plasma cutter explained maybe

[irnsrgn]

Lots of people are getting plasma cutters for thier shops and it seems they are a mystery to some. So I thought I would explain them as they were explained to me. This may clarify things or not. If I make any mistakes please feel free to correct them.

1. There are 3 states of Matter, SOLID, LIQUID AND GAS, Some say that a plasma is the 4th state of matter.

2. A PLASMA in this sense of the word is a Super Heated Gas.

3. A plasma works by super heating common air under pressure and pushing a portion of it thru a small nozzle to literally vaporize any metalic substance in its path whether it be Ferrous or Non Ferrous in nature.

4. If it says the machine uses 5 cubic foot of air a minute, this usually means that 1 cf of air comes out of the nozzle and 4 comes out around the nozzle to cool it.

5. The Plasma stream coming out the nozzle is coming out at somewhere around 200 mph and at a temperature approaching 28,000 degrees.

6. Whatever the Capacity or Thickness the machine is rated at is at a speed of 10 inches per minute. For instance if the machine says a capacity of 1 inch, It will cut 3/8 inch material very well and as the thickness increases the inches per minute of travel are greatly reduced.

7. Whatever the recommended input air pressure is, increasing it will not improve the cutting ability of the machine, but will greatly increase the slag or dross it leaves, and shorten the life of the consumable tips.

8. Plasma is usually limited to the thinner materials as it has a tendency to not cut straight thru like Oxy Acet does on thick material. If you expierience a slanted cut from your plasma, you will notice that the slant is tapered to the outside bottom on the right side of the torch and slanted in at the bottom on the left side of the torch usually in the direction of travel.

9. There are 2 types of torches, those that have to make contact with the material to cut and those with a pilot that are stand off and do not make contact with the material, the later type will usually destroy a tip if contact is made with the material.

10. Don't touch the consumable tip components with your fingers as this will shorten the life of the tip from contamination by the oils on your skin.

11. Some machines have a variable power rating, this is to conserve electricity and wear on the tip consumbables and to make a better cut.

12. PLASMA MACHINES LITERALLY VAPORIZE THE MATERIAL BEING CUT AND THIS MATERIAL IS FLOATING IN THE AIR AND CAN BE INHALED BY YOU AS YOU WORK, WEAR A MASK OR RESPERATOR DESIGNED TO FILTER THIS MATERIAL.

13. Commercial business's that use Plasma on a day to day basis a lot, will have water tables (A cutting table with water just below or covering the material being cut) to keep this contamination from entering or dispersing into the air you breath.

14. TIP - Contact type nozzles or tips do not work very well with painted or rusty material, but this may be overcome on straight cuts by using a piece of flat iron as a guide and making sure it is grounded, pull the torch along the flat iron making sure the tip is in contact with the flat iron, the torch will then perform almost as well as one with a pilot or high frequency option.

15. EYE PROTECTION IS ALSO A MUST AS THE PLASMA STREAM IS BASICALLY NO DIFFERENT THAN THE ARC PRODUCED BY A WELDER.

16. TIP - on contact type nozzles, a light coating of MIG Tip Dip applied by your finger on the contact surface will prolong tip life and also keep dross from sticking to the tip as well as increasing the ability for it to slide along on the material to reduce friction.

17. TIP - Most of you will have a water trap on your air lines, and again at the plasma machine. Oil in the air line is the biggest reason for tip failure or wear out there is. There are special oil filters that use what looks like brown course toilet paper as a filter, and these are the most efficient and sure way of filtering oil from you entering your plasma system, Water traps will not filter out oil.

[Mills]

Wow, You never cease to amaze me with your ability to explain. That really helps me now, and later when I have to tour my clients shops I'll be a bit more knowledgeable on their operations.

[T-Gold]

Woah, Jr! Thanks! That answered a lot of lingering questions that I had.

[Marc]

How about putting this in with the Blueprints to make it easier to find?

[elkdoc]

Thanks irnsrgn... Always wondered how they worked.

