For the work performance of the spindle assembly, the rotational accuracy of the spindle assembly is one of the important aspects. Spindle rotation, for a variety of reasons, the location of its center line of rotation over time and change, if a straight line on behalf of the spindle ideal center line of rotation, the actual center line of rotation and the ideal center line of rotation of the offset, known as the rotational accuracy of the spindle assembly, can also be referred to as the machine tool idling, the front of the spindle radial runout, end runout and axial runout of the size of the spindle.
The rotational accuracy of the spindle assembly mainly depends on the spindle, bearing and bearing locking mother of manufacturing accuracy and assembly quality. In the overhaul of the equipment, the spindle and bearing locking mother is mainly used to repair and restore its accuracy, while the bearing chair appraisal after scrapping is outsourced. Therefore, in the assembly process, the correct assembly method is to improve the rotational accuracy of the spindle assembly is one of the important aspects of the assembly should be measured before the assembly of the bearing and its related parts of the accuracy, and make a record, in order to assemble the optional. This article on the equipment overhaul spindle assembly process for a brief discussion:
1. spindle taper hole centerline measurement
The accuracy of the machine tool spindle directly affects the rotational accuracy of the spindle assembly, repair, and its own machining accuracy must have a certain degree of error. Field spindle accuracy detection method to measure the spindle shaft end taper hole center line of the largest deviation, make a mark, and record the direction of the error.
2. Directional assembly of bearings
Bearings are an important part of the spindle assembly, bearing assembly directly affects the radial runout of the rotating shaft and axial runout accuracy, so to ensure that the spindle radial runout and axial runout accuracy, in addition to the requirements of the spindle and bearings with a certain degree of accuracy, but also must be used in the correct assembly method.
Directional assembly of bearings: the essence is based on the principle of error compensation, the spindle chain hole centerline deviation (high or low) and the front and rear bearing inner ring deviation (low or high) placed in the same axial cross-section, and according to a certain direction of the assembly, thereby compensating for the error, in order to improve the rotational accuracy of the spindle assembly. In the front and rear bearing inner ring radial runout and spindle taper hole centerline of the deviation of the conditions of the same, different assembly, spindle inspection at the radial runout amount of different values (in the assembly before, should measure the bearing within the periphery of the runout and record the direction of its error).
As shown in the figure:
δ1 --- radial runout of the front bearing inner trap; δ2 --- radial runout of the rear bearing inner ring; δ3 --- spindle chain hole centerline;
δ --- radial runout at the spindle inspection. From Figure A according to the similar triangle property:
δ1-(δ+δ3)/δ1-(δ+δ3)L = α/α+L
it can be obtained that δ =: δ1-(δ2-δ1) × α/L-δ3
i.e., δA = δ1-(δ2-δ1) × α/L-δ3 Ⅰ
The same example is shown by Figure B:
δB = δ1-(δ2-δ1)*α/L+δ3 Ⅱ
From Fig. C:
δC = δ1+(δ2+δ1)*α/L-δ3 Ⅲ
From Fig. D:
δD = δ1+(δ2+δ1)*α/L+δ3 Ⅳ
(1) From the four graphical illustrations and the four formulas, we can see that δA <δB＜δC＜δDIn order to reduce the amount of radial runout of the spindle, according to Figure A (and Formula I) that is, the highest point of radial runout of the inner ring of the front and rear bearings are placed in the same direction, while the maximum deviation of the spindle taper hole centerline is in its opposite direction, which minimizes the radial runout of the front end of the spindle.
(2) The precision of the rear bearing should be lower than the front bearing, that is, the rear bearing inner ring radial runout is slightly larger than the front bearing. If the precision of the rear bearing and the precision of the front bearing is the same, or even higher, the radial runout of the spindle is most rather increased.
As shown in Figure E: δE = δ2 + (δ2 - δ1) * α / L - δ3 Ⅵ
3. Adjustment of the bearing locking mother
Because of the perpendicularity of the end face of the main spindle bearing locking nut and its threaded centerline and the threaded teeth of the error in the tightening of the nut is likely to result in the spindle bending and bearing tilt of the inner and outer rings, the rotary accuracy of the main spindle assembly has a great impact. Therefore, after tightening the nut, the spindle rotation accuracy should be measured to find out the highest point of radial runout, and in the opposite direction of 180 ° in the nut to make a mark. After unscrewing the nut, in the marking scraping the nut combined surface, and then reloaded to re-measurement, until the spindle rotation accuracy is qualified.
Through the implementation of the above method in the overhaul equipment, improve the efficiency of the overhaul equipment, shorten the time of overhaul equipment, and greatly improve the rotational accuracy of the spindle assembly.
What are the methods to improve the accuracy of measurement and inspection during assembly?
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