Laser Cutting and Sheet Metal Fabrication

Sheet Metal Fabrication
    Welding
    Punching

Laser Cutting
    Process
    Machines
 

Sheet Metal Fabrication

Metal fabrication is a process that involves the construction of machines and structures from sheet metal, often laser cut.

The raw sheet metal for fabrication has to be cut to size. This is done different ways;

Special metal cutting band saws have hardened blades and a feed mechanism for even cutting. Abrasive cut-off saws, also known as chop saws, are similar to miter saws but with a steel cutting abrasive disk.

Burn tables are CNC cutting torches, usually natural gas powered, but plasma and laser cutting tables are also common. Plate steel is loaded on a table and the parts are cut out as programmed.

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Welding

Welding is the main focus of steel fabrication. The formed and laser cut parts will be assembled and tack welded into place. A fixture may be used to locate parts for welding if multiple weldments have been ordered.

The welder then completes welding per the engineering drawings, if welding is detailed, or per his own judgment if no welding details are provided.

Special precautions may be needed to prevent warping of the weldment due to heat. These may include; welding in a staggered fashion, using a stout fixture, covering the weldment in sand during cooling, and straightening operations.

Straightening of warped steel weldments is done with an Oxy-acetylene torch and is somewhat of an art. Heat is selectively applied to the steel in a slow, linear sweep. The steel will have a net contraction, upon cooling, in the direction of the sweep. A highly skilled welder can remove significant warpage using this technique.

Steel weldments are occasionally annealed in a low temperature oven to relieve residual stresses.

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Punching

Punching in metal fabrication is the process of using a machine to press a shape through a sheet of metal and into a die cutter to create that shape in the metal. These machines use hydraulic, pneumatic, or electrical power to press the shape with enough force to cut the metal.

A misconception about punching is that the shape does the cutting, when in fact the shape presses the material into a die that cuts the metal. The die is also given a tolerance that is measured in thousands of an inch.

Punching can be better understood as pressing the material against a die with a huge force, this force pushes the material into the die shape and sheers of excess material.

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Laser Cutting

Process

Laser cutters usually work by a laser entering through the side of the sheet metal and cutting it through the axis of the beam. A pierce is made before every cut in order to be able to start cutting from somewhere else than the edge. Piercing usually involves a high power pulsed laser cutter beam which slowly (taking around 5-15 seconds for half-inch thick stainless steel, for example) makes a hole in the material.

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Laser Cutting Machines

There are generally three different configurations of industrial laser cutting machines: Moving material, Hybrid, and Flying Optics systems. This refers to the way that the laser beam cuts the metal. For all of these, the axes of motion are typically designated X and Y axis. If the cutting head may be controlled, it is designated as the Z-axis.

Moving material move material under a stationary laser cutting head. This ensures a constant distance from the laser generator to the workpiece and a single point from which to remove cutting effluent. It requires fewer optics, but requires moving the workpiece.

Hybrid laser cutters provide a table which moves on one axis and a laser head that moves . This results in a more constant laser beam delivery path length than a flying optic machine and may permit a simpler laser cutting delivery system. This can result in reduced lost power in the laser cutting delivery system and more capacity per watt than flying optics machines.

Flying optics laser cutters feature a stationary table and a cutting head (with optic beam) that moves over the work piece on both the x and y axis. Flying-optics cutters keep the metal stationary during processing, and usually don't require clamping the sheet metal down. The moving metsl is constant, so dynamics aren't changed by size and thickness of the sheet metal. Flying optics machines are the fastest class of machines.

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Electrical Enclosures

An electrical enclosure is a cabinet to protect electronic equipment to prevent electrical shock to equipment users and protect the contents from the environment. The enclosure is the only part of the equipment which is seen by users; in many cases it is designed not only for its utilitarian requirements, but also to be pleasing to the eye.

Electrical enclosures are usually made from metals, particularly steel and aluminum. They may be made for a specific purpose (e.g., the metal, plastic, or wooden box of a particular radio receiver) or to accommodate any equipment to which they are suited.

Enclosures for some purposes have partially punched openings (knockouts) which can be removed to accommodate cables, connectors, or conduits. Where they are small and primarily intended to conceal electrical junctions from sight, or protect them from tampering, they are also known as junction boxes; the larger, street furniture type is often called a cabinet or, in United States telephone jargon, Serving area interface.

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