Views: 2 Author: Site Editor Publish Time: 2026-09-07 Origin: Site
Never turn on the heaters immediately after walking up to the machine. Run through this 5-point physical checklist first:
Clear the hopper and barrel: Visually inspect the inside of the barrel, above and inside the hopper. A single dropped screw or a hardened chunk of residual plastic from the last shift can completely destroy the screw and die head upon startup.
Check fasteners and switches: Ensure all connecting bolts are tight, safety guards are securely fastened, and all control buttons are in their correct zero/off positions.
Verify lubrication: Ensure all lubrication points and the gearbox have adequate oil. Never wait for bearings to grind dry before remembering to lubricate them.
Test temperature and cooling: Check if the temperature controllers are responsive and ensure the cooling water lines are unclogged. A simple trick is to briefly flow cooling water to visually confirm the circuit is open.
Maintain cleanliness: Clear away dust, debris, and tools from the immediate workspace.
Once the control panel indicates that the set temperatures have been reached, do not start the main motor immediately.
The 10-Minute Rule: You must hold the temperature for another 10 minutes. While the thermocouple says the surface is hot, the internal temperature distribution across the screw and die is not yet uniform. Force-starting now will cause high torque spikes, uneven discharge, and continuous minor faults.
Hot-Tighten the Die Bolts: Use these 10 minutes to safely retighten the connecting bolts on the die head. Metal expands when heated; a bolt tightened while cold behaves differently than one tightened while hot. Retightening prevents melt leakage and bolt fatigue.
Safety Zone: Before any melt is extruded, absolutely no one is allowed to stand directly in front of the die head. A snapping bolt under pressure is a deadly hazard.
When you finally engage the main motor, remember this sequence: start slow, feed minimally, listen closely, and watch the data.
Listen and Watch: Listen for any abnormal grinding or scraping sounds. If you hear anything unusual, stop the machine immediately. Simultaneously, watch the main motor current meter. If the needle swings wildly or is highly unstable, shut down and investigate.
The 30-Minute Idling Limit: Never run the screw empty for more than 30 minutes. Without polymer inside to act as a lubricant and structural support, the friction between the screw and the barrel is severe.
Prep the Die Bolts: Before attaching the die head and pelletizer, coat the connecting bolts with a layer of molybdenum disulfide or high-temp silicone oil. This takes 30 seconds but will save you hours of struggling during the next teardown.
Start Slow: Keep the screw RPM at its minimum and ensure the initial material feed is low and steady.
Monitor the Current: Keep your eyes glued to the main motor current meter. Sudden spikes mean the screw is experiencing unstable forces—usually caused by material bridging in the hopper, uneven feeding, or localized overloading in the screw flights.
Check Temperatures Safely: Once running normally, periodically check the bearing housing temperatures. Always use the back of your hand to lightly touch the metal, never your fingertips. The back of the hand is more sensitive to heat, and your reflex to pull away is faster, minimizing the risk of severe burns.
Hands Off Moving Parts: Never touch any rotating components while the machine is energized.
You cannot simply cut the power and walk away. Your shutdown procedure depends entirely on the polymer matrix you are processing.
Stable Materials (PS, SAN, ABS, PE, PP, PMMA): These polymers have excellent thermal stability. You can simply turn off the heaters and shut down the machine. There is no need to purge the barrel.
Time-Sensitive Materials (PA, PC): For Polyamide (PA), you must turn off the heat immediately upon stopping; leaving it hot for more than 15 minutes will degrade the material. For Polycarbonate (PC) during short stops, keep the barrel at 160°C to prevent moisture absorption. For long stops, purge with PE, remove the screw hot, and clean it with a brass brush.
Heat-Sensitive Materials (PVC, POM): For PVC, turn off the heat, extrude the remaining PVC until the barrel drops to 150°C, and then flush the system completely with a stable polymer like PE. For POM, drop the pressure to zero 10 minutes before shutting off the heat, extrude continuously to empty the barrel, and flush with PE.
Screw Maintenance: When dismantling the screw for storage, clean off all residual polymer and coat it in anti-rust oil. Suspend it vertically in a dry area. If the machine will be idle for a long time, seal all ports to prevent foreign contamination.
Zero Adjustments While Running: Never attempt to adjust the die head, tighten bolts, or clear jams while the screw is turning. Always stop the machine to handle faults.
Never Leave the Station: An operator must never leave the machine unattended while it is running. A one-minute absence is all it takes to miss a critical warning sign and lose the window for a safe emergency stop.
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