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Plasma cutter advice sought

Hey All! I know ! I know ! Look at previous postings for answers on plasma cutters ! And I have read many, many of these postings. But things seem to change so fast in the plasma cutter world. I saw one advertised in Machinist's Workshop or Home Shop Machinist that was surprisingly inexpensive. I spoke to the guy selling it and he was very helpful and informative. He gave me a reference to a fellow using it in a light industrial setting as I would be. It turns out that it would not work for me, but would be great for a hobbiest. So for me it boils down to either Hypertherm or Thermal dynamics. It seems that these machines are priced closely, use consumables at approximately the same rate, and parts are easily available. So it comes down to trying each one and seeing which one feels better. But where I need help is deciding what capacity is best for my situation. Currently the thickest mild steel plate I cut is 3/4". The thickest stainless plate is 5/8" I use the oxy-acetylene torch for the mild steel and saw for stainless. All the cuts are then machined to size. Not too much welding is done in my shop but I do turn away welding business from time to time because it is such a small part of my work and I like machining better. But this will probably be changing this year. I'm looking to hire a welder with some machining experience who wants to learn machining. So a plasma cutter will hopefully be getting more work. And that work will be welded assemblies. So the cuts will preferably be final and many will be welded to other parts. Just how bad is the cut when it is "severed"? Is machining this "severed" surface hard on cutters the way a torch cut surface would be? Can the cut be improved by pre-heating the plate? How much grinding is required to make a "severed" cut close to the same quality as a proper cut? Is there a point where it is better to use a torch because of thickness? Is 3/4" near this point? Will a higher amperage machine make better cuts on thinner material? If so, can a machine that will cut 1" be used economically to cut 16 gauge? Does the cut have less bevel when using higher amperage? Can I tig weld to a plasma cut surface without any prep or with minimal prep?

I think that's it. Thank You, Eric R Snow, E T Precision Machine

Reply to
Eric R Snow
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I purchased a Hypetherm. I was lead to beleive that the consumables would be less exspensive and they would last longer than the competetion machines. This proved not to be true. The consumables are very exspensive and they have a short life span. It is cheaper to use oxy- acetelyne. I would buy one only if I needed it for cutting non ferrous materials.

Charlie

Reply to
Bogone

What are the prices based upon ? - Oxy vs. Hypertherm ? No contest in some places. Some places Hypertherm wins easy due to the restrictions.

The numbers are plasma vs. plasma by different companies.

Martin

Reply to
Martin H. Eastburn

How dry is your air? Or do you use nitrogen? I don't like torch cutting because of the surface it leaves. Plasma is so much cleaner and so requires much less time cleaning it up. I have had some pieces plasma cut for me and the cut edges were beautiful. Not so for torch cut parts. Especially if I'm the one doing the cutting! ERS

Reply to
Eric R Snow

I have a Cutmaster 75 (Thermal Dynamics?) and put a dessicant filter on it right at the back of the machine. After a full year of cutting around the farm and building an automatic firewood processor with it, I think I've gone through two or three tips and nozzles. Use very dry air and avoid using more amperage than you need and plasma cutting is super-cheap. The newer machines seem to get MUCH more milage out of consumables so don't bother with a used machine.

Jason Marshall

Reply to
Jason Marshall

Thanks Jason, that bit about new vs old is good to know. I had not decided whether to but a used machine. I haven't been looking for a used one but sometimes the welding supply has good used machines and if the price was right one of 'em might have followed me home. Eric

Reply to
Eric R Snow

I think you are on the right track by buying either hypertherm or TD. they are the hands down best machines. I currently run a Thermal Dynamics Pakmaster 75, which is nominally rated at 3/4". I find the ratings are a bit overly optimistic, and you should really overbuy in terms of size. Best policy is to go to a welding supply store, and actually cut your material with the machine you want- then you can see how it really does on real steel. My welding supply store will do this willingly- most will. And most good stores carry both Hypertherm and TD. Consumables are, well, consumable. They get used up. And they are indeed expensive. Life of consumables is directly related to number of pierces- this is the hardest on them. Theoretically, they would last a lot longer if you just made one long cut, instead of lots of short ones. It is true that a good quality water filter will help consumable life, and edge quality as well. I like the big black anodized "toilet paper" style from motor guard, available at most good welding supply stores.

As far as edge quality goes- the damn torch gets hot- 45,000 degrees or so. So even though the HAZ (heat affected zone) is very small, it does do a number on any steel that can be hardened. Edges, and slag, get hard. Slag is the hardest- I always try to knock it off before grinding or machining, as it is really hard stuff. We use an air chisel to knock it off the back side, then an aluminia zirconia mop disc on a 4 1/2" grinder, before we machine it. Slag production is directly related to proper cutting speeds- at optimimum speed, slag is minimal, and it just falls off the metal, for mild steel. At too slow of cutting speeds, slag welds itself to the base metal, and is really hard to get off. Most high amperage machines have a control for turning down the amperage, so you can cut thinner material and still get a nice clean, minimal kerf. We tig weld to the plasma cut edge all the time- and yes, we occasionally notice some bubbles from the edge, but it is rare. But we do prep all edges first- slag removal and light sanding, usually. Stainless and some bronze alloys are a lot worse in terms of slag- They need to be cut in a neutral atmosphere for good edges. So expect more grinding on them. At correct speed, the edge quality is better than oxy fuel, unless the oxy fuel is being machine cut, or run by a true expert torch man. But plasma too gives you its best cut when machine cut. I use a motorised cutting machine for my plasma cutting, and it works really well.

Reply to
rniemi

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