Figure 5: Mr. Liu Tong, System Specialist, Motion Control Department, Industry Group, Siemens (China) Co., Ltd.
The same problem is encountered when using a linear motor abroad. For example, during the movement, the headstock is square, but in reality it is oscillated under high-speed operation, and the accuracy is affected. It may not be obvious when running at low speed, but it is reflected at high speed. Linear motor technology needs to be matched with the system when it is used on the machine tool. It is not only a part, but can be applied to the work of the automobile production line for 24 hours. Therefore, this dynamic problem is an urgent problem that the host manufacturer needs to solve in the future.
The use of linear motors in large-scale equipment still has certain advantages, because the secondary of the linear motor is mounted on the machine bed through a series of continuous splicing, and the required ratio can be calculated in advance, which can reduce the cost.
Mr. Heinrich Willms: In the 1990s, linear motors entered the market as machine tool drives and were used on CNC machine tools. The biggest advantage of a linear motor is the high speed of 300m/min. At this point in speed, the linear motor exceeds the ball screw by nearly 3 times. Linear motors have unparalleled advantages in ultra-high-speed operating conditions.
However, the ball screw has its unique advantages over the linear motor: the price advantage - the price of the ball screw is much lower than that of the linear motor, and the production cost is also the same; the low energy consumption - the energy consumption of the linear motor is Many times the ball screw, it means a lot of uneconomical problems; high rigidity - the machine tool using the ball screw is more rigid than the machine using the linear motor; magnetic - the machine using the linear motor forms around the table A very strong magnetic field that absorbs iron filings and has a negative impact on the production process of CNC machine tools.
In addition to linear motors and ball screws, there are a range of linear actuators such as racks, hydraulic cylinders or pneumatic cylinders. In the past few decades, the ball screw has dominated the field due to its economy, low energy consumption and high rigidity, and its market share is increasing, and it will continue to play an important role in the future.
Mr. Yu Zhou: In high-speed and ultra-high-speed machining, high dynamic characteristics and control precision are required; instantaneous high speed and instant stop in high-speed operation; low vibration, low noise, stable operation; high reliability and long service life. Among the various linear drive components, the precision high-speed ball screw pair and linear motor are the core functional components that can meet the above requirements in the fast servo feed system of large, precise and high-speed CNC equipment.
As an electromechanical system, linear motor has the characteristics of high speed response, high positioning accuracy, high dynamic stiffness, fast speed, short acceleration and deceleration process, unlimited stroke length, quiet motion, low noise and high efficiency. The mechanical structure is simplified, the electrical control is complicated, and it conforms to the development trend of modern electromechanical technology. However, linear motors also have many shortcomings. In addition to high cost, there are still a lot of basic work in all aspects of digital control technology, heat dissipation, magnetic isolation, electromagnetic interference, zero position, increased thrust, reduced energy consumption, and modularization of components. do.
Due to the excellent rolling friction characteristics and high transmission efficiency (η=90%~95%) and the agile and flexible function of the ball screw pair, it has the advantage of speed increase. Therefore, compared with the linear motor, the precision high-speed ball screw pair not only has the advantage of low cost, but also facilitates full digital control, easy cooling, low heat generation, no electromagnetic radiation, large axial thrust, high transmission efficiency, The modularization of components has matured, and in many fields, linear motors cannot be replaced or cannot be replaced for a long time.
Contribution to safety and environmental protection
Mr. Xiao Ruihua: In terms of safety: First of all, the carrying capacity of Rexroth slider is strictly determined according to ISO international standards and verified under actual test conditions to ensure the accuracy of the data. Secondly, Rexroth's rail system has a very high carrying capacity. The peak load is met; the clamping/brake element can be selected on the machine's Z-axis rail system, so that in the event of a sudden power failure, it is guaranteed that the Z-axis table will not fall or injure the device.
In terms of environmental protection: the rail system and the ball screw are lubricated with light oil, and the pollution is small. Because it is rolling operation, the consumption of oil lubrication is very small. The front lubrication unit is used, and the relubrication cycle can reach 100,000 km. Compared with the conventional sliding friction, the rolling function can significantly reduce the friction of the sliding bearing by about 90%, and the friction of the ball guide with the low friction seal can be reduced by 50%, so the required driving power is also reduced accordingly. Small form factor products also have high load capacity. Reduce friction, such as 100 and 125 gauge roller guide systems, a variety of materials (aluminum / steel) can significantly reduce the quality, such as eline rail quality reduced by about 60%, VKK feed module with aluminum body and sleeve The tube also reduces power consumption to some extent.
Overall solution for motion control
Mr. Xiao Ruihua: Bosch Rexroth can provide a complete set of transmission, control and mobile solutions.
The Bosch Rexroth Heavy Duty Roller Guide System is a compact, roller-supported axial guide for heavy-duty machine tools, plastic machines, and molding machines. Different precision grades, with high load carrying capacity (rated static load up to 200t) and extremely high stiffness in each bearing direction, especially suitable for heavy-duty applications. The guide rails and sliders are precision machined in the raceway area to ensure that they are interchangeable within the same accuracy class. Bosch Rexroth also offers precision ball screw drive systems with a wide range of precision rolled screws and pre-tightened and adjustable pre-tight single and double nuts. The optimized ball circulation system for lower noise and higher speeds . A larger number of balls guarantee a high rated load.
Mr. Liu Tong: As an automation technology company, Siemens can provide a total solution that is more suitable for machine tool applications. Siemens cooperates extensively with the aerospace and automotive industries. Aerospace is a typical application for high-speed machining. Users will ask for one or the other in the process of cooperation. We need to continue to develop to meet these requirements, Siemens has a dedicated application for aerospace and automotive applications, so the product is more suitable.
In the solution provided by Siemens, the concept of “set†is different from other companies, and the scale is different. In addition to providing a set of solutions for machine tools, Siemens can also provide a set for the production line or the whole. Workshop, factory solutions, and networking, including fieldbus connections to the shop floor, and workshop-level industrial Ethernet hardware and software.
Mr. Yu Zhou: The Vario500-8000 rotary milling machine used by Youli Neff (Nanjing) Technology Co., Ltd. is the world's first, largest and highest precision ball screw hard-spinning machine. The machine adopts the world's most advanced numerical control system and position monitoring unit. It has five-axis CNC control, four-axis linear interpolation linkage, and remote fault diagnosis system. It has strong practicability.
At present, the company has formed a large-scale ball screw production line from outer circle processing, heat treatment to ball thread processing. We use the advanced design concept of Germany Neff to provide users with 10m whole butt-free ball wire for large CNC boring and milling machine. The rod pair solves the requirements of high precision and heavy load of large CNC boring and milling machine. We use the latest design concept to design and manufacture the high speed heavy duty ball screw pair. Its rated dynamic load reaches 50t and the rated static load reaches 150t. It has been electric injection molding. Machine manufacturers choose to use.
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