The energy loss of the mechanical power source is converted into heat, such as the motor oil pump hydraulic control box, and so on, so that the frictional heat generated by the heat-transformed transmission part of the various parts of the machine tool, such as the bearing pair gear pair guide rail pair, etc., The heat is dissipated, especially the lubricating oil pool inside the bed, which forms a large heat source, which is easy to bend and deform the bed rail.
Cutting heat. When the chips and coolant fall on the various parts of the machine tool, the heat is transmitted, which will cause the corresponding parts of the machine tool to generate corresponding heat deformation environment heat. Such as room temperature changes, sunlight, heating devices, and the like. Also, the machine section is heated unevenly. Causes thermal deformation, but when the machine tool is in operation, affected by the above various heat sources, and the complexity of the machine structure, the components are different from the heat source, forming a directional cemetery, so that the relative parts of the machine tool The change in the chat broke the machine from the original, and caused the Gading generation.
At the same time, the volume of the various parts of the machine tool is different, the size difference is large, the heat capacity is not the same, and the time to reach the heat balance is also different.
In other words, lathe grinders are idling to achieve thermal equilibrium for 461 medium-sized precision machine tools. 121 large precision machine tools often require 121 or even tens of hours. Before the machine tool reaches the thermal balance, the accuracy of the machine tool is variable. This affects the accuracy of the part plus one.
In addition, the type of machine tool is different from the main heat source, and the influence of thermal deformation on the machining accuracy is also different.
Poor, the machining batch produces a cylindricity error before the heat balance is reached.
Thermal deformation of grinding machine tools The main heat sources of such machines are the frictional heat of hydraulic systems and high-speed grinding heads, as well as the grinding heat. The temperature rise of the main bearing of the wheel frame will increase the axis of the spindle and approach the wheel holder toward the workpiece, resulting in a diameter error in the workpiece being ground.
The thermal deformation caused by the temperature rise of the workpiece grinding head of the cylindrical grinder is greater than the thermal deformation of the tailstock, so that the rotary axis of the workpiece is not parallel with the moving direction of the table. Before the heat balance is reached, the workpiece will be subjected to a taper error. 2 Thermal deformation of the surface grinder .
If it is determined by the position of the oil pool and the order of the guide rails, the heat. When the oil pool is not designed in the bed, the temperature of the surface of the guide rail 1 is higher than the lower temperature, and the bed will produce a convex three. When the oil pool is placed inside the bed, if the temperature of the lower part of the guide rail is higher than the temperature of the part, the bed is concave, and they will produce a flatness error in the plane of the workpiece to be ground.
Large-scale machine tools, such as guide grinding machines, gantry milling machines, gantry planers, etc. are also very significant. Due to the thermal deformation of the bed and the influence of the machining accuracy on the bed.
The main heat source for this type of machine is the headstock. The friction heat generated by the gear bearing in the headstock and the heat transferred to the lubricating oil causes the temperature of the headstock and the bed or the main shaft connected thereto to rise to cause large thermal deformation.
Lift the spindle. The temperature of the front bearing of the main shaft rises to the rear bearing and tilts the main shaft; the heat of the headstock is transmitted to the frictional heat between the moving pairs of the bed rails, so that the bed rails are convex upwards, and the progress of the main shaft is inclined upwards, resulting in seven The flat axis of the shaft axis rail is hot-deformed in the vertical plane. Forming a temperature of 1. This. The bed will produce a bend 3 deformation.
The thermal deformation of the body produces a corresponding change in position.
In this case, the workpiece surface will produce shape and position errors after machining.
According to the analysis of the West German Achen University of Technology, in the manufacturing error of modern machined parts, the error caused by the thermal deformation of the machine tool will be 4070 in precision machining.
3 The control of the thermal deformation of the machine tool and the prevention of the thermal deformation of the machine tool are the heat of the heat source. Reducing the heat generation of the heat source is the main measure to reduce the thermal deformation of the machine tool.
