Plasma Cutter

[Pat]

I mentioned Plasma Cutter to someone and they asked why you would cut plasma.

I finally decided that my skill level with an oxy-acetylene torch was not improving and was abysmally poor and likely to remain substandard. I resort to various schemes to avoid having to use the torch since the results are so humbling yet I have need to cut metal in ways that don't lend themselves to abrasive cut off disks, chop saws etc.

SO!!! I took the plunge and bought a plasma cutter. It has a max amperage of 27 amps and is sized for rapidly and smoothly cuting 1/4 inch steel. It will cut 3/8 pretty well and will "sever" 3/4 steel but the cut is NOT smooth or fast. I have been cutting mostly 3/16 with it and the cuts are fast and neat. I have cut 40 circles out of 3/16 and it is easy to use and does a good job, even with me using it.

I made a couple circle templates out of 3/4 inch MDF, each an inch in diameter (ID) larger than the circle I wanted to cut to allow for the 1/2 inch distance from the plasma jet to the side of the torch. The templates got singed a bit but are still servicible after each was used to do more than 20 circles. The circles were roughly 1 1/8 inch and 2 1/8 inches. I surprised myself at how neatly I could cut the 3/16 steel.

I cut off some 3/4 round bar and that was a tad messy requiring significant dressing with a grinder. That is a job better left to the abrasive chop saw. Also not having a jig for cutting pipe with the plasma I used the saw to cut up a length of 1 inch pipe into 3 inch lengths.

I don't have the optimal eye protection. My auto darkening welding helmet only turns down to about a shade # 7 and acording to the ANSI specs I need a shade # 4 or 5 depending on current setting and how shielded I am by the configuration of the workpiece and the torch. I turned the auto darkening off and just use the built in filter density but I think it is still a tad too dark. It is hard to see and follow the chalk marks of my soapstone.

What seems to work the best for me since I have trouble seeing the soapstone markings is to use a guide of some kind. For cuting a straight line I clamp a board 1/2 inch from the cut line and let the torch follow the board for a neat straight cut. Another difficulty is trying to hold the torch 1/16 inch above the surface of the steel being cut. I end up making a lot of tip to workpiece contact which at the lower current settings won't matter much but at the highest settings will eat on the "consumables" at an uneconomical rate.

Any other plasma users out there who can share their experience regarding shade# and such?

After using the plasma for a little while I can safely say I don't plan on spending much time trying oxy-acetylene anymore. I will send my tanks back to the welding supply house. I will keep my small bottles for just in case, brazing, silver soldering, or whatever but I can't think of anything I'd need the biguns for any more. (Don't say PREHEAT as I have carbon arc accessory for my Lincoln "Tombstone" which will preheat OK.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Well, Pat....... what you've done is buy the very thing that I have wanted for oh so long....a plasma cutter. EVEN THOUGH I am a virtual Rembrandt with a torch, I would still like to have a PC. Light material, stainless, and intricate shapes are so much easier to do with a plasma. I have a home made circle cutting attachment that rides on the mixer tubes of my Victor Superange at all times, It is versatile and can cut just about any circle, do radius work, trim along a wall, operate as a "drag tip" and twenty-dozen other functions. This is the sixth-generation development of the home made circle attachment and they keep getting more and more refined. This Superange is older than my youngest kid and has cut bevels around a LOT of pipe. [img]/forums/images/icons/crazy.gif[/img] I keep intending to earmark the VERY NEXT check from my writing-for-fun-and-profit business for the purchase of indulgements, but somehow Jeepchick manages to deposit them to savings before I carry through with something like yet another tractor or a.......plasma cutter. [img]/forums/images/icons/smirk.gif[/img]

[Pat]

Dave, I cut about 50 holes and it was WONDERFUL compared to how lousy I was with a gas cuting torch. I'm not so terrific freehand but I make a couple templates which workedlike a charm and clamped a guide board for a couple straight cuts.

I will be cutting my own storm shutters from sheet (using an undersized template to guide my hand) and building up with internal ribs to maximize the strength for the weight. A bit more complicated than a 1/2 inch plate but no materials over 3/16 (probably) and certainly not over 1/4 inch so within range of my MIG with innershield wire. I may use skins of 10 gauge (heavier thatn FEMA storm shelter doors.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] I've never used anything but gas on my MIG welder, Pat......why do you use innershield? Just curious... [img]/forums/images/icons/tongue.gif[/img] I was also wondering why you needed to cut plasma? [img]/forums/images/icons/crazy.gif[/img]

[GaryM]

He needs to cut Plasma because he's too old to cut the mustard! [img]/forums/images/icons/grin.gif[/img]

[GaryM]

Just wanted to get that in there before Pat came back!

