Cutting of non-metallic materials:
For the cutting of non-metallic materials such as wood, plastic, rubber, glass marble, granite, etc., although similar to the cutting of metal materials, the tools, equipment and cutting amount used have their own characteristics.
The cutting of wood-cut wood products is mainly carried out on various woodworking machines, such as sawing, planing, turning, milling, drilling and sanding.
Wood sawing usually uses woodworking circular saws or woodworking band saws (see woodworking saws). Both can be cut, cut or cut with different sawtooth shaped tools (saw blades or saw bands). Band saws have narrower kerfs, and narrow band saws cut surfaces and irregular shapes.
Planing is usually done with woodworking planers or woodworking planers (see woodworking planers). Both can be used to plan planes or profiles with a rotating planer, where the planer can be processed with higher dimensional accuracy. Woodworking precision planing can be used when the surface finish is high.
The outer circumference of the wood is usually turned on a woodworking lathe.
The opening, grooving, engraving and processing of various types of wood can be milled on a woodworking milling machine using a forming cutter.
Drilling can be done on wood drills, twist drills or flat drills on bench drills or woodworking drills. The holes can also be machined with a hand drill.
The finishing of the wood surface can be done with a woodworking sander. Plane sanding can be used with belt sander; various types of sanding can be used with roller sander; face sanding and corner chamfering can be used with disc sanding machine. It can also be sanded with woodworking lathes or woodworking drills.
The cutting speed of wood processing is much higher than that of metal cutting, so the cutting edge of the tool is thin and sharp, and the feed rate is also large. For example, the sawing speed often reaches 40 to 60 m/s; when turning or planing, the rake angle of the tool often reaches 30° to 35°, and the cutting speed reaches 60 to 100 m/s, so the amount of chip output is large. The cutting fluid is generally not used for cutting, and a large amount of wood chips that have been cut dry can be sucked away by a suction fan. High-speed rotating woodworking machines generally have motorized feed and safety guards, but many wood cutting operations still require manual feed, so special attention must be paid to operational safety.
The plastic cutting plastic is less rigid than the metal, and is easy to bend and deform, especially the thermoplastic has poor thermal conductivity and is easy to heat and soften. Therefore, when cutting plastic, it is advisable to use high-speed steel or carbide tools, use a small feed (0.1 ~ 0.5 mm / rev) and high cutting speed, and use compressed air to cool. If the tool is sharp and the angle is suitable (generally the front angle is 10°~30°, the back angle is 5°~15°), it can produce strip-shaped chips, which is easy to take away heat. If too much short chips and dust can blunt the tool and contaminate the machine, the exposed parts and guides on the machine need to be protected. When cutting celluloid, it is easy to catch fire and must be cooled with water.
When turning thermosetting plastics such as phenolic plastics, aminoplasts and tapeboards, it is advisable to use carbide tools with a cutting speed of 80-150 m/min. When turning thermoplastics such as polyvinyl chloride or nylon or bakelite, the cutting speed can reach 200 to 600 m / min.
When milling plastics, high-speed steel cutters are used, and the cutting speed is generally 35-100 m/min. With carbide tools, the cutting speed can be increased by 2 to 3 times.
Plastic drilling can be used with a twist drill with a large helix angle. When the hole diameter is larger than 30 mm, a nesting drill can be used. When using a high speed steel drill bit, the common cutting speed is 40 to 80 m/min. Due to the expansion and contraction of the plastic, the diameter of the drill used in drilling should be 0.05 to 0.1 mm larger than the required diameter. When drilling, the hard plastic board is placed under the plastic to prevent the plastic around the hole wall at the exit of the drill bit from falling.
The cutting speed of planing and cutting is low, and it is generally not suitable for cutting plastics, but it can also be used for leveling and chamfering with woodworking planers. For tapping, a high-speed steel taper with a wide groove can be used and lubricated with oil; the external thread can be cut with a thread comb. For thermosetting plastics such as nylon, bakelite and bakelite, it can be ground with loose white corundum or silicon carbide grinding wheels, or sanded with paper (paper), but it needs to be cooled with water. Since the wear debris of thermoplastics tends to block the grinding wheel, it is generally not suitable for grinding.
