Overheating of the motor in a rotary tablet press is a common problem during equipment operation. It is usually related to abnormal load, mechanical resistance, the motor's own condition, and environmental factors. Specific causes can be analyzed from the following aspects:
1. Excessive or Abnormal Load
- Incompatible Material Characteristics: If the material being pressed has high hardness, poor flowability, or contains impurities (such as metal particles), it will cause an abnormal increase in force on the die during tableting. The motor needs to output more torque to maintain operation, and long-term overload will cause the motor current to exceed the rated value, leading to overheating.
- Inappropriate Tableting Parameter Settings: When the tablet weight is too large, the tableting speed is too fast, or the pressure is adjusted too high, the motor load will increase sharply. For example, suddenly increasing the tableting speed, where the motor speed is mismatched with the load, can easily cause instantaneous overload and overheating.
- Unstable Material Supply: Blockage in the feed hopper or malfunction of the feeding mechanism (such as a stuck screw feeder) can lead to interrupted or uneven material supply, causing the motor to repeatedly switch between "idle running" and "overload" states, resulting in current fluctuations and overheating.
2. Abnormal Resistance in the Mechanical Transmission System
- Component Wear or Jamming: Insufficient lubrication, foreign object intrusion, or long-term wear leading to excessive clearance or jamming in the transmission components of the rotary tablet press (such as gears, bearings, and cams) will increase mechanical resistance. The motor must overcome this additional resistance to perform work, converting energy into heat.
- Concentricity Deviation: Excessive concentricity error in the installation of the main shaft, turntable, or motor shaft will cause eccentric friction during operation, increasing resistance and accompanied by vibration, exacerbating motor overheating.
- Improper Die Installation: Incorrect installation of the punch or die (e.g., misalignment or looseness) will cause abnormal friction with the track during rotation, creating an additional load and causing motor overload.
3. Motor-Related Problems
- Motor Aging or Fault: Aging of the motor winding insulation, inter-turn short circuits, or bearing wear, rotor rubbing (rotor-stator friction), will lead to decreased motor efficiency and an increased proportion of electrical energy converted into heat, manifesting as abnormal overheating.
- Cooling system failure: If the fan in a motor with a cooling fan is damaged, the air duct is blocked, or the cooling water path in a water-cooled motor is obstructed, heat dissipation efficiency will decrease, and heat cannot be dissipated in time.
- Power supply abnormalities: Unstable voltage (too high or too low), a missing phase in a three-phase power supply, or phase imbalance will cause abnormal motor operating current, leading to winding overheating.
4. Environmental and operating conditions:
- High ambient temperature: Poor ventilation in the tablet press's working environment, room temperature exceeding 40℃, or heat sources near the motor (such as ovens or heaters) will cause difficulty in heat dissipation, resulting in a rapid temperature rise due to the added heat generated by the motor itself.
- Excessive continuous operation time: Exceeding the motor's rated operating time (such as prolonged full-load operation) will prevent the accumulated heat from being released, especially in small motors which are more prone to overheating due to continuous overload.
5. Lack of maintenance:
- Insufficient lubrication: Failure to regularly add lubricating oil to gears and bearings in the transmission system, or dried-out or deteriorated grease, will increase the coefficient of friction and increase the motor load.
- Inadequate cleaning: Accumulated dust and oil inside the equipment not only hinder heat dissipation but may also enter the motor, affecting the winding insulation and leading to increased overheating.
If the motor temperature exceeds the rated temperature rise (typically ambient temperature + 40°C), the machine must be stopped immediately for inspection to prevent overheating and motor burnout or equipment malfunction. The specific cause can be identified by monitoring current, inspecting transmission components, and optimizing tableting parameters.