The tutorial demonstrates what you need to consider when doing relief engraving with a laser, as well as how to get good results.
Relief engraving is a deep engraving with differing heights, which are created by gray shades in the graphic. The Trotec laser automatically regulates its performance using these grayscales and so generates different heights in only one pass. Relief engravings are appealing and make any application more attractive. This form of engraving is ideally suited to gift items, jewelery or as add-ons for goblets and trophies.
Data can be generated by using grayscale fillings and gradients, which are sent to the laser via the process type "relief." Various shades of grey from 0 to 100% black can be used. These will produce different heights in the material creating flowing transitions between the different heights.
The Trotec laser automatically regulates the output power via the grayscale in the graphic. The darker the graphic, the more power is generated. The brighter, the less power. Therefore, 100% black means 100% power - i.e. 100% of the value defined as power in the parameter database. 60% black means 60% of the defined power, 10% black means 10% power, etc. Examples of what files for relief engravings can look like are shown on the screenshot. Our test files can be downloaded here.
Tip for high-quality data or photo presentations
High-quality data or photo representations for relief engravings need to be created in a 3D programme. Such programmes generate extremely fine gradations at gray steps, which is a very complex process. There are companies that offer this kind of individual data creation, e.g. www.gantryco.com
Suitable types of wood
Less suitable wood species
Oak is less suitable because its annual rings differ in density, resulting in the relief engraving having an inhomogeneous engraving pattern. Alder is also not recommended as it is very soft and discolors quickly. This makes it difficult to see the overall appearance of the relief.
For relief engraving on wood, the following method is recommended (details are based on the use of the Speedy360, 80 watt laser): In order to create the desired depth of your relief, engrave your graphics in 3-4 passes with high performance and low speed (p 100%, v30%). Follow this with one or two rounds at low power and high speed. (p 60%, v100%), which will allow you to engrave away the smoke residue.
In order to achieve very deep engraving, first engrave the cutting contour, and then only perform the deep engraving in the second step.
Use a toothbrush to clean your laser-engraved relief, using water and soap or detergent. Scrub away the traces of powder by brushing generously over the relief. Do not use too much water and dry your workpiece very well, e.g. using compressed air. This will stop the piece of wood from losing its shape.
TIP: Creating a wood relief engraving with color change
A colour change can be achieved by creating a relief engraving in wood. For this purpose, the workpiece must be cleaned very well as described above. By doing this, the smoke traces that would otherwise damage the subsequent engraving result, will be removed. Now place the cleaned and dried workpiece back in your Trotec laser and engrave with the standard values Solid Wood "black" from JobControl®. The integrated z-offset value of +6mm is important for achieving a nicely discolored engraving result. If the effect is too low, increase the z-offset value.
Relief engraving on acrylic is used to create an elegant effect on trophies or other applications. When relief engraving acrylic, it is important to work without additional Air Assist (= OFF) and with a z-offset value. This will stop the material from becoming cloudy or acquiring a milky-white discoloration.
This data is based on the use of the Speedy360, 80 watt laser: Use a slow engraving speed in combination with high power (p=90%, v=10%) and switch off the Air Assist when engraving so that the material has sufficient time to melt and -- depending on the performance of your Trotec laser -- produces an excellent texture in the first pass. Further passes create an even deeper three-dimensional effect. It is equally important to use a z-offset value of +2mm to +4mm as this preserves the transparency of the acrylic.
Remove dust from the cracks by cleaning the finished acrylic workpiece under running water with a toothbrush.