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  1. #1
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    Default Plasma cutting capacity or waterjet cutting connections?

    Simonl and I are looking to cut up a big plate of 3/4" or 20mm (will know for sure on Monday) steel.
    Does anyone on this forum in Melbourne or within 200km of Bendigo have either the capacity to cut steel this thick or know someone who will give us 'mates rates'? I'm estimating the total cutting distance is around 12 to 16m.
    The sheet is about 1800x1500mm big.
    Anyone?
    Cheers, Joe
    again completely retired - more time to contemplate projects and spend more shed time....

  2. #2
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    I can't help personally Joe, but looking at some spec sheets a plasma cutter to do that will need to be 70A or more. Probably not common in most sheds. Can you hire one? Might be the easiest option if no one has one available. Oxy cutting may be another way if either you or Simon have the skills to drive one.
    (I'm assuming you just want to rough cut and not do intricate CNC stuff)

    Michael

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    I'd second oxy cutting unless the job really needs the fine cut of a plasma cutter. Oxy will do 20mm effortlessly.

    Problem being, if you want to follow a template, it's a piece of with plasma but you have to centre punch the cut line then rub chalk into it using oxy, and the kerf will be wider and rougher.

    I almost never use oxy cutting these days except for thick stuff. I want a 100A plasma cutter.

    PDW

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    Joe, I'll ring Kennards, Coates etc on Monday. Failing that I better sharpen my 8mm drill bit! 12 - 16M, that's quite a few holes, even for me!

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  5. #5
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    I have a question for you plasma guys out there:

    If you have a plasma cutter that is rated to 16mm plate, what happens if you try to cut say 17 or 18mm plate? Will it just create a big dangerous sparking mess? Can you cut from both sides to get through?

    I want a plasma cutter to… along with lots of other stuff.

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  6. #6
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    Quote Originally Posted by simonl View Post
    I have a question for you plasma guys out there:

    If you have a plasma cutter that is rated to 16mm plate, what happens if you try to cut say 17 or 18mm plate? Will it just create a big dangerous sparking mess? Can you cut from both sides to get through?

    I want a plasma cutter to… along with lots of other stuff.

    Simon
    Plasma cutters generally have two ratings, a quality cut and a severance cut rating. For example, a plasma cutter may have a rating for a quality cut of say 12mm, but its severance rating will be 16mm meaning it will hack off a piece of 16mm, but the plasma demons of canyoning and a tapered cut will really show their presence.
    Beware that a 70A plasma cutter will be a 3 phase unit and you still need to run your workshop compressor as well, so some peoples shed power supply may be overtaxed.
    Honestly, I believe that plasma is at its best when tackling the thinner metals, say sub 5mm and obviously cutting materials other than steel.
    Given the choice between a 100A plasma and oxy lpg or oxy acetylene for cutting 20mm plate, the plasma would be left in the corner every time unless the steel was very clean.
    What are you actually cutting out? Profiles or just stripping the plate?
    Plasma cutters are temperamental and demand clean dry air. Moisture or oil in the air will see consumable life drop from say 200M cutting to as little as 100mm cutting length.
    For what you are suggesting, oxy lpg sounds like it may be the weapon of choice and it will also allow you to heat and bend in your workshop. Setup costs will be well under what a half decent plasma would cost and running costs may not be as far apart as you may think either.

  7. #7
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    I think oxy is your best option.

    I have a little plasma cutter, a Tokentools Pak-50 that's supposed to be rated for 20mm severance and 16mm cut, but there's no way I'd even consider doing a 3/4" deep cut.. I'd think it's more like 1/2" capacity.

    If you had a 100A plasma then that would be worth a try..

    There might be someone in the CNC forum who has a big CNC plasma?

    Ray

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    Quote Originally Posted by simonl View Post
    I have a question for you plasma guys out there:

    If you have a plasma cutter that is rated to 16mm plate, what happens if you try to cut say 17 or 18mm plate? Will it just create a big dangerous sparking mess? Can you cut from both sides to get through?
    It'll crater out and not cut through, or cut through in some places and not others. The cut will be a big mess.

    Yes you could do another cut from the other side but the cut will still be utter crap and consumable (tip) life is also crap.

    I can do a 'reasonable' severance cut with my Chinese 50A cutter on 12mm A36 plate but only 10mm 316 plate and really 8mm in 316 is what I consider reasonable. OTOH it cuts 6mm and under beautifully in all materials.

