Ultra-precision machining refers to precision manufacturing processes that achieve extremely high levels of precision and surface quality. Its definition is relative, changing with technological advances.
Currently, this technique can achieve submicrometric and even nanometric dimensions and shapes, with surface roughness on the nanometric scale. Ultra-precision machining methods include ultra-precision cutting (such as ultra-precision turning and milling), ultra-precision grinding, ultra-precision lapping and ultra-precision special processing.
Ultra-precision cutting
Ultra-precision cutting mainly involves turning with diamond tools, mainly used for machining non-ferrous alloys, optical glass, marble and non-metallic materials such as carbon fiber plates. The high precision achieved in ultra-precision cutting is due to the low affinity between diamond tools and non-ferrous alloys, in addition to their excellent hardness, wear resistance and thermal conductivity.
Furthermore, in ultra-precision cutting, high-precision pneumatic bearings, floating air guides, positioning detection components and measures such as constant temperature, vibration isolation and vibration damping are adopted.
This ensures a surface roughness Ra value of less than 0.025 μm and a geometric accuracy of up to 0.1 μm, making ultra-precision cutting increasingly popular in aerospace, optical and civil applications, moving towards greater precision.
Ultra-precision grinding
Ultra-precision grinding is a sub-micron level processing method, progressing towards the nanometer level. Refers to a grinding method that achieves a processing accuracy of 0.1μm or higher and a surface roughness Ra value below 0.025μm, suitable for processing hard and brittle materials such as steel, ceramics and glass.
Traditional grinding and polishing processes can be eliminated through ultra-precision grinding to achieve the required surface roughness. In addition to ensuring precise geometric shapes and dimensions, mirror-like surface roughness can be achieved through ultra-precision grinding.
Ultra-precision cutting
Ultra-precision lapping includes mechanical lapping, chemical-mechanical lapping, floating lapping, elastic emission machining and magnetic lapping. The spherical deviation tolerance of parts processed by ultra-precision lapping can reach 0.025μm, and the surface roughness Ra value can reach 0.003μm.
The main conditions for ultra-precision lapping are precise temperature control, vibration-free processing, clean environment and small and uniform abrasive particles. High-precision detection methods are also indispensable.
Special ultra-precision processing
Special ultra-precision processing technology is internationally recognized as one of the most promising technologies of the 21st century. Refers to processing methods that use forms of energy such as electrical, thermal, optical, electrochemical, chemical, acoustic, and special mechanical energy to remove or add material.
The main application objects include difficult-to-process materials (such as titanium alloys, heat-resistant stainless steel, high-strength steel, composites, engineering ceramics, diamond, ruby, hardened glass and other high-hardness and high-toughness materials, high-strength, high-melting point), difficult-to-process parts (such as complex three-dimensional cavities, holes, group holes, and narrow slots), low-rigidity parts (such as thin-walled parts, elastic elements), and processes that achieve welding , cutting, drilling, spraying, surface modification, chemical etching and fine processing with high energy density beams.
These processing methods include laser processing technology, electron beam processing technology, ion beam and plasma processing technology, electrical processing technology, etc., with only a brief introduction here.
Laser processing
Laser processing involves a laser generator that focuses high-energy density laser light onto the surface of a workpiece. The absorbed light energy instantly transforms into thermal energy, which, based on its density, can achieve precision drilling, cutting and anti-counterfeiting micro mark production.
With the rapid development of laser processing equipment and technology, high-power lasers of more than 100 kW and kilowatt-level high-beam solid-state lasers equipped with optical fiber have emerged for long-distance and multi-station work.
Due to the high level of power and automation of laser processing equipment, CNC control and multi-coordinate linkage are widely adopted, equipped with auxiliary systems such as laser power monitoring, automatic focusing and industrial television display. At present, the minimum hole diameter achieved by laser drilling is 0.002mm, the laser cutting speed of thin materials can reach 15m/min, and the cutting gap is only between 0.1-1mm.
The applications of laser surface strengthening, surface remelting, alloying and amorphous processing technology are becoming more and more widespread, and laser microprocessing in electronics, biology and medical engineering has become an irreplaceable special processing technology.
Electron Beam Processing
Electron beam processing involves the continuous emission of negative electrons from the cathode to the anode in a vacuum. The electrons accelerate and focus into a very thin, high-energy-density electron beam during the transition from the cathode to the anode. When high-speed electrons strike the surface of the workpiece, their kinetic energy transforms into thermal energy, causing the material to melt and vaporize, and is then removed from the vacuum.
Controlling the force and deflection direction of the electron beam, combined with bench numerical control displacement in the x and y directions (using CNC control and multi-coordinate linkage), can achieve punching, forming cutting, engraving, photolithography exposure and other Law Suit.
Electron beam processing technology is maturing internationally and is widely used for the combined welding of large structures of major load-bearing components such as launch rockets and spacecraft, as well as the fabrication of important structural parts such as aircraft beams. , structures, landing gear components, engines. integral rotors, casings, drive shafts and pressure vessels for nuclear power devices.
Integrated circuit manufacturing also widely adopts exposure to electron beam photolithography, which has a much shorter wavelength than visible light, achieving a line pattern resolution of 0.25 μm.
Ion beam processing
Ion beam processing involves accelerating and focusing ions produced by an ion source in a vacuum to reach the surface of a workpiece. Compared to electron beam processing, because ions carry a positive charge and their mass is millions of times that of electrons, they can gain greater kinetic energy after acceleration.
They rely on microscopic energy from mechanical impact rather than converting kinetic energy into thermal energy to process the part. Ion beam processing can be used for surface etching, ultra-clean cleaning and cutting at the atomic/molecular level.
Electrical Micro Discharge Machining
Micro electrical discharge machining involves the removal of metal in an insulating working fluid through a localized high temperature caused by a pulsed spark discharge between a tool electrode and a workpiece. The process does not involve macroscopic cutting forces; Precise control of single-pulse discharge energy combined with precise microfeeding can remove extremely fine metallic materials.
It can process microshafts, holes, narrow grooves, flat and curved surfaces. State-of-the-art EDM shaping and wire cutting can provide micrometer-level processing accuracy, capable of processing a 3um micro-axis and a 5μm hole.
Microelectrolytic processing
Microelectrolytic processing involves the decomposition of water into hydrogen ions and hydroxyl ions in a conductive working fluid. The metallic atoms on the surface of the part, serving as the anode, become metallic cations and dissolve in the electrolyte, being gradually electrolyzed. These then react with the hydroxyl ions in the electrolyte to form metal hydroxide precipitates, while the tool's cathode does not wear out.
There are also no macroscopic cutting forces between the tool and the workpiece in the processing process. By precisely controlling the current density and location of electrolysis, nanometer-level precision electrolytic processing can be achieved and the surface will not have processing stress.
Microelectrolytic processing is often used for mirror polishing, precision grinding and situations requiring stress-free processing. Electrolytic processing applications are broad, extending from integral blades and impellers to casings, disc ring components and small hole deep processing.
High-precision metal reflective mirrors can be processed using electrolytic processing. At present, the maximum current capacity of electrolytic processing machines has reached 50,000A, and CNC control and multi-parameter adaptive control have been implemented.
Composite Processing
Composite processing refers to processing technologies that utilize several different forms and methods of energy, combining their advantages, for example, electrolytic grinding, ultrasonic electrolytic processing, ultrasonic electrolytic grinding, ultrasonic electrical discharge, ultrasonic cutting, etc.
Composite processing is more effective and has a wider range of applications than single processing methods.
