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December 24, 2022
What are the difficulties in turning and milling composite materials
Turning milling composite processing is a highly precise processing technology with strong automation technology production and processing. It means that all the production processes of workpieces are under the control of CNC machine tools, and some very different composite materials can be produced and processed. Today's composite materials are widely used in all aspects of our lives, especially in aerospace and some ultrahigh precision machinery manufacturing industries.
1、 Types of composite materials for CNC machining centers
Composite materials can be divided into metal materials and metal composites, non-metallic materials and metal composites, non-metallic and non-metallic composites according to their composition. According to its structural characteristics, it can be divided into:
1. Chemical fiber composite material. A variety of chemical fiber boosters are placed in the base material and combined. Such as chemical fiber elastomer materials, chemical fiber reinforced alloys, etc.
2. The interlayer is made of composite material. It is composed of surface raw materials and core plates with different characteristics. Generally, the base material is of high hardness and thin; The core material is light and has low compressive strength, but has certain strength and thickness. It is divided into solid core skirt wall and honeycomb partition.
3. Sand composite materials. Hard sands are jointly distributed in the foundation, such as diffusely reinforced aluminum alloy, cermet, etc.
4. Doped composite materials. It is composed of two or more types of enhanced phase raw materials doped in one base material phase raw material. Compared with ordinary single phase composite materials, its impact compressive strength, fatigue limit and impact toughness are significantly improved, and it has unique thermal deformation characteristics. It is divided into intralayer doping, solid layer doping, sandwich hybrid, intralayer/solid layer doping and super hybrid composite materials.
2、 Problems that should be paid attention to when turning and milling composite materials
1. The carbon fiber composite solid layer has low compressive strength and is easy to be layered under the effect of cutting speed, so the axial force should be reduced when drilling or trimming. High speed rotation and small tool path are specified for drilling. The rotating speed ratio of the CNC machining center is generally 3000~6000r/min, and the cutting speed is 0.01~0.04mm/r. It is good to use a three point two edge or two point two edge fried dough twist drill. The sharp tip can first cut off the carbon fiber material layer, and the two edges have a repairing effect on the surface layer. The diamond inlaid fried dough twist drill is sharp and wear-resistant. The drilling of the composite material and titanium metal interlayer is a difficult point. Generally, the overall cemented carbide drill is selected, and the milling is carried out according to the main cutting parameters of titanium metal. The drilling starts from the titanium metal side until the drilling is completed. The lubricating fluid is added during the milling to reduce the scald of the composite material. Boeing Company of the United States has developed a PCD fried dough twist drill to drill holes in the interlayer.
2. The actual drilling effect of three types of new overall carbide tool composite material production turning tools is stronger. They all have some common characteristics: high stiffness, small helix angle, even 0 °. The specially designed herringbone edge can reasonably reduce the radial cutting speed of the CNC machining center, reduce the hierarchical, and their work efficiency and actual effect are very good.
3. The composite material is cut into powder, which is harmful to human health. A powerful vacuum cleaner should be used for dust collection. Water cooling and heat dissipation can also reasonably reduce smoke pollution.
4. Carbon fiber composite prefabricated components are generally large in size, complicated in appearance and structure, high in strength and hardness, and belong to raw materials that are difficult to produce and process. In the process of drilling, the cutting speed is relatively high, the drilling heat is not easy to transmit, the epoxy resin will be burnt or the resin will become soft when it is relatively serious, and the CNC blade is seriously damaged. Therefore, the CNC blade is important for carbon fiber processing, and its drilling principle is closer to cutting rather than cutting. Therefore, the drilling angular speed of turning milling composite processing usually exceeds 500m/min, so the high-speed rotating small tool path strategy is selected. Generally, the overall carbide tool extruding tap turning tool, electroplating process diamond particle sand wheel blade, diamond inlaid turning tool, copper fund steel particle woodworking saw blade are used for edge cutting production and processing of CNC blades.
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