Frequently Asked Questions - Mainstream Waterjet
Question: What is waterjet cutting?
Answer: In the battle to reduce costs, engineering and manufacturing departments are constantly on the lookout for an edge. The waterjet process provides many unique capabilities and advantages that can prove very effective in the cost battle. Learning more about the waterjet technology will give you an opportunity to put these cost-cutting capabilities to work.
Beyond cost cutting, the waterjet process is recognized as the most versatile and fastest growing process in the world (per Frost & Sullivan and the Market Intelligence Research Corporation). Waterjets are used in high production applications across the globe. They complement other technologies such as milling, laser, EDM, plasma and routers. No noxious gases or liquids are used in waterjet cutting, and waterjets do not create hazardous materials or vapors. No heat effected zones or mechanical stresses are left on a waterjet cut surface. It is truly a versatile, productive, cold cutting process.
The waterjet has shown that it can do things that other technologies simply cannot. From cutting whisper thin details in stone, glass and metals; to rapid hole drilling of titanium; to cutting of food, to the killing of pathogens in beverages and dips, the waterjet has proven itself unique.
Question: How was waterjet cutting developed?
Answer: Dr. Norman Franz is regarded as the father of the waterjet. He was the first person who studied the use of ultrahigh-pressure (UHP) water as a cutting tool. The term UHP is defined as more than 30,000 pounds per square inch (psi). Dr. Franz, a forestry engineer, wanted to find new ways to slice thick trees into lumber. In the 1950's, Franz first dropped heavy weights onto columns of water, forcing that water through a tiny orifice. He obtained short bursts of very high pressures (often many times higher than are currently in use), and was able to cut wood and other materials. His later studies involved more continuous streams of water, but he found it difficult to obtain high pressures continually. Also, component life was measured in minutes, not weeks or months as it is today.
Dr. Franz never made a production lumber cutter. Ironically, today wood cutting is a very minor application for UHP technology. But Franz proved that a focused beam of water at very high velocity had enormous cutting power - a power that could be utilized in applications beyond Dr. Franz's wildest dreams.
In 1979, Dr. Mohamed Hashish working at Flow Research, began researching methods to increase the cutting power of the waterjet so it could cut metals, and other hard materials. Dr. Hashish, regarded as the father of the abrasive-waterjet, invented the process of adding abrasives to the plain waterjet. He used garnet abrasives, a material commonly used on sandpaper. With this method, the waterjet (containing abrasives) could cut virtually any material. In 1980, abrasive-waterjets were used for the first time to cut steel, glass, and concrete. In 1983, the world's first commercial abrasive waterjet cutting system was sold for cutting automotive glass. The first adopters of the technology were primarily in the aviation and space industries which found the waterjet a perfect tool for cutting high strength materials such as Inconel, stainless steel, and titanium as well as high strength light-weight composites such as carbon fiber composites used on military aircraft and now used on commercial airplanes. Since then, abrasive waterjets have been introduced into many other industries such as job-shop, stone, tile, glass, jet engine, construction, nuclear, and shipyard, to name a few.
Question: How is high pressure water created?
Answer: The basic technology is both simple and extremely complex. At its most basic, water flows from a pump, through plumbing and out a cutting head. It is simple to explain, operate and maintain. The process, however, incorporates extremely complex materials technology and design. To generate and control water at pressures of 60,000 psi requires science and technology not taught in universities. At these pressures a slight leak can cause permanent erosion damage to components if not properly designed. Thankfully, the waterjet manufacturers take care of the complex materials technology and cutting-edge engineering. The user need only be knowledgeable in the basic waterjet operation.
Essentially, there are two types of waterjets; (1) pure waterjet and (2) abrasive waterjet. Machines are designed to employ only waterjet, only abrasive waterjet, or both. With any type, the water must first be pressurized.
The pump is the heart of the waterjet system. The pump pressurizes the water and delivers it continuously so that a cutting head can then turn that pressurized water into a supersonic waterjet stream. Two types of pump can be used for waterjet applications - an intensifier based pump and a direct drive based pump.
Direct Drive Pump
The direct drive pump operates in the same manner as a low-pressure "pressure washer" that you may have used to pressure wash a house or deck prior to repainting. It is a triplex pump that gets the movement of the three plungers directly from the electric motor. These pumps are gaining acceptance in the waterjet industry due to their simplicity. At the time of this writing, direct drive pumps can deliver a maximum continuous operating pressure 10 to 25% lower than intensifier pumps units (20k to 50k for direct drive, 40k to 60k for intensifiers).
The Direct Drive pump is a relatively new type of high-pressure pump
(Commercially available since late 1980's).
Though direct drive pumps are used in some industrial applications, the vast majority of all ultra-high pressure pumps in the waterjet world today are intensifier based.
Question: What is a pure waterjet?
Answer: Pure waterjet is the original water cutting method. The first commercial applications were in the early to mid-1970s, and involved the cutting of corrugated cardboard. The largest uses for pure waterjet cutting are disposable diapers, tissue paper, and automotive interiors. In the cases of tissue paper and disposable diapers the waterjet process creates less moisture on the material than touching or breathing on it. Unplanned down time, common to other cutting processes, cost over $20,000 per hour in some diaper or tissue plants. The waterjet provides the 24 hour per day, 7 day per week, 360 day per year operation required by such applications - maintenance can be scheduled into production.
Pure waterjet attributes:
- Very thin stream (0.004 to 0.010 inch in diameter is the common range)
- Extremely detailed geometry
- Very little material loss due to cutting
- Non-heat cutting
- Cut very thick
- Cut very thin
- Usually cuts very quickly
- Able to cut soft, light materials (e.g., fiberglass insulation up to 24" thick)
- Extremely low cutting forces
- Simple fixturing
- 24 hour per day operation
Question: What is an abrasive waterjet?
Answer: The abrasive waterjet differs from the pure waterjet in just a few ways. In pure waterjet, the supersonic stream erodes the material. In the abrasive waterjet, the waterjet stream accelerates abrasive particles and those particles, not the water, erode the material. The abrasive waterjet is hundreds, if not thousands of times more powerful than a pure waterjet. Both the waterjet and the abrasive waterjet have their place. Where the pure waterjet cuts soft materials, the abrasive waterjet cuts hard materials, such as metals, stone, composites and ceramics. Abrasive waterjets using standard parameters can cut materials with hardness up to and slightly beyond aluminum oxide ceramic (often called alumina, AD 99.9).
Abrasive Water Jet Attributes:
- Extremely versatile process
- No Heat Affected Zones
- No mechanical stresses
- Easy to program
- Thin stream (0.025 to 0.050 inch in diameter)
- Extremely detailed geometry
- Thin material cutting
- 10 inch thick cutting
- Stack cutting
- Little material loss due to cutting
- Simple to fixture
- Low cutting forces (under 1 lb. while cutting)
- One jet setup for nearly all abrasive jet jobs
- Easily switched from single to multi-head use
- Quickly switch from pure waterjet to abrasive waterjet
- Reduced secondary operations
- Little or no burr
Back to top