Machine spindle is characterized by three high and one low (i.e., high speed, high precision, high efficiency, low noise).
1, high speed: mechanical spindle CNC engraving and milling machine choose precision and high-speed paired bearings, elastic/rigid preloaded structure, you can reach a higher speed, you can let the tool to achieve the best cutting effect.
2, high speed: 7:24 taper hole for the installation of even the radial runout can be ensured less than 0.005mm, because of the high-precision coupled with high-precision parts manufacturing can be ensured.
3, high efficiency: can be used to change the speed of continuous micro-high, so that in the machining process can be controlled at any time cutting speed, so that can achieve high processing efficiency.
4, low noise: balance test shows that: where the G1/G0.4 (ISO1940-1 grade, the spindle in high-speed operation, characterized by low noise.
Mechanical spindle maintenance measures to deal with common failures:
1, spindle heating, rotary accuracy degradation problem
The phenomenon of failure: processing out of the workpiece hole precision is low, the cylindricity is very poor, the spindle heats up very quickly, the processing noise is very large.
Analysis of the cause of the failure: After a long period of observation of the machine tool spindle can be determined, the machine tool spindle centering taper holes in the process of multiple tool change damage, the main cause of damage is the use of the process of tool change in the plucking, insertion to the error, damage to the spindle centering holes in the taper, a careful analysis of the spindle components found that the cause of the failure of the spindle components have four points:
(1) spindle bearings are not the requirements of the lubricant, mixed with dust, impurities and moisture, and the spindle bearing is not suitable for use. There are dust impurities and moisture, these impurities mainly from the machining center with the compressed air is not distilled and dry, in the pneumatic chip clearing, dust and moisture into the spindle bearing grease, resulting in spindle bearing lubrication is not good, resulting in a large number of heat river noise;
(2) the spindle used to locate the tool within the taper holes for positioning the surface of the positioning of the damage, resulting in the spindle taper and the taper of the toolholder cannot perfectly match, and the machined holes are slightly eccentric;
(3) the preload of the front bearing of the spindle decreases, resulting in a larger clearance of the bearing;
(4) the spring fatigue of the automatic clamping device inside the spindle fails, and the tool can not be completely tensioned and deviates from its original position.
For the above reasons, the troubleshooting measures:
(1) Replace the front bearing of the spindle, use qualified grease, and adjust the bearing clearance;
(2) Grind the positioning surface of the taper hole inside the spindle to be qualified, and use the coloring method of testing to ensure that the contact surface with the tool shank is not less than 90%;
(3) Replace the spring of the clamping device, and adjust the bearing's preload force.
In addition to this, in the course of operation, we should always check the spindle bore, tool shank cleanliness and fit condition, we should increase the air fine filtering and drying device, we should reasonably arrange the machining process, and we should not make the machine overloaded.
2, machining center spindle parts of the tie rod ball damage
The phenomenon of failure: the spindle tool automatic clamping mechanism of the tie rod ball is often damaged, the tool shank tail taper is also often damaged.
Analysis of the cause of the failure: It was found that the spindle loosening action and the manipulator to pull the knife action is not coordinated, the specific reason is that the limit switch is installed at the end of the booster cylinder, in the cylinder's piston action in place, the booster cylinder's piston can not be in place in a timely manner, leading to the clamping structure in the clamping of the manipulator has not yet been completely loosened to carry out a violent extraction of the knife, serious damage to the tie rod steel ball and the pull tightening screws.
Troubleshooting measures: the cylinder and cylinder cleaning, replacement of sealing rings, adjust the pressure, so that the two movements are coordinated, while the regular inspection of the gas-liquid booster cylinder, and timely elimination of potential safety hazards.
3, the spindle parts of the positioning key damage
The phenomenon of failure: the sound of changing the knife is large, the front of the spindle toggle shank rotation of the positioning key local deformation.
Failure cause analysis: after research found that the process of tool changing the loud sound occurs in the robot insertion stage, the reason is that the spindle quasi-parking position has error problems and spindle tool changing reference point drift problems. Machining centers usually use Hall components for directional detection, Hall components of the set screw after a long period of time after the use of loosening, resulting in the robot inserting the tool shank keyway is not aligned with the positioning key on the spindle, so it will crash the positioning key; and the spindle tool reference point drift may be the CNC system circuit board poor contact, electrical parameters change, proximity switch fixed loose, etc., reference point drift The reference point drift leads to the tool shank inserted into the spindle taper hole, the taper surface directly hit the centering taper hole, resulting in abnormal noise.
Troubleshooting measures: adjust the installation position of the Hall element, and add anti-loosening rubber fastening, while adjusting the reference point for tool change, replace the positioning key at the front of the spindle. In addition, in the process of machining center use to regularly check the spindle quasi-stopping position and the spindle tool change reference point position change, the occurrence of anomalies should be checked in a timely manner.
Maintenance of mechanical spindle:
Reduce the working temperature of the bearing, often used methods are lubricants. Lubrication methods are, oil and gas lubrication method, oil circulation lubrication two kinds. In the use of these two ways to pay attention to the following points:
1, in the use of oil-liquid circulation lubrication, to ensure that the spindle thermostatic oil tank oil is sufficiently adequate.
2, oil and gas lubrication is just the opposite of the oil-liquid circulation lubrication, it only need to fill the bearing space capacity of ten percent when you can.
The advantage of circulating lubrication is that, in the case of lubrication, can reduce the friction heat, and can be part of the spindle assembly to absorb the heat.
There are also two types of lubrication for the spindle: oil mist lubrication and spray lubrication.
The cooling of the spindle component is mainly to reduce the bearing heat and effectively control the heat source.
Spindle component sealing is not only to prevent dust, chips and cutting fluid into the spindle components, but also to prevent lubricant leakage. Spindle parts of the seal has contact and non-contact sealing. For the use of linoleum ring and oil-resistant rubber sealing ring contact seal, pay attention to check its aging and breakage; for non-contact sealing, in order to prevent leakage, it is important to ensure that the return oil can be drained as soon as possible, to ensure that the return hole of the oil is smooth.
Good lubrication can reduce the working temperature of the bearing and extend the service life; for this reason, in the operation of the use of the following: low-speed, the use of grease, oil circulation lubrication; high-speed oil mist, oil and gas lubrication. However, in the use of grease lubrication, the spindle bearing sealing amount is usually 10% of the bearing space volume, do not fill up, because too much grease, will exacerbate the spindle heating. For oil circulation lubrication, in the operation and use of the spindle lubrication thermostatic oil tank should be checked every day to see whether the oil volume is sufficient, if the oil volume is not enough, the lubricant should be added in a timely manner; at the same time, we should pay attention to checking the temperature range of the lubricant is appropriate.