Considering a plasma cutter for a project

CrossFire ® General Discussion
21

The edge quality sucks, but part of that is the cheapo Plasma cutter I have. @TinWhisperer and @Bigdaddy2166 are magicians with Aluminum.

Still, it works for everything I need and my crappy PC handles sheet steel very nicely. However, as others have mentioned, a Plasma cut hardens steel and secondary cuts are not practical. I highly recommend the center punch method for marking holes less than 1/4". In the photo above, the slot is for an M5 bolt used to tension adjust a pulley. It works fine for that, but holes are sloppy.

I can cut stainless sheet as well, but others will advise more exotic gasses for that.

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22

I would also add that if you’re going to be using it very rarely, will it still be worth the investment for you? It’s hard to quantify the sitting 95 percent of the time statement. Do you already have a large compressor and air cleaning and drying setup? Add on at least 1,500 to 2000 for your air setup if you’re starting from scratch.

With regard to a rough cut pass, that’s a hard no. If you need to take another .02 off a part it’s back to the drawing board. 1. You’d never index the part just right to do that accurately on the table and 2 the plasma arc won’t respond to skimming the edge like that. It would ruin your nozzle and have a crap edge.

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23

Good point about the lack of use. On the counterweight side of that seeing what outsourcing this kind of work cost. I am sure the cost can be recovered.

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This is 12 gauge mild steel right off the table. I obviously did not clean it up for the photo because I wanted to show how cylindrical the holes are when slowing down the cut for better holes. This will result in more dross but it removes easily if your other settings are on target. The large hole has a diameter of 0.908 inches and the small holes are 0.188 inches (or at least that was the designed dimension).

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One hit with the fireball tool and this dross was gone. No grinding necessary.

You can see there is minimal to no dross on the other cuts because the torch was moving at the optimal speed for the amperage and thickness of metal.

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25

I agree with you. If the OP is only going to use this a few times a year then they need to just keep sending the work out to be done.

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26

Thanks for all advise and photos. The aluminum oils better than I had expected. What is the cheapest simplest or to set up for initial use with no concern for running all day? You need moisture filter obviously but what else bother than sustained pressure for the cut.

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:rofl: :rofl: :rofl: :rofl: :rofl: You will soon find out

On the other hand, you could do a search on this forum for “Dry Air”. You may find a ‘few’ posts on the subject.

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Air quality equipment is as important as the plasma cutter you choose.

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29

You need a large compressor unless you want to pause and wait for a small one to fill up. I’m talking 60 gallon 5 hp.

At a bare minimum, you need some sort of method to cool the air, this can be a refrigerated dryer, copper manifold ect… then you need an oil/water separator, and dessicant and a motorguard m60 filter. Mechanized cutting requires very clean dry air or you will trash your consumables and sacrifice cut quality. Air is crucial.

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30

I really enjoy using my pro table. Looking forward to retirement when I can really get into it.

“Sitting 95% of the time”
Not sure what else you are doing. If you or someone else have time for fun, I’d say yeah baby.

I started from scratch. Upgrade service panel/add two 240v outlets, 60 gal (should have got the 80 gal) 2 stage compressor, air lines & filters, Hypertherm 45xp (get the sync) cnc port & machine torch, and the pro table, gaming computer for cad, dedicated hp laptop to run table, yada, yada, yada…

Assuming you only need the table and cutter is aprox. 7k min

You want to make that investment and the real estate (footprint) pay. An expensive place to store your stuff. It takes time and effort to dial in good cuts.

Point is, as a business, if you don’t have repeated work, I suggest outsoursing waterjet or laser over sitting 95%

With plasma, I agree pecking a starter hole over drilling the recast. The recast is hard on drills.

My tuppence (I reckon)

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31

Thanks everyone for all the great info! Seems like it could be great addition for some projects. Still looking into costs for low end air and accessories. I manufacture a product, steel and larger plate aluminum are one off custom projects and over the years I’ve spent a lot on sending out parts to waterjet and laser that I could make a plasma work with some effort, like forgetting about tapping, it is too easy to add threaded parts so it’s not as big a concern. Dropping in a custom lasered delrin nut / weldnut / tnut / barrel nut is far faster than tapping anyway so nevermind the idea of drilling and tapping.

I am assuming the 4x3 machine does not have any air pressure sensor states from the plasma cutter so if you run out of air the CNC just keeps going but the plasma shuts off on low pressure. Worst causes you can make a new file to continue on the last part where air ran out skipping previous parts?

32

If you have THC (torch height control) on it will Sense the voltage drop and the table stops as well if the torch stops.

If you have a 60 gallon, 11.5 CFM @ 90 psi compressor you are not likely to have this problem. It is the 30 gallon, and certainly the 10 gallon, setups that just would not be efficient to run for any length of time. Sure, you could build in pauses (called “dwell” in Fusion) but that would get ‘old’ really quick.

