WHAT IS CNC LASER CUTTING?
Sheet metal work with a CNC laser cutter
Computer numerically controlled (CNC) laser cutting is a sheet metal manufacturing process carried out by CNC laser cutters. The primary form of laser cutting for sheet metal is ‘vaporisation cutting’, in which the laser beam melts the material and a high pressure gas removes the molten material. The 3 main types of laser cutter are flying optic; moving material; and hybrid laser cutting. A flying optic laser cutter has a stationary bed for the cutting material, with the laser beam head (optic) moving in the X and Y directions above. The moving material works much like the standard punch presses, with the beam in a fixed position and the material moving in the X and Y directions beneath. The hybrid usually moves the work piece in one (X) direction, and the optic head/beam moves in the perpendicular (Y) direction.
The processing range for most CNC laser cutter is from 0.3mm up to 25mm for the higher powered models. The laser cutter can cut a variety of materials including mild steel, stainless steel, aluminium, zintec steel, pre galvanised steel, copper, brass, and more. Laser cutters use various gasses to aid the cutting process, which include: compressed air, nitrogen and oxygen.
While laser cutters are capable of creating more intricate shapes, they are limited in the way they can form the material. If you have a sheet metal design which needs material being formed then a CNC punch press is more suitable i.e. dimples, knockouts, louvres, countersinks, formed threads, etc. Combi machines are available which have combined the laser cutter for intricate shapes, and a punch press turret for simple shapes and form tools. Getting the best of both worlds.
Laser cutters are generally faster than CNC punch presses when it comes to thinner gauge materials and that have fewer individual holes. This is due to the initial piercing of the material that slows the laser cutter down. This is also true for thicker gauges as more heat is required to melt through the material.
Programming components on a CNC laser cutter
Information about a design may be interpreted from a 2D file format such as DXF or DWG files or from a 3D file such as a STEP file, SAT file, etc. This information is then used to create the flat shape, altering the cut size for any bend allowances or anything that may affect the final component. Software packages can also be used to establish the most efficient layout of components from a given sheet size. This could be a standard sheet size such as 2M x 1M, 2.5M x 1.25M and 1.5M x 3.0M. It can also be off-cuts of materials from prevous jobs. This process is known as CNC nesting. Software packages like Radan® can automate this process to achieve the maximum yield from a single sheet metal panel, or even a selection of sizes of sheets as well as nesting a variety of different parts within the sheets. Creating groups of parts on the same sheet can increase the material usage efficiency.
CAM for laser cutting is generally more straight-forward than punch press programming. However, there are many factors to consider. Such as tag location, used to prevent the parts tipping in the nest; off-cutting, used to save the best size and shaped off-cut; and scrap-cutting, to turn the remnants into small sections that will fall between the slats of the laser cutter bed, to handle the whole laser cutting process.
Pros and Cons of laser cutting compared to CNC punching
Quicker on thinner gauges (approx. up to 1.2mm) than punch presses, provided few lead-ins.
Can produce more intricate designs as well as holes thinner than the gauge, within reason, e.g. 2.5mm hole through
Easier to program.
It doesn’t rely on having a wide range of tooling, which may not allow for certain sized cut-outs.
A cleaner cut through most* materials, without nibbles marks.
(*Aluminium is slightly more problematic)
Slower than punch presses through mid-range to thick sheet thickness e.g. 2.0mm and up.
Added cost for nitrogen or oxygen on thicker gauges.
Cannot form features; i.e. dimples, louvres, knockouts, countersinks, and taps.
Cannot laser cut perforated/mesh sheets efficiently.
To see more information of our Trumpf 3030 3KW fibre laser take a look at our laser website.