I usually use gas because I hate to chip slag. But from what little I've been taught, Flux Core is better for welding where there's any air movement, such as outdoors. The gas can blow away before the weld cools enough that oxygen can do any damage. With the Flux Core, the flux sitting on top of the hot bead prevents that from occuring.

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Ahhhhh..... makes sense. I once saw a continuous welding machine that was used to build up the rails on sets of Caterpillar tracks and it was welding in a pile of granulated flux that completely covered the arc. I've always known that you weren't supposed to chip the slag right away and admire the weld because of damage to the weld from rapid cooling.

[CJDave]

[img]/forums/images/icons/crazy.gif[/img] I wonder if Pat's wife knows that his plasma is cut? [img]/forums/images/icons/crazy.gif[/img]

[Pat]

Dave, Here are some answers... to your questions but in no particular order. Good luck!

My Lincoln Weld Pak 100 came with a starter roll of Innershield flux cored wire which worked well and did not require any chipping. This was way ahead of stick welding, at least at 1/4 inch material or less. I liked it and so kept buying it although my unit has a solenoid to control the gas so is "GAS READY" but has never had a bottle connected. If I try my hand at aluminum and or SS with it I will need a gas bottle and will have to swap out the flexible wire guide speedo cable looking thingy as it would contaminate a non-ferous weld. Being so lazy... I might get another welder for non-ferous use. Been thinking I might make my safety railings out of aluinum and although I have successfully welded aluminum with a flux cored electrode, it was a fluke, I'm sure.

Why cut plasma? Well there are medical conditions where your blood is too thick and dilution (cutting) is beneficial.

Well, in use it turns out I am not all that much better with a PC than with a oxy-acetylene cutting torch but enough better to warrant using the PC in place of the gas.

I bought two 5x10 ft 3/16 steel sheets and one 4x8 foot of 3/16 and it took me a few hours to cut up the 4x8. Learned a lot about what not to do and some of what to do. I find that the effort to make a template or guide is a terrific investment that returns great dividends. Trying to go slow and do a good job also pays dividends as it takes less time to do a good job than it does to do a quick job when grinder time is entered into the equation.

I am using my regular welding helmet but with the auto darken feature turned off. Its lowest setting is shade #7 and 4-5 is recommended for my size PC. The filter in my auto darkening helmet (when turned off) is still too dark and it is a tad difficult to see what you are doing. Maybe I'll do a little better freehand when I get a shade 4 or 5 to use.

I popped a 20 amp breaker running the unit on 120VAC but no probs with it on 240VAC. It is supposed to be 60% duty cycle but so far I haven't had it go into auto protection no matter how long I have cut (6 ft at a time is the most I have cut.) I have had over temp shutdown many times with the Lincoln MIG but never any damage, just a brief break while its fan cools the overheated internals.

I haven't put an "amp clamp" on the lead from the PC but the knob on the amp control goes up to 27 amps. I am some amazed at how small the diameter is of the plasma jet emitting from the torch. I can see why folks with NC X-Y tables for their plasma cutters are so jazzed. This is a neat tool, hand held, but would be a virtual miracle tool with computer control.

I have done some re-engineering on this project and found a way to do the layout of the modified plan with zero waste and all straight cuts, so.... I'll be returning the two each 5x10 ft sheets to the source and have them sheer them each into 6 equal pieces saving me 50 ft of plasma cutting in 3/16 and getting a more finished edge. Think several times, measure twice, cut once.

I'm resting from my labors today. I saved time and hassle by not taking a trailer to get the materials and having them load it in my pickup. It made the work of unloading and handling the materials at this end 10X harder. 3/16 sheet steel gets heavy quickly if the piece is more than a couple square feet. Wrestling with the 4X8 and the pieces I cut it into made me tired and sore so sheering the two 5X10's will be a welcome relief. I'd rather handle a dozen 5 ft by 20 inch pieces than have to mess with a whole sheet. If I hadn't had pallet forks on the tractor I could have had an all day sessiion just getting the sheets up on my big metal saw horses.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[Stimw]

I've had a Miller Spectrum 625 Plazma Cutter 40amp for 2 1/2 years and I would be lost without it. I only use my Ox/ Act for heating now.
I use a pair of O A glasses for cutting. I have found you don't need the helmet for Plaz.
Also do what ever you can to remove as much water from your air as possible. The moisture will eat up your tips. I have about 85' of air line (up,over,around and through) which really helps.
For anyone looking to buy a Plaz try to get as big as you can afford. The bigger the unit the more you can do and the better it will cut. Be careful, once you try it there is no going back! It is better than you can imagine.