Microwave Cavity Welding Robot Line: Resistance Spot Welding + Laser Sealing

A microwave cavity is a sealed metal box formed by stamping and welding thin sheet metal. Weld quality directly affects product safety, service life, and sealing performance. The video below shows a hybrid automatic welding line that combines resistance spot welding for structural fixation and laser sealing welding for continuous seam sealing.

A typical microwave cavity welding line follows this process: feeding and positioning, resistance spot welding, laser sealing welding, weld inspection, leak testing, and discharge. The system usually uses two six-axis industrial robots: one for spot welding and one for continuous laser seam welding. For broader robot welding cell design, see the EVST welding robot solutions guide.

Line Process Flow and Core Equipment

The core equipment includes two six-axis industrial robots, a medium-frequency inverter resistance spot welder, a 2-4 kW fiber laser welder, welding fixtures, fume extraction and purification, leak test equipment, and vision inspection. Spot welding provides structural strength; laser welding provides sealing performance. For microwave cavity production, both are normally required.

The process sequence must protect previously completed welds. After spot welding fixes the cavity corners and reinforcement plates, the part transfers to the laser station without disturbing the spot-welded geometry. A rotary table or transfer mechanism between stations can reduce transfer time and keep the cavity position stable.

Resistance Spot Welding Process Essentials

Resistance spot welding is the first welding process. It fixes the cavity corners and internal reinforcement plates before continuous seam welding. The key parameters are welding current, weld time, and electrode force. These parameters interact with sheet thickness, material coating, and joint overlap, so they should be validated through process trials before mass production.

The most common spot-welding problem is electrode tip wear. Electrode tips oxidize and deform as they contact sheet metal, which increases contact resistance and reduces weld consistency. A practical maintenance rule is to dress electrode tips by weld count rather than waiting for visible defects. Weld spacing must also be controlled: too small creates current shunting and weak welds, while too large reduces structural strength.

Laser Sealing Welding Process Essentials

Laser sealing welding is the second process. It follows the cavity seams to create a continuous sealed joint. The fiber laser transmits energy through a robot-mounted welding head. The main process variables are power, travel speed, and defocus distance. Insufficient power can cause lack of fusion; excessive power can burn through the thin sheet. Too fast a speed creates a narrow shallow weld, while too slow increases the heat-affected zone.

Start and end points need special attention. At the beginning of the seam, the sheet is still cold and lack of fusion can occur. At the end, crater formation is common. Robot trajectory planning should reduce speed at the start for preheating and decelerate at the end for crater filling. This helps maintain consistent seam quality around the full cavity perimeter.

Robot Trajectory Planning

Spot welding uses point-to-point robot motion. The robot moves to each weld point, dwells for a short time, completes the weld, and moves to the next point. The weld sequence should minimize travel distance and avoid unnecessary wrist rotation. Laser sealing welding uses continuous path motion. Microwave cavity seams are often rectangular closed curves, so corner transitions should use smooth arcs rather than abrupt stops.

Offline planning and simulation are useful before commissioning because the process mixes discrete spot-weld points with continuous laser paths. If the line includes multiple microwave cavity sizes, fixture and program changeover should be planned together rather than treated as separate tasks.

Welding Quality Control

Quality control has two levels: process monitoring and finished-part inspection. Spot welding can monitor current waveform and electrode force. Laser welding can monitor power feedback, travel speed, and protective lens condition. When the system detects abnormal values, it should alarm and prevent the part from moving to the next operation.

Finished inspection includes weld appearance inspection and leak testing. A 2D vision system can check weld width, continuity, surface marks, and visible defects. Leak testing can use a vacuum decay method: the welded cavity is placed in a sealed chamber, vacuum is applied, and pressure decay is monitored. SPC tracking helps identify drift before defects become a batch issue.

Fixtures, Fume Extraction and Changeover

Welding fixtures position the cavity repeatedly and keep the seam path stable. Pneumatic clamps, locating pins, and modular locating blocks are common. For microwave oven models with different cavity sizes, quick-change fixture elements can reduce changeover time. Modular fixture design can keep model changeover practical for mixed production.

Fume control is also part of welding quality. Welding smoke can accumulate on laser protective lenses and reduce effective power. The fixture area should include fume collection connected to purification equipment. Transparent heat-resistant collection covers can protect the work area without blocking visual inspection.

Common Pitfalls Before Deployment

Common pitfalls include delayed electrode tip dressing, laser focal position drift, excessive stamped-part gap, and smoke contamination on protective optics. A robust line should include weld-count-based dressing reminders, focal position checks every shift, gap inspection at the feeding station, and automatic air-blow cleaning for the welding head.

For related welding cell references, see the EVST welding power source compatibility guide and EVST custom welding cell case studies. For a broader integration checklist, see EVSINT’s robotic welding cell components and integration guide.

If you need similar products or project services, please contact us — we’ll provide expert support. Here are our contact details: email [email protected], message WhatsApp / WeChat +86 193 8162 6253, or submit the contact form.