Yeah sure, you might be a master of your craft. But, there’s more to something that you do than basic everyday experience. How rich are you on the lore of your tools? I wouldn’t really call someone a proper craftsman if the guy doesn’t know how his tools are functioning.
Not to worry, if you’ve been working with plasma cutters or are planning to in the near future, you’ve come to the right place. I’m going to give you the complete know-how of its functionality. Hey, I’ll even discuss the operation procedure.
I’ll also add in the types and categories. So, what are we waiting for right? Let’s get into how a plasma cutter works and how you should handle it with detail. I’m gonna begin with some basic info that’ll branch off to other advanced technical factors.
When dealing with plasma cutters, you need to know what’s plasma, right? I can’t really explain how plasma cutters do what they do if we’re not clear about what plasma is. Plasma is basically the fourth state of matter. Surprised? Wait, there’s more to it.
If you’re acquainted with physics 101, you’ll know that matter has three states: Solid, liquid, and gas. Matter can only change from one state to the other when energy comes to play. For example Heat.
Heat (The right level of it) can turn ice to its liquid state or should I rather say, water. After that, if we increase the temperature further, it’ll turn to gas. In this case, steam. Suppose the heat is increased to an extreme degree, it’ll get ionized and electrically conductive. That’s what we know as plasma.
So, what does a plasma cutter do? It just uses the electrically conductive gas to transfer energy from a power supply to a specific conductive material. This results in a much cleaner and way faster cutting process than oxyfuel. Pretty neat eh?
The next question might be, “What’s a plasma arc?” Well, a plasma arc begins when a gas like oxygen, nitrogen, argon, or even shop air is forced through a small nozzle orifice inside a torch. What happens then is, an electric arc generated from an external power supply is introduced to this high-pressured gas.
Thus, a plasma jet is formed. It’s actually intriguing that a plasma jet immediately reaches temperatures up to 40,000° F. This is absolutely great for piercing through the workpiece and blowing away the molten material.
Now that we’ve covered the rudimentary basics, let’s discuss a bit about the system components.
The Parts of the Whole
A plasma cutter isn’t just a single unit machine. A few essential components add up to make the cutter function flawlessly. Its performance and utility are highly dependent on the functionality of each component. Let’s talk about the parts that “Complete” a plasma cutter.
The Power Supply
As the name suggests, the power supply supplies the unit with power. But I assure you, there’s more to it. The plasma power supply converts single or three-phase AC line voltage into smooth and constant DC voltage that ranges from 200 to 400VDC.
It’s absolutely essential to maintain the DC voltage to maintain the plasma arc throughout the cut. Not only that, it regulated the current output that’s vital for the work process. Of course, this does depend on the material that’s being worked on and the thickness it has.
Arc Starting Console
The arc starting console, otherwise known as the ASC should be second in the list of functionalities. No spark no fire. Well, in this case, no arc no cutting. The ASC produces an AC voltage of approximately 5,000 VAC at 2 MHz.
What this does is, it produces a spark inside the plasma torch to create the plasma arc. Let’s just call it the initiator, shall we?
Let’s take this straight up. The basic functionality of the plasma torch is to ensure proper alignment and cooling of the consumables. What are the main consumables that cause the plasma arc here? The electrode, swirl ring, and the nozzle, right?
If there’s something more to add to it, an extra shielding cap may be used to further enhance the cut quality. All these parts are held together in turn by the inner and outer retaining caps. That’s pretty much all you need to know about this thing.
The Plasma Cutter Categories
As far as categorizing is concerned, I’d say, plasma cutters can be divided into two types. I’m gonna talk about how they operate in separate segments. However, let’s get down to the basic info for now.
Conventional Plasma Systems
These machines generally use shop air as plasma gas. The shape of the plasma arc created by these systems is defined by the orifice of the nozzle. If you’re guessing the basic amperage of this type of plasma arc, the answer is 12-20K amps per square inch.
Here’s some FYI, all handheld systems use conventional plasma. As it is still used in quite some mechanized applications where the parts “Tolerance Levels” are more forgiving, it’s still widely popular.
Precision plasma systems
When we’re talking about precision plasma systems, know that we’re talking about high current density. These types of cutters are crafted and engineered to produce the sharpest, high-quality cuts that are attainable with plasma.
This really isn’t as simple as the previous type that we talked about. The torch structure and consumable designs are far more complex. Not to mention, the additional pieces are included to further constrict and maintain the shape of the arc.
On the usual terms, a precision plasma arc is roughly 40-50L amps per square inch. Various gases, like oxygen high purity air, nitrogen, and a hydrogen/argon/nitrogen mixture are used as the plasma gas. Which means, optimum results on a wide range of conductive materials can be achieved.
The Operation Method
Now that we’ve covered the general concept, let’s jump into how these categories operate. Just like difference in their internal construction and efficiency, you can expect the utility to be contrastive as well.
While dealing with a typical handheld, like a Tomahawk Air Plasma, you’ll have to keep a few things into consideration. Inside the torch, the electrode and nozzle consumable parts are in contact with each other. That’s of course when the torch is in the off state.
However, when you put pressure on the trigger, the power supply generates a DC current that flows through this article. This basically flows through this connection and initiates the flow of plasma gas.
When the plasma gas builds up enough pressure, the electrode and nozzle are forced apart from each other. This in turn causes an electric spark and therefore, the air is converted into a plasma jet. As a result, the DC current flow switches from the electrode to the nozzle.
Then the results can be seen to the path between the electrode and workpiece. Just in case you’re wondering, the current and airflow goes on until the trigger is released.
Precision Plasma Operation
Now, this is a bit different from what we’ve discussed so far. Within a precision plasma torch, the electrode and nozzle don’t touch. In fact, these are isolated from each other by a swirling. This thing has small vent holes that transform the plasma gas into a swirling vortex.
Let’s talk about how it gets the cutting done step by step
The process starts with the issued start command to the power supply. It generates up to 400VDC of open-circuit voltage, inflating the pre-flow gas through a hose lead that’s set to the torch. This nozzle here is temporarily attached to the positive potential of the power supply via a pilot arc circuit.
Yes, as assumed, the electrode remains at the negative. So, what happens next is rather intriguing. A high-frequency spark gets generated from the Arc starting console. This creates a current path from the electrode to the nozzle. Thus, a pilot arc of plasma is created.
That’s not the end of it. When the pilot arc makes contact with the work piece that’s generally connected to the earth by the slats of the cutting table, the current path is shifted from the electrode to the work piece. Subsequently, the high frequency is turned off and the pilot arc circuit gets opened.
Then the power supply ramps up the DC current flow to the cutting amperage (Which is selected by the operator) and the pre-flow gas with the optimum plasma gas. This in turn ensures the material gets cut. I have to add, a secondary shielding gas is also often used that flows out of the nozzle.
This of course happens through the shield cap. The specific shape of the shield cap and the exact diameter of its orifice forces the shield gas to constrict the plasma arc even further. Resulting in a clean cut with even very low-level angles and smaller kerf.
The Final Slice
Apart from the methods I’ve discussed, some procedures require touching the torch tip to the work to create a spark. Let’s not forget the use of a high-frequency starting circuit. For example, a spark plug. However, none of these methods are compatible with CNC (automated) cutting.
With that being said, even if you didn’t know what a plasma cutter is and how it works, I think you have a pretty good idea by now. I bet that this information will not only help you with your craft but offer a better understanding of the functionality.
Even if there’s something wrong with your system, at least you have the basics to understand where the problem can lie. So, there’s no point in dragging this along. Happy crafting!