I bought a Sculpfun S30 Pro 10W laser engraver 1 month ago.
My first 5-6 attempts went well, everything was good.
After that, I decided to cut out flowers for my wife from 4 mm thick plywood.
I tested the laser settings on the first piece and everything went well, the laser cut it nicely. (speed: 340 mm/min, Power max: 100%, Air: on)
After that, I wanted to cut out 5 flowers at the same time on a larger piece of the same material. According to the software, this took about 30 minutes.
At the beginning, the laser cut out the flowers nicely (good: 0-2), but for the last two or three pieces didn’t cut through the material anymore (fail: 3-5).
The problem is not with the material, because the laser cut the first piece beautifully from the same material with the same setting.
The power supply was stable.
I cleaned the lens, but the result is the same. I have used the machine for a total of 2 hours so far, the lens should not be dirty.
Could you help me find out what could be the reason for this? Why does the laser power decrease after 5-10 minutes of work?
As your pictures show, it is plywood and unfortunately it has the property of being not consistent in the composition. The glue and knobs in the material are very randomly distributed. Sometimes you can see it when you hold a piece of (thin) plywood against the light.
You can easily test my claim by making some small test cuts in different places on that piece of wood. You will see that with the same setting you can cut nicely in some places, elsewhere it does not go.
Another issue you can have is that the wood is not perfectly flat over the entire surface. My 3mm Baltic ply comes individually wrapped in plastic. If I let it sit out foe a while (40-45% humidity) it can warp so much (3-4mm on a corner) that I have to secure it to the honeycomb. thicker plywood is no warranty for stability.
This was already mentioned, but another addition: plywood is a horrible laser material due to the glue and heterogeneous wood quality. You can have (and will have) hidden knot holes in the middle layers. Manufacturers put the worst material between the beautiful outer layers.
There is more expensive A/A plywood or “laser grade” plywood that reduces problems and is even easier to cut, usually.
In your case, there is another issue coming into play. As you can see, most unsuccessful cuts are in small and tiny areas of your objects. That’s because the laser doesn’t get to full speed here, and if you didn’t use constant power, you also won’t cut with full power because it gets dynamically aligned to the speed.
Additionally, it seems your settings are on the edge of cutting, you should always add one more pass than required, to get through the areas with more glue inside.
In general, your speed is too slow, do not cut below 600mm/min. Adjust the passes accordingly. 4mm poplar plywood should cut fine at 600/90/4.
