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Focus Lenses for Trotec Laser Machines.

Precision focus lenses for Trotec laser systems

  • Optimal laser engraving and cutting depend on choosing the right lens with the appropriate focal distance.
  • Focal distance affects beam diameter and energy density, influencing cutting precision and heat dispersion.
  • Considerations for lens selection include laser power, material type, graphic detail, and material thickness.

Achieving perfection through lens selection

In laser engraving and laser cutting, striving for optimal results depends on choosing the right lens. This principle is similar to selecting different lenses for close-up and wide-angle shots on a camera. The key distinguishing factor among lenses lies in their respective focal distances, quantified in inches. Focal distance signifies the distance from the lens to the focal point – the point at which the laser beam achieves its smallest diameter before expanding again. A smaller beam diameter translates to higher energy density, creating a more “aggressive” beam. For instance, a 2-inch focal distance implies that maximum intensity occurs when the workpiece surface being cut or engraved is positioned 2 inches (approximately 5.08 cm) below the lens.

Choosing the ideal focus lens.

Determining the appropriate lens relies on a range of considerations: laser power, material type, graphic detail and resolution (dpi), and material thickness. Here's a rule of thumb to guide your selection: Greater graphic detail warrants a shorter focal distance for laser engraving, while thicker materials in laser cutting require a longer focal distance.
The following lenses are available for Trotec laser systems:

(⚪ = optional, ⚫ = standard)

Lens 100 100 fiber 100 flexx 300 300 fiber 300 flexx 360 360 fiber 360 flexx 400 400 flexx 500 1500 3000 R400 R500
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, or focal tolerance, denotes the optimal focus area where the laser beam operates. Longer focal distances result in extended depth of field. Consequently, when using a 5-inch lens, the cut edge of thicker materials appears straighter compared to a 2.5-inch lens. However, a longer focal distance also means a larger laser beam diameter (approximately twice that of a 2.5-inch lens). This disperses the laser's energy (wattage) over a larger surface, reducing heat per unit area. A lens with a greater focal distance can be advantageous for materials sensitive to heat, such as laminates, due to the broader beam diameter.

This broader focal diameter also leads to a wider line width, facilitating quicker laser cutting of fill lines at a greater distance. The following table offers a general overview of lens applications, though we recommend customizing this information to suit your specific needs.

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. 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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