CN1274980C - Nanometer class ballscrew and driving method thereof - Google Patents

Abstract

The invention discloses a nanoscale ball screw. It has a nanoscale driving part, a lead screw, and a ball cylindrical nut in sequence, and is fixed by a support seat. A semiconductor refrigerator and a driving surface are arranged on the nanoscale driving part, and the nanoscale driving part is driven by a driving device. The driving method of the nano-scale ball screw is that the first-stage feed is completed by the ball screw, and at the same time, the temperature of the lead screw is cooled by the semiconductor refrigerator, which can improve the accuracy of the first-stage feed and reduce the heat generated by the lead screw when it is driven. Influenced by temperature, the secondary feed is completed by nano-scale drive components. The length of the lead screw is increased or shortened by nano-scale through the slight change in the power of the semiconductor refrigerator, and the method of controlling the feed amount reaches 10nm precision. Compared with the traditional structure ball screw, the present invention has the biggest advantage that the positioning accuracy can reach 10nm, the driving force can reach 500kg, the structure is simple, and the installation is easy.

Description

Nano ball screw

Technical field

The invention relates to a nanoscale ball screw.

Background technique

The ball screw pair has a history of more than 100 years since it was patented in the United States in 1874, and it has a history of development and production for more than 40 years in my country. Its function has changed from the initial "agile and energy-saving transmission" (40s to 50s of last century) to "precision positioning" (70s ~), and then from "large lead fast drive" (80s ~) to "precision high-speed Drive" (1990s~), during this process, the product was continuously upgraded and a sub-quality leap was obtained. Improving the manufacturing accuracy and positioning accuracy of the ball screw pair has always been the relentless pursuit of manufacturing enterprises. In the 1960s, my country's joint research on precision machine tools laid a solid foundation for precision machine tool thread grinding technology. The thread grinding laser feedback lead error automatic correction technology successfully developed by Beijing Machine Tool Research Institute in the 1980s and the "Seventh Five-Year Plan" of large-lead ball screw pairs completed in the late 1980s, in order to improve the large-lead angle internal and external The grinding accuracy of circular arc thread finds an effective process way. During the "Ninth Five-Year Plan" period, Hanjiang Machine Tool Co., Ltd. successfully developed SK7432 2m fully enclosed CNC screw grinder, HJ031 CNC ball nut grinder, and SK7450 5m large CNC screw grinder, which provided a solid foundation for the development of precision high-speed ball screw pairs. Key process equipment. The gap between our country and the advanced industrial countries' thread grinding technology level is approaching day by day, and the correction technology for improving the positioning accuracy of the ball screw pair in the CNC servo feed system is also constantly improving.

As a "rolling" mechanical transmission device, the precision high-speed ball screw pair has many characteristics superior to general transmission devices, but its positioning accuracy, driving speed, and acceleration (deceleration) speed have a physical limit. For this reason, relevant manufacturers at home and abroad continue to take measures to improve the high-speed performance of ball screws. The main measures are: (1) Appropriately increase the speed, lead and number of thread heads of the ball screw, and the linear motion speed of the ball screw pair is the product of the lead of the screw and the speed of the screw. Increasing the speed of the lead screw is beneficial to increasing the speed of linear motion, but increasing the speed will increase the temperature rise, thermal deformation, vibration and noise of the lead screw pair. Therefore, there is a certain limit to the increase in the speed of the lead screw. (2) Improve the structure and improve the fluency of ball movement: improve the ball circulation reverse device; improve the structure of the ball nut; The screw is forced to cool to keep the temperature of the ball screw pair constant. This measure is very effective for improving the high-speed performance and working accuracy of medium and large ball screws); the transmission mode of screw fixing and nut rotation can be adopted. (3) Further improve the manufacturing quality of the ball screw. High-speed ball screw is a kind of ultra-high-precision mechanical transmission component, which not only needs to be carefully designed, but also needs to be carefully manufactured. From the selection of raw materials, heat treatment methods, mechanical processing to assembly, all must be very particular. Finishing and assembly are generally carried out in constant temperature workshops, using various high-precision processing and testing equipment (such as high-precision CNC thread grinder, laser feedback thread grinder, ball screw pair comprehensive stroke error measuring instrument, pre-tightening torque measuring instrument etc.), and the error compensation technology can be used to further improve the working accuracy of the ball screw pair.

