How Automotive Metal Cutting Works

Plasma cutters use an ionized stream of gas to cut metal, and they can be programmed to be extremely accurate.
Plasma cutters use an ionized stream of gas to cut metal, and they can be programmed to be extremely accurate. See more pictures of power tools.
© Derics

The great artist Michelangelo is reported to have said, "Every block of stone has a statue inside it and it is the task of the sculptor to discover it."

That's fine if you're sculpting marble with a chisel, but what if the masterpiece you're working on is a car? Or a factory full of cars, all built primarily of steel?


Steel is incredibly strong, yet it's light enough to use as one of the main materials in auto manufacturing. But with a substance so tough, how do you cut it into the countless complex shapes that come together to form a working automobile?

There are actually several steps in creating a finished auto body or chassis -- installing pieces such as doors, hoods and frame subassemblies. This article will focus on just one of those steps -- cutting the metal before it's finished and attached to a car.

The cutting tools and techniques described in the next few pages are used by suppliers to the auto manufacturing industry as well as independent fabrication shops. Frequently, instead of a craftsman cutting the metal by hand, the raw pieces are placed on or inside of a computerized machine that can cut and shape the part to precise measurements. In fact, you'll discover that computers are applied to everything from cutting metal body panels to machining frame and engine parts.

Keep reading to learn about the metal cutting technologies that aid the automotive manufacturing industry.


Automotive Metal Cutting Technologies

Automotive metal cutting uses many of the same techniques and technologies as metal cutting for other fabrication industries, like shipbuilding.

For small, low-volume jobs that don't require super-precise accuracy -- for instance, the type of metal cutting done in an auto enthusiast's garage -- the tool could be as simple as hand-operated cutting shears.


But for higher volume jobs, or for those in automotive manufacturing that require very precise cuts, the equipment gets more complicated. For instance, computer-controlled lasers, plasma cutters and waterjets are commonly used for a number of reasons:

  • They can cut through lots of material quickly.
  • Computerized controls ensure that there are few mistakes.
  • The greater accuracy helps cut down on waste, and therefore, reduces costs.

In the highly competitive auto manufacturing industry, suppliers of auto components are always looking for tools that can save labor without sacrificing quality.

Here are some quick snapshots of how the precision heavy-duty cutting tools work:

Lasers: Lasers work well for cutting sheet steel up to 1/2-inch (1.27-centimeter) thick and aluminum up to 1/3-inch (0.9-centimeter) thick. Lasers are most effective on materials free of impurities and inconsistencies. Lower-quality materials can result in ragged cuts or molten metal splashing onto the laser lens.

Plasma: Plasma blows an ionized stream of gas past a negatively charged electrode inside the torch nozzle. The metal to be cut, meanwhile, is positively charged. When the gas contacts the metal, it creates a superheated area between 20,000 and 50,000 degrees Fahrenheit (11,093 and 27,760 degrees Celsius) that slices through the metal [source: Rupenthal and Burnham].

For cars to look and perform their best, their metal parts have to be cut within very narrow bands of accuracy called tolerances. To find out about advances that are improving this accuracy, go to the next page.


Advances in Automotive Metal Cutting

A stream of water blasts through a compilation of steel, concrete block and polystyrene foam during a demonstration at the University of Missouri-Rolla's High Pressure Waterjet Laboratory in Rolla, Mo.
A stream of water blasts through a compilation of steel, concrete block and polystyrene foam during a demonstration at the University of Missouri-Rolla's High Pressure Waterjet Laboratory in Rolla, Mo.
AP Photo/Kelley McCall

Automotive manufacturing is a constant game of improvement -- car buyers expect more refinement, performance and safety from newer vehicles, yet they typically don't want to pay a lot more for them. To make vehicles structurally stronger, more precisely built and still affordable means embracing technology advances like those described below:

EDM: Wire Electrical Discharge Machining, or EDM, cuts through metals by producing a powerful electrical spark. A negatively charged electrode made of molybdenum or zinc-coated brass releases a spark when in close proximity to the positively charged metal piece. The advantage of this method: It can reach an accuracy of 1/10,000th of an inch. That's 10 times narrower than the width of a human hair! [source: Ley]


EDM does have some drawbacks, though. For one, it only works on electrically conductive materials. For another, it's pretty slow -- as much as 10 times slower than our next technology [source: Rupenthal and Burnham].

Waterjets: Think of waterjets as a high-pressure, liquid sandpaper. Waterjets use a process called "cold supersonic erosion" to blast away material with water and some type of granular additive, called an abrasive. This combination allows waterjets to cut through metals up to 10 inches (25.4 centimeters) thick, and with a high degree of accuracy [source: KMT Waterjet Systems].

This metal-cutting tool has gotten high-profile exposure from the likes of car enthusiast Jay Leno and celebrity car customizing shop West Coast Customs. It's relatively easy to use and can cut through many different materials besides metals.

For more information about automotive metal cuttingand other related topics, follow the links on the next page.


Lots More Information

Related HowStuffWorks Articles

  • Hidden, Steve. "Using a Hand-held Plasma Cutter." The May 30, 2001. (Dec. 5, 2009)
  • KMT Waterjet Systems. "Automotive Cutting using KMT Waterjet Systems." (Dec. 5, 2009)
  • Ley, Brian. "Diameter of a Human Hair." The Physics Factbook. 1999. (Dec. 7, 2009)
  • Olsen, Dr. John H. "Newer linear-drive technology improves waterjet accuracy, reduces costs." The (Dec. 5, 2009)
  • Ruppenthal, Michael and Burnham, Chip. "Exploring complementary cutting methods: Comparing capabilities of laser, plasma, EDM to waterjet technology." The Sept. 4, 2001. (Dec. 4, 2009)
  • U.S. Census Bureau. "Machine Tool (Metal Cutting Types) Manufacturing: 2002." Jan. 18, 2005. (Dec. 6, 2009)