Application of Micro Robot Technology in Ultra-precision Machining

Ultra-Precision Machining technology has broad application prospects in the defense industry, information industry and civilian products. In the defense industry, the quality of the missile gyroscope directly affects its hit rate. The 1kg gyro rotor whose center of mass deviates from the symmetry axis of 0.0005μm will cause a range error of 100m and a track error of 50m. In aerospace technology, the attitude bearing of the satellite is a vacuum unlubricated bearing, and the roundness and cylindricity of the hole and the outer circle are both nanometer. Optical telescopes for satellites, television camera systems, infrared sensors, etc., high-precision aspherical lenses in optical systems must be ultra-precision machining such as ultra-precision vehicles, grinding, grinding, and polishing. In addition, large-scale astronomical telescope lenses, infrared detector mirrors, and curved mirrors for laser nuclear fusion are all manufactured by ultra-precision machining. In the information industry, computer chips, magnetic disks and magnetic heads, photoconductor drums of copiers, etc. must be ultra-precision processed to meet the requirements. Many of the products in civilian products, such as contact lenses, are machined from ultra-precision CNC lathes.

2. Implementation method of ultra-precision machining

At present, ultra-precision machining methods include: ultra-precision cutting, such as ultra-precision diamond tool mirror turning, boring and milling; ultra-precision grinding, grinding and polishing; ultra-precision micro-machining (electron beam, ion beam, laser) Beam processing and processing of silicon micro devices, LIGA technology, etc.).

Some scholars in Japan have proposed the concept of ultra-precision machining using micro- robots . This concept breaks through the traditional processing concept and designs a tiny robot that can move freely, allowing the robot group to climb on the workpiece to achieve nano-scale ultra-precision machining.

The miniaturization of the organization saves resources and energy, and because of the reduction in part size, the integration of functions per unit volume and weight is improved. Miniaturization has also opened up many new applications, such as industrial teleoperation or cell biology applications. The silicon micromachining process from microelectronics has a major impact on the miniaturization of the organization. It integrates mechanical and electronic functions on the same part and is ideal for processing MEMS systems.

3. Ultra-precision machining technology based on micro-robot

At present, micro-robots are mainly used in the field of ultra-precision machining in the following ways: micro-machining robots, dual-micro-robots, machine tools and robots, scanning tunneling microscopes and atomic force microscopes.

The main problem in precision machining of small parts is how to realize the machining and assembly of small parts with microscopic precision and low cost. Since machining error compensation and temperature compensation control based on conventional methods require a large amount of energy, in recent years, IC-based processes and deep X-ray techniques have also been successfully used for processing micromachined parts of complex processes, but processed materials. The limitations are large, and the processing and maintenance costs are also expensive. The tiny robots carrying various micro-operations, processing and measuring tools can not only process, inspect and assemble Precision Parts, but also cooperate with some processes that are difficult to complete with large-scale machine tools. Therefore, ultra-precision machining based on micro-robots is an effective way to achieve ultra-precision machining.

3.1 Micromachining robot

Shizuoka University in Japan has developed a group of tiny robots. Each robot is approximately 1 cubic inch in size and is driven by a piezoelectric crystal that is positioned on the surface of the workpiece. This robot can move not only on a horizontal surface, but also on the façade and ceiling without the need for rails. And other auxiliary devices. It also offers a modular design so that different tools such as small hammers, micro-detection tools and dust capture probes can be selected for different micro operations. In the experiment, one of the multiple robots has a reduction gear to drive the micro-drill, and the other is driven by a DC motor to drive the pinion, which can cooperate with the micro-hole machining of the workpiece surface.

Maori Shangwu et al. developed a super-small EDM machine using the “foot drive method” to realize the processing of micro-holes with a diameter of 0.1 mm, as shown in Fig. 3. Aoyama Sangzhi et al. developed a tiny robot and used it to achieve imprinting.

