Bearing

As the basic accessory of the machine tool, the spindle bearing directly affects the speed, rotation accuracy, rigidity, anti-shake vibration cutting performance, noise, temperature rise and thermal deformation of the machine tool, which affects the precision and surface quality of the machined parts. Therefore, high-performance machines must be equipped with high-performance bearings.

The accuracy of rolling bearings is generally divided into five grades: P0, P6, P5, P4 and P2. The accuracy of bearings used on precision machine tool spindles should be P5 and above, and for high-speed, high-precision machine tools such as CNC machine tools and machining centers. For the spindle support, P4 and above super precision bearings are required.

Spindle bearings for machine tools usually include six types of construction: deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings, two-way thrust angular contact ball bearings, tapered roller bearings and thrust bearings.

High-speed machining can effectively improve the machining efficiency of the machine tool and shorten the machining cycle of the workpiece. This requires the machine tool spindle and its related components to meet the needs of high-speed machining. At present, CNC machine tool spindle bearings are basically limited to four types of structural types: angular contact ball bearings, cylindrical roller bearings, two-way thrust angular contact ball bearings and tapered roller bearings.

In addition to the high-precision lead screw, nut and ball, the ball screw should also be used with bearings with high axial stiffness, low friction torque and high running precision. At present, the ball screw support adopts the single-row thrust angular contact ball bearing with the most contact angle of 60°, and the precision grade is also the rolling bearing mounted on the general drive shaft for the machine tool. The requirements and selection are the same as those of the ordinary mechanical transmission bearing. It only needs to meet the strength and life requirements, and the speed does not exceed the specified bearing limit speed.

Under normal circumstances, the machine tool bearings we refer to refer to machine tool spindle bearings and ball screw bearings, and precision machine tool bearings refer to spindle bearings and screw bearings with accuracy of P5 and above.
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What are the FAG bearing lubrication methods?

1, drip lubrication

Drip lubrication is suitable for FAG bearing parts that need to supply lubricating oil quantitatively. The amount of dripping is generally one drop every 3-8 seconds. Excessive oil quantity will cause the bearing temperature to increase.

2, circulating oil lubrication

The filtered oil is delivered to the bearing components by an oil pump, and the lubricating oil after passing through the FAG bearing is filtered and cooled for use. Since the circulating oil can take a certain amount of heat to cool the bearing, this method is suitable for bearing parts with higher rotational speed.

3, oil bath lubrication

Oil bath lubrication is the most common lubrication method. It is suitable for the lubrication of low and medium speed FAG bearings. Part of the bearing is immersed in the oil tank. The lubricating oil is taken up by the rotating bearing parts and then flows back to the oil tank. The oil level should be slightly lower. The center of the lowest rolling body.

4, spray lubrication

The high-pressure oil is injected into the bearing through the nozzle by the oil pump, and the oil injected into the FAG bearing flows into the oil groove through the other end of the bearing. When the bearing rotates at high speed, the rolling elements and the cage also form a gas flow at the relatively high rotation speed of the surrounding air. It is difficult to send the lubricating oil to the bearing by the general lubrication method. At this time, the lubricating oil must be sprayed by the high-pressure injection method. In the bearing, the position of the nozzle should be placed between the inner ring and the center of the cage.

5, spray lubrication

The dry compressed air is mixed with the lubricating oil through a sprayer to form an oil mist. In the jet bearing, the air flow can effectively cool the bearing and prevent the intrusion of impurities. This method is suitable for the lubrication of high speed, high temperature FAG bearing components.

The above five FAG bearing lubrication methods are applicable to different working conditions, and the operation methods are also different. The operator should pay special attention to the details of each method when performing lubrication work. Bearing brand is good, it also needs to be well maintained, the most important of which is lubrication. Therefore, mastering the FAG bearing lubrication method will help to extend the service life of the bearing.
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Analysis of the application range of high speed angular contact ball bearings

The ball of the angular contact ball bearing (ie, the ball) revolves and rotates, and generates a centrifugal force Fc and a gyro moment Mg. As the spindle speed increases, the centrifugal force Fc and the gyro moment Mg also increase sharply, causing the bearing to generate a large contact stress, resulting in increased bearing friction, increased temperature rise, reduced accuracy, and reduced life. Therefore, in order to improve the high-speed performance of such bearings, efforts should be made to suppress the increase in Fc and Mg. From the calculation formula of angular contact ball bearings Fc and Mg, it is known that reducing the density of the ball material, the diameter of the ball and the contact angle of the ball are all beneficial to reduce Fc and Mg, so now the high-speed spindle uses a contact angle of 15° or 20°. Small ball diameter bearings. However, the ball diameter can not be reduced too much, basically only 70% of the standard series ball diameter, so as not to weaken the rigidity of the bearing, it is more important to seek improvement on the ball material.

