What do the laser parameters mean?

Optimal laser parameters for laser engraving and laser cutting for CO2 laser applications

What do these parameters such as power, speed, ppi, Hz, pass, Air Assist, z-offset actually mean? Here is a brief explanation.

Power and speed parameters

The power and speed laser parameters are the most important settings in the material database. They can be set as a percentage between 0 and 100%. The Power laser parameter describes the output power of the laser. 100% is the maximum power. For dark wood engravings or stamp engravings, you generally need a higher power, whereas low values are used for materials such as paper. The Speed laser parameter describes the movement of the laser head. Fast speeds lead to short exposure times, slow speeds lead to long exposure times. For example, large-scale engravings of TroLase materials are engraved at high speeds between 80 to 100%. But for photo engravings with lots of detail on wood, the speed should not exceed 10%. This setting also affects the quality of the laser cut. Note that cutting and engraving speeds are not comparable. Basically, cutting is slower than engraving. A "high" cutting speed is 10%.

PPI and Hz parameters

The PPI parameter (=pulses per inch) determines how many laser pulses per inch are used for engraving. To achieve a good result, this should be the same or a multiple of the dpi selected in the print setting. In Ruby® the PPI settings are adapted to the DPI settings automatically. If you set this parameter to "Auto," JobControl automatically determines the optimal resolution of the laser pulses.

During the cutting process, the Frequency parameter is decisive and is given in Hz (=Hertz). It specifies the number of laser pulses per second. For a CO2 laser, the value can be set within a range of 1,000 to 60,000 Hz. For example, if you want to achieve a smooth edge when cutting acrylic, you need higher temperatures and thus this value is set to at least 5,000 to 20,000 Hz. On the other hand, when cutting wood, a low frequency of 1000 Hz is necessary in order to achieve an outcome such as the brightest possible cutting edge.

Pass parameter

The Pass parameter determines the number of engraving or cutting passes. For example, with some materials it can be advantageous to engrave with low power and high speed and then repeat this process several times. This means that the material is less stressed per pass. This approach can be appropriate for a relief engraving.

Air Assist parameter

Every material reacts differently to a laser process. During laser engraving and laser cutting, the supply of compressed air can significantly influence and improve the results. Furthermore, Air Assist protects the lens against damage as it prevents dust from adhering to it. The Air Assist is switched on and off automatically by the software. If the Trotec Laser is delivered from the factory with Air Assist and pump installed, the two units are directly integrated in the enclosure. Trotec laser systems are equipped with Air Assist; optional gas-kit available for connection to an external compressor.

Z-offset parameter

The z-offset describes the focus setting. If the z-offset is set to zero, it works "in focus," meaning the focus is exactly on the material surface. However, there are also applications in which deliberate defocusing is desired. For example, when engraving large areas on TroLase, we recommend defocusing 0.78'' for a consistent engraving result. The following z-offset values are possible: - 0.19'' (table moves up, i.e. closer to the material) up to 5'' (table moves down, i.e. further away from the material).