The electric spindle of the engraving machine uses high-speed bearings. To assemble this high-speed bearing, special grease must be used, and special tools and equipment must be used. The simplest is to heat the assembly and put it in the oil pan to heat it. Hit the bearing and fit it into the shaft naturally. There is also press-fitting, using a press to install, there is no such thing, just use a suit of the same size as the inner ring of the bearing to install, tap the sleeve lightly, this method has a certain impact on the service life of the bearing. , One problem is very simple. How can you install a spindle bearing with 24,000 revolutions per minute? It is almost severely worn. Don't make the idea of assembling and disassembling the spindle bearing, but use special equipment. That equipment investment is not small.
The spindle should be said to be a relatively high-precision thing! So it is recommended not to change the bearing by yourself! Generally, the bearing replacement requires professional tools to install without affecting the accuracy. If you can replace it yourself, you can, but the accuracy of the spindle is over!
Disassembly of the spindle motor of the engraving machine:
1. Disassemble the front and rear end caps, front and rear nuts of the engraving machine
2. Push out the main shaft, rear bearing seat, linear bearing and other accessories from the front end of the shaft.
3. Research and match front and rear bearing washers
① The front and rear bearings of the electric spindle are matched in series with DT
②. Support the inner sleeve according to the direction of axial force borne by the bearing, and press down the outer sleeve with the design force of the engraving and milling machine by hand (the force is roughly the same as the preload force of the spring on the bearing), adjust the gap of the washer There are two methods. One is to change the bearing and the upper and lower positions of the bearing. The other is to grind the height of the washer. Use the figure-eight grinding method to grind the washer. At the same time, rotate the position of the washer to ensure that the parallel difference of the washer is within 2um. Adjust so that the inner and outer gaskets are evenly stressed, and the preload on the two sets of bearings is even
③. If a well-matched bearing is selected, the size difference between the inner and outer gaskets should be within 2um, the parallel difference of the washers should be within 2um, and the bearings should be installed in pairs according to the V-shaped mark on the outer diameter.
④. The long-term use of the pre-tensioned spring will cause fatigue and reduce the elasticity; the pre-load on the bearing will be reduced, which will affect the design accuracy and life of the electric spindle engraving machine. At this time, a new spring of the same specification should be replaced.
⑤. If the gaskets are not properly matched, the load of one set of the two sets of bearings is small and the other set is too large, the bearing will receive uneven force and will generate heat, which will seriously affect the service life. When the inner and outer washers are subjected to the same force, two sets Uniform pre-tightening load on the bearing
4. Clean the bearing. The outer sleeve slopes downwards (or the inner sleeve slopes upwards) and rotates for cleaning (in clean gasoline). The bearings should be cleaned more than twice. Pay attention to the bearings after cleaning. The upper and lower positions of the bearings cannot be placed in the wrong position
5. Before installing the bearing, the bearing, the inner hole of the shaft housing, and the main shaft should be lubricated with oil (special lubricating oil for the electric spindle). One is to facilitate the installation, and the other is to ensure the lubrication of the bearing at the initial stage of the electric spindle.
6. Clean the other parts on the shaft, the bearing should be dried naturally after cleaning, and it is strictly forbidden to blow dry with high-pressure gas
7. Install the rear bearing first, tighten the nut, and fix the spring on the bearing seat with butter. The spring gland cannot be misplaced
8. Assemble the front end bearing, fix the front end cover and pre-press the bearing jacket. (Assemble the bearing should use a special sleeve, and the sleeve should be machined with nylon rod. The shape is as follows: D is smaller than the outer diameter of the bearing, d is larger than the inner diameter of the bearing)
9. Tighten the front nut, install the front and rear cover, pay attention to the position of the air inlet when installing the back cover, the sealing ring of the air inlet, water inlet and outlet should be intact and placed in the correct position
10. After the front and rear bearings are installed, push the spindle forward from the back end of the electric spindle into place, and push the linear bearing into place at the same time
11. After the electric spindle is installed, check whether the spindle is installed in place (push the spindle forward with a wrench, the spindle will move forward, and it will spring back immediately if you release it.
Engraving is a combination of drilling and milling in terms of processing principle, and the engraving machine has multiple data input modes as needed. There are two types of computer engraving machines: laser engraving and mechanical engraving, both of which have high power and low power. Because the application range of engraving machine is very wide, it is necessary to understand the most suitable application range of various engraving machines. Low power is only suitable for two-color boards, building models, small signs, three-dimensional crafts, etc., while carving jade, metal, etc., the power needs to be above 1500W. The high-power engraving machine can be used as a small-power engraving machine. It is most suitable for large-scale cutting, embossing and carving.
In the numerical control machine tool, the electric spindle usually adopts the frequency conversion speed regulation method. There are mainly three control modes: ordinary variable frequency drive and control, vector control drive and direct torque control.
Ordinary frequency conversion is scalar drive and control, and its drive control characteristic is constant torque drive, and the output power is proportional to the speed. The dynamic performance of ordinary frequency conversion control is not ideal, the control performance is not good at low speed, the output power is not stable enough, and it does not have the C-axis function. But the price is cheap, the structure is simple, and it is generally used for grinders and ordinary high-speed milling machines.
The vector control technology imitates the control of a DC motor, oriented by the rotor magnetic field, and realizes the drive and control by the method of vector transformation, which has good dynamic performance. The vector control drive has a large torque value when it is just started. In addition, the electric spindle itself has a simple structure and small inertia, so the starting acceleration is large, and the allowable limit speed can be reached instantaneously after starting. This kind of driver has two kinds of open loop and closed loop. The latter can realize position and speed feedback, not only has better dynamic performance, but also can realize C-axis function; while the former has a slightly worse dynamic performance and does not have C-axis function. , But the price is cheaper.
Direct torque control is another new type of high-performance AC speed control technology developed after vector control technology. Its control idea is novel, the system structure is simple and clear, and it is more suitable for the drive of high-speed electric spindles and can meet the requirements of high-speed electric spindles. The dynamic and static characteristics of high speed, wide speed range, high speed and instant stop have become a hot technology in the field of AC drive.