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Classification of mechanical equipment failures: 1. Temporary failures. Temporary failures, also known as intermittent failures, are mostly caused by external factors related to the mechanical equipment. If it is caused by operational errors or similar, the mechanical equipment can operate normally once these external disturbances are removed. 2. Permanent failures (1) Classification by the time when the failure occurs: 1) Early-onset failures: These are caused by problems in the design, manufacturing, assembly, and debugging of mechanical equipment. If the hydraulic system of a newly purchased machine tool leaks severely or produces a lot of noise. 2) Sudden failures: These are the result of the combined effect of various adverse factors and accidental external influences. Faults are characterized by their randomness and sudden occurrence; there are no prior signs, and they are generally related to the way in which the equipment is used. They are difficult to predict, but they can be easily resolved, and usually have little impact on the lifespan of mechanical equipment. 3) Progressive failure: It develops gradually due to the deterioration of the technical parameter characteristics of mechanical equipment, including corrosion, fatigue, aging, etc. Its characteristic is that the probability of failure is related to the time of use, and it only becomes apparent in the later stages of the mechanical equipment’s useful life. Once a failure occurs, it marks the end of its lifespan. Generally, it can make predictions, and most failures of mechanical equipment fall into this category. 4) Composite faults: These types of faults include the characteristics of the aforementioned faults, and their occurrence time is unpredictable. The speed of the degradation process of the working capacity of mechanical equipment is related to the performance it loses as a result of this degradation. Gradual failures are caused by the wear process of the friction pair, whereas sudden failures are triggered by external abrasive particles. (2) Classification by the form of the fault surface: 1) Functional failure: The working capacity or characteristics that mechanical equipment should possess are significantly reduced, or it may even fail to function at all, thereby losing its intended functions. Such faults can be identified through the operator’s direct perception or by measuring their output parameters. For example: loss of precision, reduced transmission efficiency, and speeds that do not meet the standard values. 2) Potential failure: The failure is gradually developing, but has not yet manifested in terms of functionality; it is however nearing the stage of occurrence. When this condition can be identified, it is considered a fault phenomenon known as a latent fault. (3) Classified by the cause of the failure: 1) Human-induced failures: Mechanical equipment loses its proper functions prematurely due to problems in design, manufacturing, major repairs, operation, transportation, management, etc. 2) Natural failures: Failures that occur in mechanical equipment during its useful life as a result of various external or internal natural factors, such as wear and aging. (4) Classified by the consequences caused by the failure: 1) Fatal failures: These are failures that endanger or result in personal injury or death, cause the scrapping of mechanical equipment, or lead to significant economic losses. 2) Serious faults: These are faults that severely affect the normal operation of mechanical equipment and cannot be resolved within a short period of time. 3) Common faults: Faults that significantly affect the normal operation of mechanical equipment and can be resolved within a short period of time. 4) Minor faults: Faults that have a slight impact on the normal operation of mechanical equipment and can be resolved using standard tools during routine maintenance. Such as: loose parts, etc. II. Factors Affecting Mechanical Equipment Failures 1. Design and Planning: (1) In the design and planning phase, it is necessary to make an accurate assessment of the future operating conditions of the mechanical equipment, taking into full account possible variations. (2) Imperfect design scheme: Inadequate review of design drawings and technical documents is an important cause of failures. 2. Material selection: In design, manufacturing, and maintenance, materials must be properly selected based on the properties and characteristics of the components. (1) Improper selection of materials, materials that do not meet standard specifications, or the use of inappropriate substitutes are the main causes of wear, corrosion, excessive deformation, fatigue fracture, aging, and other phenomena. (2) Furthermore, during manufacturing and maintenance, many materials undergo heat treatment processes such as casting, forging, welding, and heat treatment. Throughout these processes, the metal microstructure and mechanical properties of the materials change frequently, with heating and cooling having a particularly significant impact. 3. Manufacturing quality: Errors exist in every step of the manufacturing process. (1) Certain process conditions and properties of the material inevitably lead to stress concentration in the parts during casting, forging, welding, heat treatment, and machining, as well as to local defects in the metal’s microstructure and microscopic cracks. These defects are often easily overlooked during in-process inspections. (2) The poor quality of component manufacturing is a major cause of failures in mechanical equipment. 4. Assembly quality: (1) First, there must be correct fit requirements. (2) An excessive initial gap will shorten the effective service life. (3) The positional accuracy between various components during assembly is also very important; if this requirement is not met, it can lead to additional stresses and uneven wear, thereby accelerating failure. 5. Rational maintenance: Carry out maintenance in a rational manner based on the principles of sound technology, cost-effectiveness, and feasibility of production, to ensure maintenance quality. The most important and crucial aspects here are the proper selection and application of restoration techniques, paying attention to the preparations before restoration, following established procedures during the restoration process, and carrying out proper post-restoration handling. 6. Proper use: Under normal operating conditions, mechanical equipment has its own patterns of failure. As the operating conditions change, the failure patterns also change. (1) Operating load: The main causes of wear and failure in mechanical equipment are the wear and fatigue of components. Under specified operating conditions, the wear of components is directly proportional to the magnitude of the load per unit of time. Fatigue damage of parts occurs under certain alternating loads, and it intensifies as these loads increase; therefore, both wear and fatigue are related to the load. When the load exceeds the designed rating, it will cause severe damage, which is not allowed. (2) Working environment: includes the effects of climate, corrosive and other harmful substances, as well as the condition of the objects being worked on. First, rising temperatures, increased wear, and accelerated corrosion ； Second, high humidity and the presence of corrosive agents in the air lead to corrosion and wear ； Third, excessive dust levels in the air and harsh working conditions can both lead to damage to mechanical equipment. (3) Maintenance and operation: Establishing a proper maintenance system and strictly adhering to technical maintenance and operational procedures are important conditions for ensuring the reliable operation of mechanical equipment and extending its service life. In addition, it is necessary to train personnel to improve their professional skills and work quality.