Focusing the laser is just as important if not more important than leveling the bed of a 3d printer. A well focused laser will have tighter cuts, will engrave and cut faster and will have higher quality engravings. Getting the laser to a good focus point however can be difficult, and there are a few tricks to getting things to work smoothly.
The lens on the Ortur doesn’t have the tightest threading, meaning as you twist the lens to focus it, you can move it side to side and up and down which will bring it out of focus. Adding a bit of teflon tape to the threads can help with keeping the focus more consistent as you dual in the lense.
Trying to see the focus point can also be difficult even with good safety glasses. Focusing on plain paper can provide a large amount of glare making it difficult to see how well focused the laser is. Instead use black paper while focusing the laser (printing a small black box on some paper works), and using the laser safety glasses as well. This will cut down on the glare and make focusing easier, as you want the smallest dash/dot possible.
TlDr:
- Use teflon tape to get a tighter fit on the lens for more consistent focusing
- Use black paper and safety glasses to focus on to prevent some glare making it easier to see the focus dot
Additional Details
From one of the forums:
For the 15w head, the Best Focal Distance is 70-80mm . You can use 75mm. This is measured from the bottom of the heatsink to the job (not the bottom of the dial)
Focusing for cutting is a bit of an art. As the focal range is limited, if your material is 3mm thick, you should focus at the middle of the material, so you have spare focal range above and below the material.
If you focus at the very top of the material, when the laser cuts through, and reaches the bottom of the material it will be out of focus, therefore will have a difuse power