Cold Press Needle Pressing Process

2.1 Pressing process of wheelset crimp contact
Select the axle, measure the size → boring the hub hole according to the axle size → convey the wheel, spray oil, and flip it to the pre-pressing position
→ pre-pressing the wheelset → pressing the wheelset → dynamic balancing test and correction of the wheelset → marking the axle end → ultrasonic flaw detection of the wheel pressing part → completion inspection → acceptance.
2.2 Pressing process of wheelset crimp contact pin
After fine grinding, the axle is inspected by magnetic particle flaw detection, ultrasonic flaw detection, etc., to ensure that there are no cracks or scratches inside the wheel seat or on the wheel surface, and then measure the wheel seat size. Determine the wheel hub hole size according to the wheel seat size, and perform precision boring on the vertical lathe. After that, remove the burrs and oil stains on the wheel seat and the wheel hub hole surface on the matching axle and wheel, and evenly apply pure vegetable oil on the wheel seat and the wheel hub hole surface to reduce the friction coefficient during the press-fitting process. Protective sleeves should be added to both ends of the front axle where the axle contacts the wheel. When the press force reaches the required value for press fitting, the press force overcomes the friction force, and the axle and the wheel move relative to each other. When the relative displacement reaches the required distance for press fitting, the press fitting is completed. Since the temperature difference will cause thermal expansion and contraction, it will have a certain impact on the press fitting quality and the press fitting process. Therefore, the press fitting process has high temperature requirements. Generally, it is necessary to place the axle and wheel to be pressed at room temperature for at least 8 hours before press fitting. Figure 1 is a press fitting process diagram.
2.3 Press fitting process flow of wheelset contact socket crimp
2.3.1 Press fitting requirements
1) The press fitting machine must be used at an ambient temperature of 10~40 ℃.
2) Check whether the wheelset press fitting machine is operating normally. The automatic recorder and pressure gauge of the press fitting machine should be in good working condition. If not, the problem should be eliminated before press fitting.
3) Check that the axle and wheel dimensions must meet the geometric dimensions, tolerances and surface requirements of the press fitting state.
2.3.2 Parameter setting of crimp contact female press machine
1) Set the wheelset model.
2) Set the wheelset judgment criteria to the maximum and minimum tons; the press force range is 680~1160 kN.
3) The total length and wheel seat diameter of the wheelset press machine parameters are set according to the axle drawing. Figure 2 is the wheelset press drawing.
2.3.3 Pre-installation of wheelset crimp contact male
1) Wipe the axle wheel seat with a white cloth dipped in thinner, wipe the wheel hub hole and wheel seat evenly after cleaning.
2) Install the guide sleeve at the journal at both ends of the axle, hoist the wheel at the corresponding end of the axle, and wait for press installation. It is required that the static unbalance position of the two wheels of the same wheelset is in the same radial plane and on the same side of the axle.
2.3.4 Pressing of wheelset crimp socket contact
1) Input the shaft number, shaft type, wheel number, wheel type, wheel seat diameter, and wheel hub hole diameter in the press interface of the press.
2) Hang the mounted wheels and shafts on the adjusted press trolley, start the press, make the outer side of the wheel hub of one end to be pressed in good contact with the press block, and the end face of the axle of the other end in good contact with the end face of the piston. Ensure that the center of the wheel and shaft is consistent with the center of the press piston.
3) Start the press and press; after the wheelset is pressed, perform self-inspection according to the drawings and the inspection contents of this process.
2.3.5 Repair of wheelset female crimp contact
1) For wheelsets with excessive size or shape tolerance, only local processing is required without disassembly to repair qualified wheelsets. They can be corrected by machining or local grinding within the size and tolerance range specified in the drawings of each component, and re-inspected after correction.
2) If the wheelset needs to be unloaded before it can be repaired, unload the wheelset; after the wheelset is unloaded, the original axle and wheel shall not be pressed again. After the second press, if the pressure curve needs to reach the standard again before it can continue to be used, the pressure curves of the two presses should be saved.
2.3.6 Unloading of wheelset male crimp contact
1) Put the special press guide sleeves on the axle necks at both ends of the wheelset to be unloaded, and hoist it to the wheelset unloading machine. The end to be unloaded is close to the pressure head of the wheelset unloading machine, and the wheel at this end is located inside the unloading groove, and the wheel is close to the pressure wall of the unloading groove. Adjust the height of the unloading machine center frame so that the center of the axle is consistent with the center of the wheelset unloading machine pressure head. Start the unloading machine and unload.
2) When the wheel is unloaded, the unloading pressure displayed by the unloading machine pressure gauge shall not be greater than 40 MPa.
3) After unloading, check whether the axle neck is roughened.
2.3.7 Wheelset back pressure
1) The back pressure test should be carried out at least 48 hours after the wheelset is pressed. Before the test, the wheel position and inner distance of the two wheels are checked and the measurement positions are clearly marked.
2) On the wheelset press machine, the back pressure of 800 kN is gradually and evenly applied to the wheels and maintained for 30 seconds. Requirements
There is no relative displacement between the wheels and the axles.