• Hi - We're having intermittent forum issues. Posts, alerts, and anything involving email like signing up or password changes are having problems but not for everyone or everywhere. Josh is working on it. No ETA right now. Thanks Josh - BTW this is a volunteer forum so SLA's are just best effort. EDIT -> I manually batch updated about 25 people stuck on the email notification. Try logging in now with your password. EDIT -> May 8/23. I updated another bunch of users stuck on email notifications. Try to login if you are stuck. If you really can't get in contact us on facebook or if you know a forum member get them to ask us.
  • [Ad-Free Experience]
    Register Today, Craft a Post, and Enjoy an No-Advertising Experience.
    Click Here to Register

First "lunchbox size" plasma cutter experience

JimGnitecki

Active Member
I just received and tried out one of the inexpensive "50-amp" lunchbox sized plasma cutters, and I have to say I am somehwat impressed, even though my initial "technique" is inexperienced and undeducated.

The unit i have is the BestArc Pilot Arc BTC500DP 50Amps Dual Voltage 110/220V unit. This is NOT one of the very cheapest units available on places like Amazon. It's a small step above those in terms of price, but what it offers in return for the extra $100 or so, if bought new off Amazon.ca, is a very favourable bump in both features and build quality.

After finding some ads on Facebook, I had previously done a fair bit of research on plasma cutters. I realize that for professional use, the name brand, well designed and well built "lunchbox sized" 120 / 240 volt units are in the $2500 & up range here in Canada. But most DIY guys like me can't afford to spend that much, especially for the limited number times we would use one, and the modest thicknesses most of us would cut compared to commercial businesses. So, yes, there IS a need for low priced plasma cutters, provided that they have REASONABLY decent feature sets and are sensibly reliable. You probably shouldn't expect the same robust reliability you get from a unit that has a 4-digit price, but then the cheap units at Amazon and other online places have prices that are literally 1/10th the cost of the pro units.

Having said that, I watched an impressive YouTube review of the BestArc Pilot Arc BTC500DP that was done at least a year ago (maybe longer -I could not find the original date) by Mike Festiva, who does a lot of very practical metal fab reviews targeting DIY guys and gals. He really liked its features and performance, AND by the time I saw the review, he had already added comments below it noting that he had had NO reliability issues in all the time he has owned it. That's a pretty good endorsement for a product that is only about $100 CDN above the cheapest units online!

Here are a couple of photos of the unit and its trappings: (NOTE! The grounding clamp shown is NOT the one that came with it. It came with a more typical sheet metal clamp. I replaced the grounding clamp with a high quality one at the same time as I replaced the clamp on my TIG welder)

Bestarc Plasma Cutter - overall - 1.jpeg

Bestarc Plasma Cutter - front panel - 1.jpeg

Notice the generally high quality of fit and finish and features:

- A REAL 240 volt power cable and 50 amp plug, plus a 240 to 120 plug converter (versus the inferior 120V cable and plug with 240 V adaptor that the cheapest unit come with)

- Automatically recognizes whether 120V or 240V, and self-adjusts to it

- Standard male 1/4" quick disconnect supply air fitting (versus a clamp-on setup that always leaks and is a pain to connect each time)

- NO air leakage (exterior and interior), which is a relief after reading some of the horror stories on the cheapest online units

- A water trap with pushbutton drain built into the air system, easily visible but well integrated into the unit's rear (not hanging out waiting to be hit and damaged). This is a real plus as water in the air supply is really hard on both the plasma cutting torch components AND the resulting cut quality

- Pilot air system with built-in replaceable standoff (You can also buy a version that lacks the pilot air, but the saving is apparently only about $25). This makes usage and resulting performance both MUCH easier

- Adjustable air pressure knob with display gauge

- Adjustable amperage knob with digital display

- Adjustable post airflow knob with digital display

- BIG DEAL: Requires only an air supply capable of feeding 35 to 75 psi air at 1.5 to 5 CFM. From the included recommendations table, my intended usage should require only about 50 psi and maybe 2.5 CFM, which is less than my compressor can provide. Note that the user manual says to keep the psi set under 75 psi maximum - apparently anything higher is never needed given this unit's maximum cutting capabilities, and too much air pressure can hurt cut quality. This unit is therefor an appropriate "fit" for my needs and my compressor capabilities.