You can continue a “stopped” program from a line/“loop”. Most times it works out just fine.

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33

Thanks for that great info. That is making me wonder about my electrical, I have only one 30A breaker in the shop. For small one off projects here and there(not a machine shop doing outside projects) I would first try to run the air till full, kill the air then run the machine. Manually or otherwise( as discussed worst case air runs out) just pause the machine, fill the air and keep going. This way I can use the 30A AC already installed and hopefully that amperage will let me run 1/4 or less stuff.

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It will be a bit rough. Perhaps in that case, I might be inclined to set up your compressor elsewhere or use an alternative power supply. I believe @Sticks users multiple power sources for his setup in his motorhome…“trailer”… I meant trailer :crazy_face:

So consider a generator with 30A 220 output for the compressor.

You could also put in an additional storage tank for air and/or the pauses in the gcode.

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35

My PC breaker is 30A and I’ve cut up to 3/16 steel and 1/4 aluminum with my Lotos LTP5500D (55A) without any problems. The cutting voltage stays below 110V so that’s only 5.5KW. Assuming 80% efficiency and 230V supply, that comes ‘close’ to 30A at the breaker…

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36

I really can’t add to what the members here have posted. I can say however that the cut sample pictures that you see - you are not going to get that quality even after the 10th time you cut something, you will not get consistent results, not at first, not at the 10th time. These guys have years of experience and hundreds if not thousands of hours on the plasma tables.

Round holes are another elusive thing. Don’t expect them to be perfect circles every time.

There is no such thing as a “Square Edge” Everything leaves a taper, it’s a matter of how much, and flame cutting is the worst. Compound that with the torch not being 100% perpendicular to your work, cut height, consumable life…

I am not trying to discourage you, just making sure your expectations are in line with the reality of what you are wanting to do.

Additional thoughts…

You should get a quote to upgrade your panel or put in a sub panel in the garage with 220v service. A compressor big enough will need to be on 220.

The flipside as @ChelanJim said, get a generator. There is another $2k easy for a 5kw, plus running costs (gas adds up) and unless you get a “quiet” generator, the noise will wear on you and your neighbors.

All in, to do it right the first time - figure $10k. Most of the time with DIY and “I’ll just build one”, it ends up costing as much or more than just buying a thing outright.

Crossfire - Standard unit, Z height/thc, water table (especially if in a garage or neighborhood driveway) 2500
11 cfm air compressor 1200
5kw genset - 2000
Air Dryer - 600
Plasma - 1000
Not bad so far…

Accessories (Grinder, consumables for grinder and plasma, air lines, air handling and conditioning, fittings, wiring, computer This is a messy hobby/endeavor. You do not want to use your good home laptop or PC for this, stand for said computer, mop, plasma cutting fluid, water containment and transfer, material, material handling and storage, and more crap that will come up in the first month) $2k - $3K. It’s the nickel and dime crap that gets ugly quick.

Yes, yes yes. A lot of things you can DIY and do on the cheap - IF you do a lot of DIY and have other skills that will contribute to your endeavors.

Attending YouTube University and taking a swing at, lets say making a cooling manifold out of copper - lot of money there, then the stuff you need to cut and sweat it together, fixing leaks if you have never done it, re doing it, buying more copper, modifying it, your time, trips back and forth to the hardware store…Just buy an air dryer rated for the CFM your plasma will need…and the filters, and the drains,

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37

Actually the pictures I shared was the very last of a 500 part run. There’s was around 3 plus hours of actual cutting before that part was cut. I do believe it is possible to get consistent cuts over many parts. You cut much thicker steel so yes cut quality goes away faster.

Yes you are very right you can’t expect gold every cut that is also why I said people only share pictures of the best of the best

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38

My reference was to not expect those results right out of the gate. After time and experience, then yes, that quality can be expected.

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39

My bad man! I read it as after 10 parts… Nevermind. Keep burning metal and pay no attention to me.:woozy_face:

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40

I have read everyone’s post and there is lots and lots of info I agree with. I will add this

Remember everyone here has been doing this for quite a long time. They did not get here over night.

When I see your post about air compressors, and your panel I see you trying to get by with the bare minimum. Most of these guys have spent a fair amount of money on there set up’s.

Why don’t you get with some of these guys and see if they will cut you some sample parts? Than at least you can see what is possible, and keep in mind yours wont look like this at the start.

One thing I would keep in mind, is you have had parts laser cut and water jetted and have seen that quality. Now you are looking at the worst of the 3 processes that maybe hard to do.

Most people that have had a Porsche don’t want to switch to a Hyundai.

Good luck

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