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Why combine waterjet and plasma on the same machine?

Compare Advantages

Take a quick look at the advantages and disadvantages of each cutting process. You’ll see an interesting pattern emerge – everywhere waterjet is weak, plasma is strong, and vice-versa.

Waterjet cutting on a waterjet-plasma combination machine - Click for larger viewThe Advantages of Waterjet

  • Very accurate - Waterjet’s biggest advantage is it’s precision. That is why most people want to buy a waterjet machine, to cut very accurate parts that require no secondary operations.
  • Eliminates need for secondary operations – it can produce a finished part that requires no machining or grinding afterwards.
  • No Heat Affected Zone – because waterjet is a mechanical sawing operation, it creates no change to the metallurgy of the base metal.
  • Cuts almost any type of material – flexibility to cut many different metallic and not metallic parts.
  • Cuts extremely thick material – Q: How thick can it cut? A: How long can you wait?
  • Variable edge quality is easily selected – varying the speed affects the edge quality wit very predictable results.

Disadvantages of Waterjet

  • Slow cutting speeds – when compared to other cutting processes on metal plate, waterjet is very slow.
  • High cost per foot of cut – the slow speed combined with the cost of the garnet abrasive makes waterjet a very expensive cutting process.

Plasma cutting on a waterjet-plasma combination machine - Click for larger viewThe Advantages of Plasm

  • High cutting speeds on a variety of thicknesses – when cutting steel or aluminum plate, plasma is the fastest cutting process (until you get down to the very thin plate, where laser can be faster).
  • Smooth edge quality – plasma cut quality is usually sufficient for subsequent welded assemblies, or in preparation for machining a part.
  • Can cut underwater – plasma can cut either above a water table, or actual cut a submerged plate, reducing noise, glare, and smoke.
  • Low operating cost – plasma costs roughly half of the hourly cost of waterjet when cutting the same material.

Disadvantages of Plasma

  • Less precise – especially on really small holes and fine contours. The large kerf width of plasma will not allow it to get into small corners, and arc lag can cause significant taper.
  • Can only cut conductive metals – and really only mild steel, stainless steel, and aluminum are practical for plasma cutting with good edge quality.
 Result of Combining Waterjet and Plasma
A typical steel part cut with a waterjet-plasma combination machine: precision ID cut with waterjet, OD cut with plasma - Click for larger view

One of the things you might notice after looking at the above list is that waterjet and plasma fit together very nicely, each processes advantages nicely cancelling the other’s disadvantage. So these two cutting processes fit nicely together, giving a machine a very wide range of capabilities for processing almost any material.

But the biggest reason for the waterjet-plasma combination is the cost to produce parts. Many parts produced from steel plate require high precision in some areas, but not on the entire part. If you purchase a waterjet cutting machine, you have to cut the entire part using waterjet. If your competitor down the street buys a waterjet-plasma combo, he could produce the same part for less than half the cost! By combining the speed of plasma with the accuracy of waterjet, you can dramatically reduce the time and cost to cut most typical parts for metal fabrication.  


Posted in Cutting Systems , Tagged with Plasma, Waterjet