As the core component of an ultrasonic plastic welding machine, the installation precision and calibration of the ultrasonic mold (welding head) directly determine the yield rate of welded products, production efficiency, and the service life of the equipment. Improper replacement or calibration can not only lead to quality issues such as cold welds, over-welding, and product cracking, but may also accelerate the wear and tear of core components such as transducers and generators. Drawing on years of industry experience, this article provides a detailed explanation of the standard mold replacement and calibration process.
I. Preparations Before Replacement
Before replacing the mold, you must first turn off the main power supply to the equipment and wait 5 minutes to allow the capacitors to fully discharge before proceeding, to prevent electric shock. Prepare tools such as an Allen wrench, torque wrench, dial indicator, alcohol, and lint-free cloth.
Inspect the surface quality of the new mold to ensure that the working surface is free of cracks, scratches, and deformation, and that the threaded holes are intact. Also verify that the mold's resonance frequency matches the equipment; typically, the error should be within ±0.5 kHz.
II. Standard Mold Installation Procedure
1. Thoroughly clean the end face of the transducer horn and the mold's mating surface with alcohol and a lint-free cloth to ensure there is no oil, dust, or metal debris. Even the smallest impurities can affect ultrasonic transmission efficiency.
2. Gently screw the mold onto the horn and tighten it by hand until it can no longer be turned; do not use excessive force.
3. Use a torque wrench to tighten the mounting screws diagonally and evenly according to the torque values specified in the equipment manual. Generally, the torque for M8 screws is 25–30 N·m, and for M10 screws, it is 35–40 N·m.
4. Use a dial indicator to check the flatness of the mold's working surface; the error should be within 0.02 mm/m. If it exceeds this range, re-adjust and reinstall.
III. Key Commissioning Steps
After installation, perform a no-load test. First, set the power to the lowest setting, start the equipment, and observe the ammeter reading. The normal no-load current should be between 0.5–1 A. If the current is too high, it indicates a mismatch in mold frequency or improper installation; stop the machine immediately for inspection.
Next, perform load testing. Place the workpiece to be welded and gradually adjust the welding pressure, welding time, and hold time. Welding pressure is generally controlled between 0.2–0.5 MPa. Welding time should be adjusted based on the plastic material and product thickness, typically ranging from 0.1–2 seconds. During debugging, follow the "low pressure, short duration" principle, gradually increasing parameters to avoid setting them too high at once, which could damage the mold.
IV. Common Issues and Solutions
- Severe mold heating: Check whether the mold frequency is properly matched, whether connections are loose, or if there is an overload.
- Insufficient weld strength: Appropriately increase the welding time or pressure, and check whether the mold working surface is worn.
- Cracks in the product: Reduce the welding power or shorten the welding time, and increase the hold time.
V. Professional Recommendations
We recommend conducting a comprehensive inspection of the mold every 50,000 to 100,000 welds, and promptly repairing or replacing it if wear is detected. For molds with complex shapes, it is best to entrust a professional manufacturer to handle frequency matching and machining.
As a professional manufacturer of ultrasonic plastic welding equipment, we provide one-stop services ranging from mold design and machining to installation and commissioning. If you encounter any issues during mold replacement or commissioning, please feel free to contact our technical team at any time; we will provide you with professional technical support and solutions.
