The choice of machine tool bearing lubrication method is related to bearing speed, load, allowable temperature rise, bearing type and related conditions. Next, you will explain to you the precautions of machine tool bearing grease lubrication.
Grease lubrication is characterized by strong lubricant adhesion, easy to use, simple maintenance, and no need to add and replace lubricants frequently. However, the friction resistance is greater than that of oil lubrication. The most commonly used grease for machine tool bearings is lithium based grease with mineral oil as the base oil, and the compound barium based grease with synthetic double fat lubricating oil as the base oil can also be used for high-speed precision bearings. The rolling bearing should not be filled with too much grease, otherwise, the grease will melt and deteriorate due to stirring and heating, and the lubrication will be lost. The filling amount of the bearing should be determined according to the type, size and working speed of the bearing.
For high-speed precision machine tool bearings, it is recommended to fill 15% to 25% of the internal free space of the bearing according to the speed of the bearing. Grease lubricated bearings must be run in the initial stage of work, after running, excess grease is forced into the bearing raceway, so that the grease in the bearing is evenly distributed, and can ensure the heat balance temperature when the bearing is working normally. The running starts from a low speed (such as half of the speed), and increases the speed when a stable temperature is reached until the speed of the bearing is reached and the temperature is stable.
Lubrication characteristics of machine tool bearings
The choice of the lubrication method and lubricating grease of the machine tool is based on the structure of the machine tool, the degree of automation, the working conditions of the machine tool and the requirements of the precision are comprehensively measured and decided, and the machine tool lubrication should strive to avoid temperature rise and vibration while meeting the wear and consumption reduction. As a complex and precise machine, the machine tool will use a variety of transmission devices, according to the type of equipment, working environment and the required precision requirements for the viscosity of lubricating oil, oil oxidation resistance, extreme pressure resistance and other related properties have different requirements.
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Performance requirements for machine tool lubrication and machine tool oil (grease) :
Lubrication of machine tools includes lubrication of bearings, gears, guides and rails; Machine grease includes: hydraulic oil, hydraulic guide oil and lubricating oil (grease), different types of machine tools and different working conditions have different requirements for the performance of lubricating oil:
1, bearing lubrication:
1) Lubrication of sliding bearing: sliding bearing is a commonly used transmission mode, lubricating oil not only to play a lubricating role but also play a cooling role, so it is necessary to use low-viscosity lubricating oil with good lubrication performance, and it needs to have good oxidation resistance, anti-wear, anti-rust and anti-foam property. For the precision plain bearings used in the grinding stone spindle of the precision grinding machine, due to the extremely small bearing clearance (1 micron) and the particularly high speed (30000r/min or more), the lubricating oil with very small viscosity and excellent anti-wear oil should be used.
2), lubrication of rolling bearings: rolling bearings on the machine tool, due to the advantages of small friction coefficient, and quiet operation, so the machine tool has a large number of rolling bearings, inner diameter 25 mm, speed 30000r/min below, can be sealed into high-speed grease. When more than 30000r/min, forced lubrication or spray lubrication is applied. It should be noted that in addition to the special case of large and rough rolling bearings, grease containing solid lubricants can not be used in general.
2, gear lubrication:
The impact and vibration of the gear of the machine tool is not large, the load is small, and the lubricating oil containing extreme pressure additives should not be used in general. It is necessary to pay attention to how to prevent the thermal deformation of the headstock, the impact load of the press or shear machine gear, should be used with anti-wear agent gear oil, for circulation lubrication or oil bath lubrication gear oil, in addition to considering the oxidation resistance, but also consider the corrosion resistance, anti-wear, anti-rust and anti-bubble property. Select the right gear oil and the right viscosity according to the type of gear.
3. Lubrication of guide rail:
The load and speed of the guide rail vary greatly, the general load of the guide rail surface is 3-8N/cm2, but due to the frequent repeated movement of the guide rail, it is easy to produce boundary lubrication, and even semi-dry lubrication, resulting in crawling, in addition to the machine tool design and poor material lubrication is the main cause of crawling. In order to overcome the crawling phenomenon, in addition to the fluorinated resin guide rail veneer, etc., in the improvement of lubrication, the main use of lubricants containing anti-climbing agents.
4, the machine tool is a special bearing. The fixed load is not large, and now the high-speed machine tools are mostly rotary, and the compound load is large, so they are sealed with grease to lubricate.