When cutting rubber hard rubber workpieces, you can use sharp-edged carbide turning tools with a cutting edge (12°~40° for the front angle and 10°～20° for the back angle), with a cutting speed of 150-400 m/min. It can be dry or cooled with water or compressed air. If turning with a high speed steel tool, the cutting speed is lower.
Hard rubber drilling can be done with a hard alloy or high speed steel twist drill with a top angle of about 80°. When the drilling aperture is 10 to 20 mm, the cutting speed can be 21 to 24 m/min. Hard rubber parts can also be ground with a loose and soft grinding wheel.
Glass-cut glass (including semiconductor materials such as tantalum and silicon) has high hardness and high brittleness. Cutting, drilling, grinding and polishing are commonly used for the cutting of glass.
For glass plates with a thickness of less than 3 mm, the simplest method of cutting is to manually scribe the surface of the glass with diamond or other hard material, and use the stress concentration at the notch to break it by hand.
Mechanical cutting of glass generally uses a circular saw blade made of thin iron sheets (or stainless steel sheets) and adds abrasive and water during the cutting process. A commonly used abrasive is silicon carbide or diamond having a particle size of about 400. When it is required to cut a round bar-shaped semiconductor ingot into a wafer having a thickness of about 0.4 mm, an annular circular saw blade is used, and a rod-shaped ingot is cut by the inner circumference thereof, and a wafer having a thickness of 0.4 mm is cut, and the slit width is about It is 0.1 to 0.2 mm. The cutting of the square wafer plane is often broken by a thin-plate grinding wheel, and the circular wafer can also be ultrasonically cut.
Grinding and polishing glass works like metal. The surface of the polished glass is a translucent fine surface that must be polished to become a transparent glossy surface. The grinding pressure is generally 1000-3000 Pa, and the abrasive can be made of quartz sand, corundum, silicon carbide or boron carbide with a particle size of W5-20, and the ratio of water to abrasive is about 1:2. After the glass is ground, the flat surface of the rough surface often has an uneven layer with an average depth of 4 to 5 microns, and individual cracks are deep into the surface. Therefore, it is often necessary to remove a glass layer having a thickness of 20 micrometers during polishing. This thickness is about the amount of grinding removal. About 1/10, but the time required for polishing is much longer than grinding (hours to tens of hours). The material of the polishing disc is usually felt, wool or plastic, and the abrasive used is fine powder (less than 5 μm in diameter) such as iron oxide (red powder) having a particle size of W5 or less, cerium oxide and zirconium oxide. When grinding, an equal amount of water is added to prepare a suspension as a polishing agent, and the working effect is better at an ambient temperature of 5 to 20 °C.
When drilling large or medium holes in glass, it is generally used as a drill pipe with a grooved copper pipe or steel pipe at a cutting speed of 30 m/min, while injecting silicon carbide or diamond abrasive and lubricating at the drilling site. oil. When drilling, the glass must be flattened with felt or rubber to prevent crushing. For the small holes with a hole diameter of 5 mm or less, the impact drilling method is often used, that is, the carbide die is used at a speed of about 2000 rpm, and the circular chisel is applied to the glass surface with a vibration of 6 kHz by an electromagnetic oscillator. This method is very efficient, and it takes only 10 seconds to drill a hole with a hole diameter of 2 mm and a depth of 5 mm. Ultrasonic (18 ~ 24 kHz) processing of the other hole and shaped hole is most convenient.
The outer circumference of the glass is usually ground with a silicon carbide grinding wheel, or it can be turned by a diamond turning tool or a negative angle cemented carbide turning tool at a speed of about 2000 rpm.
Stone cutting processing of hard materials such as marble, granite and concrete is mainly carried out by cutting, turning, drilling, planing, grinding and polishing. When cutting, the circular saw blade can be used to add abrasive and water; the outer circle and the end face can be turned by a carbide turning tool with a negative rake angle at a cutting speed of 10 to 30 m/min. The drill can be drilled with a carbide drill with a cutting speed of 4 to 7 m/min. Large stone planes can be planed with carbide planers or knives; precision smooth surfaces can be obtained by three methods of grinding or grinding and polishing.
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