[Nolano]

Sounds like the explaination I heard of it
Except, I heard that there is an arc of electricity going over the nozzle tip, and the air blows that electricity out, heating the metal, and the air pushes it away, or something to thaqt effect.

[MrBi11]

Modern industry depends on the manipulation of heavy metal and alloys: We need metals to build the tools and transportation necessary for day-to-day business. For example, we build cranes, cars, skyscrapers, robots, suspension bridges out of precisely formed metal components. The reason is simple: Metals are extremely strong and durable, so they're the logical choice for most things that need to be especially big, especially sturdy, or both.
The funny thing is that metal's strength is also a weakness: Because metal is so good at resisting damage, it's very difficult to manipulate and form into specialized pieces. So how do people precisely cut and manipulate the metals needed to build something as large and as strong as an airplane wing? In most cases, the answer is the plasma cutter. It may sound like something out of a sci-fi novel, but the plasma cutter is actually a common tool that has been around since World War II.
Conceptually, a plasma cutter is extremely simple. It gets the job done by harnessing one of the most prevalent states of matter in the visible universe. In this article, we'll cut through the mystery surrounding the plasma cutter and see how one of the most fascinating tools has shaped the world around us.

Where Saws Failed

In World War II, U.S. factories were cranking out armor, ordnance, and aircraft almost five times faster than the Axis powers. This was largely thanks to private industry's tremendous innovations in the field of mass production.
One area of innovation rose out of the need to cut and join aircraft parts more efficiently. Many factories working on military aircraft adopted a new method of welding that involved the use of an inert gas fed through an electric arc. The breakthrough discovery was that charging the gas with an electric current formed a barrier around the weld, which protected it from oxidation. This new method made for much cleaner lines at the joints and much sturdier construction.
In the early 1960s, engineers made a new discovery. They figured out that they could boost temperatures by speeding up the flow of gas and shrinking the release hole. The new system could reach higher temperatures than any other commercial welder. In fact, at these high temperatures, the tool no longer acted as a welder. Instead, it worked like a saw, cutting through tough metals like a hot knife through butter.
This introduction of the plasma arc revolutionized the speed, accuracy and types of cuts manufacturers could make in all types of metals. In the next section, we'll examine the science behind this system.

States of Matter

A plasma cutter can pass through metals with little or no resistance thanks to the unique properties of plasma. So what is plasma?
There are four states of matter in the world. Most things we deal with in our daily lives are in the form of solids, liquids, or gases. These states are divided based on the way that molecules behave within each one. Take water as an example:
As a solid, water takes the form of ice. Ice is made up of neutrally charged atoms arranged in a hexagonal pattern that forms a solid. Because the molecules stay fairly still relative to each other, they form a solid -- something that holds its shape.
As a liquid, water takes its drinkable form. The molecules are still bound to each other, but they move relative to each other at slow speeds. The liquid has a fixed volume, but no constant shape. It changes shape to fit whatever container you put it in.
As a gas, water takes the form of steam. In steam, molecules move around at high speeds, independently of each other. Because the molecules are not bound to each other, a gas has no fixed shape or fixed volume.

The amount of heat (which translates to the amount of energy) applied to water molecules determines their behavior and therefore their state. Simply put, more heat (more energy) excites molecules to the point that they break free of bonds that bind them together. With minimal heat, the molecules are tightly bound, and you get a solid. With more heat, the molecules escape the rigid bonds, and you get a liquid. With even more heat, the molecules escape the loose bonds, and you get a gas.
So what happens if you were to heat gas even more? This brings us to the fourth state: plasma.

What is Plasma?

If you boost a gas to extremely high temperatures, you get plasma. The energy begins to break apart the gas molecules, and the atoms begin to split. Normal atoms are made up of protons and neutrons in the nucleus, surrounded by a cloud of electrons. In plasma, the electrons separate from the nucleus. Once the energy of heat releases the electrons from the atom, the electrons begin to move around quickly. The electrons are negatively charged, and they leave behind their positively charged nuclei. These positively charged nuclei are known as ions.
When the fast-moving electrons collide with other electrons and ions, they release vast amounts of energy. This energy is what gives plasma its unique status and unbelievable cutting power.