I connected it all up to do just a quick check to make sure it works, and works with my compressor and my 240V 50 amp oultet (same one I use for my TIG welder). I also made sure it can be cutting at 30 amps (my largest anticipated amperage) while my compressor is ALSO running, since my garage workshop is fed by a 50 amp subpanel, which has to simultaneously run the 240V plasma cutter, the 120V compressor, and the extensive 120V LED lighting (bright as a laboratory!). Everything worked fine. :)

My test cuts were in 3/16" 5000 series Aluminum coupons that I currently have in the shop. The thickest and worst to cut via plasma cutter material that I anticipate cutting in my shop will likely be 1/4" aluminum, so this was a reasonable way to test basic functionality of the unit, AND its being fed by my smallish "pancake" compressor (3.7 SCFM at 40 psi and 2.6 SCFM at 90 psi) which was designed to feed an air nailgun.

Note that I have zero plasma cutting experience and therefor have NO idea of what combination of air pressure and amperage is appropriate for 3/16" 5000 series aluminum. I just wanted to make sure the unit worked and that my compressor could feed it.

Results: The unit DID work, and did cut, and my compressor seemed to be adequate.

The cuts themselves were reasonably fast and easy, and had the apparently desirable slight "backward tilt" appearance. But, there was a LOT of ragged deposition on the lower (only) surface edges of the cuts (nothing on the top surfaces of the cuts). I am assuming this is because I had an inappropriate combination of amperage and psi. But I could be wrong - could this be a result of cutting aluminum? Or, did I just apply way too much or way too little of either psi or amps?? (LOTS to learn apparently)

Bestarc Plasma Cutter - test cut with uneducated settings - 1.jpeg
In the photo above, the cut was made moving from right to left ( <--- ). Note the "rearward tilt" in the cut pattern. The dark spots are probably where I got the torch "skate" caught on surface imperfections in the coupon and lost the arc temporarily??


I was astonished at how CLEAN the actual process was in terms of smoke, sparks, and residual debris on the floor (I was cutting coupons clamped to a metal tabletop at about 30 inches above the floor). I saw no fireworks at all in my autotint welding helmet. After I took my helmet off, I found only clean aluminum fragments on the floor, and not that many. I had NOT cleaned the coupons in any way, but still found no ash or other evidence of impurities.

So, success so far in basic operation.

I obviously though need to learn a LOT about appropriate combinations of air psi and and amperage. Where do I look for that kind of specific information?

Jim G
 

David_R8

Scrapper of metal
Moderator
Premium Member
I have a Cut50 blowback start for my CNC plasma and the thing is amazing in steel. The proverbial hot knife through butter.
 

trevj

Well-Known Member
Premium Member
The cut quality that you see there on your cupon, is pretty much exactly why we were telling you to use a saw of some sort, rather than Plasma on Aluminum.
Personally, my choice would be to grab my battery powered Milwaukee 5-and-whatever inch circ saw, with a metal cutting blade.

Grab yourself some 1/8 inch or so steel sheet, and have a play session with it! Use a straightedge as a guide, and work on your speed control. Moving too slow just takes extra time, but moving too fast, can and will cause the torch to outrun the cut capacity and the plasma stream starts to wallow around like a drunken dancer. Thicker material will exasperate the issue. There, speed control is a really big factor.

Did your torch come with a drag shield, or just the wire cage? If no drag shield, measure out what the clearance, plus the distance from the edge of the ceramic cup is, and thin the edge of a straight guide so that you can ride the cup on top of the guide, and keep the tip clearance constant. A pretty simple table saw job. Once you know how far to offset the guide from your desired cut line, you can cut pretty accurately to dimensions wanted.

I have made good use of one of those magnetic circle cutting jigs too, though if the clearance is a convenient thickness, you can make a series of hole templates from whatever you have that falls to hand. They are useful not just for round holes, but you can pick and choose among them to put a radius between any two straight line runs. Sorta a giant size version of those drafting templates you used to see in various school supplies places.
 

JimGnitecki

Active Member
. . .
Personally, my choice would be to grab my battery powered Milwaukee 5-and-whatever inch circ saw, with a metal cutting blade.
. . .
Did your torch come with a drag shield, or just the wire cage? If no drag shield, measure out what the clearance, plus the distance from the edge of the ceramic cup is, and thin the edge of a straight guide so that you can ride the cup on top of the guide, and keep the tip clearance constant. A pretty simple table saw job. Once you know how far to offset the guide from your desired cut line, you can cut pretty accurately to dimensions wanted.

