I. General Overview
A hot melt machine (thermoplastic welding equipment) melts the contact surfaces of plastics, PPR/PVC pipes, and other materials through heating, then joins them under pressure. It is suitable for pipe connections, plastic part welding, and hot riveting.
II. Safety Preparations
- Protective Equipment: Wear heat-resistant gloves, safety goggles, and protective clothing.
- Environment: Remove flammable materials; ensure the workspace is well-ventilated, dry, and properly grounded.
- Inspection: Verify that the power supply, air supply, molds, emergency stop button, and temperature control are functioning normally.
III. Installation and Commissioning
1. Installing the Molds
- Select the appropriate die head/hot mold; ensure it is securely fastened, clean, and free of burrs.
- Align the upper and lower dies to ensure concentricity and parallelism to prevent uneven pressure.
2. Parameter Settings (Reference)
- Temperature: PPR approx. 260°C, PE approx. 220°C, plastic parts 180–250°C.
- Heating Time: Approx. 5 seconds for 20mm pipe, approx. 7 seconds for 25mm pipe.
- Pressure: Pneumatic 0.2–0.4 MPa (2–4 kgf/cm²).
- Holding/Cooling: 10–30 seconds (depending on material and dimensions).
3. Machine Testing
- Conduct an empty machine test to verify that the up/down movement, emergency stop, and temperature control are functioning normally.
- Perform a test fusion using scrap material; inspect the fusion results before proceeding to mass production.
IV. Standard Operating Procedure
1. Workpiece Preparation
- Ensure the cut surface is flat, deburred, and clean; mark the insertion depth.
2. Heating
- Wait until the machine reaches the set temperature (indicator light stabilizes).
- Insert the workpiece vertically into the die head up to the marked line; do not rotate and apply even pressure.
3. Welding
- Once the set time is reached, quickly withdraw the workpiece; within 3 seconds, insert it straight into the mold, ensure it is fully seated, and maintain pressure.
- Do not twist or move the workpiece during cooling.
4. Quality Inspection
- The joint should have a uniform weld bead (double-sided), be free of bubbles, and have no gaps.
V. Shutdown Procedure
1. First, turn off the heating switch and wait for the temperature to drop below 100°C.
2. Then turn off the gas supply and power.
3. Clean the mold and work surface, and organize the tools.
VI. Safety Precautions
- Do not perform welding until the set temperature is reached.
- Never touch hot molds or workpieces with bare hands.
- Press both start buttons simultaneously with both hands; do not use a single button.
- Do not leave the workstation during operation; press the emergency stop in case of abnormalities.
- Before performing maintenance or changing molds, ensure power and gas are disconnected and the machine has cooled down.
VII. Maintenance and Care
- Daily: Clean the mold and heating plate to remove any adhesive residue.
- Weekly: Lubricate the guide rails and guide pins.
- Monthly: Inspect the power cord, heating elements, cylinders, and seals.
- Annually: Calibrate the entire machine and replace wear-prone parts.
VIII. Common Faults and Troubleshooting
- Temperature does not rise: Damaged heating elements, malfunctioning thermostat, loose wiring.
- Poor bond: Insufficient temperature, time, or pressure; contaminated workpieces; inadequate cooling.
- Over-welding/burning: Excessive temperature, excessive time.
- Abnormal operation: Insufficient air pressure, air cylinder leak, solenoid valve failure. Check if the stop button has been reset.