Inside a Plasma Cutter

Plasma cutters come in all shapes and sizes. There are monstrous plasma cutters that use robotic arms to make precise incisions. There are also compact, handheld units that you might find in a handyman's shop. Regardless of size, all plasma cutters function on the same principle and are constructed around roughly the same design.
Plasma cutters work by sending a pressurized gas, such as nitrogen, argon, or oxygen, through a small channel. In the center of this channel, you'll find a negatively charged electrode. When you apply power to the negative electrode, and you touch the tip of the nozzle to the metal, the connection creates a circuit. A powerful spark is generated between the electrode and the metal. As the inert gas passes through the channel, the spark heats the gas until it reaches the fourth state of matter. This reaction creates a stream of directed plasma, approximately 30,000 F (16,649 C) and moving at 20,000 feet per second (6,096 m/sec), that reduces metal to molten slag.
The plasma itself conducts electrical current. The cycle of creating the arc is continuous as long as power is supplied to the electrode and the plasma stays in contact with the metal that is being cut. In order to ensure this contact, protect the cut from oxidation and regulate the unpredictable nature of plasma, the cutter nozzle has a second set of channels. These channels release a constant flow of shielding gas around the cutting area. The pressure of this gas flow effectively controls the radius of the plasma beam.

Plasma on the Job

Plasma cutters are now a staple of industry. They are used largely in custom auto shops as well as by car manufacturers to customize and create chassis and frames. Construction companies use plasma cutters in large-scale projects to cut and fabricate huge beams or metal-sheet goods. Locksmiths use plasma cutters to bore into safes and vaults when customers have been locked out.

Plasma Art

In the past, plasma cutters were prohibitively expensive and were used primarily for huge metal-cutting jobs. In recent years, the cost and size of plasma cutters have dropped considerably, making them available for more personal projects. Artists and metal workers use handheld cutters to create unique works of art that would never be possible with conventional metal-working tools. This single tool gives artists the ability to bevel cuts, bore precise holes and cut in just about any way they can conceive.
The plasma cutter is one of the most interesting and powerful tools developed in the 20th century. Using basic principles of physics to harness the fourth state of matter, the plasma cutter performs with nearly magical results. One can only imagine, as our understanding of plasma grows, how many more tools and applications will utilize this fascinating force of nature.


credit: http://howstuffworks.com

[mike-hr]

This is a great thread! I got so energized when I finally understood this subject, I almost burst into the 4th state of matter! Okay, so I ate a can of chili for dinner, my wife said it's not inert gas...
Thanks for diving into this, folks. I learned a lot.

[J W Bennett]

It has been a good month"Valentines day is great". I am going to reinvest the profit, I looked at Plasma cutters Thursday and Friday. My local welding supply that I use has made me a real good deal on a Hypertherm 380. It looks like a good one and it burns good.
Has anyone on here ever run or possibly have a Hypertherm and can tell me if they are dependable machines. Or if you have a good unit of another brand that has served you well I would appreciate the info.
Oh yeah, I am mainly going to use it for light gauge up to 1/4" mild steel. I have a good victor journeyman torch set for the heavy stuff. At this point I don't see much aluminum work but may start some stainless.

JWB

[T-Gold]

I have spent a fair bit of time on a Hypertherm -- cannot remember the size at the moment. They are solid dependable machines, and I am inclined to believe that parts will be available for a long time to come. Consumables are reasonably priced for the one I use.

[J W Bennett]

T-Gold,
Thanks for the input. I am going to pick it up this afternoon. I looked around on the net last night and read some more and the price is good. Since it's local I got to try it first, plus these guys have never steered me wrong yet.

