As a key equipment in the plastic processing industry, the operation of plastic granulators involves various precautions such as mechanical safety, process control, and maintenance. A comprehensive analysis will be conducted from four dimensions: equipment use, safety protection, maintenance, and process optimization
1、 Equipment usage precautions
Raw material adaptability
Material matching: Select the appropriate cutting blade and screw speed based on the type of plastic (such as PP, PE, ABS, etc.). For example, high melting point plastics such as PC need to reduce the cutting speed to avoid blade overheating.
Pre processing requirements: Ensure that the raw materials are dry and free of impurities, with a moisture content of less than 0.5%, otherwise it may cause particle adhesion or equipment blockage.
temperature control
Melting temperature: Strictly set the temperature of each area of the extruder according to the material characteristics (such as PE, which is usually 160-220 ℃). Temperature fluctuations exceeding ± 5 ℃ may cause material degradation.
Cooling water temperature: The water temperature in the pelletizing tank should be controlled at 20-30 ℃. If it is too high, it may cause the pellets to adhere, while if it is too low, it may cause the pellets to become brittle.
Maintenance of cutting blades
Regular grinding: If the blade wear exceeds 0.2mm, it needs to be ground or replaced in a timely manner, otherwise it will cause irregular particles or generate dust.
Installation accuracy: The gap between the blade and the template needs to be adjusted to 0.05-0.1mm. If the gap is too large, it can easily produce long strips, while if it is too small, it can increase the blade load.
2、 Safety protection requirements
Mechanical safety
Protective device: Ensure that the protective cover of the cutting area is intact, and it is strictly prohibited to open the protective door during equipment operation.
Emergency stop device: Each device must be equipped with at least two emergency stop buttons, and the operator must test their effectiveness monthly.
Electrical safety
Grounding protection: The metal casing of the equipment must be reliably grounded with a grounding resistance of ≤ 4 Ω.
Leakage protection: A 30mA leakage protector should be installed on the main power supply, with an action time of ≤ 0.1s.
Operating Specifications
Prohibited behavior: It is strictly prohibited to clean the granulation area directly with hands. Special tools must be used and the machine must be stopped for operation.
Personal protection: Operators are required to wear goggles, anti cutting gloves, and dust masks.
3、 Key points of maintenance and upkeep
routine maintenance
Cleaning and maintenance: Clean the templates, blades, and sinks after daily production to prevent plastic residue from hardening.
Lubrication management: Replace the gear oil in the gearbox every 500 hours, and add high-temperature resistant grease to the bearings every month.
regular maintenance
Template inspection: Check the wear of the template holes every 2000 hours, and replace them if the aperture expands by more than 10%.
Electrical testing: Check the motor insulation resistance (≥ 1M Ω), frequency converter parameters, and circuit aging every quarter.
Spare Parts Management
Key spare parts: Reserve vulnerable parts such as blades, templates, seals, etc., with inventory levels sufficient to meet 24-hour production needs.
Lifetime tracking: Establish a spare parts usage ledger, record replacement time and reasons, and optimize spare parts procurement cycle.
4、 Suggestions for process optimization
Quality control of pellet cutting
Particle size control: By adjusting the blade speed (500-1500rpm) and extrusion rate (50-200kg/h) to match, ensure particle size uniformity (CV value ≤ 5%).
Dust control: Install a cyclone separator to collect particulate dust, and the emission concentration must comply with the GB 16297-1996 standard (≤ 120mg/m ³).
energy consumption management
Variable frequency speed regulation: The motor speed is controlled by a frequency converter, which saves 15% -20% energy compared to fixed frequency operation.
Waste heat recovery: By using the waste heat from the extruder to preheat the raw materials, energy consumption can be saved by 5-8kWh per ton of plastic.
Fault prevention
Vibration monitoring: Install vibration sensors to monitor the spindle vibration value in real time. If it exceeds 7.1mm/s, stop the machine for inspection.
Pressure monitoring: Automatic alarm when the melt pressure exceeds 25MPa to prevent screw breakage.
5、 Response to special working conditions
High humidity environment
Increase the drying time of raw materials to 4-6 hours, or use a dehumidification dryer (dew point ≤ -40 ℃).
Add rust inhibitor to the granulation water tank, with a concentration controlled between 0.5% and 1%.
Use of recycled materials
The proportion of recycled materials is ≤ 30%, and they need to be mixed evenly with new materials.
The lifespan of the cutting blade is shortened by 20% -30%, and the inspection frequency needs to be increased.
Multi color switching
Before switching colors, use cleaning material (such as PP) to clean the screw and machine head. The amount of cleaning material used should be at least twice the screw volume.
The granulation water tank needs to be emptied and cleaned of residual color particles.