Focus Lenses for Trotec Laser Machines

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Laser machine lenses

The right lens for perfect results

A laser lens is a components of laser equipment. Using different lenses during laser engraving, laser cutting or laser marking can help you achieve the best results. This works in the same way as a camera that uses different lenses for close-up and wide angle shots. The various lenses differ by their respective focal distances—which the distance from the lens to the focus and indicated in inches.

The focus, in turn, is the smallest beam diameter (before and behind the focus, the beam expands again). A small beam diameter means a high energy density, resulting in an ‘aggressive’ beam. A focal distance of 2 inches, for example, means that the maximum intensity is reached when the workpiece surface to be cut or engraved is positioned 2 inches (or 5.08cm) underneath the lens.

How to choose the right focus lens

The decision on which lens to use depends on a number of factors: your laser machine, laser power, type of material, degree of detail and resolution of the graphic (dpi) and thickness of the material. It’s useful to apply the following rule of thumb:

The greater the degree of detail of the graphic, the shorter the focal distance during laser engraving. The thicker the material during laser cutting, the greater the focal distance.

The following lenses are available for Trotec Speedy laser systems:
(O = optional, S = standard)

Lens 100 100 fiber 100 flexx 300 300 fiber 300 flex 360 360 fiber 360 flex 400 400 fiber 400 flex 500 1500 3000
1.5 inch CO2 ⚪ ⎯ ⚪ ⚫ ⎯ ⚪ ⚪ ⎯ ⚪ ⚪ ⎯ ⚪ ⎯ ⎯ -
2.0 inch CO2 ⚫ ⎯ ⚪ ⚪ ⎯ ⚪ ⚫ ⎯ ⚪ ⚫ ⎯ ⚪ ⚫ ⎯ ⎯
2.0 inch CO2
clearance lense		 ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⚪ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯
2.5 inch CO2 ⚪ ⎯ ⚪ ⚪ ⎯ ⚪ ⚪ ⎯ ⚪ ⚪ ⎯ ⚪ ⚪ ⚫ ⚫
2.5 inch CO2
clearance lens		 ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⚪ ⎯ ⎯
2.85 inch flexx ⎯ ⎯ ⚫ ⎯ ⎯ ⚫ ⎯ ⎯ ⚫ ⎯ ⎯ ⚫ ⎯ ⎯ ⎯
3.2 inch fiber ⎯ ⚫ ⚪ ⎯ ⚫ ⚪ ⎯ ⚫ ⚪ ⎯ ⚫ ⚪ ⎯ ⎯ ⎯
3.75 inch CO2 ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⚪ ⎯ ⚪
4.0 inch CO2 ⎯ ⎯ ⎯ ⚪ ⎯ ⚪ ⚪ ⎯ ⚪ ⚪ ⎯ ⚪ ⎯ ⎯ ⎯
5.0 inch CO2 ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⚪ ⚫ ⚪
5.0 inch fiber ⎯ ⎯ ⎯ ⎯ ⚪ ⚪ ⎯ ⚪ ⚪ ⎯ ⚪ ⚪ ⎯ ⎯ ⎯
7.5 inch CO2 ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⚪ ⚪

The depth of field (focal tolerance), in turn, specifies the area in that laser mean that is optimally focused. The longer the focal distance, the longer the depth of field. This means that the depth of field of a 5 inch lens will be about twice as long for a 2.5 inch lens. For this reason, the cutting edge of thicker materials will turn out straighter when a 5 inch lens is used than when a 2.5 inch lens is used.

At the same time, the laser beam diameter will be greater the longer the focal distance is (for a 5.0 inch lens approximately twice as big as for a 2.5 inch lens). As a result, the energy of the laser (wattage) will be distributed onto a larger surface. Consequently, less power (here in the form of heat) per surface area will be applied. The use of a lens with a greater focal distance can therefore be advantageous for materials that react sensitively to heat (.e.g laminates). The greater focal diameter means a greater line width. Filling lines can therefore be cut with the laser at a greater distance and therefore faster.

The table below gives you a general overview of the various areas of use. However, you should tailor this information to your specific application.

1.5 inch CO2 Graphics with fine detail, (resolution > 500 dpi), rubber stamps with thin letters
 		 Lower laser power, thin materials (e. g. paper), acrylic < 6 mm, wood of medium hardness < 8 mm.
2.0 inch CO2 Graphics with medium detail and resolution (resolution 500 dpi; with reduced definition up to a resolution of 100 dpi), standard engraving
 		 Medium laser power, acrylic < 8 mm, wood of medium hardness < 12 mm.
2.0 inch CO2 clearance lens Mainly used for cutting See 2.0 inch lens.
Increases the distance between laser head and material. Is especially useful if the increased distance is required due to the material and the graphic
2.5 inch CO2 Graphics with low detail, low resolution (< 500 dpi). Engraving on heat-sensitive materials (e. g. laminate) if large areas have to be removed completely sind. High laser power, acrylic <12 mm, wood of medium hardness <15 mm
Better quality of edges during laser cutting than for lower focal distances
2.5 inch CO2 clearance lens Mainly used for cutting.
 		 See 2.5 inch lens.
Increases the distance between laser head and material. Is especially useful if the increased distance is required due to the material and the graphic.
2.85 inch flexx

Standard lens for Speedy 300 flexx. Is transmissive for both CO2 lasers and fiber lasers. Both laser sources can be used without changing the lens.

Other characteristics as 2.5 inch CO2 lens or 3.2 inch fiber lens

 Characteristics as 2.5 inch CO2 lens or 3.2 inch fiber lens
3.2 inch fiber Standard lens for fiber lasers with extremely small focal diameter. Graphics with fine detail, ( > 500 dpi resolution)
 		  
3.75 inch CO2 Lens for SP500 rotary engraving unit. Permits engraving of round objects with diameters of less than 50 mm
 		  
4.0 inch CO2 Engraving by burning of wood, laser engraving of graphics with low detail with high laser powers
 		 Foam rubber
5.0 inch CO2 Is not used for laser engraving High laser power, acrylic < 25 mm, wood of medium hardness < 20 mm
Better quality of edges during laser cutting than for smaller focal distances
5.0 inch fiber Lens for fiber lasers if materials that are not absolutely plane are to be labeled. The greater focal distance results in a greater tolerance during focusing.  
7.5 inch CO2 (for SP1500) Is not used for laser engraving
 		 High laser power, acrylic < 40 mm,
Better quality of edges during laser cutting than for smaller focal distances
Lens Area of use engraving / marking Area of use cutting

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