For 1/4" plate with the Powermax380 you will run wide open on amperage (27 amps) ....and follow the suggested speeds listed in the manual that came with the system. 1/4" is just about maximum thickness for that system, so speeds will likely be in the 10 to 13 inch per minute range, standoff should be maintained at about 1/16", if you drag cut you will have to slow the cut speed about 10 to 15%. There are no FineCut consumables available for the Powermax380.
If you don't have the manual, you can download it on the
www.hypertherm.com website, click on download libraries tab.
Jim colt