The new process we would like to describe today is waterjet cutting. As we always noted – we are not connected with any machinery and probably are also not perfectly specialized in this process so some our our information could be not precise or requested to be better described by the real specialist.
First, let us describe the main part. Waterjet cutting is the process of cutting flat materials with a water jet supplied with high pressure. Usually, the process of waterjet cutting is used for applications with “soft materials” like textile, rubber, leather, foam, wood, probably some carbon fibers, plastic, etc. For all hard materials including metals and stone is used the process with the supply of water under high pressure together with small particles of sand – this process is called “abrasive cutting” “mixed waterjet cutting” or “abrasive waterjet cutting”.
According to the article on Wikipedia: While using high-pressure water for erosion dates back as far as the mid-1800s with hydraulic mining, it was not until the 1930s that narrow jets of water started to appear as an industrial cutting device. In 1933, the Paper Patents Company in Wisconsin developed a paper metering, cutting, and reeling machine that used a diagonally moving waterjet nozzle to cut a horizontally moving sheet of continuous paper. These early applications were at low pressure and restricted to soft materials like paper.
Now let us speak more in detail. We already mentioned waterjet cutting as one of the technologies for cutting sheet metal before other operations such as press brake bending, but today we will try to make more explanation about only this technology itself and probably some comparison to other cutting processes.
First, we will tell that one of the main applications for waterjet machines is for producers and manufacturers of various types of stone plates to be used in buildings and decorations. For them, the waterjet cutting is completely the process N1 without any alternatives with a lot of possibilities for any figure cutting as required. It is very important together with notice that waterjet cutting has very good precision, can cut really big thicknesses, and with very clean cut with no necessity for any other operations.
But because we are talking about sheet metal production technologies we want to talk about waterjet cutting (for sure here and after we mean cutting with sand) of sheet metal. And a small review of why to use waterjet cutting compared to other cutting technologies:
- waterjet cutting allows perfect precision for cutting.
- possibility to cut enormous thicknesses like 200 mm plate. With any other technology, it was nearly impossible or use such technologies as gas-flame cutting with very bad quality and precision. Compared with laser cutting machines before the limits for CO2 lasers were 20-25 mm thickness but even now if we speak about high technology fiber lasers even 80 or 100 Kw the limits like 100 mm thickness with not-so-clean cutting edge.
On the Internet, there are videos for cutting complete gears and solid shapes which will be completely final part after and it is amazing. Any other process of machining will cost more, investments will be more and probably the process will be slower. So in some applications, waterjet is a brilliant solution.
- cutting in cold without any thermal impact. It means that there is no thermal touch of the edge of metal to destroy or change the cellular structure of the material. This could be very important in such fields as aerospace, chemical, medical, etc. when no change of material structure is permitted. Together with this probably in some materials cutting with thermal is also not permitted based in fact to destroy the edges like foam or carbon fiber. So for some materials, waterjet will be the unique solution if the geometry of cutting is not straight for the saw.
- No differences in materials. For example, cutting copper and brass with CO2 laser cutting machines was a big problem in terms of reflection to not damage the mirrors and there were possibilities only for very small thicknesses.
- Angular cutting – necessary for some applications. Mainly waterjet machines have 5 axes – X, Y, Z + 2 additional axes for head rotation. Together with high precision, it allows a lot of possibilities.
- Clean edge and no necessity for any cleaning or deburring operations. For sheet metal even clean laser cutting or punching makes the small burr on the edge that is probably important to remove after.
- No special ventilation and fumes extraction necessary – there are no toxic fumes during the process of waterjet cutting.
Now about disadvantages:
- Running costs cutting bigger compared to laser cutting for example. For sure it requires the comparison with details on the application so it is just in general we found on the Internet.
- Probably today with so wide a market of laser cutting machines investment costs to waterjet will be bigger in terms of purchasement of the machinery.
- Incredibly slow. It is even impossible to compare the speeds of waterjet because compared to laser cutting it is slow not in times but a dozen times. Sometimes if possible for production, the operator put several sheets as a stack on the table for cutting to cut one sheet but five together. To enlarge the speed on the market are presented Multi-head cutting machines which means that there will be several cutting heads on the machine traverse to cut the same parts simultaneously.
- Sand abrasive waterjet cutting is not a completely clean process. A constant mixture of waste of sand makes water and mud thicken in the bin under the table.
- After the distance the jet becomes thicker so the precision will fall during the cutting of big thicknesses.
- Noise level during waterjet cutting could reach 90 dB.
Conclusion: We usually say that factory management is the most important point and choosing the technologies based on the applications. For example, if we are talking about classical sheet metal jobs where the most of work covers 1-10 mm steel materials the waterjet cutting machine will be completely not interested in technology for them. But if we speak with the subcontractor of aerospace parts and a variety of materials to proceed probably the waterjet cutting technology will be an excellent solution. Moreover, sometimes it is interesting to speak not about the complete parts but of steps mixing – for example cutting of contours and shapes of metal parts before the further transfer to the milling machine for final work. Probably in this case factory can optimize the processes, costs, and expenses for the parts to make their production more effective and competitive.