Ultrasonic Sealing Process for Vacuumized Copper Tubes in Pressure Gauges

In the manufacturing of pressure gauges—especially vacuum gauges, low-pressure indicators, and precision instruments—it is essential to maintain a dry and clean internal environment. After vacuum extraction, the copper tube connected to the gauge must be hermetically sealed to preserve its internal vacuum.

Traditional sealing methods such as flame welding, brazing, or crimping suffer from limitations including low efficiency, heat distortion, and inconsistent sealing quality. To address these issues, QiJiang Precision utilizes ultrasonic metal welding technology to perform fast, clean, and reliable sealing of copper tubes, significantly improving product quality and production efficiency.

Applicable Products

This ultrasonic sealing process is widely used for the following pressure gauge types:

Precision pressure transmitters and sealed assemblies

Ultrasonic Sealing Process :

Step 1: Tube Preparation

One end of the copper tube is connected to the pressure gauge; the other end is extended (usually 8–15 mm) for vacuuming and sealing.

Step 2: Vacuum Extraction

The tube is connected to a vacuum pump system. Once the desired vacuum level (e.g., –0.08 MPa) is reached, the system holds the vacuum steady for several seconds.

Step 3: Ultrasonic Sealing

The copper tube is positioned inside the ultrasonic welding mold (anvil and horn).

The horn clamps the tube and applies pressure.

The ultrasonic system (typically 20 kHz) generates high-frequency mechanical vibrations.

The vibrations cause the copper material to plastically deform and fuse at the contact point.

After a short cooling period (approx. 0.5 s), the sealing process is complete.

The welding head lifts automatically, and the sealed tube is removed.

Step 4: Optional Leak Test

The sealed end can be tested for air-tightness to ensure there are no leaks or weak welds.

 Key Technical Specifications

Advantages

✅ High Efficiency: Each sealing cycle takes just 0.5–1 second
✅ No Open Flame: Non-contact “cold welding” method, safe and environmentally friendly
✅ Consistent Quality: Strong, uniform seals with minimal variation
✅ Automation-Friendly: Easily integrated into automated production lines
✅ Traceability: Supports data logging and process traceability

Application Case Studies

✅ A major pressure gauge manufacturer adopted our 20 kHz/1500 W ultrasonic sealer, producing over 2 million sealed units annually with a 99.98% pass rate.

✅ For a Japanese client, ultrasonic sealing replaced laser welding in a high-precision sensor line—successfully passing IP67 and UL leak-tightness tests.

Ultrasonic copper tube sealing is a key process in modern pressure gauge and precision instrument production. QiJiang Precision has years of experience in developing customized ultrasonic systems, welding molds, and automated sealing solutions.

Phone:+08615006191865
Email:qjmachinery@gmail.com
Website: https://www.qjmachinery.com.cn/en‍