Measures to improve the rotation accuracy of machine tool spindle components

Abstract: The spindle assembly is one of the important parts of the machine tool. When the machine tool is working, the workpiece or the tool directly participates in the surface forming movement by the spindle. Therefore, in the production, the rotation accuracy, static stiffness, vibration resistance, thermal deformation and wear resistance of the spindle assembly have high requirements. This article only briefly describes the measures to improve the rotation accuracy of the spindle assembly.

When machining parts, machining errors will always occur, which will affect the accuracy of the parts and cause serious waste. According to a large number of practical proofs, the main factors affecting machining accuracy are theoretical design errors, machine tool manufacturing errors and component wear, fixture errors, tool errors, elastic deformation and thermal deformation of the process system, errors caused by the mechanical properties of the workpiece itself, and operators Measurement errors, etc., as far as the machine tool is concerned, the spindle assembly is a key part that determines the position and movement of the workpiece (tool). Its rotation accuracy error has a great influence on the machining accuracy and surface roughness of the part. The rotation accuracy of the spindle assembly can be improved Machining accuracy of machine tools.

1. Measures to improve spindle rotation accuracy in machine tool manufacturing

The rotation accuracy of the spindle refers to the radial and axial runout values of the workpiece or tool at the front end of the spindle under the condition of no load and low speed after the machine is assembled. To improve the rotation accuracy of the main shaft, in addition to ensuring a certain accuracy of the main shaft and bearings, technological measures can also be taken.

(1) Finishing after assembly. For CNC machine tools, the spindle is relatively precise, requiring high enough rigidity and rotation accuracy. In machine tool manufacturing, the machining accuracy of shafting components is relatively high. It is very difficult to control the machining quality of the parts one by one to make the whole machine reach a certain accuracy index. For example, for the spindle assembly of a coordinate boring machine, the tolerance of the spindle taper axis axis runout is only 0.001~0.002mm. If it is guaranteed by the accuracy of the spindle or bearing, it will require accuracy that cannot be achieved at present. In order to ensure the accuracy of the spindle components, the method of assembly and finishing is adopted in the process. The assembly is completed first, and the outer circle of the spindle sleeve is finely ground on a precision cylindrical grinder based on the tapered holes at both ends of the spindle. The outer circle of the cylinder is the reference, and the taper hole of the spindle is finely ground. After finishing the fine grinding and passing the inspection, it is disassembled and cleaned, and then assembled, the finished product. During maintenance of this type of machine tool, if the bearing needs to be disassembled, mark should be made between the outer ring of the bearing and the casing or sleeve hole, and between the inner ring of the bearing and the journal before disassembling. Otherwise, once it is misaligned during reassembly, it will be disassembled. The accuracy before disassembly cannot be guaranteed, and the result is half the effort.

(2) Error matching method. For a spindle with a tapered hole, when measuring the rotation accuracy of the spindle, it is necessary to match the measuring rod with the tapered hole of the spindle. The radial runout of the end of the measuring rod is equal to the error a caused by the front bearing , the error b caused by the rear bearing and Since the machining error c of the spindle taper is twice the vector sum of the three, a , b , and c all have a certain direction. Therefore, if these three errors are assembled in a certain direction, the errors can cancel each other out. First, measure the radial runout Δ a , Δ b and the direction of the inner ring of the front and rear bearings , and then a and b can be calculated . The directions of a and b are determined by the directions of Δ a and Δ b , respectively . Put the main shaft (without bearing) on the V-shaped iron, the size and direction of the machining error c of the tapered hole can be measured. Adjust the positions of the inner ring of the front and rear bearings and the main shaft, adjust the three errors into a straight line, make the smaller two ( a , b ) face one direction, and the largest ( c ) face the other direction, so that the error can be It is reduced to d , but it cannot be completely offset, as shown in Figure 1. If you choose to match according to Figure 2, it can be completely offset, but accurate drawing calculations are required a ,The angle between b and c .