Parallel machine tools, also called virtual axis machine tools or parallel robots, are high-tech products created by the combination of robot technology and machine tool technology. International academic circles and engineering circles attach great importance to the research and development of parallel machine tools, and have successively introduced several prototypes with similar structures and different names. This paper introduces the research progress of the parallel machine tool in detail, and shares the latest achievements of domestic and foreign research with readers. The article also further explores the research direction of parallel machine tools.
At the CIMT exhibition held in April this year, CNC equipment company of Harbin Measuring & Cutting Tool Group exhibited a LINKS-EXE700 with a new type of parallel structure machine tool with breakthrough significance. The feature of the parallel machine tool is that the structure is further simplified, and the machining range is increased. The coverage space is 2m in the x-axis direction, 1m in the y-axis direction, and 0.5m in the z-axis direction. The action is rapid, and the x and y-axis rapid feed reaches 125m/min respectively. , Acceleration 3g, Z axis direction 45m/min, Acceleration 1g, Rigidity and precision increase, Five-axis linkage NC programming and the use of conventional, can process pentahedron, in the case of special workpiece clamping, but also for six-sided processing, This is currently impossible for any machine tool structure. With different functional configurations, it can be widely used in aerospace, aviation, automotive, and mold industries for cutting, grinding, welding, riveting, burrs and assembly. It can be used stand-alone or as a production line. The structure of the parallel machine tool is completely different from all conventional machine tools. The traditional machine tool structure is based on the Cartesian coordinates in the direction of the three coordinate lines and the rotation around the three coordinates are stacked in series to form the desired tool movement trajectory, all of its geometric accuracy error, force transmission and stiffness loss, will Is cumulative in series. The parallel structure machine tool that emerged in the last twenty years moves the spindle head by moving the multi-bar structure in the space at the same time. Compared with the series structure, it has a series of advantages such as simpler, higher rigidity and better dynamic performance. About twenty or thirty companies are engaged in research and development in this area. There are also seven or eight teams in the Chinese machine tool industry that are conducting R&D work. Parallel machine tool research process (Parallel Kinematic Machine, referred to as PKM) is also called virtual axis machine tool or parallel robot. It is a high-tech product combining robot technology and machine tool technology. It has high precision, high rigidity, high speed and high speed. Acceleration, high flexibility, high flexibility, high thrust, light weight and other excellent performance. In 1994, Ingersoll and G&L Corporation of the United States exhibited their first parallel machine tool at IMTS. Since its first appearance on the IMTS, it has been hailed as the "21st century machine tool" and has become the most vital new member of the machine tool family. This new type of machine completely broke the concept of traditional machine tool structure, abandoned the tool guide method of fixed guide rails, used a multi-rod parallel mechanism to drive, greatly improving the rigidity of the machine tool, so that the machining accuracy and processing quality have greatly improved. In addition, because of its increased feed rate, high-speed, ultra-high-speed machining is easier to achieve. Due to its high rigidity, high load-bearing capacity, simple mechanical structure, low manufacturing cost, and high degree of standardization, this machine tool has been successfully applied in many fields and has received extensive attention from the academic community. The parallel-joined CNC machine tools, which are composed of parallel and series, not only have the advantages of parallel machine tools, but also have practical value in use. With the continuous development of high-speed cutting, the structural rigidity of the traditional tandem mechanism construction platform and the high speed of the mobile station have gradually become the bottleneck of technological development, and the parallel platform has become the best candidate. Compared to the tandem machine tool, the parallel working platform has the following features and advantages. Simple structure and low cost The number of mechanical parts of machine tools is greatly reduced compared with the series construction platform, mainly consisting of ball screws, Hooke hinges, ball hinges, servo motors and other general components. These common components can be produced by specialized manufacturers, thus the manufacture of this machine tool. And the cost of inventory is much lower than the traditional machine with the same function, easy to assemble and carry. High structural rigidity Due to its closed-loop structure, it has the advantages of high rigidity and high speed. Its structural load flow line is short, and the tension and pressure of load decomposition are simultaneously supported by six connecting rods. From the point of