Hi Andriette
If you was able to engrave on the plastic or paper, that is say the laser beam path is normal.
I guess that might be you should be considering to the focal distance of the lens, are you sure that's right for the focal distance of lens.
You know, i am just setting the power on 30% an speed on 500, and it will get a good the engraving result, i just used a 50 watt laser tube.
When you press the "Laser Contour" button the LCD, i guess this time the laser tube will coming out the laser by 100% power percent.
I think that you would check the lens whether it has some dust or the focal distance is correct?