I had the same problem using a China CNC 3018 PRO with a 60W laser.
Solutions:
- 4 passes at 800 mm/min @ 95% power (burning everything around
) -
do it on 1.5 mm balsa with only 2 passes at 1000 mm/min @ 80% power - Buy a CO2 laser $$$$$€€€€€€
- Have someone else cut it for you.
I choose #2 and am very happy with the result (for the price I paid)