What Is The Best Way To Automatically Cut Aluminum?

Discussion in 'Metal Boat Building' started by John Stream, Feb 28, 2014.

  1. John Stream
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    John Stream Junior Member

    I have heard different things about these methods:

    1. water jet
    2. laser
    3. plasma
    4. router/cutter

    Are there any others?
    What are the trade-offs?
    Which is the cheapest?
    Which is the fastest?
    Are there any limitations?
    Where can you get it done?
    What computer file format is required?
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    One assumes you do not have your own cutter, thus you're subcontracting this out, yes?
    In which case it si which ever is the cheapest for you.

    The "best" is the water cutter. The edge is smooth and there is no HAZ from the heat. Beyond that, they are pretty much similar. So long as you can get the parts at the price you want and the edges are smooth not jagged. The only reason for getting jagged edges is because the speed of the arc/torch is too high, i.e. quicker/cheaper for the mill.
     
  3. John Stream
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    John Stream Junior Member

    Yes, I am subcontracting.
     
  4. Stumble
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    Stumble Senior Member

    There is a caviat however. The edge of a water jet cut is actually slightly beveled, which in very precise applications may be a problem. For boat building I can't envision it as an issue, but it could depend on the application.

    However there are newer machines that have tilting heads that can correct for this to some degree.
     
  5. alan white
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    alan white Senior Member

    Don't forget a table saw.
     
  6. Westfield 11
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    Westfield 11 Senior Member

    Or a jig saw..... Or a Skilsaw for that matter.
     
  7. SukiSolo
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    SukiSolo Senior Member

    Second a table (circular) saw, you need the correct blade for non ferrous metals/plastics. It has no set with an angle right, clearance tooth, angle left configuration. My 250mm (10") one has 80 teeth. Gives smooth cut on al and plastics, even 25mm thick acrylic kitchen work tops.....

    Routers are good too if 1/2" and set at 10,000 rpm. Very good for putting in holes of large diameter say 100mm+ as they are hard to punch (when sheet is thin enough) and the edge finish is much better. TCT or solid carbide blades only though.
     
  8. John Stream
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    John Stream Junior Member

    I am more interested in the robotic, automatic or CNC cutting methods right now.
     
  9. pdwiley
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    pdwiley Senior Member

    First, you need a design.

    Second, you need a CAD model of that design.

    Third, you need software that 'unpeels' the hull to make flat surfaces.

    Only after you get to this stage is your question WRT the best way of cutting it out even remotely worth considering.

    The answer is - it depends.

    I realise that this is a useless answer, but your question is akin to asking how many angels can dance on the head of a pin. Ask a better question.

    PDW
     
  10. John Stream
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    John Stream Junior Member

    pdwiley:

    Yes you are right. It is a useless answer.

    Assume I have performed your three steps.
     
  11. pdwiley
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    pdwiley Senior Member

    Now tell us which options are available to you within feasible freight distance, and the cost per linear metre of the cutting, whether you want the cut edges ready for welding or you are prepared to do some hand work on them.

    As you can see - the answer still depends....

    Personally I'd probably go for water jet cutting if it was available and affordable, followed by CNC routing but that's because those methods have the best chance of minimising the time spent on edge preparation before welding.

    FWIW I cut all my material with a plasma cutter and did it myself, but that was a steel boat. I'd probably do the same if I was building one from aluminium, for tricky shapes, and a circular saw for straight cuts or gentle curves. A CNC cut kit is a lovely idea but as many others have observed, get some weld induced distortion and you can spend a lot of time chasing your tail.

    PDW
     
  12. John Stream
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    John Stream Junior Member

    Thanks. Yes, I will need to balance the cost with the quality.

    I am looking at doing this project in a place that has very low labor costs. So some edge preparation would be fine.

    From what I have read, many say water cutting gives you the best quality. But one drawback there may be is that it leaves some very small grit on surfaces that can contaminate welds. It seems like this should not be a major problem with some edge cleaning.

    In view of this, perhaps the best option is router cutting.
     
  13. Ad Hoc
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    Ad Hoc Naval Architect

    Not if you prepare the metal properly for welding. You must remove the oxide layer prior to welding, but must be done in a short time period as the oxide layer grows quickly. In doing do, you also remove such grit and dirt etc. Thus if welded properly using correct procedures to prepare the joint, this is not an issue!
     
  14. pdwiley
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    pdwiley Senior Member

    Excellent point. I was advised by the designer of my boat, and one of my staff at the time who used to be a welder for Austal shipbuilders, not to build out of aluminium. The gist of the advice was, there was a lot more traps for the inexperienced than building in steel. I'm sure they were right.

    PDW
     

  15. Ad Hoc
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    Ad Hoc Naval Architect

    As also noted here:

    Aluminium should be treated like it is composite. In so much as, quality control is essential and taking short cuts simply lead to problems, sometimes significant ones, later. It also takes some time to gain enough experience to produce quality welds etc, unlike that of steel. Heck, even I did some half decent welds in steel on my first attempt!
     
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