Waterjet cutting is one of the most common processes nowadays in modern manufacturing and fabrication. With extensive benefits and no drawbacks, this cutting method is used in a variety of applications, from mining to metalworking to arts and furniture.
Due to a lot of different applications, there are very different types of waterjet cutting methods developed that are more suited to particular uses. Abrasive water jet machining is one of the most widely used waterjet cutting techniques out there.
In this article, you will learn all about abrasive waterjet cutting, why it is used, and its different types. Without waiting any further, let us get into the main topic rightaway:
What is Abrasive Waterjet Cutting?
To understand abrasive waterjet cutting, let us first get our head around the basics of waterjet cutting itself.
Waterjet cutting is a cold cutting process in which a very narrow beam of water is used to create the incision on the workpiece. Generally, the water beam is enough in itself to create the cut and the method is called Pure Waterjet Cutting.
However, when material thickness or density is hard, you need extra force besides the force of water. This extra force is achieved by adding abrasives to the water.
When the water stream containing the abrasives falls on the workpiece at high pressure, it generates a lot of friction which results in clean and precise cuts. The high pressure is generated by a reliable high-pressure pump attached to the waterjet cutting machine.
Commonly used abrasives in waterjet cutting are silicon carbide, aluminum oxide, sand, and garnet. Garnet abrasive is the most common abrasive used due to its physical properties.
What is the purpose of using abrasive material in a water jet?
Pure water jet cutting can easily cut through soft materials like foam, paper, rubber, and thin plastics. However, when with hard materials like metal, stone, and hard plastics, pure water cutting doesn’t work or the process becomes too unfeasible and time-consuming.
The purpose of using abrasive materials in a water jet is to make waterjet cutting usable for these harder or thicker materials. With the addition of abrasives, all the benefits of waterjet cutting can be used on stainless steel, aluminum, copper, and even stone.
Different types of abrasive water jet machining
Abrasive water jet machining is achieved by two different methods, thereby leading to two different types of abrasive water jet machining. These two methods vary mainly in the way the abrasive is added in the cutting process.
Abrasive Water Injector Jet (AWIJ) Cutting:
In abrasive water injector jet cutting, the abrasive is added to high-pressure pump water after the nozzle and just before the cutting head.
The abrasive, along with air, is combined with water in the mixing chamber and sprayed out as an abrasive stream. After that, the water is sprayed out through the cutting head. This is a three phase cutting process, the three phases being waterjet, abrasive, and air.
Abrasive Water Suspension Jet (AWSJ) Cutting:
In an abrasive water suspension jet, a suspension (liquid mixture) of water and abrasive is created beforehand and then pressurized at a later stage. This pressurized suspension is then passed through a focusing nozzle (cutting head) for the cutting action.
A major difference in this method is the absence of air as in the previous method. Due to the absence of air, the abrasive waterjet stream does not expand during cutting, leading to a lower kerf width and higher accuracy.
Due to this very reason, abrasive water suspension jet cutting can also be used to create faster cuts or to efficiently cut thicker materials. AWSJ is also extensively used for underwater cutting applications, such as offshore installations or bomb disposals.
The water stream that comes out of the cutting head is a two-phase cutting stream, the two phases being water and abrasive.
What is the Difference Between Abrasive and Pure Waterjet Cutting?
Up till this point, you probably have a clear and basic idea about what abrasive waterjet cutting is and how it differs from the conventional pure waterjet cutting method.
In a wider aspect, the advantages of abrasive waterjet cutting over traditional cutting methods and pure water cutting are more than what they seem.
Imagine if you were cutting a sheet of paper with a very blunt scissor. It might get the job done, but it can ruin the edges of the cut or crumple the paper itself. Now if you do the same job with a sharp tool, you will get a clean and neat cut.
This is how abrasive waterjet and pure waterjet cutting function. Even if pure waterjet cutting is able to cut hard materials in addition to soft materials, it will take a long time and the edges of the cut will considerably get damaged. Abrasive waterjet cutting does the job quickly, precisely, and neatly.
Abrasive vs. Pure water cutting
Here is an overview of the different aspects in which abrasive waterjet differs from pure waterjet cutting.
Supported Workpiece Materials:
Pure Waterjet Cutting: Pure waterjet cutting can be used to cut soft materials like food items, paper, foam, rubber, felt, and soft plastics.
Abrasive Waterjet Cutting: Abrasive cutting can be used to cut metals, hard plastics, ceramics, stone, glass, wood, and almost any other material you can think of.
Pure waterjet cutting is obviously slower than abrasive waterjet cutting. This is because abrasive waterjet has finer particles to create considerably greater friction, leading to faster cutting action.
Both pure and abrasive waterjet cutting machines have similar power requirements. However, since the abrasive waterjet machine can do the job quickly, it will consume less power overall.
In simple terms, the kerf is the amount of material removed during cutting (much like sawdust during woodworking). Pure waterjet cutting requires a greater time to cut the material. Water expands on leaving the cutting head, so the greater time leads to greater expansion and a higher kerf.
As the water stream passed through the workpiece material, it loses momentum through the thickness of the material. Adding abrasives in water increase the force through which the water hits the surface. Therefore, an abrasive waterjet machine is capable of cutting through a greater thickness of the material.
Accuracy and Cutting Tolerances:
Abrasive waterjet machines are well-known due to their highly precise and accurate nature. As mentioned earlier, the difference between abrasive and pure waterjet cutters is similar to sharp and blunt scissors.
When you should use abrasive water jet cutting machines over pure waterjet cutters?
Abrasive waterjet machines will always create better cuts than pure waterjet cutters. This might make you wonder why should you or anyone even consider pure waterjet cutting for any project.
The answer to this is simple- the cost of abrasives. The cost of abrasives is the major cost fraction in abrasive waterjet cutting. Therefore, for projects that can make do without abrasives, pure waterjet cutting is preferred.
Most of the projects that commonly employ pure waterjet cutting are paper industry, foam cutting, and rubber cutting. Other than this situation, requirements where hygiene is a factor (such as food cutting) also require pure waterjet cutting.
On the other hand, any project dealing with fabrication, stone cutting, woodworking, or even cutting of hard rubber calls for the need for abrasive waterjet cutting.
Abrasive waterjet cutting is one of the gifts that modern technology has provided us. Even though the science behind it has been used for more than a century, the latest machines still seem a marvel when you witness what they are capable of.
Take for instance the range of abrasive waterjet cutters provided by PWRpack. From fabrication workshops to aerospace projects, these machines are being used everywhere. They are capable of cutting through thick sheets of hardest materials like metal as if it were a single page of paper.
If you are thinking about buying a new cutting machine for your next project or your workshop, abrasive waterjet cutters are something you should definitely consider.
Frequently Asked Questions (FAQs)
1. Which type of materials cannot be machined using abrasive jet machining?
Abrasive waterjet machining can cut almost any material. except for diamonds and tempered glass. In theory, you can cut any material through abrasive waterjet cutting provided the abrasive is harder than the material you are cutting.