Improve the quality of the rolling bearing to change the oil mist lubrication of the main bearing and the transmission bearing, and the high rigidity structure of the grinding wheel shaft of the machine tool and the grinding wheel flange. Suppress the eccentricity of the grinding wheel operation. Ensure high speed operation and stability. Ceramic bearings and oil and gas lubrication are used on the grinding wheel shaft. Prevent fever prevention; 1 speed burn and assembly quality. Due to the warm sweat of the mechanical bearings. If the diameter is negative, the factory and the friction coefficient are used to change the lubrication conditions of the bearing. Dynamic pressure oil film bearings and hydrostatic bearings are also available. It is possible to reduce the friction coefficient. At the same time reduce the heat of the bearing.
Reduce the shackles of the rail pair. The sheet should be sufficient to reduce the friction between the rails of the guide unit and the rails with a low friction coefficient rail material. Here, the friction coefficient is mainly reduced. The household and the workpiece re-view and the amount of Dingtai Taiwan currency. Can not change. 1 The heating scene and the speed of movement 1 have AI, increase. 2 is also ± large. The temperature rises by one. Like + formation ratio. therefore. Reducing the late rub coefficient is an important measure to reduce the temperature rise of the guide rail. Static pressure rail. The feeding guide rails play a superiority in this sitting.
An electric motor that was originally cooled by air. It can be cooled with hydrogen helium. Because their thermal conductivity is 510 times higher than the gas. therefore.
Switch to hydrogen helium to cool. Its cooling effect is much better.
5 Improve the surface finish of the various parts of the machine tool, paint oxidation and surface treatment, can improve the surface endothermic conditions. Thereby controlling the influence of the seed heat source.
Use a hot air or oil sump to equalize the temperature field.
If the oil sump is completely removed from the bed, the top of the bed will have a top temperature higher than the bottom due to the frictional heat of the table. There will be a middle middle convex question on the top of the bed. Such as the 6 765 must face grinding machine. The bed is long. During the processing, the longitudinal movement speed of the table is fast, so the heat generated in the body of the bed is large, so that the temperature difference in the lower part of the bed is easily formed, and thermal deformation is caused. At this time, the oil pool can be removed from the main engine and made into a separate fuel tank, and a thermal compensation oil groove is arranged in the lower part of the bed. The return oil with residual heat flows through the lower part of the bed. The temperature in the lower part of the bed is reduced to 12, and the convexity in the guide rail is separated from the original heat source and forced cooling.
The isolated heat source can fundamentally reduce the thermal deformation of the machine tool, and any heat source that may be separated from the machine tool, such as the motor gearbox hydraulic system cooling system, should be removed. Make it a single one. For heat sources that cannot be separated, the performance can be improved from structural lubrication and the like to reduce heat generation. At the same time, the heat-generating component can be separated from the machine tool by a heat-proof material.
The upper main motor is placed on the top of the main drive phase, and the fan is sucked out, not only the heat of the motor is easy to be used by the various parts of the machine. Gradually. Lit, while they dissipate heat to the surrounding medium in various heat transfer modes. Due to the heat source of the components of the various parts of the machine tool, the heat generation position and the action time are different. The heat capacity of each part is not the same, so the temperature rise of each part is not the same as the component. Different, hot air can be used to equalize the temperature field.
In the style plane, on the bed. Use hot air to heat the temperature lower and lose. And mouth. The main drive é’” ffl7 heat dissipation conditions are better. The heat of the column is reduced and the top of the column is heated evenly, thereby improving the bending deformation of the column.
For heat sources with large heat generation, forced air cooling can be used to cool with oxygen gas, and large flow water cooling measures. Large CNC machine tools.
The machining center machine tool uses a freezer to forcibly cool the lubricating oil cutting fluid. The effect is better.
Reduce the thermal deformation with a reasonable machine tool component structure.