JWB

[Ten Hammers]

I have a Hypertherm 350. Bought it new 9 years ago. OUTSTANDING tool. I cut mostly 14-16 ga sheet for production work. I DO also use the torch for building tooling and virtually any other need in the shop. I have gouged welds with it. I have cut a go-zillion miles of steel with it. 5 pack of consumables is about $40.- ( both electrode and cup for this price). I replaced the torch/gun about 2 months ago. This was due to hanging the torch on the edge of cut sheet while changing places with the pattern to cut the next piece. $ 230.- or so for the new parts. I must stress again how much steel this plasma has cut. When time to update I will buy a 600 or mebbe a 1000 but for now, I'm happy. As Junior stated, you need a good source of CLEAN DRY AIR.

Ten

[T-Gold]

Oh, I forgot to mention -- because of how plasma cuts, you can sever twice the thickness it's rated to if you can get to the opposite side of the piece. This is a LOT harder with OA than it is with plasma, though OA also cuts thicker stock (crank that oxy!). I have cut 1" with our shop cutter, which is rated to sever 1/2". (Couldn't find any torch tips bigger than 00. Oxy cranking only goes so far.)

[J W Bennett]

I picked it up monday afternoon. Used it to cut out 8 sets of rose petals and 2 tulips. It's alot quicker and cleaner than a torch. I think it'll save alot of time on cleanup too. I'm still working on the settings, It'll cut alot faster than I can stay on my lines. Still have a small amount of dross on the edges. I think thats just a matter of settings an operator error.
Thanks for all the info. I think between gas cylinder prices and less clean up time it will pay for it's self pretty quick.

JWB

[stixman55]

I want to thank both IRNSRGN and Mr Bi11 for there imputs. I have been considering buying a Plasma cutter and though I sence a diference in there opinions of the plasma cutter, the both of them have layed out very inteligent assessments of the cutter both in principle and application. I have to admit though, now that I have read there commentaries I am sure that I still need to look into the cutter a bit more before deciding weather to buy one or not. I do want to cut faster, straighter and more accuratly but is there health risks that I should consider that are more demanding with the plasma cutter than over the conventional Oxy-Asc cutting? Mmmm I do use common sense but is that enough with the plasma?:confused:
I really want to hear more;)

[Ice Czar]

In World War II, U.S. factories were cranking out armor, ordnance, and aircraft almost five times faster than the Axis powers. This was largely thanks to private industry's tremendous innovations in the field of mass production.
One area of innovation rose out of the need to cut and join aircraft parts more efficiently. Many factories working on military aircraft adopted a new method of welding that involved the use of an inert gas fed through an electric arc. The breakthrough discovery was that charging the gas with an electric current formed a barrier around the weld, which protected it from oxidation. This new method made for much cleaner lines at the joints and much sturdier construction.
In the early 1960s, engineers made a new discovery. They figured out that they could boost temperatures by speeding up the flow of gas and shrinking the release hole. The new system could reach higher temperatures than any other commercial welder. In fact, at these high temperatures, the tool no longer acted as a welder. Instead, it worked like a saw, cutting through tough metals like a hot knife through butter.
This introduction of the plasma arc revolutionized the speed, accuracy and types of cuts manufacturers could make in all types of metals. In the next section, we'll examine the science behind this system.


''''''''

If you boost a gas to extremely high temperatures, you get plasma. The energy begins to break apart the gas molecules, and the atoms begin to split. Normal atoms are made up of protons and neutrons in the nucleus, surrounded by a cloud of electrons. In plasma, the electrons separate from the nucleus. Once the energy of heat releases the electrons from the atom, the electrons begin to move around quickly. The electrons are negatively charged, and they leave behind their positively charged nuclei. These positively charged nuclei are known as ions.
When the fast-moving electrons collide with other electrons and ions, they release vast amounts of energy. This energy is what gives plasma its unique status and unbelievable cutting power.

the only problem with that (courtesy of howthingswork) is that its shading from misleading to outright wrong (historically)

Atomic hydrogen welding - Wikipedia
Atomic Hydrogen Welding - Specialty Welds

A jet of hydrogen is disassociated as it passes through an electric arc. H2 > H + H = 422kJ. The temperature of the arc is in excess of 3700

Edited December 10, 2008 by Ice Czar