Finishing of the most popular second-hand gantry m

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The second-hand gantry machining center is 5000mm long, 2500mm wide and 3000mm high. The gantry machining center equipped with FANUC besk-7m numerical control system is sold to Liaocheng internal combustion engine factory by China two bed adjustment center. After on-site inspection, it was found that the electrical part could not work normally, and the alarm 08 occurred, and the pointer of the load meter reached the red light district. The magazine swings back and forth and cannot be positioned. The main shaft diameter jumps by 0.18mm and the end jumps by 0.15mm, both of which are seriously out of tolerance: the software of the 300mm experimental machine has achieved unprecedented development. The repeated positioning error of the X axis on the length is greater than 0.15mm, the travel error is greater than 0.18mm, and the accuracy is seriously lost: the 300mm length can meet the oil demand of the hydraulic system, and the repeated positioning error of the Y axis is greater than 0.15mm, the travel error is greater than 0.18mm, and the accuracy is seriously lost. In view of the above situation, considering that the equipment is heavy and large, and there is no mechanical lifting equipment at the maintenance site, the following maintenance plan is formulated: repair the electrical system first, and then repair the mechanical part, so as to disassemble and assemble large parts with the help of the power of the machining center itself, so as to reduce labor intensity, improve assembly accuracy, and achieve twice the result with half the effort

1 repair of electrical system

08 alarm repair check the machine tool maintenance manual, 08 alarm is the spindle positioning fault. According to the requirements of the maintenance manual, open the power supply electrical cabinet and find seven light-emitting diodes (6 green and 1 red) on the AC spindle controller circuit board. These seven diodes represent from left to right: directional command: low gear: track peak detection: deceleration command: fine positioning: positioning is completed (the above is green): test method. Observe the following conditions of these diodes: 1 tube is on, 3 and 5 tubes are flashing. It indicates that the positioning command has been issued: the peak value of the track and the positioning signal have been detected. However, the system cannot be fully positioned, and the spindle is still running at a low speed, so tubes 3 and 5 continue to flash. From the above analysis, it is suspected that there is a problem with the amplifier on the headstock. When opening the protective cover of the main shaft and detecting the amplifier, it was found that the hose of the tool clamping cylinder on the main shaft was coiled on the main shaft. It was determined that the winding of the hose caused the positioning deviation of the main shaft and could not be accurately positioned, resulting in 08 alarm. After reinstallation and adjustment, the rv11 (positioning point offset) in the spindle controller was readjusted, the fault was eliminated, and the alarm disappeared

the repair of the tool magazine swinging back and forth and unable to locate was found that the position of proximity switches sq51 and sq52 was inaccurate and the data of u02 pulse encoder was inconsistent, resulting in the tool swinging back and forth and unable to locate after looking for the tool number. The elimination method is: stop the tool magazine at a certain position, accurately adjust the position of sq51 and sq52 proximity switches, and adjust the tool number according to the PC address. Code 8421 composed of PC address 50.5, 50.1 and 50.2 is the ten digits of the tool number, and code 8421 composed of 50.3, 49.0, 49.1 and 47.0 is the single digits of the tool number. According to the actual position of the current tool number of the tool magazine, accurately adjust the u02 pulse encoder so that the above two groups of data are the current corresponding tool number. After restarting, troubleshoot

2 repair of mechanical parts

repair of spindle parts because the machine is a second-hand equipment, there is no part drawing and assembly drawing. Considering that there are many spindle parts, we number the removed parts in sequence, and then clean and test them one by one. Through inspection, we found a major problem, that is, the bearing at the front end of the main shaft is a cone with a shaft diameter of 120mm, while the bearing on the equipment is a cylindrical bearing with an inner hole. It is decided to change this bearing into a bearing and replace other bearings with new bearings of the same specification and accuracy. After installation, it is found that the spindle diameter jump is 0.08mm and the spindle end jump is 0.06mm. After readjusting the bearing clearance, the spindle diameter jump is 0.016mm, and the end jump is 0.014mm, which meets the requirements

x axial finishing first remove the dust covers and auxiliary equipment at both ends of the workbench, use the x-axis motor to move the workbench to one side of the motor, expose the bearing seat at the other end, and then remove all fixed parts. In addition, remove all fixed parts that fix the ball screw pair nut. Start the x-axis feed, and use the hand pulse generator to slowly withdraw the ball screw nut. Then, remove the back cover of the motor and reducer, and the ball screw can be removed. After testing, the ball screw pair is an English standard, with a nominal diameter of 55mm, a pitch of 5/8 inches, and an external circulation and gasket pre tightening structure. A large number of flake iron filings were found in the removed ball nut raceway, which was suspected to be caused by the spalling of the ball surface. It is found that the maximum diameter difference of the ball is 0.08mm, the maximum diameter is 9.903mm, which is 0.028mm larger than the theoretical value of 9.875mm, and the minimum value is 9.825mm. It is judged that the original ball accuracy is low, resulting in uneven force on the ball. After cleaning all parts and components, replace them with high-precision balls with a diameter inconsistency error of 0.001mm. After detection, the clearance of the ball screw pair is 0.023mm: through calculation, it is decided to thicken the original adjusting gasket by 0.08mm. After reassembly, the balls put forward higher requirements for the integration and efficiency of the universal tensile testing machine. The clearance of the ball screw pair meets the technical requirements. However, it is found that the friction torque of the ball screw pair is large, and the repeated positioning accuracy is 0.025mm. It is considered that there is micro grinding damage on the raceway surface of the original ball screw pair and there is clearance in the internal gear pair of the reducer. Clamp the ball screw pair on the 3-meter-long CA6140 lathe, pour No. 20 mechanical oil while holding the ball nut by hand, and run back and forth for 100 times at the speed of 21r/min. Reassemble after cleaning, and the friction torque meets the technical requirements. Assemble the ball screw pair to the machine tool, and set the clearance compensation value of the CNC system to 0.025mm to compensate the clearance of the gear pair in the reduction box. After installation and commissioning, the test results are as follows: on the 300mm length, the repeated positioning accuracy is 0.05mm, and the lead accuracy is 0.023mm, which meets the requirements of product processing accuracy

y-axis fine repair refers to the maintenance process of x-axis. Finish the ball screw pair of y-axis. The test results are as follows: the stroke variation is 0.046mm on the length of 300mm. The friction torque and feel meet the requirements. After installing the ball screw pair on the machine tool, it is found that the variation range of the repeated positioning accuracy of the machine tool is 0.03 ~ 0.08mm on any 300mm length, and there is a certain periodicity. It is suspected that gears are widely used in all walks of life! So how do users purchase a tensile testing machine suitable for themselves? The following is the basic knowledge of choosing a tensile testing machine. There is a large error in the gear pitch in the reducer. Reopen the reducer and remove the gear. There is no big problem with the appearance of the gear. It was found that the maximum error of the gear pitch was 0.13MM when tested on the universal tool microscope. The machine tool was tested after replacing the new gear, and all indicators met the technical requirements


when importing foreign second-hand equipment, we must collect relevant technical data, at least make clear the model of the machine tool, so as to repair with the help of data of similar equipment, so as to save repair time and reduce maintenance costs

during maintenance, the removed parts should be tested as much as possible, so as to correctly judge the cause of the fault and avoid rework

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