FAQ Answers to the most frequent questions.
Laser cutting is a very productive process. However, waterjet cutting offers some advantages over laser cutting:
- No limitation in strength
- No problems with reflecting materials like brass and aluminium
- No heat influence and therefore no burning and no change in material structure from the heat
- The waterjet can be used to cut heat-sensitive materials like plastic, rubber or composite materials as well as like glass, stone and very hard ceramics.
- Material change: only the cutting speed is adjusted. Neither gas nor optics has to be replaced
- Additional cutting heads can be attached readily for expanded production.
- The maintenance of laser systems is more specialised and more difficult to complete.
- The distance between nozzle and material is not as critical by far.
- Waterjet systems require less acquisition capital than laser systems.
EDM is very precise but also very slow. It calls for electrically conducting material and changes the material structure with heat.
If you cut the edge of the material as well as holes or want to do blind bores and create threads, the abrasive waterjet is usually a lot faster, easier to program and also cheaper than a mill.
This can be especially attributed to the fact that we cut in one go and that we do not generate metal cuttings. And also, waste is worth more in one piece than as chippings.
Plasma cutting is a hot process. It subjects the work piece to a great amount of heat leaving a heat-influenced zone.
The surface created by a waterjet is generally better. There is no burr on the bottom of the material eliminating the need for finishing. The abrasive waterjet is not subject to any cutting thickness limitations and several working areas of one jet can be close together.
You can achieve greater accuracy with waterjet cutting than with flame or plasma cutting systems. And waterjet cutting systems can also cut thicker materials than laser systems.
In addition, waterjet cutting machines have numerous additional advantages over other solutions.
More than 80% of waterjet system users worldwide cut with an accuracy of ±0.1mm or less.
The biggest advantage is the reduction of the cutting noise to less than 75 dBA. The down side of underwater cutting is that you can see the workpiece poorly or not at al during cutting. The workpiece is also handled under water – unless you have water level management for the water tank. One should also add that the cutting process suffers a reduction in performance of approx 5% at 1mm overlap with water.
Steel and titanium with a thickness of up to 200 mm are cut during production. There were cases in which thicknesses of 300 mm and 400 mm have been cut. The majority of users cut materials that are between 10 mm and 60 mm though.
420 MPa is the maxiumum pressure of the pressure intensifier. It has been proven that the fastest and most powerful cut can be realised at a pressure of 380 MPa. Higher pressure results in shorter maintenance intervals for the high pressure pump.
This depends on the power of the high pressure pump and the water nozzle respectively.
High pressure pump:
19 kw: 1,9 l/min
37 kw: 3,8 l/min
45 kw: 4,6 l/min
75 kw: 7,6 l/min
0,1: 0,32 l/min
0,15: 0,71 l/min
0,2: 1,22 l/min
0,25: 1,87 l/min
0,3: 2,66 l/min
0,35: 3,57 l/min
0,4: 4,60 l/min
0,5: 6,82 l/min
The kerf is approx. 15% broader than the focusing tube diameter. In a 0.8 mm focusing tube, the kerf width is 1.0 mm. With an increase in the focusing tube diameter the kerf also increases in width.
The resulting tapering is a function of the cutting speed. The largest possible tapering equals the maximum cutting width on the material surface (for example: 0.8 mm) and 0.0 mm on the bottom of the material. While the cutting speed is reduced, the tapering also gets smaller until you have parallel sides. The usual tapering for precision cuts is between 0.05 and 0.10 mm.
The waterjet creates its own start hole without any further effort with most materials. Pump pressure must be reduced for some composite materials and a special vacuum assist piercing device must be used.
700 mm of water in the water tank.
There are the following minimum requirements for water quality:
- pH value 7.0 – 8.5
- A carbonate hardness of 20–60 ppm corresponds to 2–6 ° dH
- Calcium carbonate (Ca) 35–107 ppm
- Chloride content (Cl) ? 100 mg/l
- Entry temperature for feed water 10–25 °C
- Electrical conductivity at +25°C 450 µS/cm
- Dry filtrate residue 350 mg/l
- Free, dissolved chlorine 1 mg/l
- Feed water supply pressure 0.2 – 2.5 MPa
Deviations from these values lead to shorter service lives of the high-pressure seals of the pump and of the nozzles. We therefore recommend a water analysis and appropriate water conditioning, if necessary.
