Today, water jet cutting has become a highly advanced and widely used manufacturing process, but the concept of using water to shape and cut is certainly not a new one. The Roman Empire was one of the first civilizations to use this process, and they used it to help with mining and developing land. Obviously, they did not have the technology to pressurize the water like we do today, so instead they eroded the earth for development by redirecting rivers and streams. Similar, yet more advanced, techniques were used in California during the gold rush. These processes continued to evolve and improve finding use in underground hydraulic mining and eventually developing into the process we use today.
An industrialized use of this process was not developed until the 1930’s when a water cutting device was introduced. These devices were used to cut, meter, and reel paper. Now realizing the processes usefulness in industrial manufacturing, it began to quickly evolve, improve, and expand. With the technology to reach higher pressures and the ability to incorporate abrasive materials, water jet cutting could then be applied to stronger and more diverse materials like brick, stone, metals, and glass. Thus the current water jet cutting procedure was born which utilizes high pressure jets to spray water out at extremely high speeds and quickly erode many different materials. Throughout its history, the process has continually evolved, becoming more controlled, more reliable, more accurate, and much faster. The industry today is continuing the trend, always looking for innovative ways to apply or improve the process.
Waterjets can cut just about any material that can be made into a sheet and placed in front of them.
The most popular materials are metals (especially aluminum, because it’s relatively soft and cuts quickly), because waterjets can cut intricate shapes to a high precision quickly and economically. Since metals are the most common material cut by machining shops, waterjets tend to cut a lot of metal.
Waterjets also commonly cut stone and glass, because the waterjet can get intricate shapes not possible using traditional machining methods. These materials are popular with artists who like to work with these materials and waterjets because it lets them create almost anything they can envision.
Among the very few materials that waterjets cannot cut are diamonds and tempered glass. Diamonds are too hard to cut (and there may be a few other very hard materials that can’t be cut). Tempered glass will shatter when it is cut with a waterjet (tempered glass is designed to shatter when it’s disturbed and is frequently used in windshields for this very reason).
A few advanced ceramics are so hard that it’s not economical to cut them. Some composite materials (layers of different materials sandwiched together) can’t be cut because the water can seep between the layers and “delaminate” the material. Many composite materials cut just fine, though, and there are some techniques to cutting laminated materials.
There is a reason that waterjet machining has rapidly grown in popularity since the mid-1990’s. Actually there are a number of reasons, listed below, but they mostly come down to “versatility.” A waterjet is a versatile and flexible machining tool. You can cut a wide variety of material efficiently and cost-effectively and can create a wide variety of parts.
Cut virtually any material
Because waterjets cut using water and abrasive, they can work with a wide variety of materials. These materials include:
- Copper, brass, aluminum:
- Pre-hardened steel
- Mild steel
- Exotic materials such as titanium, Inconel and Hastalloy
- 304 stainless steel
- Brittle materials such as glass, ceramic, quartz, stone.
- Laminated material
- Flammable materials
One of the few materials that cannot be cut with a waterjet is tempered glass. Because tempered glass is under stress, as soon as you begin to cut it, it will shatter into small fragments—as it is designed to do.
Fast setup and programming
With waterjet machining, a flat piece of material is placed on a table and a cutting head moves across the material (although in some custom systems, the material moves past a fixed head). This simplicity means that it’s fast and easy to change materials and that no tool changes are required. All materials use the same cutting head, so there is no need to program tool changes or physically qualify multiple tools.
The movement of the machining head is controlled by a computer, which greatly simplifies control of the waterjet. In most cases, “programming” a part means using a CAD program to draw the part. When you “push print,” the part is made by the waterjet machine. This approach also means that customers can create their own drawings and bring them to a waterjet machine for creation.
Little fixturing for most parts
There are very low sideway forces with waterjet machining–cutting the material doesn’t push it. The downward forces are also small, in the range of a few pounds. Typically, the largest force is from the water in the tank pushing back up against the material.
Fixturing is generally a matter of weighing down the material by placing weights on it. Small parts might require tabs to prevent them from falling into the tank.
The low side forces, means you can machine a part with walls as thin as 0.01″ (0.25 mm). This is one of the factors that make fixturing is so easy. Also, low side forces allow for close nesting of parts, and maximum material usage.
Almost no heat generated on your part
What little heat is generated by the waterjet is absorbed by the water and carried into the catch tank. The material itself experiences almost no change in temperature during machining. During piercing 2″ (5 cm) thick steel, temperatures may get as high as 120° F (50° C), but otherwise machining is done at room temperature.
The result is that there is no heat affected zone (HAZ) on the material. The absence of a HAZ means you can machine without hardening the material, generating poisonous fumes, recasting, or warping. You can also machine parts that have already been heat treated.
No mechanical stresses
Waterjet machining does not introduce any stresses into the material.
Machine thick material
While most money will probably be made in thicknesses under 1″ (2.5 cm) for steel, it is common to machine up to 4″ (10 cm). The thicker the material, the longer it will take to cut. A part made from material twice as thick will take more than twice as long. Some companies make low tolerance parts out of metal that is up to 5″ to 10″ thick (12.5 cm-25 cm), but it takes a long time and tends to be an occasional operation. Typically, most waterjet parts are made from metal that is 2″ (5 cm) or thinner.
Are very safe
Obviously, you don’t put any body parts in front of a waterjet machining head while it is on. Anything that can cut through 2″ steel will make short work of flesh and bone. Aside from this, however, waterjets are very safe. A leak in a high-pressure water system tends to result in a rapid drop in pressure to safe levels. Water itself is safe and non-explosive and the garnet abrasive is also inert and non-toxic. One of the largest hazards is cuts from the sharp edges of material created by the waterjet.
Modern systems are now very easy to learn
Control of the waterjet head is complicated and requires careful calculation to get the proper speed that will give the best result. This means that the system needs to be controlled by a computer, which means that the user-interface for the system can be simplified and made friendlier. Modern systems are designed the same way as many other computerized CAD systems and are quickly learned.
As long as you are not machining a material that is hazardous, the spent abrasive and waste material become suitable for land fill. The garnet abrasive is inert and can be disposed of with your other trash.
If you are machining lots of lead or other hazardous materials, you will still need to dispose of your waste appropriately, and recycle your water. Keep in mind, however, that very little metal is actually removed in the cutting process. This keeps the environmental impact relatively low, even if you do machine the occasional hazardous material.
In most areas, excess water is simply drained to the sewer. In some areas, water treatment may be necessary prior to draining to sewer. In a few areas, a “closed loop” system that recycles the water may be required.
The pumps do use a considerable amount of electricity, though, so there is some additional environmental (and cost) impact due to this.
No start hole required
Start holes are only required for materials that are difficult or impossible to pierce. A few poorly bonded laminates can fall into this category, in which case pre-drilling or other special methods may be used.
Narrow kerf removes only a small amount of material
The amount of material removed by the waterjet stream is typically about 0.02″ (0.5 mm) wide, meaning that very little material is removed. When you are working with expensive material (such as titanium) or hazardous material (such as lead), this can be a significant benefit. It also means that you can get more parts from a given sheet of material.
When machining or roughing out expensive materials such as titanium, your scrap still has value. This is because you get chunks, not chips.