Ultrasonic processing characteristics
Not subject to the restrictions of whether the material is electrically conductive; tools on the workpiece of the macroscopic force is small, the thermal impact is small, and thus can be processed thin-walled, narrow slits and thin pieces of the workpiece; the brittle the more brittle the more easy to process the material, the harder the material or the more strength, the greater the toughness of the more difficult to process; due to the crushing of the workpiece material is mainly dependent on the role of abrasives, abrasive hardness should be higher than the workpiece material hardness, while the tool's hardness is higher than that of the material. The hardness of the material is high, and the hardness of the tool can be lower than the workpiece material; can be combined with a variety of other processing methods, such as ultrasonic vibration cutting, ultrasonic EDM and ultrasonic electrolytic processing.
Ultrasonic machining is mainly used for various hard and brittle materials, such as glass, quartz, ceramics, silicon, germanium, ferrite, gemstones and jade, such as punching (including round holes, shaped holes and curved holes, etc.), cutting, slotting, socketing, engraving, batches of small parts deburring, mold surface polishing and grinding wheel dressing.
Ultrasonic drilling hole diameter range is 0.1 ~ 90 mm, the processing depth of up to 100 mm or more, hole accuracy up to 0.02 ~ 0.05 mm. Surface roughness in the use of W40 boron carbide abrasive processing glass can be up to 1.25 ~ 0.63 microns, processing carbide can be up to 0.63 ~ 0.32 microns.
Ultrasonic machining machine generally consists of by the power supply (i.e., ultrasonic generator), vibration system (including ultrasonic transducer and amplitude change rod) and machine tool body three parts.
Ultrasonic generator will be converted to ultrasonic frequency electrical power output, power from a few watts to a few kilowatts, up to 10 kilowatts. Usually used ultrasonic transducer magnetostrictive and electrostrictive two types. Magnetostrictive transducer and metal and ferrite two kinds, metal is usually used for more than kilowatts of high-power ultrasonic machine; ferrite is usually used for kilowatts of small power ultrasonic machine. Electrostrictive transducer made of piezoelectric ceramics, mainly used for small power ultrasonic processing machine.
Variable amplitude rod plays a role in amplifying the amplitude and polymerization, according to the rule of change of the cross-sectional area has a cone, the index curve shape, hanging chain line shape, ladder, etc.. Machine tool body generally have vertical and horizontal two types, ultrasonic vibration system is placed vertically and horizontally accordingly.
Ultrasonic processing applications
1, molding
Ultrasonic processing of various hard and brittle materials, round holes, holes, cavities, grooves, shaped through-hole, bending holes, micro-fine a hole, nesting and so on. Although its productivity is not as good as EDM, electrolytic machining, but the machining accuracy and surface quality of the workpiece is better than EDM, electrolytic machining. For example, the production of hard metallurgy instead of alloy tool steel manufacturing technology deep molds, wire drawing dies and other molds, its durability can be increased 80-100 times. The use of electric discharge machining, the surface of the workpiece often appear micro-cracks, affecting the mold surface quality and service life. And the use of ultrasonic processing is not this defect, and dimensional accuracy can be controlled within 0.01-0.02mm, bore taper can be trimmed to 8'. For silicon and other semiconductor hard and brittle materials such as nesting and other processing, more show the characteristics of ultrasonic processing. For example, in the diameter of 90mm, 25mm thick silicon wafer, can nesting processing out of 176 diameter of only 1mm components, time only 1.5min, pass rate as high as 90% -95%, processing accuracy of plus or minus 0.02mm. In addition, in recent years, ultrasonic machining has been excluded from the obstacles to the field of microfabrication.
2, cutting processing
Ultrasonic precision cutting of semiconductors, ferrite, quartz, gemstones, ceramics, diamond and other hard and brittle materials, than the diamond tool cutting with thin slices, narrow kerf, high precision, high productivity, good economic advantages. For example, ultrasonic cutting of germanium wafers with a height of 7mm and a width of 15-20mm can be cut in 3.5min with a thickness of 0.08mm; ultrasonic cutting of monocrystalline silicon wafers can be cut in 10-20 slices at a time. Again, in the ceramic thick film integrated circuits with components, processing 8mm, 0.6mm thick ceramic sheet, can be processed within 1min 4 pieces.
3, welding processing
Ultrasonic welding is the use of ultrasonic frequency vibration effect, the removal of the oxide film on the surface of the workpiece, so that the new surface of the body to show up, and in the two welded surface molecules of the surface of the high-speed vibration of the impact of friction and heat. Affinity bonding together. Its not only can weld nylon, plastic and the surface is easy to generate oxidized strands of aluminum products, etc., but also in ceramics and other non-metallic surfaces hanging tin, silver, coated with thin layers. As ultrasonic welding does not require external heating and flux, welding heat-affected zone is very small, applying a small pressure, so you can weld the diameter or thickness of a very small (0.015-0.03) of different metal materials, but also weld plastic thin fibers and irregularly shaped hard thermoplastics. At present, large-scale integrated circuit lead connection, etc., has been widely used ultrasonic welding.
4, ultrasonic cleaning and processing
Mainly used for geometrically complex, cleaning quality requirements of small and medium-sized precision parts, especially the workpiece on the probe small holes, micro-holes, curved holes, blind holes, grooves, narrow slits and other parts of the fine cleaning. Using other cleaning methods, the effect is poor, or even can not be cleaned, the use of ultrasonic cleaning is effective, high productivity. At present, in the semiconductor and integrated circuit components, instrumentation parts, electro-vacuum devices, optical parts, precision machinery parts, medical equipment, radioactive contamination and other cleaning applications. It is generally believed that ultrasonic cleaning is due to the cleaning fluid (water-based cleaning agents, chlorinated hydrocarbon solvents, petroleum fluxes, etc. should be ultrasonic cavitation effect under the action of the results. Cavitation effect produces a strong shock wave, directly to the cleaning parts of the dirt, etc., and make it come off; cavitation effect produced by the cavitation bubbles penetrate into the dirt and the surface of the cleaned parts, prompting the dirt to fall off; in the case of dirt dissolved by the cleaning fluid, the cavitation effect can be accelerated by the dissolution process. Ultrasonic cleaning, should be a reasonable choice of working frequency and sound pressure intensity, in order to produce good cavitation effect, improve the cleaning effect. In addition, the temperature of the cleaning fluid should not be too high to prevent the weakening of the cavitation effect, affecting the cleaning effect.