All processes in which the shape of a workpiece is changed by removing the material cohesion at the machining point and thus reducing the overall material cohesion are called cutting processes. The most important group is machining, in which material is removed in the form of chips (sawing, planing, milling, drilling, …). Other important cutting processes are shear cutting (punching), flame cutting or spark erosion. Dismantling for disassembly is also part of cutting. Copper can already be processed with little effort in terms of lubrication and tool surface. The low forming forces, the simple formation of a load-bearing lubricating film and the ductility of the oxide layers always present on the surface work together to advantage here. Cutting according to DIN 8588 is the mechanical separation of materials of any type and shape without the formation of chips.
Shear cutting (punching)
Stamped parts are defined in DIN 9870-1 as parts that are manufactured by a combination of cutting, forming and joining operations. Each of these manufacturing operations is carried out in one stroke by two-part form-bound tools. Thus, different non-cutting manufacturing processes, such as shearing, bending and deep drawing, are usually combined in one tool. This is used almost exclusively for the production of sheet metal components. Colloquially, components that are only manufactured by shear cutting or a combination of shear cutting and forming are often referred to as
stamped parts. Stamping is used in particular for the production of components in large quantities. Due to the good conductivity in combination
combined with excellent formability, a large number of electronic components such as connectors, contact sheets and lead frames made of copper and copper alloys are produced by stamping. Other applications include decorative automotive emblems or heat sinks.
Typical copper alloys used in stamping are pure copper grades such as Cu-ETP, Cu-HCP, Cu-DHP and Cu-OFE, the bronzes CuSn4 to CuSn8 and the brass grades CuZn5 to CuZn40. Copper aluminium and copper nickel alloys can also be found. In addition to the product-specific desired properties such as strength or electrical conductivity, the formability must also be taken into account when selecting materials. Corresponding material data sheets to assist in the selection process can be found here.
Copper materials are cut by sawing with hacksaws, metal band saws and cold circular saws. Cutting with cold circular saws is becoming more and more important. In the meantime, there has been a shift from solid steel blades to saw blades with inserted teeth made of high-speed steel or carbide. Here, rake angles g = 15° are recommended for tough materials (such as copper, copper-nickel) and g = 5° and large teeth for short-chipping materials. In both cases, clearance angles g = 8° are selected. All recommendations for cutting geometry apply to both HSS and HM. For band saws, the angles are selected about 2° smaller. In the case of tough materials, a subdivision of the cutting width by alternately back-ground teeth or by dividing the teeth into roughing and finishing cutters has proved successful. In this case, the first teeth chip the middle third of the kerf and the latter teeth the outer thirds of the kerf width. The sawing of copper materials is done with intensive cooling by emulsion. In the case of short-chipping materials, the emulsion must be monitored because fine tinsel can cause the emulsion to lean.
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