Injection molding machines are core equipment in plastic production, but improper operation can lead to safety risks or product defects. This step-by-step tutorial covers the entire operation process—from pre-start checks to shutdown—with a focus on safety protocols and efficiency optimization, suitable for both new operators and those needing a refresher.
1. Pre-Start Preparation: Ensure Safety & Equipment Readiness
Before powering on the machine, complete these critical checks to avoid malfunctions or accidents:
Safety Inspection: Verify that all safety guards (e.g., front door, side shields) are properly closed and locked—most modern machines have interlock systems that prevent startup if guards are open. Check emergency stop buttons (red, mushroom-shaped) to ensure they’re not stuck and can trigger immediately.
Material & Mold Check: Confirm the plastic material (granules or pellets) matches the production order—check for moisture, contamination, or clogs in the hopper. Inspect the mold: ensure it’s clean (no residual plastic from previous runs), properly clamped to the platen, and aligned with the injection nozzle.
Mechanical & Fluid Checks: Examine hydraulic hoses (for leaks or cracks) and electrical cables (for fraying). Check hydraulic oil levels (use the machine’s sight glass) and ensure the oil temperature is within the recommended range (typically 45–55°C; preheat if too low). For full-electric machines, verify servo motor connections are secure.
Tool Preparation: Have essential tools on hand: mold release agent (for sticky materials), a torque wrench (to adjust clamp force), and a material scoop (for adding pellets to the hopper).
2. Power-On & Parameter Setting: Match to Production Requirements
Once pre-checks are complete, power on the machine and input key parameters—these vary by material (e.g., PP, ABS) and product (e.g., thin-walled cups, thick battery housings):
Power-On Sequence: Turn on the main power switch (usually on the machine’s side), then press the "Power On" button on the control panel. Wait for the machine to initialize (1–3 minutes); the control screen will display "Ready" when done.
Basic Parameter Input:
Temperature: Set the barrel temperature based on the material: for PP, 180–220°C; for ABS, 220–260°C. Ensure each barrel zone (feed, compression, metering) has the correct temperature—too low causes incomplete melting; too high leads to material degradation.
Injection Speed & Pressure: Start with medium speed (30–50% of max) and pressure (40–60% of max) for most materials. Thin-walled products need higher speed (60–80%) to fill molds quickly; thick products need lower speed (20–40%) to avoid air bubbles.
Clamp Force: Calculate based on mold area (clamp force = mold projected area × material pressure). For example, a 500 cm² mold for PP needs ~250 kN clamp force (500 cm² × 50 MPa). Too little force causes flash (plastic leakage); too much damages the mold.
Test Run Confirmation: After setting parameters, press "Heating" to warm the barrel. Once the temperature reaches the set value (confirmed by the control screen), perform a "Dry Run" (no mold) to check if the injection unit moves smoothly. Then, do a "Mold Test"—inject a small amount of material to confirm mold filling is even.
3. Formal Production: Monitor & Adjust in Real Time
During production, maintain focus on quality and safety, and make minor adjustments as needed:
Startup Operation: Press "Auto Mode" to start continuous production. The first 5–10 products must be inspected: check for defects like flash (adjust clamp force up), short shots (increase injection pressure/speed), or warpage (adjust cooling time).
Real-Time Monitoring:
Watch the control screen for key metrics: cycle time (should be stable ±0.5s), temperature (no fluctuations over ±5°C), and pressure (no sudden spikes).
Check material flow: Ensure the hopper doesn’t run empty (add pellets when the level drops to 1/3). For hygroscopic materials (e.g., PET), confirm the dryer is working (moisture content <0.02%).
Safety Reminders: Never put hands near the mold or injection nozzle during operation. If a jam occurs, press "Emergency Stop" first, then clear the jam only after the machine cools down.
Parameter Fine-Tuning: If defects appear:
Air bubbles: Increase holding pressure or extend holding time.
Sink marks (dents on thick parts): Extend cooling time or raise mold temperature.
Black spots: Clean the barrel (run a cleaning agent) or replace contaminated material.
4. Shutdown Process: Protect Equipment & Clean Up
When production ends, follow the correct shutdown steps to prolong machine life:
Stop Production: Press "Stop" to end auto mode. Once the last cycle finishes, press "Manual Mode" to retract the injection unit and open the clamp.
Material & Mold Handling: Empty remaining material from the hopper (store in sealed bags to avoid moisture). Apply mold release agent to the mold, then close it slightly (1–2 cm gap) to prevent rust. For long shutdowns (over 1 week), remove the mold and store it in a dry place.
Machine Cleaning: Wipe the machine surface with a clean cloth (avoid water on electrical parts). Clean the injection nozzle with a brass brush (when cool) to remove residual plastic.
Power-Off Sequence: Turn off the heating system first, then wait for the barrel to cool to below 80°C. Press "Power Off" on the control panel, then turn off the main power switch. Record production data (total parts, defect rate) in the machine logbook.
5. Common Faults & Troubleshooting
Fault Type
Possible Cause
Solution
Machine won’t start
Safety guard open / emergency stop pressed
Close guards / reset emergency stop
No material injection
Barrel temperature too low / screw stuck
Increase temperature / clean screw
Mold won’t close
Clamp force too low / mold misaligned
Raise clamp force / realign mold
Hydraulic oil leak
Hose damage / valve loose
Replace hose / tighten valve (after shutdown)
By following this guide, operators can ensure safe, efficient operation of injection molding machines while maintaining consistent product quality. Regular training (every 6 months) on new machine features or material updates is also recommended to stay current with best practices.
