Learn what to think about when you do a relief engraving with a laser to attain good results.
What is a relief engraving?
A relief engraving is a deep engraving consisting of different heights generated by the grayscale values of an image. Trotec lasers automatically regulate their power level through these values and can therefore create different depths in a single pass. Relief engravings are big eye-catchers that can instantly make any application more alluring. They are perfect for gift items, jewelery or add-ons to goblets and trophies.
Preparing data and sending it to the laser
Data can be made through the usage of grayscale fillings and gradients sent to the laser with the "relief" process type. Shades of grey from 0 to 100% black can be used to create different depths in the material. A grayscale gradient can make a smooth transition to different depths.
Trotec lasers control the laser power through the image's grayscale values. The darker the graphic is, the more power that is used. The lighter it is, the less power that is used. For the laser, 100% black is 100% power. In other words, 100% black is 100% of the value given in the parameter database for power. 40% black is 40% of the defined power, 18% black is 18% power, etc. The screenshot on the left gives examples for what relief engraving files could look like. You can download our test files here:
If you require high quality data or photo representations for relief engravings, they should be made in a 3D program because these programs can create incredibly fine gradiations in gray steps. This method is very complicated. There exist companies that provide this kind of individual data creation like www.gantryco.com.
Which materials are suitable for relief engraving?
Relief engravings can be performed on materials with the same layers throughout or are otherwise completely permeated with colour, giving them a uniform appearance. The most suitable materials are:
Oak is less fitted for relief engraving, because its annual rings differ in density. This results in an engraving with an inconsistent pattern. Alder is also not recommended, because it is extremely soft and discolours quickly, making the relief hard to see.
Engraving process
For relief engraving wood, we recommend using the following process (based on using a Speedy 360, 80W laser): Engrave your image in 3-4 passes with high power and low speed (p=100%, v=30%) to make your engraving the depth you want. Then, we recommend one or two rounds with low power and high speed (p=60%, v=100%) to remove any smoke residue.
If you want an extremely deep engraving, we recommend you first engrave the cutting contour then only do the deep engraving.
Cleaning
Clean your relief engraving with a toothbrush and soapy water or detergent. Liberally brush over the relief and scrub away any traces of powder. However, be sure not to use too much water and dry your workpiece well, for example by using a method like compressed air. Otherwise, the piece of wood could lose its original shape.
TIP: Creating a wood relief engraving with color change
It is also possible to make a relief engraving on wood and change its colour. For this, we recommend thoroughly cleaning the workpiece after engraving, as mentioned above. Doing this gets rid of any smoke traces that otherwise would impair the subsequent engraving result. Place the clean, dry workpiece back into your Trotec laser and engrave it with the standard Solid Wood "black" values in JobControl®. An integrated z-offset value of +6mm is crucial for attaining a nicely discoloured engraving. If the effect is not enough, then increase the z-offset value.
Relief engraving acrylic
Acrylic relief engravings create a nicely refined effect on trophies and other applications. When relief engraving acrylic, it is imperative to work without any Air Assist (= OFF) and with a z-offset value so that the acrylic does not become cloudy or gain a milky-white discolouration.
Engraving process
This method is based on a Speedy 360, 80W laser: When engraving, use a slower speed mixed with a high power (p=90%, v=10%) and turn off Air Assist. This will give the material enough time to melt and, depending on your Trotec Laser's performance, produce an exceptional texture on the first pass. Additional passes will create an even deeper three-dimensional effect. Just as important is to use a z-offset value of between +2mm and +4mm. This will preserve the acrylic's transparency.
Cleaning
To clean your finished acrylic workpiece, run it under water with a toothbrush to get rid of any dust from within the cracks.