view of material mechanics, when the external force is constant, the amount of stress and deformation of the cantilever is the largest, the build-in is the second, and the second is the simply-supported, and the second is the compression. The force structure, the stress and the deformation are the two-strength structures subject to tension, and therefore have the highest rigidity. Its stiffness to weight ratio is higher than traditional CNC machine tools. High processing speed and low inertia. If the forces experienced by the structure will change direction (between tension and pressure), the two-force member will be the most material-saving structure, while the weight of its moving parts will be minimized and at the same time Six actuators drive, so the machine is easy to speed up and has a low inertia. High processing accuracy Because it is composed of multi-axis parallel mechanism, six retractable rod lengths individually act on the position and attitude of the tool, so there is no phenomenon of geometric error accumulation and amplification of traditional machine tools (ie, tandem machine tools), even There is also an averaging effect (averaging effect); it has a thermal symmetry structure design, and therefore has less thermal distortion; therefore it has the advantage of high accuracy. Multi-functional flexibility. Because the machine tool mechanism is simple and easy to control, it can be easily designed as a special machine tool according to the processing object, and it can also be developed into a general-purpose machine tool for milling, boring, grinding, etc., and can also be equipped with necessary measurements. Tools make it a measuring machine to achieve the versatility of the machine. This will bring great application and market prospects, and it will have very broad application prospects in national defense and civilian use. long lasting. Due to the reasonable structure of the force, the wear of the moving parts is small, there are no guide rails, and there is no iron filings or coolant entering the inside of the guide rails, resulting in scratches, abrasions or rust. The Stewart platform is suitable for modular production. For different machining ranges, simply change the length of the connecting rod and the position of the contact point, and maintenance is also easy. There is no need to remake or adjust the mechanical parts, just enter the new mechanism parameters. Transformation coordinate system is convenient Because there is no solid coordinate system, the conversion between the coordinate system of the machine tool and the coordinate system of the workpiece is entirely accomplished by software, which is very convenient. When the Stewart platform is used in machine tools and robots, static errors (due to high stiffness) and dynamic errors (due to low inertia) can be reduced. The disadvantage of the Stewart platform is that it has a small working space, and it has a singularity limitation in the workspace. When the controller in series works, when the controller encounters a singularity point, it will calculate a drive command that cannot be achieved by the drive device and cause control. Error, but the Stewart platform loses the ability to support part of the direction of the force or moment in the strange position, unable to complete the fixed load object. Research Achievements of Parallel Machine Tools at Home and Abroad In 1997, at the European International Machine Tool Exhibition (EMO'97), US, UK and German manufacturers exhibited more than 10 parallel machine tools. The European "Innovation Manufacturing Initiative (IMI)" alliance has incorporated parallel machine tools into its research program called "Aviation Manufacturing Rapid Response." Japan also has more than 10 companies and research institutions in the development and production of parallel machine tools. At the 47th International Conference on Mechanical Processing Technology (CIRP) held in 1997, the Machine Tool Design Committee (MTC) listed parallel machine tools as the subject of the 1998 conference. At the April 2002 International Workshop on Parallel Machine Tools held in Germany (PKS'2002), experts and scholars from various countries published the latest research results on parallel machine tools. At present, the international academic community and the engineering community attach great importance to the research and development of parallel machine tools, and they are very optimistic about the application prospects and market potential of this new type of CNC machining equipment. They have invested a lot of manpower and material resources to compete for development, and have introduced several similar structures. Different prototype prototypes. The research of parallel machine tools began in 1965 when Stewart proposed the famous Stewart platform organization. From then on, the virtual machine tool research based on Stewart parallel mechanism was started. But at the beginning, people just stayed in the theoretical analysis of such institutions. In 1994, the parallel six-legged machine tool (also known as a parallel machine tool) exhibited for the first time in the United States at the IMTS Expo in Chicago, which caused the world's sensation. After a global follow-up wave that lasted for three years, it gradually cooled down in the world. This is because the parallel machine tool has a series of problems in theory and practice