3.2 macro-micro combined drive mode

The combination of industrial robots and micro-motion robots can be used to manufacture precision robots for ultra-precision machining and assembly. The advantage of this method is that it can overcome the shortcomings of low precision of industrial robots, and use micro-motion robots to improve the accuracy; at the same time, it can eliminate the weak points of the micro-robot movement stroke, so that the robot can carry out a wide range of operations. For example, robots are often used in large scale integrated circuit assembly. However, the accuracy and speed of conventional robots often fail to meet the requirements. The low accuracy is due to drive/servo accuracy and the transmission error of the mechanism. The slow response time is due to the narrow bandwidth of the system resonant mode. In order to achieve precise and fast operation, Japan's Electric Communication University has designed a high-precision assembly robot system combining ordinary industrial SCARA robots and piezoelectric ceramic actuators for IC chip processing, which is very effective, as shown in Figure 4. The system macro motion is completed by the SCARA robot. The jog is realized by a pair of precision worktables, respectively, and the table is driven by piezoelectric ceramics.

3.3 Machine tool and micro robot technology combined

Diamond precision lathes, various precision grinding machines, etc., which are used most in ultra-precision machining, need to be carried out in a highly clean workshop because the environment has a great influence on the machining accuracy. And in order to reduce the error, vibration and transmission errors should be minimized to achieve micro feed. The micro-robot is mainly used for vibration suppression, numerical control and measurement, and micro-feed system of the bed and base of the machine tool. If the mirror disk is turned by a diamond lathe, the feed rate of the turning tool is 5 μm, which is realized by a micro-robot. The elastic film and the electrostrictive device are combined into a micro-feed mechanism, and the telescopic movement of the electrostrictive device is used to drive the table to realize micro-feeding. Wang Jiachun and others use the piezoelectric ceramics to elongate and contract to make an active vibration control system for ultra-precision lathe slides. Combined with the fuzzy neural network control method, the vibration of the slide can be suppressed and the machining accuracy can be improved. Zhang Yun et al. applied the micro-motion robot technology to the new type of boring machine, and used the piezoelectric ceramic to control the radial feed of the boring tool to design the deformation boring bar, which can process the high-precision piston shaped pin hole. The mechanism is small in size, simple in structure, light in weight, and easy to manufacture and assemble.

3.4 scanning tunneling microscope

Scanning tunneling microscope can also be regarded as a kind of micro-motion robot. It is generally driven by piezoelectric ceramic crystal. It can realize nano-scale movement in three directions of XYZ. It is mainly used for surface detection of parts, and can also be used for molecular and atomic relocation and reorganization. The working principle is shown in Figure 5. Atomic force microscopy is capable of manipulating molecular size particles and has broad application prospects in the future assembly of nanoscale parts. MIT has established a project called Nanowalker to further explore the integration of micro-manipulators and develop a number of tiny, flexible micro-manipulators with multiple functions. As shown in Fig. 6, the micro-robot can be combined with a tool such as a scanning probe to provide functions such as nano-operation, three-dimensional micromachining, and surface detection.

3.5 Future development trends

Ralph Hollis et al. proposed the concept of a micro-factory for precision assembly, including sensor-based micro-operations and automated assembly systems to complete the assembly of complex MEMS systems. Hitosh built a model of a micro-factory. On a workbench, a small lathe, a grinder, a punch, a robot, an operator, etc. are concentrated, and the processing and assembly of the micro parts can be realized. It is characterized by small space, low energy consumption and light weight. It can be reconstructed according to the needs of production and has high flexibility.

4 Conclusion

In summary, micro-robot technology has an irreplaceable role in ultra-precision machining, inspection and assembly. Using micro-robot technology to transform traditional machine tools and industrial robots can improve processing quality and reduce processing costs. From single robot operation to multi-robot collaboration, to desktop micro-factory, micro-robot technology combined with modern communication technology, micro-machining technology, detection technology, etc., not only opens up new application fields for robot technology, but also will be in the advanced manufacturing field in the future. Play a bigger role.