During operation, the overload protection mechanism of a precision servo press unit must comprehensively cover multiple potential failure modes to ensure the safety and stability of the equipment under complex working conditions. Its failure modes can be summarized into five categories: mechanical structure failure, electrical system failure, thermal effect failure, environmental adaptability failure, and software control failure. Each type of failure mode requires targeted design for prevention and response.
Mechanical structure failure is one of the most common failure modes of a precision servo press unit, mainly including connecting rod fracture, crankshaft fatigue, and guide rail deformation. These failures are usually caused by cyclic loading or instantaneous overload, especially in high-speed, high-precision press-fitting scenarios, where mechanical components must withstand alternating stress. If the material strength is insufficient or there are stress concentration points in the structural design, fracture or plastic deformation can easily occur. For example, a connecting rod may fracture due to fatigue crack propagation during long-term reciprocating motion, while a crankshaft may bend due to localized stress concentration. Therefore, overload protection mechanisms rely on mechanical overload protection devices (such as spring collets and cam mechanisms) for basic protection. When the pressure exceeds a set value, the device triggers a switch to cut off the power, preventing the motor from continuing to rotate and avoiding further damage to the mechanical structure.
Electrical system failures focus on the protection of the motor and driver. Servo motors may experience winding insulation aging or even burnout due to excessive current under overload conditions; drivers may trigger protection actions due to power exceeding limits. For example, when a motor is subjected to a load exceeding its rated torque, the current will rise sharply. If the protection mechanism does not respond in time, the motor winding temperature may exceed the safety threshold, causing insulation failure. Therefore, overload protection needs to combine electronic protection devices (such as current sensors and power sensors) with software algorithms to monitor motor current, speed, torque, and other parameters in real time. Once an abnormality is detected, the voltage should be immediately reduced, the current decreased, or the motor stopped. In addition, temperature sensors (such as thermistors and thermocouples) can monitor the internal temperature of the motor, triggering protection actions when the temperature is too high to prevent thermal damage. Thermal failure is another key issue to consider in precision servo press units. When the motor runs for extended periods or the ambient temperature is too high, internal heat is difficult to dissipate effectively, potentially leading to increased winding resistance, decreased efficiency, and even thermal aging of the insulation material. For example, for every 10°C increase in ambient temperature, winding resistance may increase by 7%. Without a temperature compensation mechanism, the overload protection factor may fail due to the temperature rise. Therefore, the overload protection mechanism needs to integrate temperature compensation functionality, dynamically adjusting the protection threshold through a built-in temperature model or real-time temperature feedback. For instance, when a Japanese brand servo detects a winding temperature exceeding 80°C, it will automatically reduce the overload protection factor by 15%-20% to adapt to high-temperature operating conditions.
Environmental adaptability failure involves the impact of external factors such as humidity, corrosion, and vibration on the equipment. In humid environments, electrical connectors may experience increased contact resistance due to oxidation, leading to intermittent overloads; in corrosive environments, metal components may suffer reduced strength due to chemical corrosion, increasing the risk of breakage. For example, connector terminals undergo fretting wear under vibration, increasing contact resistance from less than 20mΩ to over 100mΩ, leading to abnormal signal transmission or motor power fluctuations. Therefore, overload protection mechanisms must use high-reliability connectors (such as those with gold plating thickness of 1μm or more) and strictly control the crimping process to ensure contact resistance remains stable below 10mΩ. Simultaneously, the equipment housing must have a protection rating (such as IP65) to prevent dust and moisture intrusion and extend service life.
Software control failures stem from incorrect parameter settings or algorithm defects. For example, an error in the electronic gear ratio (EGR) setting may cause the actual motor speed to exceed the nameplate value, triggering a hidden overload; improper acceleration curve settings may cause inertial shocks, resulting in excessively high peak current. Furthermore, if the software protection algorithm does not fully consider load characteristics, it may falsely trigger protection actions, affecting production efficiency. Therefore, overload protection mechanisms need to be combined with a composite debugging method, optimizing the control algorithm through a complete record of "parameters-phenomena-data". For example, in the commissioning case of a photovoltaic module string welding machine,engineers measured the peak process load using a torque tester, set the overload protection coefficient accordingly, and optimized the electronic gear ratio and acceleration curve to ensure the equipment met process requirements while avoiding overload risks.
