Plasma cutting basics

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I just did a search on the site and I might have missed a few things, but I was hopeing to find a thread on basic use. I'm a complete rookie with welding and I just finished the stick course of my welding school. I've been looking around for info on plasma cutting and haven't had to much luck. Is there a formula for setting the amperage? Like with TIG, it's 1 amp pre thousand of an inch. How do you judge the travel speed? My guess is that it based off of the same tech that is used for O/A cutting. So I was hopeing some of you guys could give me the basics of how to set up the plasma and what I need to do when cutting. Plasma is the last course in the class and it's something I'm interested in.
Reply:I dont know the "proper" technique for setting the amperage on my plasma but, I know what works. I keep it turned all the way up. Ive cut 22 guage through 1" with equally satisfactory results. As far as travle speed, I only move the torch as fast as the arc can pass through the material and keep a continuous cut going. Once you use or see someone use a plasma , you'll understand what Im describing, I think."I need this parade like I need a hole in the head"~John F.Kennedy
Reply:Most manufacturers will provide a recommended amperage setting and cut speed for a given thickness and type of metal. Running at max amps and adjusting your speed so that you are going as fast as possible while cutting all the way through works but that doesn't always provide the cleanest cut. Check out some of the manufacturers web sites like Hypertherm and look up the recommendations. That will give you a starting point.As an example, I run my Powermax 1000 at 40 amps ( 60 is max ) and cut at a speed of about 150" per minute on my CNC table for 16ga cold rolled steel. I have cut the same steel using 20amps at slower speeds. The difference is how much dross is produced and how much taper is in the cut.
Reply:Well I got a chance to play with a plasma today. It's an import 30 amp cutter. I was cutting 1/8" and .085 wall 1x2 square tube. I put it on full and tried to cut both. I could get it to cut the 1/8" at 20 amps. Slow but it cut without to much dross. I even had it down to 5 amp and it notched or something like etched the metal. I still wish there was some kinda of basic guide, but I keep trying different things until I find out what works best. Any more suggestions would be welcomed.
Reply:anyone care to expand on this?  i want to buy a plasma cutter but dont know if i need to use a special air filter unit for my compressor?
Reply:Originally Posted by okie2500anyone care to expand on this?  i want to buy a plasma cutter but dont know if i need to use a special air filter unit for my compressor?
Reply:Originally Posted by CrackerI dont know the "proper" technique for setting the amperage on my plasma but, I know what works. I keep it turned all the way up. Ive cut 22 guage through 1" with equally satisfactory results. As far as travle speed, I only move the torch as fast as the arc can pass through the material and keep a continuous cut going. Once you use or see someone use a plasma , you'll understand what Im describing, I think.
Reply:I use Motor Guard filters.  The filter element looks like a roll of toilet paper (maybe it is?).  Seems to work fine.I use full amps on my 60 amp Longevity and the cut quality is OK.  I adjust my travel speed to get a smooth, steady stream of sparks with the spark stream angled toward the direction of travel.   I usually use a 1/4" thick guide which gives me a 1/8" (+/-) gap.  I'm sure my tip is shot but I just keep wire wheeling it and reusing the same tip.  If/when I need a smooth cut I'll change the tip.  Understand I'm a rank amature and I'm sure my technique could stand improvement.One thing I'll add....plasma cutting is filthy.  There's a very, VERY fine dark grey powder covering everything in my garage/shop...including my sinus' and lungs.  At first I thought it was only in the immeadiate area of the torch but now I see it's all over the place...even in the spider webs in every corner of the ceiling.  This can't be good.  I'm definitely going to invest in a half face respirator.  Even with the respirator, I'm thinking that plasma cutting is more of an outdoor sport and not for enclosed spaces. Attached ImagesMiller 211 w/ spool gunMiller Dynasty 200DXLongevity 60i IGBT plasmaO/A w/ crappy chinese torch/gaugesSouth Bend 10K latheGrizzly 4029 10x54 millGrizzly 7x12 hor bandsawangle grnders, bench grnder, bench belt sndr7.5 hp 80gal cmprsor
Reply:I borrowed a thermal dynamics cutmaster 38 from a neighbor 2 weeks ago....never plasma cut in my life, but the overall process like most anything is trial by fire... -amps/travel play w/ until dialed in w/ particular machine and thickness of mat'l to be cut-compressor, drain before every use, dry air critical, motorguard filter the bomb, roll of TP will fit and works like a champ..purge air lines before hooking to machine ...dial in recommended psi every day of use-worn tip and/or electrodes bad ju ju, don't ream the tip w/ an oxy torch cleaner-slag on top of cut indicates bad ju ju (moisture, air loss, tip bad, electrode..etc..)-easily knock slag (dross) off bottom side of cut w. chippie hammer-clamped angle iron is a great fence, better to have a crisp edge or you can run up on the angle...you'll know when you do-wear leather gloves w/ cuffs and proper eye protection (full face)this I learned all w/ trial and error in past week...wish that plasma was mine....here's pix of recent project w/ 10 ga steel, all stick welded..column was assembled from 5" strips w/ 6011 stick welds, the ellipse shape was freehand after trace..... Attached Images
Reply:Here is a link to basic plasma info.http://www.thermadynenewsroom.com/thermaldynamicsvideo/TP does not make a great filter element for the Motorguard.  The paper fibers blow off the roll and can accumulate downstream in your torch and leads, leading to problems down the road.Most plasma operator's manuals include a cut chart with recommendations for cut current and cut speed.  The critical variable in any hand cutting application is the operator, but one of the advantages of plasma cutting is that you can see what you are doing and make adjustments.  The cut charts will give you a good start point.