A power rating of 37 kW must be taken into consideration per installed abrasive cutting head.
You will need several cutting heads if you want to generate many identical parts. Either connect a second cutting head to the existing Z-axis or install a second Z-axis on which additional cutting heads can be attached. It is important hereby to supply each individual cutting head with the same pressure and the same flow rate to realise an even cut.
The high-pressure seals have to be replaced if they are leaking! With a constant working pressure of 400 MPa, the seals should be replaced after 400 to 1,200 cutting hours.
Granite sand is by far the most commonly used abrasive. It shows a convincing performance in the fields of acquisition costs, cutting speed, mixing head service life and health hazard. Other abrasives contain olivine sand, aluminium oxide and some artificial materials.
Required quantity for optimal cutting performance at 400 MPa working pressure:
- Nozzle 0.15 mm / focus 0.6mm 150g/min.
- Nozzle 0.25 mm / focus 0.8mm 350g/min.
- Nozzle 0.35 mm / focus 1.0mm 450g/min
The grating cover will last for many hours of cutting, provided you do not always cut on the same spot. The grating covers can be moved, replaced and turned over just as with laser or plasma cutting systems.
Focuses made with good ceramics-carbide will last about 100 hours. Focuses with the highest ceramics-carbide quality will last approx. 30% longer than focuses made of other materials.
Such a focusing tube can last up to 150 cutting hours if the diameter is expanded by 0.5 mm. Many of our customers use already slightly used focuses to create parts that do not require great accuracy.
A sapphire nozzle lasts 25 cutting hours. Diamond nozzles (the highest nozzle quality) last a lot longer but also cost about 30 times more and are usually used only for the pure water cutting.
STM waterjet cutting systems with standard CNC equipment are not harder to program than any other cutting process. Standard CAM software simply converts DXF files into the cutting program; only the cutting speed has to be adjusted to the different materials. The Windows-based software EasyCut makes programming very easy! There is no need for fiddly mental work. That means projects can be programmed and cut quickly and accurately.
The force working on the workpiece is very small (less than 1 kg for precision cuts and less than 5 kg for average cuts) so there is no need for elaborate clamping devices. Most users take simple light weights to keep their workpieces in place.
Costs, security and environmental compatibility
The usual charge for a custom cut on an abrasive waterjet cutting systems is between € 120 and € 220 per hour.
The costs per hour start at € 19 for a small cutting head (nozzle: 0.15 mm / focus 0.6 mm) and range all the way to € 35 for a large cutting head (nozzle 0.35 mm/ focus 1.0 mm). These figures include all machine-relevant costs. Work, leasing and depreciation still have to be added in.
Prices for abrasives range between € 280 and € 300 per ton ex factory A-5531 Eben im Pongau.
It will be cut off. The safety devices around the machine were therefore planned very diligently. Operators of abrasive waterjet cutting systems are subject to stricter safety restrictions than most machine operators in other industries.
The noise generated during waterjet cutting depends on the distance of the free jet to the surface of the workpiece – i.e. the path that the waterjet travels in the air with supersonic speed. Cutting under water reduces the noise level to below 75 dBA. If you cut above water, the noise level rises up to 105 dBA depending on the distance of the cutting head to the surface of the work piece. The entire work surface is covered in extreme cases.
Neither water nor granite sand contain toxic materials. The water can therefore be drained into the sewer after the suspended sediment has sunken or been filtered out. The abrasive can be disposed of as construction waste. Waste water and abrasive have to be disposed of as hazardous waste if the processed material is toxic or hazardous to health!
Yes. Most customers use tap water. The water must be filtered to 0.5 micron before it gets to the high pressure pump. Deionisation as well as osmotic systems are not recommended. These systems clean the water too much – and water that is too pure is highly aggressive which will increase the wear of the high-pressure system.
We offer recycling systems – but we would also like to point out beforehand that they do not provide a reasonable cost-benefit ratio because of the low water consumption of approx. 200 l/h.