Laser engraving entails the use of a laser beam to cut through or engrave a material. For best results, the laser engraver is calibrated to create an attractive visual effect and this is where depth control comes in.
So what exactly influences the laser engraving depth control?
The biggest determinant of the laser engraving depth is the material. For instance, most metals allow a maximum depth of 0.020” but you can go up to 0.125” for stronger metals like granite. For acrylic, you can go as deep as 0.01” and approximately 0.02” for wood products.
These are just a few examples to give you a rough idea. The actual depth is determined by the line width of the material amongst other factors. The right line width and depth ratio ensure the light beam hits the center stronger than the edges. But the deeper you cut into a material, the higher the chance of warping and burning it. For an efficient laser engraving depth control, play with the width of the characters. You can also change the speed, frequency, number of passes and utilize bold characters.
Line width and depth ratio
A laser machine needs a certain amount of draft to produce a pattern. Sure, you can manually adjust the settings on your machine to reduce the draft angle but this will not really get you home. The draft is a necessary parameter whether you are engraving into aluminum, stainless steel, or graphite.
The draft angle is important in controlling the light heating the material. The right angle ensures that the laser beam heats the center with a higher intensity than the edges. This is what you want to achieve a deep cut. A laser needs more passes to ensure a deep engraving. If the depth of your cut is greater than the line width of your letters or numbers, the draft angles from the sidewalls will intersect somewhere on the floor of the engraving blocking further cutting.
With this in mind, the best strategy to increase the depth of your engraving is to widen the width of your characters. As a rule, the line width should be either equal or greater than the depth. For instance, you cannot sustain a flat floor finish by engraving a 0.0025” wide design over a depth of 0.001”. The best approach here would be to keep both the width and depth at a steady value of 0.025”.
Important tips and tricks of laser engraving depth control
Increasing the line width of your characters or design is one way to achieve laser engraving depth control. You can also try a few more for even better results. Here are some of them:
- Utilize bold font: A bold font is obviously wider than normal font. Using characters and letters of bold font certainly increases their line width and ultimately allows for a deeper engraving. If you want an effortless way of reducing the draft angle and digging a little deeper, consider using bolded characters. It will certainly give a flat and easily readable surface, especially in molded plastic.
- Use a vector line around the characters: another timeless strategy that can help you improve the quality of your engraving is using a vector engraving line around your characters. Doing this adds crisp to the edges of the design, text, letters, or picture. Unfortunately, this method only works with certain materials and not others. A good rule of thumb is to use heavy raster engraving on plastics and medium raster engraving (plus a medium vector outline) on wooden materials. Test your pieces out with different settings before engraving on your final design.
- Increase the number of passes: deep engraving can also be achieved through multiple passes. To increase the passes, change the number of copies contained in the print dialogue box. Like all other materials, the grade and hardness control the number of passes and the settings needed to cut to a certain depth.
- Use the appropriate equipment: unless you don’t care much for deep engraving, you want to purchase a laser machine with the right power output. The recommended threshold is a maximum wattage of 30—50 watts. Any less wattage may not dissipate sufficient light energy to ensure deep cuts on some materials.
- Play with the speed: the speed of the laser engraver also plays an important role in the depth of your cuts. Ideally, moderate speeds of between 20 and 30% coupled with more passes ensure the material chips away and thus a deep engraving project. If you want a relatively shallow cut, increase your speed and reduce the number of your passes.
- Alter the frequency of the laser engraver: most deep engraving projects implement a frequency range of between 1-5%. Basically, a lower frequency range offers more laser power per pulse and helps to ablate the material. Higher frequency, on the other, provides lower power per pulse and avoids deep engraving.
Bonus tips for deeper engraving
The techniques above are good for controlling the depth of your laser engraving. Unfortunately, they can only do so much. What if you want to go deeper than the maximum value stipulated by the techniques? There are two ways of achieving this:
- Combine laser engraving with a secondary process to get rid of the material. Examples include cutting through a huge portion of the material using a table saw or a milling machine. By doing this, you essentially lessen the load for the laser engraver and let it cut deeper into your material.
- Stack up several layers to form your structure. You can control the depth of your cutouts and cavities by playing with different layers stacked up together. Place a solid layer at the bottom and reduce the sizes of the subsequent layers. This creates a change in depth during laser engraving.
So, there you have it – ingenious tricks of controlling the depth of your laser cuts. The short of it is that the line width of your characters has a direct impact on their depth. The speed and frequency of the laser, the number of passes, and the bolding (or lack thereof) of the characters also play a role in the laser engraving depth control. Adjust these settings accordingly to achieve your desired depth.