TECHNOLOGY

How does the power of water prevail?

 

The destructive power of water in the context of erosion has been known for millions of years. We know many examples of the impact of this force even in our immediate environment. The canyons, river valleys that delight in their sight today are, in fact, the products of the immense power of water.

The exploitation of the aforementioned properties of the jet of water goes back several decades. In the 1930s, American and Soviet engineers took first steps in the direction of using high-pressure water jets for mining stone and brown coal. Since then, the technology has been constantly evolving. This process was significantly boosted by the involvement of the American aviation industry through which it was made possible to incorporate materials that had never been used before. In addition to previous cutting procedures, waterjet cutting allowed for the machining of new types of technical materials, which was not previously possible.

In the late 1960s, American aircraft factories used this technology to cut fibre-reinforced, cellular, and sandwich materials. These substances, often subjected to significant mechanical interventions, are particularly sensitive to high-temperatures. Traditional flame cutting, sawing, shear procedures can significantly damage the structure of these materials.

What are the benefits of waterjet cutting over other procedures?

The greatest advantage of waterjet cutting over other technologies is that it is a cold cutting process, suitable for cutting virtually all materials.

Other procedures fall short in certain areas.

Heat intake procedures for example can involve combustion and melting along the cutting surface.

During laser and plasma cutting, tensions can form in the material, leading to hairline cracks, damage to the material connection in alloys as well as the creation of toxic gasses that need to be neutralised.

In contrast, when cutting with waterjet, there is no gas, no surface strain, no conicity and no deformation caused by heat. It is the only procedure that works for hard plastics and plastic-coated metals as it does not damage the surface. It is also a number one choice when cutting thicker and tougher metals such as titanium, acid-resistant steel, copper and aluminium, as tool wear during other procedures represents a significant cost.

 

What can you expect of cutting procedures?

Demand for industrial cutting has increased dramatically in recent years. Better productivity and higher cutting speeds are the focal point of today’s development as well as accuracy when dealing with complex forms and an increasingly good surface quality.

What solutions does waterjet cutting provide?

  • high precision parts
  • cut edges are not damaged
  • a high-quality surface that does not require further machining
  • the normal homogeneous cutting surface is easier for any further machining
  • cutting any complex shape
  • the small size changes and the unique patterns can be handled flexibly
  • the machine can start cutting anywhere
  • improved material utilization thanks to minimal cutting gap

 

How can water cut?

From a technological point of view, the materials to be cut are divided into two groups: one of which is cut with clean water, and another that uses abrasive material (granite sand) mixed into the water stream. The difference between the two technologies is clearly visible in the two schematics below

 


  • Clean water cutting

The high pressure (3600 bar) can cut, including rubber, 3-4 mm foamed PVC, styrofoam, linoleum, foam materials. The cutting gap is 0.1-0.2 mm.

  • Abrasive cutting

The energy of the water, along with the abrasive effect of the sand leads to the to the material being cut. In this case, the cutting gap is between 0.8 and 1 mm


 

What factors affect the cutting surface?

There are two factors that largely determine the use of technology and its area of applicability. One is the formation of conicality along the thickness and the other is undercuts from radiation deflection.

  • conicity problem: the diameter of the radius leaving the nozzle is 0,8 mm, which determines the width of the cutting gap on the material to be cut. However, as we move lower in the material thickness, the beam loses its strength, so the water on the back can only cut a gap of 0.4-0.5 mm. By reducing the speed, you can minimize the conicalness that you can see in the attached photo. However, the visible quality can be achieved by a third of the normal cutting speed. At this point, traces of the beam cannot be seen on the surface.
  • undercuts: the direction of cut at the corners during the cut suddenly changes, which causes the jet of water to bend and possibly intersect the material in an unwanted manner on the exit side. This may be a problem with size accuracy, but for our new-build machine, these adverse effects can now be eliminated by controlling the minimum decision of the head.

 

 

What can and should not be cut with water?

 

Almost all materials can be machined with this procedure, at least what we have cut so far:

 

  • Heat-resistant, stainless steels and hardenable steels
  • In practice up to a thickness of 150 mm (theoretical value), it is no longer recommended to be above 80 mm.
  • Aluminium, brass, copper, bronze, armour plate
  • Composite materials, with fiberglass and carbon fibre reinforcement
  • Sandwich-structure materials (dibond plates)
  • Granite 60 mm thick
  • Graphite sheet material thickness: 2 mm
  • Glass in normal condition
  • Industrial rubber sheet
  • Foam materials
  • Decorative and industrial plastic sheets

 

Waterjet cutting does not provide a solution:

  • Tempered glass
  • Cardboard
  • Natural wood
  • Materials with a higher hardness than granite
  • Industrial metal oxide ceramics