I recently received an "inexpensive" Chinese laser cutter (40W) and have successfully cut 3 and 6mm acrylic.

However I've noticed that while the edges are polished, they are not perfectly smooth - showing fine vertical lines running along the direction of the laser beam.

Is this normal?

Example :

http://www.imajeenyus.com/workshop/2...ylic_cut_3.jpg

I thought it might be the pulsing of the laser beam, or maybe some play in the gantry.

Anyone know what causes it?

Steve