CNC Plasma vs. Waterjet
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  1. #1
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    Default CNC Plasma vs. Waterjet

    Were starting to do some welding assembly here and we need to make some plates and flanges for bolt together applications, nothing more precise than a 16th or so. Thickness never over 1/2 and usually around 5/16 or so. We cut these plates from full 5X10 sheets. Trying to evaluate whether we want to go with plasma or waterjet. I worked at a place that had a waterjet and all i remember was that it was high maintenance and dealing with the abrasive was a real pain in the side. I haven't much experience with a CNC Plasma. Any thoughts, also what can I expect as far as price for a machine (either set-up) that can cut 1/2" and accept a full sheet of material? Sales reps get to be a pain in the side too!!!

    Thanks!
    bucknut

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    Go for the plasma. A friend has one in his shop making parts for suspensions etc for custom built cars,hot rods etc. His is only capable of 1/2 but most of his work is 1/4-3/8 Takes full sheets. Good finish 95% of the parts are ready to weld the rest a quick pass with a scraper type tool removes what little slag that might be there. Much faster than water jet and no abrasive waste to deal with. Now if you ever want to do material other than steel that changes things as a plasma cutter only really does steel well.

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    Plasma.

    Waterjet is great... But... It is a mess. Unless you have a dedicated building the spray will get everywhere.

    and its noisy,

    and it sucks power.

    and there are tons of consumables,

    and there is a heck of a lot of upkeep.

    CNC plasma will run forever just keep the tips changed.

    Ok, a little exaggeration. But you get the idea.

    But, if you are in an area with not very many places doing water jet you could probably keep the thing going 24hrs a day with outside work.

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    There are advantages and disadvantages to both plasma and water jets processes. Water jet can produce some very accurate parts on steel with no heat affected zone but at agonizingly slow speeds, while plasma can provide a bit less accuracy, but at extremely high speeds.

    Keep in mind that their are different classes of plasma....at Hypertherm we separate them into 3 distinct classes: Entry level air plasma, Conventional Oxygen Plasma, and High Definition Class Plasma.

    Also to keep in mind...the best plasma systems will not produce good cut quality if the machine that they are mounted on is not accurate. Necessary components of a good cnc plasma machine are: Height control system with the ability to accurately findd the surface of the plate before every pierce, accurate pierce height as well as accurate cut height control. The x and y axis of the machine should be able to maintain acceleration in the 40 miligee range...this allows the plasma torch to quickly get to its required speeds during cornering and fine features as well as to produce good holes. There are many choices in plasma as well as cnc machines that the plasma is mounted on....I'd be happy to help steer you in the right direction.

    Jim Colt Hypertherm

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    I think everyone has provided great info and advice thus far. If your material is limited to steel (Carbon or Stainless) plasma is probably the better choice.

    I highly agree with what Jim from Hypertherm said. A plasma system is only as good as the components its built with. If you find a deal that sounds too good to be true, it probably is. There are a lot of low end systems in the under $30k range that use cheap drives, cheap height control, cheap controls etc. These systems may provide acceptable cut quality in the short term, if you are lucky. The more you use them the more they will wear down and you will lose tolerance (you'll get ovals instead of holes) and cut quality, etc.

    There are a ton of used systems out there as well, but these require even more caution. If you look at a used system the first two things you want to look at are the CNC control and the plasma unit. Make sure both are still supported and you can get parts. You might find a late model used system that sound great, but all it takes is to have an obsolete control go down and you are out a quick $10k-15k for a replacement.

    Id say to get a pretty decent quality brand new machine you are probably in the $60k ballpark. To get into a production quality machine (AKS, MG, etc) you will step up to the $80k+ range pretty quickly.

    Where are you located? I know SOME sales reps are a pain in the side, but I can see if I might be able to recommend one that is easy to deal with!


    Good Luck!

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    Most of the waterjet cut parts that I have had other people supply me have had an angled kerf at the edge, as opposed to the laser cut parts having a roughly square edge. I assume plasma cut edges are square as well. I'm not sure if that factors into your evaluation, but something to consider.

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    There are plenty of waterjets that will give you a cut with a straight edge. (But with double the angled kerf at the other cut edge).

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    Thanks for all the great and more importantly, highly technical info! I'm an engineer by nature so I appreciate all the technical reasoning to the decision. I've worked with water jets before and they are definitely a pain in the neck. I think I'm going to stay away from used b/c it's hard to find one in decent shape and my banker would rather loan me money for new.

    Thanks Jim for your brief sales pitch, I may be in touch in a few weeks.

