For a machine tool, the level of accuracy is the most important criterion for evaluating the quality of the machine tool. It can even be said that precision is the soul of machine tools. In actual operation, the accuracy of the machine tool will suddenly decrease due to various reasons, which is not very annoying.
Causes of abnormal machining accuracy failure
The cause of abnormal machining accuracy is concealed and difficult to diagnose. Five main reasons are summarized: the feed unit of the machine tool is changed or changed; the zero offset of each axis of the machine tool is abnormal; the axial backlash is abnormal; the motor Abnormal operation status, that is, abnormal electrical and control parts; mechanical failure, such as screw, bearing, shaft coupling and other components.
In addition, the programming of processing programs, the selection of tools and human factors can also cause abnormal processing accuracy.
Principles of Fault Diagnosis for CNC Machine Tools
1. The external first, then the internal CNC machine tool is a machine tool integrating mechanical, hydraulic and electrical, so the occurrence of its failure will be reflected by these three comprehensively. Maintenance personnel should first conduct investigations one by one from the outside to the inside, and try to avoid unpacking and disassembling at will, otherwise it will enlarge the fault, make the machine tool lose its accuracy and reduce its performance.
2. First mechanical and then electrical Generally speaking, mechanical failures are easier to detect, while the diagnosis of CNC system failures is more difficult. Before troubleshooting, first pay attention to eliminating mechanical faults, which can often achieve a multiplier effect.
3. Static before moving. Under the static state where the machine is powered off, through understanding, observation, testing, and analysis, the machine can be energized only after it is confirmed as a non-destructive fault; under operating conditions, perform dynamic observations, Check and test to find faults. For destructive failures, the danger must be eliminated before powering on.
4. Simple first, complicated later. When multiple faults are intertwined and concealed and cannot be solved for a while, the easy problems should be solved first, and the more difficult ones should be solved later. Often after simple problems are solved, difficult problems may become easier.
Fault diagnosis method of CNC machine tool
1. Intuitive method: (look, hear, ask, cut) ask-machine failure phenomena, processing conditions, etc.; watch-CRT alarm information, alarm indicator lights, capacitors and other components deformed, smoked and burnt, protector tripping, etc.; listen-abnormal sound; smell -Burnt smell and other peculiar smell of electrical components; touch-heat, vibration, poor contact, etc.
2. Isolation method: For some faults, it is difficult to distinguish whether it is caused by the CNC part, the servo system or the mechanical part, and the isolation method is often used.
3. The same kind of adjustment method: Replace the suspected faulty template with the spare board of the same function, or exchange the same function templates or units with each other.
4. Function program testing method: Write some small programs for all the instructions of G, M, S, T, and run these programs when diagnosing faults to judge the lack of functions.
If the problem has not been resolved except for the above-mentioned faults, you need to pay attention to the problem of mechanical faults. You can find the cause from the logic of the system, the location of the machine tool, and the motor.