All about plasma cutting 2

Here is some good info:

I get these emails and phone calls every day about when to change consumables and how long they should last.

You should check your consumables before you start cutting and make sure they are good.

The electrode is the most important consumable as if its bad it can lead to torch damage faster then any other consumable.

The part of the electrode that makes the arc it called Hafnium, it is in the center of the electrode and will get 3200+ degrees when cutting. As it wears little parts fall out and you get a divot/hole in the end of the electrode. The Hafnium is only about 1/8" deep so you have to keep this in mind before making long cuts or cutting out something on a CNC table.

The time to change the electrode is when the divot/pit/hole in the end of the electrode get to be 1/16" deep or so.

There are a few other reasons to change the electrode also, even if it does not look bad. It is not firing dead center, this will cause poor cutting and excess tip/nozzle wear. Also a bad electrode will cause miss fires or pilot arc problems.

NOTE: YOU CAN NOT SAVE THE ELECTRODE BY SANDING, GRINDING, FILING OR WIRE WHEELING IT!!! SO GET THIS OUT OF YOUR HEAD!!!

This picture shows the Hafnium in the electrode and what happens to the electrode when it is all used up. I used a S45 electrode as a sample, but this will apply to almost all electrodes for all plasma cutters no matter what name you put on them.

Flame management from your plasma cutter to the metal being cut by hand or on a CNC table will make things very nice or very ugly. Now some people out there that has used a OA torch for a lot of years under stand flame management. They can take that knowledge and apply it to the plasma cutter. Now with people getting into plasma cutting by hand or on a CNC table need to learn flame management a little better.

The best way I can think of to help others understand this is to use a drill bit set standard or metric. To help understand why the plasma cutter uses different size cutting tips ( some call them nozzles, I will use the word tips ) and different air pressures settings to manage the cutting flame. Keep in mind that the plasma cutter cutting tips have a very small orifice hole that the air and flame comes out of. This also relates to the cut kerf and this should help you under stand. Now take these drill bit out and lay them on the table 1/16", 1/8", 3/16". 1/4", 5/16", 3/8", 7/16" and 1/2" or what they are in metric. Next we take the plasma cutting tip size and amp rating and match it with the drill bits 1/16"/20 amp, 1/8"/30 amp, 3/16"/40 amp, 1/4"/50 amp, 5/16"/60 amp, 3/8"/70 amp, 7/16"/80 amp and 1/2"/90 amp, etc. As you can see the orifice hole gets larger for that amp size cutting tip.

Now that you have an idea of orifice hole size to amp rating. You can also see how this affects cut kerf width. An example would be cutting a snow flake out of 18 gauge at 20 amp with an orifice hole size of 0.6mm or about .025 thousands of an inch this will give you a small kerf that will also give you more detail for the item being cut out. Go back to your drill bits and see how that cut would be affected with a 1.1mm/60 amp tip with a .045 thousands of an inch orifice hole and the wider kerf.. Even if you turned the plasma cutter down to 20 amps you still have the same .045" kerf width. Turning the plasma cutter amperage down with out using the right size cutting tip has no affect on the kerf width.

Here is were we get into air pressure settings for the amp rating and thickness of the metal being cut. Some manuals and cut charts give you air pressure setting for amperage needed for the thickness of metal being cut. Here is a chart I came up with that seems to work well if you do not have a cut chart.

This is what I have found to work with most plasma cutter nozzles/tips that most people have in their shops or garages. NOTE: Orifice hole size 1mm = .03937"

20 amp tip - 0.6mm/.025" - 15 to 20 amps - 50 to 55 psi

30 amp tip - 0.8mm/.030" - 21 to 30 amps - 55 to 60 psi

40 amp tip - 0.9mm/.035" - 31 to 40 amps - 60 to 70 psi

50 amp tip - 1.0mm/.040" - 41 to 50 amps - 65 to 75 psi

60 amp tip - 1.1mm/.044" - 51 to 60 amps - 65 to 75 psi

70 amp tip - 1.2mm/.047" - 61 to 70 amps - 75 to 80 psi

80 amp tip - 1.3mm/.051" - 71 to 80 amps - 75 to 80 psi

Or check with your owners manual for settings.

NOTE: Read your manual for the rated input air pressure and SCFM need to operate your plasma cutter. This in most cases is 90 to 120 psi and 5.5 or more SCFM at 90 psi to maintain the needed air flow to the plasma cutter. Then you set your output or cutting pressure to the chart. I recommend a 3/8" ID hose.

If we take the example from above and were cutting 18 gauge using 50 to 55 psi at the 20 amps thing work well. If you set the air pressure to 75 psi the flame is almost to the point of being blown out. The flame is very erratic and not stable. Now back to the example so you had a 60 amp tip, 50 to 55 psi of air and set at 20 amps. You have a flame that is flared out with no real definition or what you would call a hot spot. What is meant by a hot spot in a flame. A flame has different levels of heat. If you look closely you will see that it has different colors to it. The blue/white area is the hottest part that is were most of the cutting heat is for cutting. So you need to get that part of the flame closest to the metal for the fastest and cleanest cuts.

Now we get into cut height. Most manuals and charts use the standard cut height of .060" This works well for most things but at lower amps with less air pressure this may need to be lowered to .045" to get the hottest part of the flame on the metal. If you are using a 80 amp or more plasma cutter and cutting thick metal at max amps and air pressure you may need to raise the cut height to say .080" or more.

There are a lot of plasma cutters on the market. They all do a good job of cutting metal depending on their capabilities. If your plasma cutter has a torch that only has one size cutting tip then you do all your cutting at that orifice hole size no matter what amps your plasma cutter is set at. This is Ok as long as you under stand that it will not give you the finer cuts as a plasma cutter with a torch that has different size cutting tips do..To give you the finer cuts you may be looking for.

I hope this helps some people under stand more about cutting with a plasma cutter by hand or on a CNC table.

So how important is the swirl ring? Do you ever replace it? Does it wear out? Does it affect the cuts? Lets see if this can help answer some or all of these questions.

The swirl ring does 5 thing when installed.

#1 Its a spacer between the torch head and the cutting tip

#2 Its a air seal between the torch head and the cutting tip

#3 Its an insulator between the torch head and the cutting tip

#4 It has air holes to swirl the air around the electrode to keep it cool (note: the hafnium in the end of the electrode becomes 3500 to 4000 degrees when cutting)

#5 it has air holes to swirl the air that comes out of your cutting tip to help keep a plasma flame uniform. ( Note: over air pressure will deform the flame )

Now to me the answer to the questions are YES the swirl ring is very important and should not be over looked. It wears out the same as other consumables and should be replaced if you start having cutting issues.

Here are five swirl rings as you can see they are not the same. But they will all somewhat fit your torch. The first one on the left is for the Trafimet S45 torch. The second one is for the Tecmo PT/IPT 40/60 torch. The last three are Chinese cops and are all different. Using the right swirl ring for the torch you have will make it work at its best as well as give you better cuts.