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    Not meant to be a sales pitch. There are many that just talk plasma as all on capability....when there are dramatic variations in capability from the low cost entry level plasma systems (air plasma) to the relatively high cost high definition class plasma. Comparing a small cnc cutting machine with an air plasma to a water jet machine is like comparing a Yugo to a Mercedes Benz.

    A high Definition class plasma mounted on a precision cnc machine may cost $100k, but it is the plasma that should be campared to water jets....which can be in the $250k range!

    If I needed tight precision and a non heat affected zone, and had no concrens with productivity...I would choose a water jet over a plasma. And I work for Hypertherm!

    Jim

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    plasma, water jet, and laser all have their niches depending on the application. We did some very thin gauge work with tight tolerances and some had no HAZ requirements plasma and laser wouldn't get there.

    now talking about welding applications usually water jet is over kill because you're gonna get a huge HAZ on any welded joint and the tolerances off laser and water are more than fine enough.

    in the production sheet metal shop we used a laser and CNC turret punch press for all our sheet metal forming. I came in after so I never saw the economic justification, but they met our needs well.

    That being said for one-off and prototype work I like water jets because you can cut a very wide range of materials and hit good tolerances. albeit slowly and with a much more repeating maintenance cycle.

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    What can I expect as far as price for a lower level system? I don't want to go with a downdraft b/c it seems like a lot of ducting and wasted heat, and I'd like something that can take a full 5 X 10 sheet.

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    I agree with Macona water jet. Plasma is some what limited in what you van cut. Now a good water jet opens up the possibliy of taking on other cutting jobs/materials to keep the machine running (making dough).

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    Default CNC Plasma

    Earlier this year I bought a 4x4 plasma table from Torchmate so we could do prototyping and short production runs of steel, stainless and aluminum parts up to 3/8" thick.
    I couldn't afford torch height control at the time so it has some trouble with thin material but overall I'm pleased with the capabilities of this machine. Entry cost was around $8K not including the plasma cutting machine, which we already had.
    The table came with an ok 2D cad program so we're designing our own pieces and cutting them on demand, with no lead time or quantity requirement for cost savings.
    So far this year I haven't ordered any laser or waterjet parts from our two suppliers, but we will occasionally need some precision parts that can't be produced with the cnc plasma table. I think we'll save enough $$ in two years to pay for the machine.

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    Default best 4x4 cnc plasma water table

    what is it gonna cost me to get a quality 4x4 or 5x5 complete setup? I want to buy the best I can afford. I am looking to cut up to 1/2" thick. I know you have to oversize plasma cutters because I have a miller 625 i think it is, it says it can do up to 3/4" or something and that is a joke. it struggles at 1/4".

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    my shop room mate in Sarasota set up a weterjet using a ShopBot cnc router. He later bought a plasma cutting head for it.

    He always uses the plasma head when he cuts sheet metal and wants to go fast and the precision isn't as important.

    I would estimate if you buy a used ShopBot that was used very little for wood then convert it on your own for plasma (by buying a plasma cutting head). You would probably be in the $8-$10 K range for a barely used ShopBot and a new plasma cutting head with the capacity of a 4 x 8 sheet. If you need the full 10 feet for parts that are almost the full 10 feet then you would need to find a longer ShopBot table or go to another model (most ShopBot's are 4 x 4 or 4 x 8 I think). if you just use the 4 x 10 sheets but cut smaller parts you just slide the sheet along and since it bends it will lay flat enough to start cutting parts and then cut off the end when you have finished with the top area and use the rest of the sheet. That's what my shop room mate does.

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    You can buy a 4 x 4 cnc plasma machine with a (Hypertherm Powermax45) with height control and software for around $12k. Or you could buy a 4 x 4 high end ballscrew cnc plasma with a Hyperther HPR130 High Definition class plasma, height control, software, etc....for about $100k.

    There is a wide range in capability and proce with plasma systems...from entry level machines with air plasma to high precision machines that are built to last for 30 years of 3 shift a day operation. Tolerances, cut quality, cut speeds, and operating cposts will be different as well.

    The low cost machines are great for small shops and shops that do not have extremely tight tolerance needs or high production rates.

    Jim Colt Hypertherm


    Quote Originally Posted by tfpent View Post
    what is it gonna cost me to get a quality 4x4 or 5x5 complete setup? I want to buy the best I can afford. I am looking to cut up to 1/2" thick. I know you have to oversize plasma cutters because I have a miller 625 i think it is, it says it can do up to 3/4" or something and that is a joke. it struggles at 1/4".


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