. . . you can make a series of hole templates from whatever you have that falls to hand. They are useful not just for round holes, but you can pick and choose among them to put a radius between any two straight line runs. Sorta a giant size version of those drafting templates you used to see in various school supplies places.
All great ideas! Thank-you!

I id try cutting some 1" square aluminum tubing with 1/16" wall thickness on my woodworking bandsaw, and it worked fine! That produced and left some fine aluminum particles on the bandsaw and its stand, but almost no noise compared to a circular saw! I will try cutting some of the 3/16" aluminum weld coupons next on the bandsaw.

I had seen several references to using templates, and in fact at least one DIYer made his out of masonite clipboards! Apparently they last quite a while before needing replacement, and can often be "re-used" by simply enlarging their radius by removing a thing circle of worn masonite! :)

No drag shield came with the plasma cutter,, but then I would not recognize a drag shield if I saw one! How does it make dragging the torch head over the workpiece easier than using the wire cage?

Jim G
 

JimGnitecki

Active Member
The cut quality that you see there on your cupon, is pretty much exactly why we were telling you to use a saw of some sort, rather than Plasma on Aluminum.
I thought I had screwed up in my uneducated choice of psi and amperage combination. Are you saying that the cut in the photo I showed is what I should expect for 3/16" thick 5000 series Aluminum??

Jim G
 

Tom Kitta

Ultra Member
I actually never used my plasma cutter on aluminum. It cuts so easy with a saw. I used to have Cut50 and recently upgraded to Cut60. Cheapest ones. I actually sold my old Cut50 for same price as new Cut60 so upgrade was free.

Cut50 worked fine for few years no issues.

Main problem is advertised cut maximum is rather ... optimistic. Sure adding feature such as post flow & PSI selector is very nice. I have no idea why anyone would buy pro unit new for hobby use or light commercial. Higher end (i.e. 100 more) units are quite good.
 

trevj

Well-Known Member
Premium Member
I thought I had screwed up in my uneducated choice of psi and amperage combination. Are you saying that the cut in the photo I showed is what I should expect for 3/16" thick 5000 series Aluminum??

Jim G
You may be able to tweak it a bit better than that, but, yeah, that is kinda what was meant when we were talking about the cuts being dirty on aluminum. Honestly, read the instructions, follow any charts that they may have included, and have a play session, and try changing things to see if different feed rate, amperage, or pressure, end up making things better or worse.

Though it does raise an interesting question, one that just popped to mind...

I wonder what feeding an inert gas through the plasma torch would do for a difference? I'd bet someone has tried it, probably either just grabbed a Nitrogen Bottle, or maybe an argon one...

Like I said before, grab some basic mild steel sheet or light plate stock, and play with it. Watch the cut as well as you can, and see what the feed rate changes do and how they affect the finished cut. Seen a fair few guys that thought they were wielding Luke Skywalker's light saber, and that they should be able to wave the torch at the material, then stand back and watch the parts slide apart. It's not that. Like any process, there is a bit of a learning curve to contend with, and a little bit of hand skills to build.
 

trevj

Well-Known Member
Premium Member
All great ideas! Thank-you!

I id try cutting some 1" square aluminum tubing with 1/16" wall thickness on my woodworking bandsaw, and it worked fine! That produced and left some fine aluminum particles on the bandsaw and its stand, but almost no noise compared to a circular saw! I will try cutting some of the 3/16" aluminum weld coupons next on the bandsaw.

I had seen several references to using templates, and in fact at least one DIYer made his out of masonite clipboards! Apparently they last quite a while before needing replacement, and can often be "re-used" by simply enlarging their radius by removing a thing circle of worn masonite! :)

No drag shield came with the plasma cutter,, but then I would not recognize a drag shield if I saw one! How does it make dragging the torch head over the workpiece easier than using the wire cage?

Jim G
A Drag Shield does almost exactly the job of the wire frame, but is easier to use against a template, as you can apply pressure against the template in all directions, without having to worry about the cage popping of, or going under, or over, your template. A combination of a spatter shield and guide.
It also prevents the cutter tip, from shorting against the work, if that is an issue with your torch/machine.
 

