I needed to fix ceiling light. The old bulb holder gets corrupted and I need to make circular hole to plastic cover.
I thinked that burn through 2.2mm plastic would not be a problem. It seems that even 20W LASER needed 20 circular passes to burn through at speed 400mm/min. The most problematic is that most of material is gone, but I need 6 additional passes to burn out small bridges. Bridges are visible on photo.
Plastics are, and probably always will be a problem for visible spectrum diode lasers.
Rather than evaporate as it should, most plastics usually melt -at least to a degree- and the surface of the liquid plastic can also reflect or diffract the beam, making the lasers ability to cut the material even harder to accomplish.
The 20W optical power figure that we use to compare the cutting capacity of our lasers with, is for the optimal focus point, ~0.1mm or thereabouts in diameter for Your diode laser I assume?
The width of the cut on Your lamp fixture base seems to be significantly wider than that, ~2mm?
When the optimal focus point is far above the surface to be cut, the cross sectional area of the beam on the surface of the material to be cut increases dramatically, and while the power is obviously the same 20W, the surface area that the beam hits is significantly larger.
So, because of that increase of area when the power stays the same, the energy density decreases and the cutting ability decreases with it.
Exactly the same way as sunlight and a magnifying lens/glass behave.
Yes, you are right. The LASER has been positioned slightly above optimal height. I have no choice - because the cutted area is below upper edge of cutted object. I cannot jail LASER position in a specified area (I dont know this lightburn feature). The callibration height cylinder is depicted on this photo so you can guess height.
Also please keep in mind that the camera has been saturaded with extra bright point and the size of LASER ray was different. After saturating CCD chip, the “charge” flows and saturates neighbour pixels.
Minimal width of ray is 0.3mm for this LASER type.