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Plasma: A Cut Above the Rest

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Cabe Atwell
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Blogger
Cost effect
Cabe Atwell   2/1/2013 5:07:36 PM
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I used to draft and build steel bridges. Plasma was the workhorse tech behind it all. Cuts were perfection. For the home machinist, I don't this this is a cost effective option over the laser alternatives. Maybe I am wrong?

C

Larry M
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Platinum
Re: Cost effect
Larry M   2/4/2013 9:36:36 AM
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Hmm. They seem to be available on Amazon, Harbor Freight, and eBay. Affordable for the serious hobbyist, I would say.

jf
User Rank
Iron
Re: Cost effect
jf   2/4/2013 11:57:51 AM
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In the past several years, economical rigs from Hypertherm, Miller, and others have started to make plasma-cutting affordable to home/hobby users.  I have a 60-Amp unit that works fine on plate steel up to around one inch.  One safety consideration that new users must not forget is a good respirator.  Even when cutting ordinary steel, the plasma process produces a fog of microscopic rust particles that is miserable to breath.  Users should visit their local welding-supplier and consider purchasing a disposable N95 welding-fume respirator.  I wear eyeglasses so I prefer a respirator with a valve (eg 3M #8515) so moisture does not fog my lenses when I exhale.  If I cut any galvanized steel, then I also rely on the welding respirator to filter out any zinc particles which are known to cause "metal fume fever" if inhaled.  Anyone cutting stainless steel should be aware that the plasma process creates "hexavalent chromium" particles, and anybody who saw the film "Erin Brockovich" can relate to what chromium-six does to people, so stainless-cutters will want to have respirators that are rated for hazardous materials such as chromium.  I use a 3M #8212 in this case.  I have listed my personal preferences (from 3M) but several other manufacturers offer suitable products as well.  I buy them in small quantities from my local welding supplier for under $20 each, a small price compared to the expense of treating bronchitis, or worse, cancer.

bob from maine
User Rank
Platinum
Re: Cost effect
bob from maine   2/4/2013 5:45:05 PM
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Cabe; I haven't found a Laser cutter anywhere near the 'affordable' range for a home hobbyist or a small shop. Plasma works well, but is fairly expensive, it only works where there is power and compressed air, and it only cuts. I've gone back to oxy/acetylene. I use it for cutting, heating, brazing and occasionally welding where power isn't available. The edges always need grinding using hand held Plasma or oxy. The major benefits of plasma are the ability to cut stainless, starting holes in the middle of a sheet or piece of pipe, the narrow kerf, relatively clean cut and less heat distortion. If I was running a shop, I'd use plasma for every possible cut but as a hobbyist I can't justify the space or cost.

William K.
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Platinum
The plasma cutter
William K.   2/4/2013 8:56:06 PM
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Aside from the quite toxic fumes, which I had not considered, a plasma cutter is quite hazardous due to the very high temperature plasma, which is able to deliver a whole lot of heat energy to almost anything almost instantly. So while they can produce very good cuts, it is mandatory to keep in mind the whole process at all times. There are lots of ways to get into trouble very fast when using a plasma cutter. This article did address a few of them.

Gorski
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Platinum
Plasma cutting
Gorski   2/5/2013 5:36:32 PM
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While this method sounds like it has promise, one thing stuck in my mind. The plasma stream is energized and creates heat. Is the heat high enough to distort the workpiece? If so, this would affect the aciracy of parts produced by this process.

 

GORSKI PE

Gorski
User Rank
Platinum
Plasma cutting
Gorski   2/5/2013 5:36:32 PM
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While this method sounds like it has promise, one thing stuck in my mind. The plasma stream is energized and creates heat. Is the heat high enough to distort the workpiece? If so, this would affect the aciracy of parts produced by this process.

 

GORSKI PE

jf
User Rank
Iron
Re: Plasma cutting
jf   2/6/2013 9:59:36 AM
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I have not experienced significant distortion when making plasma cuts.  Quite the opposite.  The plasma jet is *so* hot and so localized that the work material is liquified and blown out of the cut before the remainder of the work piece can be affected.  Anything that touches the plasma is removed, and anything not touched by plasma is left behind.  Overall heating of the piece is much less compared to cuts using an oxy/fuel process.  On thinner material (<1/4") you can *almost* handle the pieces within a few seconds of completing the cut, though obviously that is not recommended practice.  The kerf (width of cut) is also significantly smaller than with oxy/fuel, and the cutting time is less as well.

For what it's worth, the History Channel has a Modern-Marvels episode where they show 3" steel plate being cut by robotic plasma cutter at the Newport-News shipyard.  The plate is actually submerged under water to suppress the fumes and ensure there is no thermal distortion, which would be impossible with an oxy torch.

streetrodder
User Rank
Gold
About to buy one...
streetrodder   2/6/2013 10:59:42 AM
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I guess I'm about to qualify as a serious hobbyist.  You can tell by my tag what one of my hobbies is.

In street rodding, plasma has become the preferred cutting method, especially for sheet metal.  The minimal heat distortion and accuracy reduce the amount of 'massaging' needed to realign the metal.  This is particularly important when chopping or sectioning the body. 

As it looks like I'll be 'slicing and dicing' a '32 Chevy sedan next, it's time for me to buy a plasma cutter.

Cabe Atwell
User Rank
Blogger
Re: About to buy one...
Cabe Atwell   2/8/2013 4:51:08 PM
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Yes, CNC plasma cutter prices are out of this world. I am surprised someone hasn't taken those portable plasma cutters ($500) and combined it with a CNC router (some at $500 as well). Perhaps it is due to the frightening accidents that could happen? Or the routers not able to withstand the heat? I don't think I would want to use a DIY/hobbyist made CNC plasma cutter for those reasons.

 

C

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