What causes "rough" edges when laser cutting acrylic?

[shobley]

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

[Rodney Gold]

Striations on the cutting edge are caused by many things , large "flats" are caused by bad interpolation of curves , smaller "bite" type striations are caused by motion slop in the system , but general striations are caused by a combination of air assist and melt/resoldify issues
The air assist does 2 things , 1 : stop flaming , 2: eject the melt through the kerf. In doing so it cools the cut and thus sometimes promotes resolidification of the cut surfaces and thus leads to striation effects. Not much you can do about it barring slowing cutting speed and fiddling with your pulse per inch setting , direction of air assist (if you have a seperate nozzle) and air assist pressure.

[Tweakie]

Steve,

I used to get edges like that but now I don't.

Reduce your speed and power levels.
Reduce the air assist to minimal - just enough to protect the lens.
Remove the protective coating if it is paper based (to prevent flare up).
Use high resolution images for the toolpath.

Tweakie.

[Litografa]

Key words are "inexpensive" Chinese laser cutter (40W)"
On this type of lasers low quality stepper motors are installed and this is the reason. Put here picture of your laser if possible.