Have you registered with Hypertherm on Xnet?
For 18ga Stainless
cut height should be 0.02"
pierce height 400% or 0.08"
cut speed should be 325ipm
current set at 45A
pierce delay 0.2secs
Gas should be set at 85 to 135psi (flowing)
Are you using THC or fixed height?
Try these settings and let us know how you get on.