Laser cutting

Laser cutting is a thermal cutting process in which a focused laser beam melts or vaporizes material in a small spot and a stream of assist gas blows the molten material out of the kerf. The cutting head moves over the sheet according to a CNC program and cuts any 2D contour. Besides flatbed lasers, there are machines for tubes and profiles as well as five-axis lasers for trimming formed parts.

For metals, fiber lasers with a wavelength of about 1 µm now dominate. They are fast in thin and medium gauges and can also cut reflective materials such as aluminum, copper and brass. CO2 lasers, with a wavelength of 10.6 µm, are used today mainly for non-metals: wood, plywood, acrylic (PMMA), textiles and leather.

The assist gas affects both speed and edge quality. Oxygen is used for mild steel, where the exothermic reaction speeds up the cut but leaves an oxide layer on the edge. Nitrogen gives clean, oxide-free edges on stainless steel and aluminum at the cost of higher gas consumption. Compressed air is a cheaper compromise for thin sheet.

The kerf is typically 0.1 to 0.5 mm wide depending on thickness, and the machine compensates for it automatically. Contour accuracy on thin sheet is usually around ±0.1 mm. It decreases as thickness grows, and the cut face develops striations and a slight deviation from squareness. Cut quality and dimensional tolerances of thermally cut parts are classified by ISO 9013. Sheet from a few tenths of a millimeter up to roughly 20 to 25 mm of mild steel is cut routinely, and high-power machines can handle more.

Laser cutting is the default choice for sheet metal parts in one-off and low-volume production: flange plates, brackets, covers, nameplates, stiffeners and flat blanks for sheet metal bending. It needs no part-specific tooling, so a design change means only a new program, and different parts of the same material can be nested on one sheet. That makes it a good fit for prototypes as well as repeat runs with changing variants.

For very thick material, for parts that must not have a heat-affected zone, and for stone, glass or composites, waterjet cutting is the better option. For large runs of simple parts with formed features, punching or stamping can be cheaper.

An edge cut with oxygen carries an oxide layer to which powder coating adheres poorly. For parts that will be powder coated, specify nitrogen cutting or ask for the scale to be removed, for example by blasting. On higher-carbon steels, the edge can harden and make drilling or tapping difficult. Holes smaller than the sheet thickness are problematic, and precise holes for pins are better drilled or reamed. PVC and other chlorine-containing plastics are never laser cut, because cutting them releases corrosive and hazardous gases.

For a quote, supply 2D contours at 1:1 scale (for example a DXF file) with closed outlines and no duplicate lines, or a 3D model and a drawing. State the material with its grade, the thickness, the quantity and whether deburring is required, and for cosmetic stainless or aluminum parts also the grain direction and protective film. Agree where the marks left by microjoints (the small tabs that hold parts in the sheet during cutting) may remain, and check whether the specified tolerances match the normal accuracy of the laser.