How can you properly laser engrave on wood?

Posted by JohnAndrews89 on August 26th, 2019

Wood is an excellent decorative material. It has many advantages, such as interesting appearance, ease of processing, relatively low price, pleasant smell or touch. The rooms decorated with wood became cozier and gave the impression of contact with nature.

The decorative appearance of wood can be further improved thanks to modern laser engraving technology. Tools that enable us precise burning of patterns and graphics on wood can now be easily bought at a good price. It is recommended to use a 3D printer or CNC machine with an additional attached laser head. These machines can now be easily controlled by CNC control software which supports CNC laser.  

Which CNC laser is the best choice - CO2 or diode laser module? 

For wood engraving, both lasers such as infrared CO2 lasers and blue lasers heads based on a laser diode are suitable. However, CO2 lasers are large, expensive to buy and to operate. They must be purchased as a complete device, which can only cut or engrave wood with its laser. They are more dangerous to health due to their high power and invisible to human's laser radiation, but C02 lasers are better in marking and engraving metal and some types of plastic. They can also be used without any special preparations to work with transparent materials such as glass or colorless Plexiglas.

On the contrary, the blue laser heads are small and inexpensive to operate. They can now be simply connected to your CNC machine or 3D printer and thus will expand the capabilities of these devices. The cost of such a laser head is much lower than the entire CO2 laser. Usually, even the cost of a machine with an attached blue laser head is lower than a CO2 laser. Blue CNC laser is more energy-efficient despite significantly lower nominal power. It works very well during engraving on different materials - wood, wood-based materials, leather or fabrics. It is also safer owing to lower power, visible laser beam and much lower electrical voltages inside the device. The weakness of the blue laser is engraving on metals and fully transparent materials. Despite this, a small CNC machine with laser engraving head is a perfect home laser engraver, useful in a home workshop.


How to achieve marvelous wood engravings with a blue CNC laser?

If you want to properly use a machine with a blue laser head, some issues should be considered before buying a laser head or even a CNC device.

1. What power of the laser head should I choose?

Blue CNC laser heads are usually medium power lasers (2-3 Watt) and high power lasers (about 6 Watt).

In the case of branded laser heads, you will achieve good results even with a 2 Watt laser head. However, it is worth remembering that the working time will be significantly longer than in the case of a branded 6 Watt laser head. However, 2 Watt laser head will provide a better rendering of small details thanks to the smaller spot. The 6 Watt head is a better choice if you are focused on short work time. In addition, in the case of cheap, unbranded laser heads, only this nominal power will translate into actual laser power which is sufficient for relatively comfortable operation. No-name Chinese laser heads always have much less power than declared.

2. How you can prepare wood for laser engraving?

For best results, choose the most uniform color and hardest piece of wood. Thanks to this, the finished image will be more visible and burned in a more homogeneous way (due to smaller differences in wood heating). Hardwood is also more resistant to unwanted burning. It is also important to ensure that the wood surface is as even as possible. By maintaining the same distance between the wood surface and the head you will prevent it against differences in the size of the laser spot (laser spot). This will translate into a more homogeneous effect.


3. Which engraving method you should choose?

There are two main ways of laser engraving - raster method (engraving the entire surface) and vector method (engraving with following design lines). The first method allows you to engrave entire images, but it is time-consuming. The second method is very fast, but it can only be used for engraving patterns and outlines.

In the raster engraving method, the biggest limit is usually the speed of the laser head, which depends on the driver of the CNC machine. If we engrave using a slower machine it is good to consider diagonal engraving which engraves the surface diagonally. This will shorten the entire process. The engagement of motors for both axes usually results in faster laser head movement, but the final result depends on the machine's controller software.

For fast machines, it is worth buying a high power laser head that will maximize the power of the engines.

It is optimal when a single course of the head at the high speed allows you to get a color that corresponds to black. If not the waveforms must be repeated twice or even three times which reduces the laser power. Here, however, it is worth paying attention to the rigidity of the structure when we change the direction of movement. Less rigid structures can change the desired engraving shade.

Change of the laser spot is an interesting engraving technique for images that will be viewed from a distance. During pixels engraving with a larger spot, you will lose some of the details, but your engraving process will be faster. 

4. How can you choose settings for the material?

Unfortunately, it is not possible to provide detailed laser power and head speed setting tables in order to achieve the best engraving results for each type of wood. The engraving speed depends on a number of changing factors such as temperature, humidity, color density, material hardness, wood grain density, surface and many more. 

Therefore, the best method to obtain good results is always to carry out previous tests on a specific material. Only on their basis, we can choose the right settings for the head.


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