JimGnitecki

Active Member
I AM going to experiment with psi, amps, and feed rate. I have been Googling info on those parameters since my last posting, and am finding that the recommendations differ WIDELY from manufacturer to manufacturer.

When I say "widely" varying recommendations, I mean specifically the feed rate. The psi and amp recommendations for 3/16" material are at least close (20 to 30 amps @ 40-50 psi), but for the feed rates for 3/16" material, some specify aluminum versus steel but some don't, but the net recommendations for cut speed vary from 14 to 100 in/min !!

Hypertherm seems to have the best user manuals (which I expected given their great reputation), so I am going to determine which of their units is at least "similar" in basic attributes to mine: lunchbox sized inverter unit, dual 120 / 240 with similar 30 to 50 max amperage rating, etc. and see what THEY say.

Jim G
 

JimGnitecki

Active Member
I know you guys recommend using circular saws and bandsaws for cutting aluminum, and I agree - when the cuts are straight line cuts.

But my plans include lots of curves, and some of curves will be INTERNAL cuts (i.e. they would not start at an outside edge of material), and a bandsaw cannot do that because the blade is a continuous loop. A circular saw cannot handle curves and is WAY noisy and not great for safety. A jigsaw is a possibility but the reciprocating motion and resulting vibration makes it a little harder to control the smoothness of the cut and it too is pretty noisy.

Although a plasma cutter triggers the air compressor to go on, at least on longer cuts, it offers the potential for easy internal cuts via either drilling or piercing starts, and really good control of the cut. So I am not ready to accept a rough cut outcome without some in depth research and reasonable practice time and effort! :)

Jim G
 

Engmaxx

(Michael)
Don't hate me: sounds like you could use a router and a two flute spiral bit to do what you are aiming to do. Cheaper and likely cleaner than the plasma. Even if you take a couple of passes to do it, you might like the results better and easier cleanup. IMHO.

BTW, do you mind saying what you paid for the plasma cutter?
 

JimGnitecki

Active Member
Don't hate me: sounds like you could use a router and a two flute spiral bit to do what you are aiming to do. Cheaper and likely cleaner than the plasma. Even if you take a couple of passes to do it, you might like the results better and easier cleanup. IMHO.

BTW, do you mind saying what you paid for the plasma cutter?
The current Amazon.ca price for that unit is $349 with zero shipping cost if you have Amazon Prime.

The router idea is a reasonable one I had not thought of, and I do have 2 routers, one large heavy duty one and one smaller one! However, I find it relatively hard to do precision curved cuts with a router because the visibility is not ideal, AND when cutting metal, I like to keep my head FAR away from where those very high speed bonded-on blades are spinning against metal and producing lots of metallic debris, even though I wear face protection. I think plasma cutting would be safer.

Jim G
 

JimGnitecki

Active Member
trevj: I love the idea of exploring use of Argon as the air supply for plasma cutting. I already have an 80 cu ft Argon cylinder for my TIG welding training, and it has a quick disconnect to the TIG welder, so could easily be snapped onto the plasma cutter's QD.

The plasma cutter suppliers do not show pure Argon as having any obvious advantage over air, but I think they are maybe focused on productivity. Since air is about 20% oxygen, I suspect that it probably causes some of the roughness I saw on my primitive test cuts, by oxidzing the aluminum within the plasma. Argon is inert and MIGHT therefor make for a somewhat smoother cut.

Two other nice things about Argon for plasma cutting:

1. The Argon gas cylinder can provide any CFM I could conceivably want or need, unlike my pancake compressor.

2. No compressor noise!! That would make the netire cutting process much more relaxing :)

Rate of consumption and cost of that consumption would be something to analyze, since an 80 cubic foot Argon refill locally costs, with tax, about $90 as I recall (I have not yet needed to refill, but I recall the invoice for the purchase of the cylinder and gas showing a breakdown that puts the gas at about $90 when tax is added).

The cost per inch of cut would of course depend upon what cutting rates are actually achievable and practical and provide the best compromise between productivity and quality.

I am seeing online cutting rate claims that range fantastically, from 14 to 100 inches per minute!

IF the actual rate is say 14 inches per minute, and the CFM required is truly in the 2 to 5 CM range, then I need to do some math and see what a 3" cut in, for example, 3/16" aluminum, stainless steel, or steel would cost!