Now to achieve high-speed feed can be used: ball screw; linear motor; parallel virtual axis mechanism. Generally speaking, the ball screw can continue to be used in medium and low-grade high-speed machine tools after being improved at high speed. For high-end and medium-to-high-end high-speed machining centers and ultra-high-speed machine tools, linear motors should be the first choice. Together with the electric spindle, they can fully realize the "zero transmission" of high-speed CNC machine tools. Using the parallel virtual axis mechanism as a new feed system for high-speed CNC machine tools involves a fundamental change in the layout of the entire machine tool. The problem is more complicated and can only be advanced step by step.

Contents of Invention

The object of the present invention is to provide a nano-scale ball screw.

The nanoscale ball screw has a nanoscale driving part, a lead screw, and a ball cylindrical nut in turn, and is fixed by a support seat. A semiconductor refrigerator and a driving surface are arranged on the nanoscale driving part, and the nanoscale driving part is driven by a driving device. The driving device is composed of an electric probe, a microprocessor, a power supply, a feed setting device, a display, a printer, a semiconductor power amplifier, a semiconductor refrigerator and a lead screw, and the microprocessor is connected with the power supply and the feed setting device respectively. , display, printer, semiconductor power amplifier, and inductive probe are connected, and the semiconductor power amplifier is connected with semiconductor refrigerator and lead screw.

Advantages of the present invention:

1) The integration of primary and secondary feeding. The first-level feed completes the rough feed and quickly approaches the moving target, and the second-level feed is completed by nano-scale drive components, the control feed reaches 10nm precision, and the driving force is 500kg. The two can be performed step by step or simultaneously.

2) Integration of heat dissipation and compensation. In the field of ultra-precision machining, the error caused by thermal deformation accounts for 40% to 70% of the total processing error, and the ball screw generates a lot of heat when it is running. The innovative idea of nanoscale driving components is to change the passiveness of thermal deformation in traditional methods. The compensation is active feeding, which is based on this idea. The principle of the driving part is to control the feeding of the deformed body to nanoscale by changing the power of the heat source or cold source. The ball screw with this structure integrates the nano-level driving parts and the ball screw. During the first-stage feed, the temperature of the lead screw is cooled by the semiconductor refrigerator, which can improve the accuracy of the first-stage feed and reduce the transmission time of the screw. The effect of the generated heat on the ambient temperature, during the two-stage feed, the length of the lead screw is increased or shortened in nanometers by a slight change in the power of the semiconductor refrigerator.

3) Less impact on the environment. Due to the use of two-stage feeding mechanism, the second stage is nano-level, and the feeding amount is small, and because the ball screw is relatively long, it is only necessary to slightly change the power of the semiconductor refrigerator to realize nano-level feeding.

4) Simple structure and easy installation. No structural modifications are required for existing ball screw applications.

Description of drawings

Figure 1 is a three-dimensional structural diagram of a nanoscale ball screw;

Figure 2 is a three-dimensional structural diagram of a ball screw driven by one end;

Fig. 3 is a block diagram of the secondary feed drive device;

Figure 4 is a schematic diagram of the principle of the structure applied to the grinding machine; in the figure: nanoscale drive components 1, screw 2, balls

Cylindrical nut 3, semiconductor refrigerator 5, workbench 7, bed 8, floor 9, column 10, guide rail

11. Grinding head body 12, grinding wheel 13, parts to be processed 14, heat insulation device 15.

Detailed ways

The nanoscale ball screw has a nanoscale driving part 1, a lead screw 2, and a ball cylindrical nut 3 in turn, and is fixed by a support seat 4. A semiconductor refrigerator 5 and a driving surface 6 are arranged on the nanoscale driving part 1. Part 1 is driven by a drive. The driving device is composed of microprocessor, power supply, feed setting device, display, printer, semiconductor power amplifier, semiconductor refrigerator and lead screw, among which the microprocessor is connected with power supply, feed setting device, display, printer, etc. , The semiconductor power amplifier is connected, and the semiconductor power amplifier is connected with the semiconductor refrigerator and the lead screw.

1. Nanoscale drive components

Theoretical verification of key technologies was carried out before the test: since metal materials generally have greater compressive strength, the nanoscale drive components used in the test can be made of different metal materials, and the heat source is a semiconductor refrigerator, which can be achieved by simply changing the voltage Change its heating and cooling to achieve the purpose of controlling the feed. The large driving force device in the laboratory is designed with the principle of leverage, and can apply different feed forces such as 50kg, 100kg, 150kg, 200kg, 250kg, 500kg, etc.

