HIGH
PRESSURE WATER JET CUTTING
High pressure water jet cutting is a technique that cuts materials with a jet of water forced from a nozzle at a speed three times that a sound. To produce this speed, the water has to be raised up to a pressure of 400 MPa (4,000 bar) which is done by intensifier. For cutting hard materials like stone, glass, steel and non-ferrous metals, an abrasive medium (silica sand) is added to the water.
Water Jet
Advantages of the water jet
Comparism to other technologies: laser, plasma, milling, press
Maintenance
Materials
that can be cut with plain water
Paper,
corrugated cardboard, plastics, composites, form plastic, sealing
materials, foodstuffs.
Materials
suitable for abrasive water jet cutting
Plate
glass, bullet-proof glass (not toughened glass), natural and artificial
stone, special steel, iron and artificial stone, special steel, iron and
non-ferrous metals, hardened steel, etc.
Advantages of using a high pressure water jet cutting
- No thermal stress on materials
- High flexibility thanks to integration of water
jet
into two or multi-axis guide systems - Little swarf due to narrow width of cut
- Minimum reaction forces
- No deformation of material surface
- Commencement of cutting at any point
- Cheaper than other processes
- Cut thin stuff, or thick stuff
- Make all sorts of shapes with only one tool.
- Only one tool to qualify / No tool changes required
- No mechanical stresses
- Fast Setup: Fast turn around on the machine.Make a part, then 2 minutes be making a completely different part from a completely different material
- Leaves a satin smooth finish, thus reducing secondary operations
- Clean cutting process without gasses or oils
- Makes its own start holes
- Narrow kerf removes only a small amount of material.
- Your "scrap" metal is easier to recycle or re-use (no oily chips!)
- Modern systems are now very easy to learn
- You can trade off tolerance vs speed from feature to feature on your part
- Can easily switch between high production, and single piece production, on the same machine, with no extra effort
- Are very safe
- Draw the part and cut the part. It is that easy! Everyone in your shop can learn to use it quickly.
- Abrasive jets can machine many materials that lasers cannot. (reflective materials in particular such as aluminum and copper.
- Uniformity of material is not very important to an Abrasivejet.
- Abrasive jets do not heat your part, no thermal distortion or hardening of the material
- Precision abrasive jet machines can obtain about the same or higher tolerances than lasers (especially as thickness increases).
- Your capital equipment costs for water jet are generally much lower than that for a laser
- Abrasive jets can machine thicker materials
- Abrasive jets are safer. No burnt fingers, no noxious fumes, and no fires
- Abrasive jets are more environmentally friendly
- Maintenance on the abrasive jet nozzle is simpler than that of a laser
- Abrasive jets are capable of similar tolerances on thin parts, and better on thicker parts thicker
- Abrasive jets do not loose much "focus" when cutting over uneven surfaces
- While lasers are often faster on thinner materials, it may be cheaper and faster to simply buy two or three abrasive jet machining centers to do the same work. Also, you can stack materials
- Modern abrasive jets are typically much easier to operate and maintain than lasers which means that every employee in your shop can be quickly trained to run one!
- You can't stay long at the same point with laser or fusion of material will occur
- Laser cut is under inches (near 4 inches for WJ), but can do a better job in controlling depth of cut (ex.: cutting slot in tubing is possible with a laser but difficult with abrasivejet)
- Laser has higher power consumption (power factor about 2%) (ex.: for 1 kw output you need 50 kw input for YAG) (CO2 more efficient, but less precise ray)
- Laser needs a good "chiller" for cooling.
When comparing with Plasma / flame cutting
- Abrasivejets provide a nicer edge finish
- Abrasivejets don't heat the part
- Abrasivejets can cut virtually any material
- Abrasivejets are more precise
- Plasma and flame cutting are typically faster
- There is only one tool to qualify on an abrasivejet
- Setup and fixturing typically involves placing the material on the table with an abrasivejet
- Clean-up is much faster with an abrasivejet
- Programming is easier and faster
- Machine virtually any material.
- Lower cost per piece for short runs
- Place holes closer to the materials edge
- Fast turn-around
- Minimal setup
- Thick materials are fine
- Brittle materials ok
- Hard materials are easy
Waterjets certainly require maintanence. Expect to change nozzle parts frequently (daily), pump parts less frequently but regularily enough. Expect that things will break when forced to operate at 35,000 to 60,000 PSI. That is a lot of pressure! It is also wise to keep some critical spares at hand. Generally speaking, the higher the pressure and the more on/off cycles the equipment has to go through, the more frequently it will need maintenance.
Anyone can keep an abrasive jet going with a days training. Mixing tubes, (part of the nozzle) wear out and are easy to replace (often similar to replacing a drill bit). Pumps will need periodic seal changes.
When maintaining your critical parts such as nozzle and seal components, do so with care. Critical components are sensitive to dirt, dust, microscopic scratches, etc. Our advice is to take these components into a different room, wash them down (often with soap and water / or ultrasonic cleaner), and then assemble them in a clean environment. If you have dirty water, you will either need to maintain everything more often, or purchase a good water filtration system.
Copyright © 2004 Sped GmbH
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