    I disagree about the utility of a big plasma cutter vis a vis oxy-fuel cutting. The plasma is faster, cleaner, less heat, less distortion and can use templates made from 3mm ply or MDF so making relatively complex cuts quite simple. If I had a 100A plasma cutter I suspect I'd never use my oxy cutting rig at all except for 30mm and above plate - and I need to cut stuff that thick once in a blue moon so I'd borrow, rent or farm the job out.

    No rental on a plasma cutter. Bottle rental adds up fast.

    But - I do have 3 phase power and plenty of it, so running a big plasma cutter and a decent compressor isn't an issue.

    BOC has a 100A unit on eBay for $1600. Tempting.

    PDW

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    Thanks for the info and explanation guys. I'm tempted to look at LPG oxy. There are kits on ebay for about $300. I assume all you need after that is the oxy cylinder and an BBQ bottle?

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

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    Quote Originally Posted by PDW View Post
    It'll crater out and not cut through, or cut through in some places and not others. The cut will be a big mess.

    Yes you could do another cut from the other side but the cut will still be utter crap and consumable (tip) life is also crap.

    I can do a 'reasonable' severance cut with my Chinese 50A cutter on 12mm A36 plate but only 10mm 316 plate and really 8mm in 316 is what I consider reasonable. OTOH it cuts 6mm and under beautifully in all materials.

    I disagree about the utility of a big plasma cutter vis a vis oxy-fuel cutting. The plasma is faster, cleaner, less heat, less distortion and can use templates made from 3mm ply or MDF so making relatively complex cuts quite simple. If I had a 100A plasma cutter I suspect I'd never use my oxy cutting rig at all except for 30mm and above plate - and I need to cut stuff that thick once in a blue moon so I'd borrow, rent or farm the job out.

    No rental on a plasma cutter. Bottle rental adds up fast.

    But - I do have 3 phase power and plenty of it, so running a big plasma cutter and a decent compressor isn't an issue.

    BOC has a 100A unit on eBay for $1600. Tempting.

    PDW
    Plasma produces an inferior cut quality on the thicker plates. Oxy fuel gas cutting produces a cut that is effectively parallel, plasma produces a tapered cut. Lincoln Electric state the point where plasma is slower than oxy fuel as being 25mm. My experience of it, (100A Lincoln plasma), would rate it at closer to 16mm. The best thing with oxy fuel is it works first time, every time. I have yet to see a plasma approach the same degree of reliability and repeatability, particularly when the plate is less than pristine. Distortion really only becomes an issue sub 4mm in my experience.
    They are brilliant for thinner work and metals other than carbon steel. Our 100A plasma at work spent the majority of its time in the corner while the oxy was used on a daily basis. Oxy fuel gas can do far more than just cut into the bargain.
    I will agree though that the ability to use plywood templates is a handy feature.
    Just thinking about it, I was mentally going through my mind the engineering companys that I frequent and their utilisation of plasma cutters. It seems to me that plasma cutters have not made the inroads into industry that mig and tig welders have for example. They are out there, but I see the oxy fuel gas far more in general usage.

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    Quote Originally Posted by simonl View Post
    Thanks for the info and explanation guys. I'm tempted to look at LPG oxy. There are kits on ebay for about $300. I assume all you need after that is the oxy cylinder and an BBQ bottle? Simon
    Dead right SimonL. I made the swap from oxy acetylene about 6 months ago and I haven't regretted it once. You do lose the ability to fusion weld but can still braze. If heating is your game, oxy lpg absolutely kills acetylene as far as the bazooka sized superheating barrels that it can run. Think of an FA/18 in full afterburn and you will get the idea.Oxy acetylene may have a small advantage sub 5mm when cutting, but nothing you will really notice. Replacement tips are around 30% more expensive, but these aren't what you would term a high use item if looked after reasonably well.The best thing is that a 9kg lpg cylinder, $38 swap, is equivalent to a "G" size acetylene, a $300 refill.Multiple uses too, cutting, heating, bending, brazing, pre heating before welding, melting. The list goes on.

