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5000mm long, 2500mm wide, 3000mm high, equipped with FANUC-BESK-7M numerical control system gantry machining center, China's second-hand machine tool transfer center sold to Liaocheng internal combustion engine plant. After on-site inspection, it was found that the electrical part did not work properly, and there was a 08 alarm. The load meter pointer reached the red light area. The magazine swings back and forth and cannot be positioned. Main shaft diameter jump 0.18mm, end jump 0.15mm, all serious over-difference: 300mm length X-axis repeatability positioning error greater than 0.15mm, stroke error greater than 0.18mm, serious loss of accuracy: 300mm length Y-axis repeatability positioning error greater than 0.15mm, The stroke error is more than 0.18mm and the accuracy is seriously lost. In view of the above situation, taking into consideration that the equipment is a major equipment and there is no mechanical lifting equipment on the maintenance site, the following maintenance plan has been formulated: First, the electrical system is repaired, and then the mechanical part is repaired so as to use the power of the machining center itself to make larger parts. Disassembly and assembly, thereby reducing labor intensity, improve the assembly accuracy, to achieve a multiplier effect. 1 repair of electrical system 08 alarm repair check machine maintenance manual know, 08 alarm spindle positioning fault. According to the requirements of the maintenance manual, the power supply electrical cabinet was turned on. Seven light emitting diodes (6 green and 1 red) were found on the circuit board of the AC spindle controller. These 7 diodes are shown from left to right respectively: Directional command: Low gear: Track peak detection: Deceleration command: Fine positioning: Positioning completed (above, green light): Test method. Observe these diodes as follows: 1 tube light, 3, 5 tube flashes. Indicates that a positioning command has been issued: The track peak and positioning signals have been detected. However, the system cannot be fully positioned and the spindle is still running at a low speed, so the 3 and 5 tubes continue to flicker. From the above analysis, it is suspected that there is a problem with the amplifier on the headstock. When the spindle guard is turned on and the amplifier is detected, it is found that the tool clamping cylinder on the spindle is coiled around the spindle, and it is determined that the coiling of the hose causes the spindle to be misaligned and cannot be accurately positioned, resulting in an alarm 08. After reinstalling the adjustment, the RV11 (positioning point offset) in the spindle controller is re-adjusted. The fault is eliminated and the alarm disappears. The magazine can't swing back and forth and can't fix the manual. The manual analysis concludes that the proximity switches SQ51 and SQ52 are inaccurate and the U02 pulse encoder data is inconsistent, causing the tool to swing back and forth after finding the tool number. The exclusion method is: stop the tool magazine at a certain position, precisely adjust the position of the SQ51 and SQ52 proximity switches, and at the same time adjust the tool number according to the PC address. The 8421 code consisting of the PC addresses 50.5, 50.1, and 50.2 is the ten-digit number of the tool number. The 8421 code consisting of 50.3, 49.0, 49.1, and 47.0 is the single digit of the tool number. According to the actual position of the current tool magazine number, the U02 pulse encoder is precisely adjusted so that the above two sets of data are the current corresponding tool numbers. After the restart, the fault is eliminated. 2 Repair of mechanical parts Spindle parts repair Because the machine is a used equipment, there are no parts drawings and assembly drawings. Considering that there are many parts of the spindle, we will order the removed parts in order, and then perform cleaning and inspection one by one. Through testing, we found a major problem: the shaft of the front end of the spindle is a cone with a Ø120 mm shaft diameter, while the bearing on the equipment is a 4429924 bearing with a cylindrical bore. It was decided to change the bearing to 4382924 bearings and replace other bearings with new ones of the same specification and the same accuracy. After installation, it was found that the main shaft diameter jump was 0.08mm, and the main shaft end jump was 0.06mm. After re-adjusting the bearing clearance, the main shaft diameter jumps to 0.016mm and the end jump is 0.014mm, which meets the requirements. X-Axial Finishing First remove the dust cover and auxiliary equipment at both ends of the worktable. Use the X-axis motor to move the worktable to the motor side to expose the other end of the bearing seat, and then remove all the fixed parts. In addition, all the fixed parts of the fixed ball screw nut are also removed. Start the X-axis feed and use the hand pulse generator to slowly withdraw the ball screw nut. Then, the ball screw can be removed by removing the motor and the gearbox back cover. After testing, the ball screw pair is an imperial standard, nominal diameter 55mm, pitch 5/8 inch, external circulation, gasket pre-tightening structure. Inside the ball nut raceway that was removed, a large amount of flake-shaped iron scrap was found, which was suspected to be due to peeling of the ball surface. The diameter of the ball was found to be 0.08mm in diameter and 9.903mm in diameter, which is 0.028mm larger than the theoretical value of 9.875mm and the minimum value is 9.825mm. It is judged that the precision of the ball is low, resulting in uneven force of the ball. After cleaning all parts, replace them with 0.001mm high-precision balls with inconsistent diameter. The clearance of the tested ball screw is 0.023mm: After calculation, the original adjustment gasket is thickened by 0.08mm, and then reassembled. Ball screw clearance meets technical requirements. However, it was found that the ball screw pair has a large frictional moment and the repeatability of positioning is 0.025 mm. It is considered that there is microscopic damage on the surface of the raceway of the original ball screw pair and there is a gap in the gear pair of the reducer. The ball screw was clamped on a CA6140 lathe with a length of 3 meters. While pouring No. 20 mechanical oil, the ball nut was held by hand and reciprocally run at 21r/min for 100 times. After cleaning and re-assembly, the friction torque reaches the technical requirements. Assemble the ball screw assembly to the machine tool. The gap compensation value of the CNC system is set to 0.025mm to compensate for the gear pair clearance in the reduction gearbox. After the installation and commissioning, the test results are as follows: In the length of 300mm, the repeat positioning accuracy is 0.05mm, and the lead accuracy is 0.023mm, which meets the product processing accuracy requirements. Y-axis finish Refers to the X-axis repair process. The Y-axis ball screw pair is finish-finished. The inspection result is as follows: The stroke variation is 0.046 mm over a length of 300 mm. Friction torque and feel are in line with requirements. After installing the ball screw pair on the machine tool, it was found that the range of repeatability of the machine tool in any 300 mm length was 0.03-0.08 mm, and there was a certain periodicity. It is suspected that there is a large error in the gear section in the gear box. Re-open the gearbox and remove the gear. There is no problem with the appearance of the gear. Detected on a universal tool microscope, it was found that the maximum error of the gear section was 0.13mm. After replacing the new gear, the machine tool was tested again. The indicators met the technical requirements. Experiences and experiences: When importing foreign used equipment, it is necessary to collect relevant technical data. At the very least, it is necessary to clarify the model of the machine so that repairs can be performed with the aid of similar equipment to save repair time and reduce maintenance costs. When repairing, it is necessary to test the removed parts as much as possible in order to facilitate the correct judgment of the cause of the malfunction and avoid rework.
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