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Processing and measuring method of high-precision sleeve parts

Jan 09, 2020

The drawings of large cylindrical parts (such as hydroelectric shafts) require full beveling of the outer circle and the stop 0.02 mm, as shown in Figure 1. Both ends of the total length are required to be 0.02 mm. The size of the two stop is reduced to H6, and must be clamped at one time Due to its large aspect ratio, small dimensional tolerances, and tight form and position tolerances, the replacement of a vertical lathe cannot meet the drawing requirements at all. On a horizontal lathe, a one-clamp one-frame clamping method is used. Although the tail end and the outer circle at the end of the lathe can be processed, the end stop and end at the end of the lathe cannot be processed. After the workpiece is turned and clamped, it cannot be guaranteed Requirement of full stop of 0.02 mm. In the case of a hollow workpiece, it is necessary to ensure that the two ends of the stop and the outer circle are processed in one clamping. Only the mandrel is installed on the core of the workpiece, so that the end of the insert, the end and the outer circle can be processed at the same time.

 Figure 1 Sketch of heavy cylinder part

1.Mandrel structure

According to the diameter of the inner hole of the sleeve part and the size of the supporting claw, a mandrel with a suitable diameter is selected. In order to reduce the deflection of the mandrel, a through-hole with an appropriate diameter is processed in the center of the mandrel, and at the same time it plays a role in reducing weight The two ends of the shaft are designed with center holes, which can realize two top clamping workpieces, or one clamping one rack clamping workpiece. 8 sets of adjustable supports are evenly distributed on the mandrel, and can be adjusted radially by screws and nuts. Before installing the mandrel into the hole, initially adjust the position of the supporting claw, leaving a gap of 10 mm on one side; after installing the mandrel into the hole, adjust the screw to make the mandrel coaxial with the inner cavity, and the coaxiality is less than 0.5 mm; then Secure the position of the screw with a nut.

 

As shown in Figure 2, after the mandrel is installed and adjusted, the alignment stop can be completed in one clamping, and the processing of the two total length ends and the outer circle can effectively ensure the position tolerance such as coaxiality and runout.

 Figure 2 Structure diagram of mandrel

2. Measurement method of stop

Under normal circumstances, a horizontal lathe is selected in a clamping one rack or double bracket clamping method to process the end stop.In this case, the machine tailstock can be completely separated from the workpiece, and the tool has enough space to complete the end stop. Machining. After the machining is completed, the inner diameter micrometer is used to complete the measurement of the stop diameter. The above-mentioned method of assembling the mandrel is used to process cylindrical parts, although the shape and position tolerances are effectively guaranteed, but it brings difficulties to the accurate measurement of the stop.In addition, when the diameter of the inner hole or the diameter of the mandrel changes, Space is not always the same. In this case, a universal and accurate measurement method is needed to realize the measurement of the stop at both ends.

 

After removing the original two-end measuring heads of the outside micrometer, after installing the components, you can use the ruler bow to measure the size of the mouth, as shown in Figure 3. The nut fixes the connecting rod at one end of the ruler bow, and the inner micrometer head is connected to the connecting rod through a thread. The measuring range can be adjusted and the gauge pressure can be controlled by adjusting or combining the inner micrometer. The nut fixes the screw at the other end of the ruler bow. The meter base is connected to the screw by a thread. A dial indicator is installed in the meter base. The dial indicator is fixed in the base by a pressure plate and screws.

 Figure 3 Improved outside micrometer

According to the diameter of the caliber, the measuring length can be combined with different sizes of the outer micrometer bow and the inner micrometer to obtain different sizes to ensure that the distance from the dial gauge to the other measuring head meets the caliber diameter measurement.

The measurement method is similar to that of the internal micrometer.The measurement steps are as follows:

(1) Select the appropriate outer micrometer bow and inner micrometer according to the diameter of the caliber and the diameter of the mandrel.

(2) Fix the measuring head and dial indicator, and reserve a certain amount of pressure gauge.

(3) Use another micrometer for proofreading.

(4) Perform data measurement.

 

3.Machining precision and measurement error analysis

Use the method of installing the mandrel to process large cylindrical parts. The coaxiality and full runout fully meet the requirements of the drawing. After installing the mandrel, make sure that the supporting claw on the mandrel has a sufficient contact surface with the inner hole. During the process, there is relative displacement between the supporting claw and the inner hole, and the machining precision will be reduced.

After processing, the diameter of the stop is re-measured with an internal micrometer. The error between the two measurements is less than 0.01mm, which can fully meet the horizontal measurement. Because the dial is fixed on the ruler, the data can be read simply and intuitively. Control of stop diameter in lathe during processing.

 

4.Conclusion

By designing an adjustable mandrel, the problem of difficult processing of large sleeve parts is solved, and dimensional accuracy and form and position tolerances are ensured. By improving the caliber measurement method, the caliber processing steps are simplified, the auxiliary time is shortened, and the processing efficiency is improved. Although it is necessary to design and manufacture related parts, the design and processing of related parts are extremely simple and have good versatility.


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