In this tutorial we highlight the key areas that you need to be aware of when laser cutting and engraving woods.
As wood is a natural material, various characteristics such as density and resin content have to be considered during processing.
As a rule of thumb:
The more uniform the colouring and grain of the wood, the better and more even the laser engraving result will be.
Overview of suitable wood types for laser cutting and engraving
|Soft woods||Woods such as balsa wood or poplar, require a lower laser power level and can be engraved and cut faster. Laser engraving produces a lighter contrast.|
|Hard woods||Woods such as oak or cherry are examples of dense woods. These woods require a higher laser power level for laser cutting and engraving. The laser engraving itself is more contrasting than on soft wood.|
|Coniferous woods||Woods such as larch or fir, are not suitable for laser engraving. They usually have a large number of uneven grains which are typically very hard. The surrounding wood ("non-graining") is rather soft, which makes it difficult to find the right parameters.|
|Veneers||These are made of real wood and therefore show the same engraving properties as solid wood panels.|
|Plywood||This consists of at least three layers of wood whose grain is glued and pressed at an angle of 90°. Plywood is available in various types of wood and is offered in different thicknesses. The type of glue is important for laser processing, especially during laser cutting. Choose white-glued plywood panels or plywood panels made specifically for laser processing.|
|MDF (Medium density fiberboard)||MDF is a homogeneous wood-based material made of finely defibrated, mainly bark-free, softwood, which is gently pressed in the longitudinal and transverse directions. The surface and edges are smooth and firm. So MDF can be easily engraved and cut. However, it should be noted that the cutting edges will become very dark during laser cutting.|
As a rule of thumb for laser engraving:
Laser processing hard woods will result in dark marks, soft woods will produce light marks.
As a rule of thumb for laser cutting:
The drier and more resin-free the wood, the brighter the laser cutting edge is.
Determining the laser engraving parameters
With the grayscale matrix you can quickly and easily determine the laser engraving parameters for yourself.
Tip: The more you defocus (z-offet: approx. 0.5 - 2 mm), the darker the laser engraving will be. Defocussing the laser beam increases the laser spot size, decreases the performance density and burns more wood instead of letting it pass directly into the gaseous form. The disadvantage of this process is that details can be lost.
Determining the laser cutting parameters
You can test the laser cutting parameters by drawing a rectangle with two differently rounded corners. Send this graphic to the laser. For 3mm thick wood, start with high performance and a cutting speed of 2-5% and gradually reduce your cutting speed to reach your desired quality.
The sticky dust generated by the laser wood should also not stick to the engraving object. Simply glue an application tape onto the working surface, which will serve as a short-term surface protection and can be easily engraved. After laser processing, it is simply removed. Application tape is well suited for laser engraving of larger areas and for laser cutting.
However, it is not suitable for photo-engraving or fine laser engravings as many of the small parts have to be removed later. When selecting the application tape, be sure to use PVC-free material and that it is removable.
The right laser optics
Laser cutting wood is a sublimation process. Accurate focusing and the right choice of the optics are crucial for this process. A distinction must be drawn between engraving and/or cutting. While laser engraving, please pay attention to the following: The finer the details, the shorter the focal length of the lens should be. As a rule, 1.5" or 2.0" lenses are suitable for almost any laser engraving appication on wood. This is different for laser cutting as the thickness of the material plays an important role here. The thicker the material, the longer the focal length of the lens used. For 1/8 inch thick wood we recommend the use of a 2" lens, for 1/4 inch thick we recommend a 2.5" lens.
The connection of compressed air is recommended especially when laser cutting wood. A small-diameter nozzle should be used to protect the lens. The small nozzle diameter also directs the compressed air straight into the cutting gap. As a result, dust and gas are removed quicker and the laser cutting quality is significantly improved.
Cleaning hardware and optics are important factors when laser processing wood. Wood dust is extremely sticky due to the resins and oils it contains, and the dust tends to settle inside the laser machine. This means it is important to regularly clean the machine.
Suitable exhaust system
During laser engraving and laser cutting wood, dust and gases are produced which must be properly extracted, making a suitable exhaust system essential.
Relief laser engraving on wood
Wood is a great material for relief engraving. In a relief engraving, grayscales are converted into different laser power levels, which produces three-dimensional engraving. You can engrave in several passes with relatively high performance, and then perform one or two cleaning passes to remove the smoke residue.
Inlays in wood
Wood inlays (intarsia) are also particularly popular application. In an inlay, different woods are laid on a flat surface in such a way that they create a smooth surface, which now contains differently coloured and differently structured inlays. Usually the base material is engraved first, and then the material to be laid (usually wood veneer) is cut and inserted. For the veneer, make sure that the width of the laser beam (cutting gap) is adjusted. This means that the carrier must be slightly larger.