goal of using these materials is to reduce the energy consumption while using the product while maintaining the strength of the product.

In terms of composite processing, the related Cutting Tools and methods of use are quite different from the past. Typical representative of composite materials - Carbon Fiber Reinforced Plastics (CFRP) and Metal Matrix Composites (Metal Matrix)
Composites, MMC) contains hard materials that are difficult to machine in the base material with good machinability, so the tool wear is severe. When processing a composite material containing a hard material, it is quite effective to use the hardest diamond on the earth as a tool material from the viewpoint of suppressing abrasive wear. This article mainly introduces the processing examples of Cutting difficult-to-machine composite materials with diamond-coated tools.

CFRP processing

There are about 14,300 jets in operation in the world, and it is expected to increase to 31,700 by 2024 20 years later. Affected by the recent surge in oil prices, and in order to meet the increasing demand for aviation, people strive to reduce the weight of aircraft to achieve efficient transportation and reduce energy consumption. The composite materials used by Boeing are represented by CFRP. In its new Boeing 787, its usage rate accounts for about 50% of the weight of the fuselage, and there is a further trend in the future.

CFRP is a composite material obtained by repeatedly laminating carbon fibers having directionality in a matrix resin and firing them. The main role of carbon fiber is to increase the strength of the material. In the actual product manufacturing process, the laminated CFRP sheets need to be cut and drilled to be processed into a finished shape. When such a composite material is processed, there is a problem that the fiber cannot be completely cut to cause burrs or the life of the tool is shortened by the hard material.

For example, a CFRP laminated plate having a thickness of 5 mm was cut with a φ10 mm cemented carbide end mill (cutting conditions: 6000 r/min, 1200 mm/min, cutting length 0.5 m, blowing cooling). Glitch is usually present on CFRP workpieces when machining with conventional conventional shape end mills. In contrast, when the tool helix angle is changed from 30° of the conventional shape to 10° of the test tool, the generation of burrs is effectively suppressed. It is generally believed that when the helix angle is large, the effect of pulling up the carbon fiber by the upward component force is large, so that burrs are easily generated; by reducing the helix angle, the occurrence of such a phenomenon can be suppressed.

In the second processing example, a CFRP laminated plate having a thickness of 5 mm was cut by four φ10 mm end mills (cutting conditions are the same as in the above example). According to the 0.5m cutting length, the uncoated end mill has a large wear on both sides; the TiAIN coated end mill and the DLC diamond-like coated end mill also have large wear and coating at the edge. The base material is exposed due to complete wear and the degree of wear is not much different from that of the uncoated end mill. The wear of the diamond-coated end mill is small and the substrate is not exposed at all. It can be seen that when CFRP is processed, the tool wear is severe, and the wear resistance of the TiAIN coated tool and the DLC coated tool are poor. Therefore, the selection of the diamond coated tool is an effective solution.

MMC processing

High-performance MMC materials are mainly used for automotive parts, semiconductor device parts, and heat exchangers. However, due to the production cost and product shape freedom, the development lags behind the improvement of alloy materials. Despite this, due to the increased awareness of energy conservation, the demand for high-strength, lightweight MMC materials is increasing.

MMC is a composite material made of ceramics as a reinforcing material and a metal matrix. It can be combined with various materials. Among them, the use of MMC containing aluminum as a main component in the alloy and containing several tens of percent of alumina and silicon carbide is increasing. When processing MMC, the high hardness of the ceramic component contained in the material is likely to cause tool wear is the main problem.

Practical machining examples include various machining operations from shape machining to Drilling. The following is an example of drilling: drilling test of Al-30% SiC MMC workpiece with φ2.6mm diamond coated drill bit produced by three companies (cutting conditions: 5000r/min, 500mm/min, hole depth 7.8mm) , water-soluble cutting oil). After processing 50 holes, the two faces of the front end of the diamond coated drill bit of Company A and Company B were very worn, and the peeling of the coating was clearly observed. The drill bits of the two companies A and B failed after processing 127 holes and 140 holes respectively. While Mitsubishi's diamond-coated drill bit is machined with 50 holes, the cutting edge is only conventionally worn, and the diamond coating is still attached to the tool base. The tool continues to be drilled to 256 holes before it fails. When machining with an uncoated drill bit and a TiAIN coated drill bit, a few holes are drilled and the machining is severe and the machining cannot be performed. It can be seen that when machining MMC composites, tool wear is the biggest problem, and diamond coating is an effective solution. Mitsubishi's coating has a high bonding strength with the substrate and is the key to long tool life.

In order to stably process composite materials represented by CFRP and MMC, this paper describes the processing examples of diamond coated tools. We believe that in order to meet the diversified needs of products, the effective use of Diamond Tools in the process of processing difficult materials will become more and more important.