The assembly precision of parts is poor, the transmission mechanism is skewed or too tight, and they are not parallel to each other. If the center of gravity or the guide plate is too tight, the friction of the transmission system will increase, and the transmission force will decrease and the guide rail will crawl. Elimination method: The hand movement inspection of the machine tool transmission mechanism is used to find out the improperly assembled parts to be adjusted or disassembled and reassembled, so that the fit is good and the frictional resistance between the parts is reduced.
Elimination method: 1 Use wear-resistant coating to repair the dent of the strain, carefully repair the guide rail, make it straight, and the surface roughness returns to normal. Use the oil with good oil and proper viscosity. 2 rust or burr in the repairing cylinder, when the degree of pulling is serious, the boring machine can be processed according to the gap, and the hydraulic system oil with good oil quality is selected.
The rail surface is short of oil, or the oil is improperly oxidized or deteriorated. Elimination method: 1 The machine guide rail surface must have sufficient lubricating oil to produce oil film to reduce friction. 2 If you use oil improperly, you will also crawl, and you need to have good viscosity and wear resistance. 3 to ensure the quality of the oil, because the lubricating oil under the conditions of temperature rise, easy to generate oxidized colloid, acid corrosion, so that the surface is bun.
Therefore, the oil return of the machine tool is cooled and cooled, the oil is changed regularly, the acid project is detected, and the formation of oxidized gel is prevented. Insufficient rigidity of the transmission mechanism (1) The rigidity of the transmission mechanism is poor, and the transmission strength is insufficient. Due to the poor rigidity of the rotating bracket or the fastener of the machine table, the "elastic" state occurs under the transmission pressure, and the power cannot be transmitted uniformly, or There are too many layers of transmission, and the frictional resistance of the transmission offsets a part of the power and causes the transmission to be insufficient to generate creep.
Elimination method: 1Strengthen the rigidity of the transmission component, increase its rigidity and avoid the "elastic" state. 2 Renovate the transmission system and shorten the mechanical transmission level to ensure sufficient transmission force. 3 Use oil-proof anti-climbing oil to lubricate the guide rail. (2) The hydraulic system pipeline leaks, the oil seal ring at both ends of the cylinder is too tight, and the piston rod is bent, which will cause the oil pressure friction resistance to increase and the power to be insufficient to cause crawling.
Elimination method: Check the leakage point in the system to keep the hydraulic system power intact. Such as tightening, padding, replacing the sealing material, adjusting the tightness of the oil cylinder and the oil cover, and straightening the piston rod to eliminate the factors that increase the frictional resistance and prevent creep. (3) The presence of air in the hydraulic system can cause creep.
That is, when the oil level in the fuel tank is lowered and the sealing is poor, once the machine is stopped, the air is drilled, the air is compressed when the machine is started, the air bubbles in the oil pipe and the oil cylinder cause the oil pressure to drop, and the hydraulic driving force is reduced to cause creep.
Elimination method: start the machine tool, quickly start the worktable to reciprocate for a quarter of an hour, so that the air is automatically removed from the return pipe. Some machine tool table is equipped with a bleed valve on one side, open the vent valve, and let the work table reciprocate 4~5 times Gas, eliminate creep.
The inertia of the moving parts is large (1) The high-speed rotating parts are in dynamic balance, and the unbalanced points generate centrifugal vibration and mechanical vibration waves, which cause the crawling rails to cause crawling.
Elimination method: Perform motion balance treatment on the motor and other high-speed components, such as installing elastic support plate on the base, adding adjustable jack as support to offset the centrifugal force generated by high-speed rotation, reducing self-excited vibration, or anti-vibration material such as rubber wool felt To reduce the influence of mechanical vibration on the guide rail.
(2) It is known from the critical speed of creeping vc=FfAckm that the mass m can be reduced to lower the critical speed vc value. Therefore, the weight of the moving parts should be reduced as much as possible, as the stiffness allows. For heavy-duty machine tools, the weight is often impossible to reduce. Therefore, it is easier to generate crawling. Therefore, hydrostatic guides are often used on heavy-duty machine tools to solve the creep problem.
The factors that cause crawling are single and comprehensive. When it is difficult to work by a certain method alone, it can be combined in several ways. If the rigidity of the transmission member is properly increased, the guide rail is fitted with a plastic soft belt; the rail oil is used to appropriately increase the oil supply pressure, and the guide rail is partially unloaded.
Conclusion Crawling is a complex phenomenon of frictional self-excited vibration, which has great influence on the performance of machine tools. It is a problem that must be paid attention to. There are many factors affecting the crawling of machine tools, mainly the difference between the friction coefficient, the lack of rigidity of the transmission mechanism and the large inertia of the moving parts. This paper proposes corresponding countermeasures for these reasons, which has certain practical conditions. Value.
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