and it is difficult to solve in a short time. At present, many companies and research institutes at home and abroad are studying virtual axis machine tools. China's parallel machine tool research started late, but the results are significant. Among them, Tsinghua University is one of the first companies in China to begin research on virtual axis machine tools. It has conducted in-depth research on virtual axis machine tools and related fields. On December 25, 1997, it cooperated with Tianjin University to jointly develop China’s first place. Large prototype boring and milling virtual axis machine prototype - VAMT1Y. In the virtual axis machine tool design theory and prototype construction and other key technologies have reached the international advanced level, some of which theoretical results are international initiative. Three different types of machine tools jointly developed by Kunming Machine Tool Co., Ltd., Jiangdong Machine Tool Factory, and Dalian Machine Tool Plant have been introduced and exhibited at CIMT in 2001, and are expected to be commercialized in the near future. The XNZ63 virtual axis machine tool jointly developed with Kunming Machine Tool Co., Ltd. can realize multi-axis linkage CNC machining, assembly and measurement of multiple functions, and can meet the processing of complex special parts. Its comprehensive index has reached the international advanced level. A gantry-type virtual axis machine tool developed jointly with Jiangdong Machine Tool Works adopts a two-column gantry worktable movable to achieve 4-axis linkage. The DCB-510 5-axis linkage series and parallel machine tool jointly developed with Dalian Machine Tool Works can realize the movement of X, Y and Z directions through the parallel mechanism, and adopts the traditional series connection to realize the A and C direction rotation of the spindle head. In addition, the parallel machine tool designed by Tianjin University and jointly developed with the Tianjin First Machine Tool Plant has also been successful and has reached a practical level. HIT and the Qiqihar Second Machine Tool Enterprise Group jointly developed a BJ-1 parallel machine tool. The DSX5-70 three-bar virtual axis machine tool developed by Northeastern University is a five-degree-of-freedom virtual axis machine consisting of a three-degrees-of-freedom parallel mechanism and a two-degree-of-freedom series mechanism. The Galaxy-2000 virtual axis machine tool jointly developed by the National University of Defense Technology and the Hong Kong University of Science and Technology is a parallel type six-degree-of-freedom machine tool developed from the traditional parallel machine tool. It maintains many advantages of the original parallel mechanism, such as high rigidity. With a high degree of accuracy and a high speed of movement, the range of motion of the machine tool has been expanded with a variation mechanism. Abroad, the Swedish company Neos Robotics adopts the parallel plus series solution, starting from a low-level application, gradually accumulating experience and financial resources, developing to high-level applications, and adopting the corrective measures such as a three-pole central central tube, etc. Machine tool products have long been practical. The 6x machine tool developed by the Fraunhofer Machine Tool and Forming Technology Research Institute in Germany is suitable for high-speed machining of molds. Its main technical parameters are: Table: 630×630, X, Y, and Z strokes are all 630mm, and two rotation degrees of freedom are 30°, the maximum spindle speed is 3000r/min, the power is 16kW, the maximum feeding speed of the leg is 30m/min, and the acceleration is 10m/s. U.S. Index’s US subsidiary uses a parallel machine tool for lathes to produce an “inverted vehicle†for the V100 type three-bar parallel mechanism (ie, the spindle and workpiece are moved in X and Z directions, and the tool is not moving, but can be changed back. Knife, but no vertical movement of the vertical lathe, China is known as "inverted car"). It has the following advantages: 1 Compact shape. Unlike the machining center, the lathe has a relatively small range of movement relative to the tool, which overcomes the weakness of the space-efficient utilization of the parallel mechanism. 2 Lathes generally require only two degrees of freedom (X and Z axes). Three-bar geometry is now used to obtain X, Y, and Z degrees of freedom. A redundant degree of freedom can be used for free loading and unloading. In addition, in order to increase the stiffness, Index uses two rods that act as a rod, similar to the structure of China Tianjin First Machine Tool Plant. Hexel Corporation of the United States has applied a 6-pole parallel structure as a separate component to a turret milling machine. This can upgrade a low-cost ordinary milling machine to a 5-axis milling machine. The Swiss Institute of Technology (ETH), the Institute of Machine Tools and Manufacturing Technology (IWF) and the Robotics Institute (IFR) also jointly developed a Hexaglide virtual axis machine called the IWF. So far, we have learned that virtual axis parallel machines have two degrees of freedom, three degrees of freedom, three degrees of freedom on the face, three degrees of pure movement with four degrees of freedom, five degrees of freedom with symmetry, and six degrees of freedom. Virtual axis CNC parallel machine tools are