Hi Motohead1!
Go check out: http://www,weldreality.com By world reknown MIG/Flux-cored expert, Ed Craig... I'm sure that you'll like what you'll find there!!!
You'll find the answers to most of your questions there!!!
As far as a chart goes, I looked at one in Howard B. Carey's book "Modern Welding Technology" 4th edition, published by Prentice Hall... I looked in the back at thesheetmetal welding schedules chart and I found that for 0.030 wire dia. is recommended for 22 & 24 gage sheetmetal so, that could also be a problem.. try using a 0.35 dia wire. This means that you'll have to check to see if you have to change your drive rolls & associated parts, gun conduit, and contact tip...The chart lists for 16 &20 gage, volts should be set at 18 for 16ga. and 17 for 20ga. Amperage parameters should be 80-110 for 16ga. and 55-85 for 20ga. Both gage thicknesses require 20 to 25 cfh (Cubic Feet per Hour gas flow rate) and around 25 cfh should work well for the gas you're using because of the lesser density in Helium which would require a slightly higher flow rate... Remember that these voltage and current settings are probably for mild steel and not stainless so, experiment first on scrap to get the desired results bfore you start on actual production!!!
On your gas regulator you have a flowmeter, you should have a knob to set your flow rate and you should be able to read on the flowmeter in cfh. Set the ball in the flowmeter so that the bottom of the ball is resting on the line that corresponds to 20 - 25cfh start with 20cfh and weld a sample bead or joint with some scrap if available, then inspect your result to see if you have sufficient coverage. if you still see porosity then set the ball in the flowmeter to 25cfh. this should setting should provide you with adequate gas coverage...
Normally I suggest to my students to set the ball in the flowmeter so that the ball (sphere) equator or the center is where the recommended flow rate should be set at but since you're using a shielding gas that for the most part, has a lighter density then, the ball rest on top of the recommended flow rate should used if your flowmeter only has settings for Argon and Carbon Dioxide. If yours does have a gauge for Helium then set it to that scale with the ball equator at the recommende setting... The chart I have also lists recommended travel speeds for both 16 and 20ga. sheet metal.. they are 32 ipm's (inches per minute) for 16ga. and 37 ipm's for 20ga. so this means you have to travel faster when you weld on the 20 ga. material...
On my Millermatic Calculator, for 16 ga. stainless stl., It recommends for short ciruit transfer which I presume you're using, the volts should be set at 19-20, amps or current at 70-80, wire feed speed at 180-205 if you're using 0.035 dia. wire with the same gas mix you're using... It does'nt have any recommended settings for 20 ga. but, it does have settings for 18 ga. stainless stl. so, if you like, you can adjust your settings to slightly lower than the low end of these settings!
They are: 19-20 volts (I would recommend 17-18 on this), 50-60 amps or current, 120-150 ipm's for your wire feed speed (I would recommend to start slightly lower at 110 ipm's then work your way up until you get the desired sound and feel) you'll know what's the correct welding schedule when you experiment on scrap first so, "tweak" around abit with your machine before you start welding on the actual work FIRST!!! Do'nt forget to visit Ed Craig's site first before you make your experiments so that you have the opportunity to see what you find there!!!
Good Luck and let us know your results!!!
Respectfully,
SSBN727 Run Silent... Run Deep!!!