  12. #12
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    Quote Originally Posted by Karl Robbers View Post
    Dead right SimonL. I made the swap from oxy acetylene about 6 months ago and I haven't regretted it once. You do lose the ability to fusion weld but can still braze. If heating is your game, oxy lpg absolutely kills acetylene as far as the bazooka sized superheating barrels that it can run. Think of an FA/18 in full afterburn and you will get the idea.Oxy acetylene may have a small advantage sub 5mm when cutting, but nothing you will really notice. Replacement tips are around 30% more expensive, but these aren't what you would term a high use item if looked after reasonably well.The best thing is that a 9kg lpg cylinder, $38 swap, is equivalent to a "G" size acetylene, a $300 refill.Multiple uses too, cutting, heating, bending, brazing, pre heating before welding, melting. The list goes on.
    Hi,
    I'd be real interested to know what kit you have etc. I was thinking about one a while ago but couldn't get much info locally. I handed my oxy acet bottles back about 12 months ago now, rent was just too much. My main uses are brazing and cutting thick plate.

    Cheers,
    Ewan
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  13. #13
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    Quote Originally Posted by Karl Robbers View Post
    Dead right SimonL. I made the swap from oxy acetylene about 6 months ago and I haven't regretted it once. You do lose the ability to fusion weld but can still braze. If heating is your game, oxy lpg absolutely kills acetylene as far as the bazooka sized superheating barrels that it can run. Think of an FA/18 in full afterburn and you will get the idea.Oxy acetylene may have a small advantage sub 5mm when cutting, but nothing you will really notice. Replacement tips are around 30% more expensive, but these aren't what you would term a high use item if looked after reasonably well.The best thing is that a 9kg lpg cylinder, $38 swap, is equivalent to a "G" size acetylene, a $300 refill.Multiple uses too, cutting, heating, bending, brazing, pre heating before welding, melting. The list goes on.
    Agree. I use oxy-LPG for thick cutting as well. Works fine. I found it a bit of a learning curve at the start as the heat input isn't as great as using acetylene so preheat takes longer. Other than that, no dramas and I've cut up to 40mm plate.

    Funnily enough I've found that using a 1mm disk in an angle grinder makes a great scribe line for easy viewing when cutting and the slight edge comes up to cutting temp fast too.

    As I also have a LPG kitchen stove and a few other things, I always have a couple spare bottles so running out of LPG simply isn't something to worry about, and the swap & go place is 10 minutes away anyway.

    I bought a new kit off of West Aus Welders via ebay. Then I found all the missing bits for my old Comet 3 set so I have 2! Got some spare oxy regulators and I think I've got a spare new LPG regulator that I don't really need.

    PDW

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    Thanks everybody for your input.
    I'll investigate what options we have locally. I'm on good terms with one of the construction firms here in town and will get a price from them for oxy cutting the plate - before I go and buy it....
    I'll aslo call the firm Simonl suggested and one of the waterjet cutting firms in Melbourne. Anyone have any ideas on price for water cutting?
    Yes, they are just straingt lines.
    Cheers, Joe
    again completely retired - more time to contemplate projects and spend more shed time....

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    Quote Originally Posted by Ueee View Post
    Hi,
    I'd be real interested to know what kit you have etc. I was thinking about one a while ago but couldn't get much info locally. I handed my oxy acet bottles back about 12 months ago now, rent was just too much. My main uses are brazing and cutting thick plate.

    Cheers,
    Ewan
    The kit I have is my old comet 3 Oxy Acetytlene gear with a Tesuco brand LPG regulator. Tips are type 44, once again made by Tesuco, (Tesuco are a South African manufacturer and their prices are around 50-60% of the comparable Cigweld gear). I haven't really geared up in the brazing side of things at this point due to no use for it at present, but type 544 blowpipes are available to suit the standard comet mixer.
    When running the superheating burners, you need a 13mm mixer, suitable barrel and of course the burner in your chosen size to screw on the end. Technically, you are meant to replace your hoses as the petroleum can cause your acetylene hoses to break down over an extended period. The advice I was given was that if your hoses were in decent condition to just run them as external damage will usually kill your hoses before the internal breakdown will, so that is what I have done.
    Early days yet, but at this point, I would say that the 9kg LPG/G size oxygen seem well matched.
    One final point. You use dufferent tip cleaners for oxy LPG due to the slotted design of the preheat gas holes.
    It truly amazes me that more engineering companies have not adopted Oxy LPG, particularly with the price of Acetylene as it is.

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