The summary introduces what PLC can make up Cheng controller to safeguard, watchful item and measure answer when the overhaul, how to undertake analysis and processing with specification of example of PLC system breakdown. Label of document of TP307 of date of classification of the graph in maintenance of firmware of maintenance of keyword PLC exterior line piles up B one, safeguard of PLC daily 1. The examination of power supply source. The quality of power supply source affects the utilization reliability of PLC directly, also be the component with higher fault rate, the 110 ％ of 85% ～ that check voltage to whether satisfy rated limits and inspect voltage wave motion is frequent. Frequent voltage wave motion can accelerate the ageing of component of voltage module electron, the proposal is added hold regulated power supply. To using 10 old PLC systems, if often appear,the program carries out a mistake, should consider quality of voltage module power supply above all. 2. The examination of moving environment. (Temperature of 1)PLC moving environment is in 60 ℃ of 0 ～ . Temperature is exorbitant will make PLC in-house component function aggravation and breakdown increase, especially because of,CPU is met " the electron is migratory " phenomenal acceleration and the life that lowers PLC. Temperature on the low side, the safety factor of imitate loop also is met decrescent, the likelihood when ultralow temperature causes control systematic movements is abnormal. Settlement way is to controlling ark to install appropriate axis to shed fan to perhaps add outfit air conditioning, notice to often be checked. (2) environment relative humidity is between 95 ％ of 5% ～ . It is in the environment with bigger humidity, moisture passes the blemish of the metallic surface of the IC on module easily to invade interior, cause the aggravation of in-house component function, make in-house insulation property is reduced, can cause short circuit because of high pressure or surge voltage; Below extremely dry environment, because of,MOS integrated circuit is met electrostatic and cause breakdown. (3) should be blown regularly sweep in-house dirt, with assuring air channel expedite the insulation with component. Of proposal PLC electronic-controlled ark uses sealed construction, and electronic-controlled the air inlet of ark and give blast tuyere to add outfit filter, can hold back majority dirt enter. 3. Check the installation status of PLC. Each PLC unit is secured firm, whether do all sorts of I/O module terminal become loose, of PLC telecommunication cable child mother connector is inserted whether completely and come back close, exterior jumper has nondestructive to hurt. 4. Whether does the batteries of the program memory that checks PLC need to change. 2, the maintenance of PLC can divide maintenance of the exterior line that it is ① according to the characteristic of maintenance, include element of switch of communication bus line and sensor of I/O place connective, connector, relay, spacing, protection, jumper and transducer to wait. The firmware of ② PLC is maintained, the in-house circuit that includes module of CPU unit, I/O unit, intelligence unit, power supply is maintained. PLC controller has certain self check capacity, and have in systematic cycle of run diagnose processing phase oneself. In systematic work process no matter happen why to be planted breakdown, maintenance technician should follow particular operation move. 1. Examination PLC power supply is normal. If POWER indicator light is not bright, can check power supply circuitry and fuse. 2. Examine PLC system. The PLC that start is examined " RUN " the directive is normal, have without call the police happen. The PLC system that using normally produces this kind of breakdown very hard. 3. The examination of I/O module. I/O module is the passageway that CPU and communication of channel of exterior control object cease, also be the part of the easiest attaint, because of the main content that this makes maintain. (Voltage of power supply of module of 1) examination I/O is normal. (2) detects it is normal that the signal that inputs output port and corresponding port indicator light show, indicator light does not shine is firmware breakdown, settlement way is to undertake firmware is maintained. If have redundant port, can pass port of I/O of process designing redefine. If use appearance not to detect to the signal with input due port, and output port has output signal, but place controls yuan of parts of an apparatus or equipment does not work, fasten exterior line breakdown. 4. The examination of working environment. The element of main effect is temperature and humidity. 5. The maintenance of firmware. Should affirming is PLC firmware attaint, best method is to change to spare parts newly. 3, PLC breakdown analyses example 1. The magnetism of limited company of glass of plated film of Luoyang brilliant embellish accuses to splash shooting plated film product line was 1993 introduce from American AIRCO company, what the system uses is the PLC of AB company. The much controller establishing a point with indoor control appeared to cannot append report to 3 target material. Breakdown analysis reachs processing: (1) spot observation sets bit of controller more (process of MSPC) self check, did not discover fault. The entrance guard switch of material of switch of water of target material loop, temperature protection switch, target and ark of power source control it is normal to show, explain the condition that append report is already contented. (2) hand moves MSPC of direct operation equipment, give 3 target material to append report through menu of a parameter, can make inside 10s power is worth to set, explain power source of target material, control does not have breakdown. (3) controls PLC to increase electric order to MSPC through personal computer, as a result control fails. 27 terminal that measure MSPC with digital avometer do not have 24V DC. Its signal has output of I/O of ranking intelligence module, this module model is 1791-IOBX, 128 POINT, corresponding output terminal is " 016T " , it is normal that indicator light shows, but detect be less than voltage. Judgement is port attaint, need firmware maintenance. (4) opens I/O module, interior has two circuit board, above one is by with sheet piece machine the circuit to control core board, below one is circuit of input output interface board, two are needle type is inserted receive. Disassemble the circuit above board want special caution, want to prevent electrostatic voltage. (5) checks interface board, its output interface is by compositive module NEC1523H is controlled, because cannot examine integrated circuit data, increased to maintain difficulty, if its module appearance pursues 1. According to circuit characteristic, use " black box principle " measure circuit to dominate data, conjectural principle pursues and prove, get principle of modular block control pursues, if the graph is shown 2 times, it is normal to after be being replaced with this circuit, be used. 2. What the company of Austrian Li Saike that brilliant benefit firm recommended 1995 produces is full automatic vitreous cut machine, model is GFB-37/26. Among them PLC is production of German SIGMATEK company, the data after composing of cut machine occurrence personal computer cannot transmit PLC normally. Breakdown analysis reachs processing: (1) starts vitreous cut chance afresh, process of observation PLC self check did not call the police happen, two indication windows show the DI on CPU unit and D2 " 00 " , explain PLC system is regular. (Of 2) yellow " TxBus " of indicator light and green " RxBus " indicator light shows " bright " , explain PLC and communication of Control Panel ET805 are normal. (3) operates personal computer to transmit data to ET805 of operation face plate, "S1 " indicator light is not ablaze, PLC cannot implement cut. Suspect personal computer has trouble to ET805 communication. (4) cuts off the power stop machine, hand of gold of the MODEM inside cleared personal computer points to the oxidation layer that go up, and change a new data line, switch on the mobile phone the test is normal. (5) observation staying behind, after making an appointment with 40min breakdown as before, consider Luoyang then July is high temperature weather, whether is suspicion concerned with temperature, check air-conditioner, it is normal to move. Open control ark to feel air current temperature is higher, feel calm of air cooling air channel with the hand, examination hind fastens attaint of air cooling fan, the trouble removal after repair. Pass (4) pace breakdown processing, false appearance giving a person is trouble removal, it is after cut off the power control ark temperature is reduced actually, make PLC can go up normally, after working for some time, because personal computer is mixed,all sorts of relay, silicon controlled rectifier builds up ceaselessly quantity of heat, make PLC too lukewarm protection. CNC MillingCNC Machining