mostly used for virtual axis six degrees of freedom CNC machine tools. The research direction of parallel machine tools researches the problems such as the calculation of the degree of freedom of parallel machine tools, the type of motion, the type of hinges, the kinematics analysis, modeling and simulation. The study of parallel machine tool motion space includes analysis of motion space and simulation, reachable work space solution (such as numerical solution method, spherical coordinate search method, etc.), machine tool interference calculation and position analysis. The structural design of the parallel machine tool includes many contents, such as the overall layout of the machine tool, the design of the safety mechanism, the design of the numerical control system (including the construction of the numerical control platform, the programming of the numerical control system, the simulation of the numerical control process, etc.), the stiffness, accuracy, flexibility, and dexterity of the parallel machine tool. Research. The characteristics of the closed loop of the parallel mechanism make the parallel machine tool more rigid than the traditional series machine tool, but the coupling problem caused by this characteristic is relatively difficult to form in the dynamic analysis, so its research should be given enough attention. . The research on the accuracy of parallel machine tools is still an international problem, including the study of the hardware of the machine tool system and precision design and accuracy description of the machine tool, system output accuracy, and output data processing and accuracy evaluation after machine tool manufacturing. The study of flexibility of parallel machine tools includes flexibility analysis, flexibility evaluation indicators and their distribution in the workspace. The dexterity mainly studies the dexterity index and its distribution. Parallel machine tool error research includes error analysis, modeling, error accuracy assurance, and measurement system design. Parallel machine tool module design and creation. According to the space type and plane type of workpiece processing, parallel machine tools are divided into two categories: space-type parallel machines and plane-type parallel machines. Parallel machine tools can be divided into the following functional modules according to function and structure: 1 executive module; 2 stand module (static platform module); 3 movable platform module; 4 rack module; 5 positioning module; 6 drive module; 7 control and Display module; 8 lubrication and cooling module. Research on a New Virtual Axis CNC Machine Tool . Virtual-axis CNC machine tools are "machines to be manufactured using mathematics" because the design and operation of such machine tools requires very complex mathematical calculations and inferences. At present, some critical conclusions have been obtained for the theoretical research of the Stewart platform. It is necessary to further study the comprehensive analysis of the Stewart platform to provide a theoretical basis for the development of virtual axis CNC machine tools. Research of parallel machine tool control includes high-speed, high-precision control algorithms, direct control of the tool path, and open CNC systems. The most important feature of the virtual axis machine tool is its simple mechanical structure and complicated control. Therefore, the research in this area plays a decisive role in the research of parallel machine tools.
Ti2V2AlC3
[ Basic Information ] :
1. Chemical formula: Ti2V2AlC3
2. Component elements: Ti,V,Al,C,
4. Chemical status: micro-nano size particles
5. Appearance and properties: black brown particles with micro/nano size
[Packaging specifications] : Fixed packaging 2/5/10/20g, or packaging according to customer requirements;
[Intended use] : Used for chemical etching preparation of MXenes, physical chemistry experimental research needs;
[Storage Conditions and Expiry Date]
This product should be stored at room temperature in a dry place away from light, avoid contact with acid, alkali and other liquids, long-term storage will occur slow oxidation.
[Inspection method]
This product can be confirmed by X-ray powder diffractometer crystal results; Confirmation of element composition by energy dispersive X-ray detector; Homomorphologic characterization was used to characterize the particle morphology. And the particle size distribution was evaluated by laser particle size analyzer.
[Safety Protection]
1. Health hazards
Hazard type: non-hazardous chemicals Chemical type: ceramic powder;
Invasion route: inhalation, ingestion;
Health hazards: the dust irritates the eyes, and oral administration irritates the gastrointestinal tract.
2. First aid measures
Skin contact: Take off the contaminated clothing and rinse the skin thoroughly with flowing water.
Eye contact: Lift eyelid and rinse with plenty of running water or normal saline for at least 15 minutes;
Inhalation: quickly leave the site to a place with fresh air;
Ingestion: drink enough warm boiled water to induce vomiting and seek medical treatment;
3. Ignition and explosion characteristics and fire protection
Flammability: non-flammable;
Registrant/Manufacturer Name: Jilin Yiyi Technology Co., LTD
Residence/Production address: Beihu Science Park, New District, Changchun City, Jilin Province
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