Machine spindle maintenance measures to deal with common failures:
1, spindle heating, rotary precision decline
The phenomenon of failure: processing out of the workpiece hole precision is low, cylindrical degree is very poor, the spindle heat very quickly, the processing noise is very large.
Failure analysis: after long-term 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, the repair of the mechanical spindle recognition of machinery, professional quality assurance, careful analysis of the spindle components found that the failure of the spindle components have four reasons:
(1) the spindle bearing grease is not required, mixed with dust impurities and water, these impurities mainly from the machining center with no distillation and dry compressed air, in the pneumatic chip clearing, dust and moisture into the spindle bearing grease, resulting in spindle bearings are not well lubricated, resulting in a large number of hot river noise;
(2) the spindle used to locate the tool in the taper hole positioning surface There is damage, resulting in the taper surface of the spindle and the taper surface of the toolholder can not be a perfect match, and the machined holes have a trace eccentricity;
(3) the preload of the front bearing of the spindle decreases, resulting in the clearance of the bearing becomes larger;
(4) the spring fatigue of the automatic clamping device inside the spindle fails, and the tool can not be completely tightened, and it is deviated from the 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 a qualified level, and use the color-coating 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 robotic tool insertion when the keyway of the tool shank is not aligned with the positioning key on the spindle, so it will be crashed positioning key; mechanical spindle maintenance recognition, and the spindle tool reference point drift may be the CNC system circuit board poor contact, electrical parameters change, proximity switch fixed loose, etc., the reference point drift may be the circuit board contact, electrical parameters change, proximity switch fixing Loose, etc., 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 spindle front positioning key. 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 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 components is mainly to reduce the bearing heat, effective control of heat sources.
The sealing of spindle parts should not only prevent dust, chips and cutting fluid from entering the spindle parts, but also prevent the lubricant from leaking. Spindle parts of the seal has contact and non-contact sealing. For the use of linoleum ring and oil-resistant rubber seals contact seal, pay attention to check its aging and breakage; for non-contact seal, in order to prevent leakage, it is important to ensure that the return oil can be drained off as soon as possible, to ensure that the return hole is smooth. Good lubrication effect, can reduce the working temperature of the bearing and prolong 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 should be done every day to check the spindle lubrication thermostatic oil tank, see whether the oil is sufficient, if the oil is not enough, then should be added in time lubricant; at the same time, pay attention to check the lubricant temperature range is appropriate.
Mechanical 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 process of machining can be controlled at any time cutting speed, so you 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.
Machine spindle development situation:
10 century before the 1930s, most of the machine tool spindle using a single oil wedge of plain bearings. With the improvement of rolling bearing manufacturing technology, later appeared a variety of spindle with high precision, high stiffness rolling bearings. This kind of bearing is easy to supply, the price is low, the friction coefficient is small, the lubrication is convenient, and can adapt to the rotational speed and the load variation amplitude of the working conditions, so it is widely used. But the sliding bearing has the advantages of smooth work and good vibration resistance, especially a variety of oil wedge dynamic bearing, in some finishing machine tools such as grinding machines used a lot. 50's after the emergence of liquid hydrostatic bearings, high precision, high stiffness, friction coefficient is small, and has good vibration resistance and smoothness, but need a set of complex oil supply equipment, so only used in high-precision machine tools and heavy-duty machine tools. Gas bearings high-speed performance, but because of the small carrying capacity, and gas supply equipment is also complex, mainly used for high-speed internal grinding machines and a few ultra-precision machining machine tools. early 70's electromagnetic bearings, both high-speed performance and carrying capacity of the advantages of a larger, and can be adjusted during the cutting process by adjusting the magnetic field so that the spindle for a small amount of displacement, in order to improve machining of the dimensional accuracy, but the cost is higher, can be used for ultra-precision machining Machine tool.
The milling machine is a widely used machine tool, in the milling machine can be processed on the plane (horizontal, vertical surface), groove (keyway, T-slot, dovetail groove, etc.), gear parts (gears, spline shafts, sprockets), spiral surface (threads, helical grooves) and a variety of curved surfaces. In addition, it can also be used for the surface of rotating bodies, internal hole processing and cut-off work. When the milling machine is working, the workpiece is mounted on the table or indexing head and other accessories, the milling cutter rotates as the main movement, supplemented by the table or the milling head's feed movement, the workpiece can obtain the required machining surface. Because it is a multi-flute intermittent cutting, thus the productivity of the milling machine is high. Simply put, the milling machine can be milling, drilling and boring workpiece processing machine tools.