The characteristics of the lathe mechanical spindle unit are three high and one low (i.e., high speed, high precision, high efficiency, low noise).
1, high speed: lathe mechanical spindle unit CNC engraving and milling machine choose precision and high-speed paired bearings, elastic/rigid preloaded structure, can reach a higher speed, which allows 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 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.
The accuracy of the lathe mechanical spindle unit:
The spindle component's movement accuracy and structural rigidity is an important factor in determining the machining quality and cutting efficiency. Measure the performance of the spindle component index is mainly rotary accuracy, stiffness and speed adaptability.
①Rotational accuracy: spindle rotation in the direction of affecting the machining accuracy of radial and axial runout (see shape and location tolerance), mainly determined by the spindle and bearing manufacturing and assembly quality.
② dynamic and static stiffness: mainly determined by the spindle bending stiffness, bearing stiffness and damping.
③Speed adaptability: the maximum permissible speed and speed range, mainly determined by the structure and lubrication of the bearing, and heat dissipation conditions.
Maintenance of lathe machinery spindle unit:
Reducing the operating temperature of the bearing, often used method is lubrication. 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 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 seals, in order to prevent leakage, it is important to ensure that the return oil can be discharged 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 operation and use should be done every day to check the spindle lubrication thermostatic oil tank to see if the oil is sufficient, if the oil is not enough, then should be added in time to lubricate; at the same time to pay attention to check the lubricant temperature range is appropriate.
The lathe mechanical spindle unit speed mode:
1, stepless speed
CNC machine tools generally use DC or AC spindle servo motor to achieve stepless speed change of the spindle.
AC spindle motor and AC frequency drive (cage induction AC motor configuration vector conversion frequency control system), because there is no brush, does not produce sparks, so the long service life, and performance has reached the level of DC drive system, and even in the noise has been reduced. Therefore, the current application is more widely used.
The relationship between the power or torque transmitted by the spindle and the speed. When the machine tool is in continuous operation, the spindle speed in the range of 437~3500r/min, the spindle to transfer all the power of the motor 11kW, for the spindle constant power region Ⅱ (solid line). In this region, the maximum output torque (245N.m) of the spindle becomes smaller as the spindle speed increases. The spindle speed in the range of 35~437r/min, the output torque of the spindle is unchanged, which is called the constant torque region Ⅰ (solid line) of the spindle. In this region, the power that can be transmitted by the spindle decreases as the spindle speed decreases. The dotted line in the figure shows the constant power region and constant torque region when the motor is overloaded (allowed to be overloaded for 30 min). The overload power of the motor is 15kW, and the maximum output torque of overload is 334N.m.
2, segmented stepless variable speed
CNC machine tools in actual production do not require constant power throughout the entire variable speed range. General requirements in the medium and high speed section for constant power transmission, in the low speed section for constant torque transmission. In order to ensure that the spindle of the CNC machine tool has a large torque at low speeds and the spindle speed range as large as possible, some CNC machine tools in the AC or DC motor stepless speed on the basis of gear speed, making it a segmented stepless speed.
The development situation of lathe mechanical spindle unit:
Before the 10th century 30's, 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 tools.