Glossary · Setting
Line interval
The distance between the lines that the laser runs side by side when engraving an area. Smaller intervals give denser, darker areas.
Explained in more detail
In area engraving, the laser scans the area line by line. The line interval sets how far apart the lines are, given in millimetres (line interval) or as lines per inch (LPI). The conversion is 25.4 mm divided by LPI, so 254 LPI corresponds to 0.1 mm. For diode lasers, 0.05 to 0.1 mm is common. For photo engravings, you base the interval on the spot size so that lines neither overlap heavily nor leave gaps. In LightBurn, the value for images is shown as DPI; it is 25.4 divided by the line interval in millimetres.
Where does the term come from?
Line interval means the spacing between lines. LPI stands for lines per inch and, like DPI (dots per inch), comes from printing technology; one inch is 25.4 mm.
In practice
- Rule of thumb: line interval about as large as the focus spot. Smaller intervals make the area darker but lengthen the engraving time.
- If you halve the line interval, the engraving time doubles, because twice as many lines are run.
- For photos on wood with a diode laser, 254 to 318 DPI (0.1 to 0.08 mm) is a good starting point, and often less on slate.
- Intervals that are too small burn the surface and blur details; in that case increase the interval or reduce the power.
Not to be confused
The line interval for lasers is not the print resolution in UV printing, even though both can be given in DPI.
Frequently asked questions
What line interval should I use for engraving?
A good starting value for diode lasers is 0.08 to 0.1 mm. Slightly smaller for dark, even areas, rather larger for light photos on dark material.
How do I convert LPI to mm?
Divide 25.4 by the LPI value. 254 LPI gives 0.1 mm, 318 LPI about 0.08 mm.