Jim G
 

JimGnitecki

Active Member
About using Argon instead of compressor air for plasma cutting:

Airflow can be measured with different units, the most common ones being CFM =cubic feet per minute, and CFH cubic feet per hour. These 2 units are of course radically different: For the same number, CFM is 60 times larger than CFH!

So, when we hear "20 CFH" used to describe gas flow for welding, an 80 cu ft cylinder is good for 80/20 = 4 hours = 240 minutes of actual laying down of bead. At typical TIG bead laying rates of 5 to 10 inches per minute, that's 1200 to 2400 inches of bead.

But when we hear "5 CFM" used to describe air flow for plasma cutting, that = 300 CFH! So, an 80 cu ft cylinder is good for only 80/300 = 0.27 hr = 16 minutes!

Plasma cutting rates apparently run anywhere from 14 to 100 inches / minute.

SO, an entire 80 cu ft cylinder of Argon would last only 224 to 1600 inches of cutting.

On thinner materials, a 2 to 3 CFM gas consumption rate would be realistic for plasma cutting. So, then we get 40 minutes (at 2 CFM) to 27 minutes (at 3 CFM) of cutting. So, on reasonably thin materials we'd get maybe 378 to 4000 inches of cutting from that gas cylinder.

At about $90 per 80 cu ft refill, the 378 inches of cutting would cost $0.023 to $0.24 per inch, depending on your specific mix of fast versus slow cutting and what psi your mix of cutting would require.

$.023 per inch is reasonable, but $0.24 per inch not so much, unless you only do that VERY occasionally in special situations.

To put that in perspective, if I want to cut my 3" x 6" weld coupons out of 3/16" thick 3" wide flat bar aluminum using a plasma cutter, it would cost between $0.069 and $0.72 per coupon. $0.069 is acceptable, but $0.72 is not.

So, the lack of RELIABLE and CONSISTENT inches per minute cutting rates data needs to be remedied before an intelligent decision can be made on where plasma cutting using an Argon gas cylinder is or is not a cost effective way of cutting.

I've got online research, and in-workshop testing, to do. :)

Jim G
 

phaxtris

(Ryan)
Premium Member
Premium Member
Normally anyone that uses an inert gas for plasma/laser uses a "pig", a cryo tank with liquid nitrogen, I don't know the numbers exactly but 1 average cryo tank has like 10x the volume of a 255 cylinder possibly more

So the usage is not much of a concern, just an operating cost
 

JimGnitecki

Active Member
Argon won't work on its own because of its low conductivity. It needs to be paired with another gas such as hydrogen.
What I have read is that Argon-Hydrogen is BETTER than pure Argon, but pure Argon works fine and is apparently much less costly.

Here's one source of info that says Argon alone works:


Also, adding hydrogen creates a potential safety (explosive) issue when cutting Aluminum, that gets even worse when a water table is used, either for the actual cutting, or just as a "trap" to catch, cool, and hold the hot debris. It can be done safely, but requires avoiding any metal in the tank that the products of cutting can get underneath to form bubbles. Apparently, plasma cutting Aluminum chemically promotes the undesirable potential outcome of producing Hydrogen gas which is explosive if not done just right.

Jim G
 
Last edited:

JimGnitecki

Active Member
Normally anyone that uses an inert gas for plasma/laser uses a "pig", a cryo tank with liquid nitrogen, I don't know the numbers exactly but 1 average cryo tank has like 10x the volume of a 255 cylinder possibly more

So the usage is not much of a concern, just an operating cost
Hmm. I don't think I'll be doing enough plasma cutting to justify a Nitrogen pig. I can see where it would be a HUGE advantage in a production shop.

Jim G
 

JimGnitecki

Active Member
Another website



says:

ARGON

For materials that are greater than ½ an inch thick, argon is good to use. Argon does not react with metals when cutting, which is why it is classified as an inert gas.

For aluminium cutting:

  • High-quality cut
  • Ideal for thick materials
For carbon steel cutting:

  • Not recommended
For stainless steel cutting:

  • Excellent cut quality
  • Ideal for thick materials
Since I will be cutting mostly aluminum and stainless steel, Argon sounds good to me for plsama cutting where appropriate, BUT not with mild steel apparently!

Jim G
 
Top