Such as recruiting 5 not. There are no large parts and structures and cloths, especially for the general ten-face grinding machine of the Ligong Center machine. Set the pot on the bottom of the bed. The thermal characteristics of the 3 machine tools are greatly affected. For this type of machine. The single-column structure design is easy to produce distortion. If the double-column initial error is used, the vertical coordinate movement correction amount is used to compensate. Therefore, in the machining center machine tool, the double-column structure, that is, the symmetrical structure of the machine tool spindle, should be designed, and the thermal deformation relative to the table is much smaller than that of the single-column structure. In the gearbox, the main shaft bearing transmission gears should be arranged symmetrically to make the temperature rise evenly of the box, thus reducing the deformation of the box.
Reasonably select the installation of the machine part of the 1 bearing position to reduce thermal deformation.
Reasonably arrange the position of the support. The effective part of the thermal displacement of the calving affects the machining accuracy is reduced.
The middle grinding wheel frame is called the installation structure form, and the middle wire 3 frame 7 is placed opposite the wire 8 to support the influence of the thermal displacement of the local wheel frame. The effective length of the ball is in the (4), so the heat is deformed to produce another In the design of the machine tool structure, an automatic thermal compensation device can also be used = a double-sided grinding machine has experienced an excessive head extension. The thermal elongation reaches 0. The temperature rise of the front bearing reaches 27. In view of the above situation, the following measures can be taken to reduce the heat of the bearing by adding a grease to the bearing and adding a transition between the front body and the front bearing. When the bearing is hot, the transition sleeve is extended backward to compensate for the heat dissipation measures of the spindle 1 in the forward 7 process. 1 Maintain a constant ambient temperature in the area where the machine is installed, and various heating devices and sunlight in this area. The horizontal direction of the heat flow should not be square and private, respectively, and the corresponding thermal deformation is square and 4, which causes the center of the spindle to shift to the upper right direction, thereby also causing a positional change between the workpiece axis and the cutting edge of the tool. If the connection form is changed to the form of 10, the center 0 is placed directly above the vertical mounting surface 0, and 5 and 5 are zero, only the displacement in the vertical direction. Therefore, the machining tip of the diameter is greatly increased to increase the normal boring plus one. The main flash factor affecting the diameter error is the process of controlling the temperature state of the machine tool. Firstly, the artificial power source is added, and the temperature of the machine tool is used to realize the influence of the thermal error of the machine thermal error on the machining accuracy. Or eliminate the time for the machine to warm up, therefore. From the essence of 1. The machine thermal compensation control process is a temperature process. Temperature control adjusts and stabilizes the temperature and distribution of the machine by adding the heat of the artificial heat source. Therefore, the thermal excitation device of the artificial heat source plays an important role in the thermal compensation process, which can achieve high control of the machine temperature. The design of the thermal excitation device has been introduced at home and abroad, and the environment temperature of the machine tool is controlled. The temperature is 20; in winter, it can be taken from 17. The season of taking 23 to maintain the thermal balance of the art system is known from the law of thermal deformation.
For most machine tools, their thermal deformation occurs during the period after the machine is started. When the heat balance is reached, the hot deformation tends to be stable.
Processing accuracy is easy to guarantee. Therefore, for precision machine tools, especially large machine tools. The heat source can be idling or controlled in advance at a high speed. Artificially heating the machine to achieve a faster thermal balance before processing, for the same reason, precision machining to avoid stopovers.
4 Conclusion In summary, to control and prevent the influence of machine tool thermal deformation on machining accuracy, the reasonable structural design of the machine tool and its technological measures can be adopted.
The other way is to innovate the materials used in the machine parts.
The linear expansion coefficient of the flower rock light alloy fine ceramics and the like can be made small. The glass machine is used to make the precision machine tool shaft. It is a material of the technology and has good vibration attenuation due to this special material. The thermal stability is better than the heat, and the thermal conductivity is small and the size is stable and easy to take. Therefore, the influence of the thermal deformation of the machine tool on the processing viscosity can be reduced. The use of machining error automatic compensation technology is another way to improve machining accuracy. By comprehensively using the software compensation of the sensor inspection technology size prediction and automatic adaptive control method, the influence of the thermal deformation of the machine tool on the machining error can be realized.
1 Gu Chong title and so on. The first edition of Mechanical Manufacturing Technology. Shaanxi Science and Technology Press, 1990123
(Finish)
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