[BorisTheMidget]

Hi Folks, i've recently purchased a 100w Co2 laser and having a few problems. Firstly, i am not getting "clean" cuts through the material - it looks fine on top, but its rough as heck at the bottom. It looks like it burns and melts the material. The material is 20mm 12kg/m PE opencell sponge foam.

This video and sample was done using a laser head - 20 dia, and focus lens 60.5FL

Could i kindly ask for some suggestions on the laser cutter settings you use? your lens, head and FL?

Secondly, any advice on how to prevent the blackening / charring of the material on the bottom?

see video here:
https://s3-ap-southeast-2.amazonaws....906_112608.mp4

sample cut here:
https://s3-ap-southeast-2.amazonaws....m/test+cut.jpg

thank you kindly

[fixtureman1]

I would try a pin bed. I made one using pop rivets. If you can keep the foam up it may cut through cleaner as it is not getting the flash back

[GerryG]

Either a pin bed or a hex mesh bed will help with the charring and flash, but that sort of thickness is going to have significant focal issues at the lower end - unless you're using a machine with really decent optics, you're going to lose focus to a significant degree after the first ten mm.

As a rule, drop the speed a fair chunk and power a bit - I tend to go with 30:20, so take 30% off the speed, and 20% off the power if I'm working with stubborn materials. I know it sounds a bit counterintuitive - the obvious thing to do is to crank the power up, right? Well, proportionally speaking, you are. You'll generally get a cleaner cut, and can dial the speed and power in a bit more afterwards. If you just crank the power up to account for it instead, you'll usually get more charring.

[fixtureman1]

You could lso try a 4 inch focal lens

[BorisTheMidget]

Hi Folks, thanks for the replies - super helpful. I'll try and order a 4" FL, is there any particular brands or types that you'd recommend?

Can i also ask, Fixtureman1, would it be possible for you to post a picture of the pinbed?