Compared with GCr15 bearing steel, the density of tantalum nitride (Si3N4) ceramic is only 41%. The ball made of tantalum nitride is much lighter. Naturally, the centrifugal force and gyro moment generated during high-speed rotation are also small. many. At the same time, the elastic modulus and hardness of tantalum nitride ceramics are 1.5 times and 2.3 times that of bearing steel, and the thermal expansion coefficient is only 25% of bearing steel, which can improve the rigidity and life of the bearing, and make the bearing fit. The gap has small change under different temperature rise conditions, and the work is reliable. In addition, the ceramic is resistant to high temperature and does not bite with the metal. It is obvious that the ball made of tantalum nitride ceramic is more suitable for high-speed rotation. Practice has shown that the ceramic ball angular contact ball bearing can increase the speed by 25%~35% compared with the corresponding steel ball bearing, but the price is also higher.

Bearings in which the inner and outer rings are made of steel and the rolling elements are ceramics are collectively referred to as hybrid bearings. At present, there are new developments in hybrid bearings: First, ceramic materials have been used to make roller for cylindrical roller bearings, ceramic cylindrical hybrid bearings have appeared on the market; second, stainless steel (such as FAG's nitrided stainless steel Crodinur30) has been used instead of bearing steel. The inner and outer rings of the bearing are made, especially the inner ring. Since the coefficient of thermal expansion of stainless steel is 20% smaller than that of the bearing steel, the tendency of the contact stress caused by the thermal expansion of the inner ring is naturally suppressed during high-speed rotation.
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Eccentric bearing installation guide

1. The assembly site should be as clean as possible and free of dust;

2, to avoid eccentric bearings contaminated with dust, pollutants and moisture (contaminants have adverse effects on the operation and service life of rolling bearings);

3. Check the dimensional accuracy and cleanliness of the mating surface on the bearing housing bore and the shaft;

4. Apply a little oil or a little grease to the mating surface of the bearing ring;

5. Ensure that the shaft and housing bore have a 10°~15° guide chamfer;

6. Do not overcool the eccentric bearing (the moisture generated by condensation can cause corrosion of the bearing surface of the bearing and the bearing);

7. After installation, fill the bearing with lubricant and check that the bearing configuration is working properly.

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Shaft bearing selection

The accuracy of the bearing used on the machine tool spindle should be ISOP5 or above (P5 or P4 is the ISO accuracy level, usually from low to high (P0, P6, P5, P4, P2), and for high speed CNC machine tools, machining centers, etc. For high-precision machine tool spindle bearings, ISOP4 or higher accuracy is required. Spindle bearings include angular contact ball bearings, tapered roller bearings, and cylindrical roller bearings.

1, precision angular contact ball bearings

Precision angular contact ball bearings are widely used. The rolling element of an angular contact ball bearing is a ball because it is a point contact (distinguished from the line contact of the roller bearing), so it can provide higher rotation speed and smaller heat generation. And higher rotation accuracy. In some ultra-high-speed spindle applications, hybrid bearings with ceramic balls (usually si3N4 or Al203) are also used. The metal processing reporter believes that compared with the traditional fully hardened steel ball, the ceramic ball material itself gives the ceramic ball bearing the characteristics of high rigidity, high rotation speed, high temperature resistance and long service life, so as to meet the high-end customer's bearing product products. demand.

2, precision cylindrical roller bearings

In machine tool spindle applications, double row precision cylindrical roller bearings are also used, usually in combination with precision angular contact ball bearings or thrust bearings. These bearings can withstand large radial loads and allow for higher rotational speeds. The two rows of rollers in the metal machining in-line bearing are arranged in a crosswise manner. The fluctuation frequency during rotation is greatly improved compared with the single row bearing, and the amplitude is reduced by 60%-70%. These bearings usually come in two forms: NN30, NN30K two series bearing inner ring with ribs, outer ring can be separated; NNU49, NNU49K two series bearing outer ring with ribs, inner ring can be separated, of which NN30K and NNU49K series The inner ring is a tapered hole (taper 1:12), which cooperates with the tapered journal of the main shaft, and moves the inner ring axially to make the inner ring expand, so that the bearing clearance can be reduced or even pre-tensioned (negative clearance) status). Cylindrical bore bearings are usually hot-fitted, with an interference fit to reduce bearing clearance or to pre-tension the bearing. For the NNU49 series bearings that can be separated from the inner ring, the main shaft is usually mounted on the main shaft and then the raceway is finished to improve the spindle rotation accuracy.

