Laser cutting -Technical Issues

We have been experiencing numerous issues with laser cutting both the 4mm and the 6mm poplar. As this is a natural material, there can be irregularities that lead to inconsistent cuts from the laser. We tired changing the timing and power in small increments to achieve a more reliable and even cut without burning the material. We tried re-cutting the material a second time, this created issues with our tolerances for our junctures.