How microwave ovens are made
The part that cooks your food is a vacuum tube first developed to power wartime radar.
- stations
- 10
- things upstream
- 87
- raw sources
- 27
- steps from the ground
- 10
The short version
Inside each oven sits a vacuum tube, the magnetron, making waves near 2.45 gigahertz. Presses stamp the steel frame, a charged paint tank coats it, and workers build the tube from its anode, cathode, magnet and cooling fins. Chassis, door, transformer and stirrer fan bolt together, a roll-formed case slips over them, and scanners hunt for leakage around the door before shipping.
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Press the frame
Automatic metal-forming presses shape the cavity and door parts from steel, often galvanized or stainless. An alkaline wash takes off dirt and oil, and plain water rinses away the wash.
12 to 15 parts per minute
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Dip in charged paint
A zinc phosphate treatment prepares each part for electro-deposition. Parts sink into a live paint tank and pick up a coat about 1.5 mils thick, which is then baked hard.
200 volts for 2.5 minutes, then 300 °F for 20 minutes
Goes in -
Fix the door screen
A perforated metal plate goes over the window opening in the painted door. Its holes are far smaller than the waves, so it turns them back while light still gets through.
Goes in -
Build the magnetron
A filament goes on the cathode, and the cathode goes inside an anode cylinder, almost always copper. Cooling fins are welded on and a strong magnet wraps around. An antenna in a glass tube is fitted on top, and air is pumped out of the tube to leave a vacuum.
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Mount cavity on chassis
Working on a pallet, assemblers screw the cavity to the main chassis, hang the door on its hinges and bolt the magnetron to the side. A waveguide carries the waves into the cavity.
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Wire the high voltage
The circuit that powers the tube needs a big transformer, a rectifier and a capacitor filled with oil. All three sit right on the chassis near the magnetron.
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Fit stirrer or turntable
A fan on top of the cavity scatters the waves, driven by a pulley from the blower motor or by its own motor. A shield keeps out grease that could cause arcing in the waveguide. Many models rotate the food on a ceramic or glass plate as well.
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Add switches and controls
Relays, timers and door switches are mounted, and the front panel goes on with its circuit board behind it. Regulations demand two independent interlocks that kill the waves the moment the door opens.
Goes in -
Roll the outer case
A roll former wraps metal into a one-piece case. It slides over the built-up unit and is bolted to the chassis, and the power cord and knobs go on.
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Run and scan
One older account says makers ran each unit continuously for 50 to 100 hours, though modern lines generally use much shorter power tests. A computer-controlled scanner checks for leaks around the door, window and back, against a federal limit of 5 milliwatts per square centimeter about 2 inches away.
5 milliwatts per square centimeter leak limit
Worth repeating
- Over one billion magnetrons are in use in microwave ovens.
- The first Radarange was 1.8 meters tall and weighed 340 kilograms.
- Early commercial microwave ovens cost about $3,000, a price that kept them in hospitals and hotels.
Back to the ground
Follow every input upstream and microwave oven starts as these 27 raw sources.
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Sources
Cite this page: "How microwave ovens are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/microwave-oven