The metal material of the driving part is 45#, the heat capacity c=486, the thermal conductivity λ=45, the density ρ=7753, the heat exchange coefficient α=100, the linear expansion coefficient α _t =0.00001159. It is composed of drive components, afterburner device, high-precision electric probe, WS16PC-VH sampling interface card, detection and control computer, drive system and actuator. The high-precision electrical probe has a resolution of 2nm and a measuring range of 80μm.

2. Integrated ball screw

Manufacturing of ball screw pair: diameter 80mm, lead 10mm, accuracy 0.05mm/300mm, thread length 1500m, screw total length 2500mm, in which the cross-section of the nano-level driving part is square (40×40mm), and its center of symmetry is the same as the wire The centers of the bars coincide, as shown in Figure 1. The material of the ball screw is CF-53 quenched and tempered hardness steel, the surface hardness reaches HRC58-62, the shaft center and both ends of the ball screw are quenched and tempered; the material of the ball nut is 16MnCr5, and the reverser is an internal circulation method. (Other materials can be selected for the screw and nut) The double nuts are preloaded with pins or gaskets. Figure 2 is a structural diagram of one-end drive, in which the semiconductor refrigerator is circular.

Processing technology of ball screw: Option 1, turning - milling - quenching - rough grinding - fine grinding;

          Option 2, rolling-milling-quenching-grinding (suitable for large batches, saving time and cost).

The test was carried out on a vibration isolation table in a constant temperature room, and a dual-mode control strategy based on a single-value model algorithm was used for control. Through a large number of test results, it was verified that the feed rate can be controlled with an accuracy of 10nm when the temperature changes by 1.2°C.

In summary, the dual-mode control strategy based on the single-value model algorithm is used for control, and a large number of tests have been carried out on the two structures shown in Figure 1 and Figure 2, and the control effect at the nanometer level has been obtained. The characteristics of this structure are summarized: (1) There is a long delay time at the beginning of heating, and there is obvious hysteresis, so the nanoscale drive components should be avoided at this stage; (2) The response speed of the drive components It is slower, so a two-stage feed scheme is adopted to improve feed efficiency; (3) The delay time of the working stage is greatly shortened, which is one of the reasons why it can achieve nanoscale feed accuracy with large feed force. It is based on the above three points that the present invention has broad application prospects in quasi-static drive devices that require nanoscale positioning accuracy with large feed force and low response speed.

3. Application examples

The ball screw is applied to the surface grinder to complete the feed in the Z direction. The nano-scale driving parts can work after the temperature field of the deformed body reaches equilibrium. At this time, the waiting time for work is relatively long; it can also work in the unbalanced stage, as shown in Fig. 4 is a schematic diagram of the structure principle applied to the surface grinder.

Working principle: The working principle of the original grinding machine is still guaranteed, but the original ball screw is replaced by a new ball screw.

Working process: Fix the workpiece on the workpiece table, and the first-stage feed of the ball screw drives the grinding head body to quickly approach the workpiece. When the grinding wheel is about to approach the workpiece, stop the first-stage feed, start the nano-level drive components, and reach the nanometer positioning accuracy. Finishing.

(Conceptual distinction) Definition of deformable body: In the test stage of nanoscale drive components, the deformable body is the test piece. The integrated rear ball screw is called a ball screw for the first-stage feed, and it is called a deformed body for the second-stage feed. lengthened or shortened.

Claims (1)

1. A nano-scale ball screw is characterized in that it has a nano-scale driving part (1), a screw (2), a ball cylindrical nut (3) in turn, and is fixed by a support seat (4), and driven at the nano-scale The component (1) is provided with a semiconductor refrigerator (5) and a driving surface (6), and the nanoscale driving component (1) is driven by a driving device, which is set by an inductive probe, a microprocessor, a power supply, and a feed rate Device, display, printer, semiconductor power amplifier, semiconductor refrigerator and lead screw, in which the microprocessor is respectively connected to the power supply, feed setting device, display, printer, semiconductor power amplifier, inductance measuring head, semiconductor power amplifier It is connected with semiconductor refrigerator and lead screw.

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