First, the content of fault diagnosis: the basic concept of system reliability: system reliability refers to the ability of CNC system to complete the specified functions within the specified conditions and time, and fault refers to the system losing the specified functions within the specified conditions and time. CNC machine tool is a complex and large system, which involves many technologies such as optics, mechanics, electricity, liquid, etc., and failures are inevitable. Mechanical corrosion, mechanical wear, mechanical failure, aging of electronic components, poor contact of plug-in, current and voltage fluctuation, temperature change, interference, noise, software loss or hidden trouble, dust, operation error, etc. Will lead to the failure of CNC machine tools.
1) action diagnosis: monitor all the moving parts of the machine tool and determine the parts with poor action. The diagnosis part is ATC, APC and machine tool spindle.
2) State diagnosis: Observe the running state when the motor of the machine tool drives the load.
3) Spot check diagnosis: Spot check hydraulic components, pneumatic components and strong electrical cabinets regularly.
4) Operation diagnosis: monitoring operation errors and program errors.
5) Fault self-diagnosis of CNC system.
Second, the diagnosis methods of various numerical control systems: The diagnosis methods of various numerical control systems currently used can be roughly divided into three categories.
1. Start-up diagnosis: the internal diagnosis program of CNC system automatically performs the diagnosis every time from power-on to preparation for normal operation. The content of diagnosis is the most critical hardware and system control software in the system, such as CPU, memory, I/O unit and other modules, CRT/MDI unit, paper tape reader, floppy disk unit and other devices or external devices.
2. On-line diagnosis: refers to the automatic diagnosis and inspection of the CNC system itself, servo unit, servo motor, spindle servo unit, spindle motor and external equipment connected with CNC equipment through the built-in program of the CNC system during the normal operation of the system. Generally speaking, it includes two parts: status display of self-diagnosis function and fault information display.
① Interface display: it is necessary to know the connection state between CNC and PLC or CNC and machine tool, as well as the internal state of CNC, so as to distinguish whether the fault occurs inside CNC, PLC side or machine tool side.
(2) Internal status display: (a) Status display of instructions not executed due to external factors. (b) Reset the status display. (c)TH alarm status display, that is, horizontal and vertical verification of paper tape, shows the position of paper tape error hole when the alarm occurs. Abnormal state display of bubble memory of inlet pump (D). (e) display position deviation. (f) Display the frequency detection result of resolver or inductosyn. (g) servo control information display. (h) display the stored contents, etc.
(3) The content of fault information display is generally hundreds, up to 600. Most of this information appears in the form of alarm numbers and appropriate comments. Generally, it can be divided into the following categories: (a) overheat alarm category; (b) system alarm; (c) Memory alarm category; (d) Programming/setting classes are all soft failures caused by operation and programming errors; (e) Servo category: namely, fault alarm related to servo unit and servo motor; (f) the travel switch gives an alarm; (g) Connection failure between printed circuit boards.
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