3, precision tapered roller bearings

In some machine applications with heavy loads and speed requirements, such as roughing of forgings, wire machines for oil pipelines, heavy duty lathes and milling machines, the selection of precision tapered roller bearings is an ideal solution. Because the roller of the tapered roller bearing is designed for line contact, it can provide high rigidity and load to the main shaft. In addition, the tapered roller bearing is a pure rolling bearing design, which can reduce the bearing operation. Torque and heat to ensure spindle speed and accuracy. Since the tapered roller bearing can adjust the axial preload (play) during installation, this allows the customer to better optimize the bearing clearance adjustment throughout the life of the bearing.
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How to operate the stone engraving machine regularly

Steps to properly operate the stone engraving machine:

1. Before starting the stone engraving machine, first make sure that all connections between the machine and the computer are normal, then turn on the machine power and computer power. After the system is started, enter the NCStudio CNC system.

2. Select the "Return to machine origin" menu after opening the control system. The machine will automatically return to the machine origin and correct the system coordinate system. In some cases, after the normal shutdown as above, the power is turned back on and the last operation is continued, and the user does not have to perform a mechanical reset operation. The NCStudio system saves the current coordinate information when it exits normally. In addition, if the user confirms that the current location is correct, you can not do this.

3. Before processing, the user usually loads the required machining program. Otherwise, some functions related to automatic machining are invalid. Selecting the "Open (F)|Open (O)..." menu will bring up the Windows standard file operation dialog, from which you can select the drive, path, and file name where you want to open the file. After clicking the "Open" button, the machining program is loaded into the system.

4. Determine the workpiece origin, manually move the X and Y directions of the stone engraving machine to the desired origin position on the workpiece, select the "Set the current point as the workpiece origin" menu, or set the coordinate value of the current position in the coordinate window. Cleared, so that when the machining program is executed, the current position is used as the starting point for machining.

Woodworking engraving machine daily maintenance manual

The appearance of woodworking engraving machine greatly improved the efficiency. After many customers purchased the woodworking engraving machine, they paid little attention to the usual maintenance work. When the technicians of Lulu Machinery were on-site training, they would teach the customer the precautions and Maintenance method, here is a simple explanation of the usual maintenance work of the woodworking engraving machine.

First of all: the brain part of the woodworking engraving machine belongs to the electronic equipment. The dust in the factory will accumulate in the mainframe of the computer. Especially in the summer, if the computer does not dissipate heat well, it will easily burn the circuit board, in order to keep the computer running smoothly. Also need to regularly disinfect and defragment the disk.

Secondly, it is necessary to clean the lead screw, industrial control box and circuit board regularly, and clean the work surface in time, including the material debris next to the guide rail and the guide rail to prevent the machine from appearing during the working process due to debris interference.

Again: slowly move back and forth after adding oil to ensure that the lubricant can be evenly applied to the guide rail and the lead screw. If the machine is not used for a long time, it should be refueled regularly to ensure the flexibility of the transmission system. First clean the rails and lead screws, and use a cloth (without hair removal) to clean off the oil and material scraps on the rails and lead screws. Due to the low temperature, both the guide rail and the lead screw can be added with oil. It is best to add antifreeze oil. The refueling cycle is twice a month, that is, every two weeks. Add cooling water or coolant to the CNC economic woodworking engraving machine, and keep the cooling water free of impurities.

Finally: When using woodworking engraving machines in winter, be sure to pour out the water in the tank when not using the machine to prevent the water tank and water pipes from freezing. The temperature of the operation workshop is preferably higher and higher, and the winter is likely to cause ice formation in the woodworking machine water tank. The temperature has little effect on the woodworking engraving machine, but because the user adds butter to the screw, the winter also forgets to clean up, which leads to the opening of each boot. Some studios have very low temperatures. Although the oil is added, it can still be frozen. On, the machine can't run.