Example analysis of the hottest CNC machine tool m

2022-08-18
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Numerical control machine tool maintenance example analysis

numerical control machine tool is a product of electromechanical integration, which includes mechanical technology, computer and information processing technology, system technology, automatic control technology, sensing and detection technology, servo transmission technology. Its technology is advanced, complex structure, expensive, so its maintenance method is different from that of ordinary equipment. The maintenance of CNC equipment can rely on equipment condition monitoring technology and equipment diagnosis technology, make full use of the data provided by CNC system and machine tool manufacturers, and comprehensively analyze the fault phenomenon, which can achieve twice the result with half the effort. The following introduces several examples to analyze the thinking process of maintenance in detail

example 1: a Daewoo T380 drilling center should use FANUC 0I system at more than 5 points in the calibration of each range. After the machine is stopped for a few days, the machine starts up, and 2021 alarm appears after the machine starts up: insufficient air pressure. Fanuc 0I system 2000-2999 alarm is the machine tool PMC alarm. It is specified in the ladder diagram programming language of the system that to display an alarm message on the screen, the corresponding message display request bit (A-line diagram) must be set to 1. To clear this alarm, the message display request bit (A-line diagram) must be set to 0. We can find the address of the alarm request bit (A-line diagram) through the PMC diagnostic function, from │ system │ │ PMC │ pmcdgn │ │ status │, enter "A0" and press │ search │ to display

7 654321 0

2008 2007 2006 2005 2004 2003 2002 2001

a0000 000 000 000 00 00 00

2016 2015 2013 2012 2011 2010 2009

a001 00 00 00 00 00 00 00

2024 2023 2022 2021 2020 2019 2017

a002 01 00 00 00

confirm a2.4 = 1. Then refer to ladder diagram │ system │ │ PMC │ pmclad │ input a2.4, press │ search │ where x5.4, k5.1, a2.4, r652.7, k7.6 are all connected, k5.1, k7.6 are hold relays, and the state is not controlled by the adjustable pin holes with a spacing of 0.5 designed and processed on the longitudinal beam of the frame of other electric hosts. A2.4 is interlocked, so a2.4 can be set to 0 as long as x5.4 is disconnected. According to the electrical instructions of the machine tool, x5.4 is the air supply pressure switch of the machine tool. Check that the air supply pressure is within the normal range. Replace the pressure switch, x5.4 is normally closed and disconnected. At this time, a2.4 should be set to "0", and r652.7 should be normally closed and disconnected (r652.7 should be set to 1)

only g8.4 (emergency stop signal) is closed. If r652.7 is set to 1, only f1.1 is set to 1 or x32.7 is set to 1, and f1.1 is a reset signal. So press the reset key, r652.7 is set to 1, a2.4 is set to 0, the alarm is cancelled, and the fault is eliminated

example 2: a grinder of Beijing No.2 machine tool factory uses FANUC 0I MB system. When G00 command runs c-axis in automatic mode, c-axis does not move, the program does not execute downward, and there is no alarm information. Switch to manual mode for operation, move c-axis with handwheel, and the machine tool is normal. Use the conventional method to check. Open the diagnosis screen and check the diagnosis number 000 ~ 015. Only 001:motion (executing the automatic operation movement command) is 1, and the others are 0. Everything is normal. Let's check again. Operate in manual mode, move the c-axis back and forth with the hand wheel, and when it is found that the speed is very fast, the machine tool alarms 411: the position deviation in the movement of the c-axis is greater than the set value. Check that the value of diagnosis No. 300 (deviation of detection axis position) is 24, and then check that the set value of parameter 1826 (in place width of each axis) is 20. The deviation of C axis is actually detected, and the position deviation of C axis is set. Press the reset key to clear the alarm, quickly move the c-axis again, and write down the 300 diagnostic values of 411 alarm for several times: 51, 80, 22, 78. Because the deviation of c-axis actually detected for several times is very different and irregular, it should not be a problem of parameter 1826 setting, but a hardware fault. The parts of the fault may be: encoder, servo amplifier, encoder signal transmission line, servo motor, servo motor power line. From easy to difficult, Check the servo motor power line first, and there is no poor contact and heating trace; Replace the servo amplifier, and the fault remains the same; The reason is that the encoder socket is in poor contact, causing the position feedback signal to work unstable and causing 411 alarm

example 3: a Daewoo t360 machining center uses FANUC 21i-mb system. When the machine tool returns to the reference point, the y-axis cannot move towards the reference point, and the manual operation mode is normal. The y-axis uses the block back to reference point mode. Under the back to reference point working mode, it moves at a specific speed. When the zero switch detects a signal, the y-axis decelerates and stops. Then, after the y-axis passes through the stop, it slowly moves to the position of the first grid point to stop, so as to complete the y-axis return to the reference point. The reasons why the y-axis cannot move towards the return direction of the reference point are:

(1) the speed is too low. Check the magnification switch: if the magnification is at the speed F0, check that the parameter 1421 (F0 speed) is 400; If the magnification is at 20%, 50% and 100%, confirm that x33.6 and x33.7 (magnification switch input address) are 1, 0, 0, 1, 1 and 1 respectively through the PMC status screen, which are normal. Then check parameter 1404.1 (reference point regression speed selection). If it is 0 (high export growth is difficult and fast), check the value of parameter 1420 (high speed setting value), which is 48000; If it is 1 (manual moving speed), check the value of parameter 1424 (manual moving speed) and it is 24000, which is also normal

(2) the starting position of the return reference point is too close, which has made the zero switch detect the signal. Use the handwheel to move the y-axis reference point in the opposite direction for a certain distance, and then return to the reference point. The fault remains the same. Is the zero switch broken? Open the PMC status screen and find that x9.1 (Y-axis zero position switch address) is 1. Move the y-axis back and forth with the handwheel for a long distance, and the x9.1 signal does not change, which confirms the hypothesis just now. Open the x9.1 zero position travel switch and find that there is a lot of cooling water inside the switch, and the waterproof rubber band of the travel switch contact is damaged. Replace a new travel switch, restart the machine, the y-axis returns to the original point, and the machine tool is normal. Through the above fault analysis, the key for maintenance personnel to improve the electrical maintenance skills of CNC machine tools is to be familiar with the performance characteristics and control principle of CNC machine tools, and the fault handling methods of servo system and CNC system. In the process of maintenance, constantly explore, accumulate experience, flexibly apply the learned maintenance technology, expertly eliminate the faults of CNC machine tools, reduce the downtime of CNC machine tools, improve the utilization rate of CNC machine tools, and make the production of the company go smoothly

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