How LED Light Bulbs Are Made

One-hundred-and-thirty years ago, Thomas Edison completed the first successful sustained test of the incandescent light bulb. With some incremental improvements along the way, Edison’s basic technology has lit the world ever since. This is about to change. We are on the cusp of a semiconductor-based rechargeable light bulbs revolution that will ultimately replace Edison’s bulbs with a far more energy-efficient lighting solution. Solid state LED lighting will eventually replace almost all of the hundreds of billions of incandescent and fluorescent lights in use around the world today. In fact, as a step along this path, President Obama last June unveiled new, stricter lighting standards that will support the phasing out of incandescent bulbs (which already are banned in parts of Europe).

To understand just how revolutionary LED light bulbs are as well as why they are still expensive, it is instructive to look at how they are manufactured and to compare this to the manufacture of incandescent light bulbs. This article explores how incandescent light bulbs are made and then contrasts that process with a description of the typical manufacturing process for LED light bulbs.

So, let’s begin by taking a look at how traditional incandescent light bulbs are manufactured. You will find that this is a classic example of an automated industrial process refined in over a century of experience.

While individual incandescent light bulb types differ in size and wattage, all of them have the three basic parts: the filament, the bulb, and the base. The filament is made of tungsten. While very fragile, tungsten filaments can withstand temperatures of 4,500 degrees Fahrenheit and above. The connecting or lead-in wires are typically made of nickel-iron wire. This wire is dipped into a borax solution to make the wire more adherent to glass. The bulb itself is made of glass and contains a mixture of gases, usually argon and nitrogen, which increase the life of the filament. Air is pumped out of the bulb and replaced with the gases. A standardized base holds the entire assembly in place. The base is known as the “Edison screw base.” Aluminum is used on the outside and glass used to insulate the inside of the base.

Originally produced by hand, light bulb manufacturing is now almost entirely automated. First, the filament is manufactured using a process known as drawing, in which tungsten is mixed with a binder material and pulled through a die (a shaped orifice) into a fine wire. Next, the wire is wound around a metal bar called a mandrel in order to mold it into its proper coiled shape, and then it is heated in a process known as annealing, softening the wire and makes its structure more uniform. The mandrel is then dissolved in acid.

Second, the coiled filament is attached to the lead-in wires. The lead-in wires have hooks at their ends which are either pressed over the end of the filament or, in larger bulbs, spot-welded.

Third, the glass bulbs or casings are produced using a ribbon machine. After heating in a furnace, a continuous ribbon of glass moves along a conveyor belt. Precisely aligned air nozzles blow the glass through holes in the conveyor belt into molds, creating the casings. A ribbon machine moving at top speed can produce more than 50,000 bulbs per hour. After the casings are blown, they are cooled and then cut off of the ribbon machine. Next, the inside of the bulb is coated with silica to remove the glare caused by a glowing, uncovered filament. The label and wattage are then stamped onto the outside top of each casing.

Fourth, the base of the bulb is also constructed using molds. It is made with indentations in the shape of a screw so that it can easily fit into the socket of a light fixture.

Fifth, once the filament, base, and bulb are made, they are fitted together by machines. First, the filament is mounted to the stem assembly, with its ends clamped to the two lead-in wires. Next, the air inside the bulb is evacuated, and the casing is filled with the argon and nitrogen mixture.

Finally, the base and the bulb are sealed. The base slides onto the end of the glass bulb such that no other material is needed to keep them together. Instead, their conforming shapes allow the two pieces to be held together snugly, with the lead-in wires touching the aluminum base to ensure proper electrical contact. After testing, bulbs are placed in their packages and shipped to consumers.

You may also like

Leave a Reply

Your email address will not be published.