Abrasive water-jet cutting Flashcards
Be able to produce a basic diagram of water-jet and abrasive water-jet cutting.
Refer to the abrasive water-jet lecture.
What are the applications of water-jet cutting and explain why this industry has grown?
WaterJet Applications;
Cut blanks or finished parts
Rapid prototyping
Short runs of specialized parts
This is one of the modern fastest growing machining processes as it is one of the most versatile machining processes. This process compliments other technologies such as milling, laser, EDM, plasma, and routers.
The true cold cutting process has no Heat Affected Zone (HAZ), mechanical stress or operator and no major operator and environmental hazards. This process is also not limited to machining as it can be utilized within the food industry.
Explain the basic properties of Pure Water-Jet Cutting
Pure waterjet cuts soft materials – corrugated
cardboard, plastic, papers, automotive interiors.
Very thin waterjet (0.1-0.5mm diameter)
Extremely detailed geometry can be produced
Very little material loss due to cutting
Can cut thick, soft, light materials like fiberglass
insulation up to 24” thick or thin, fragile materials
Very low cutting forces and simple fixturing
Water jet erodes work into small particles
Water inlet pressure between 20k-60k psi
Forced through hole in jewel 0.1–0.5mm
diameter
Sapphires, Rubies with 50-100 hour life
Diamond with 800- 2,000 hour life, but they are expensive
What are the properties of Abrasive Water-Jet Cutting?
Abrasive jet machining first started in 1982. Before abrasive jets, there were waterjets which have been in use since 1970.
Abrasive jet machining is widely popular in industries such as the automobile, aerospace, and glass to create precision parts from virtually any material.
An abrasive jet pressurizes water up to 55,000 pounds per square inch (psi) [380,000 kilopascals (kPa)] and then forces it through a small sapphire or diamond orifice at 750 meters per second, or about two and half times the speed of sound.
Garnet abrasive is then pulled into this high-speed stream of water, and mixed with the water in a long composite carbide mixing tube. A stream of abrasive-laden water moving at 300 meters/sec exits the ceramic tube. This jet of water and abrasive is then directed at the material to be machined.
The jet drags the abrasive through the material by forcing the abrasive particles through the workpiece.
Abrasivejet machinings’ cutting action is a grinding process, but rather than using a solid grinding wheel, the forces and motions of the cutting action are provided by water.
What are the tolerances of water-jet machining?
Achievable Machining Tolerances:
Typically +/- 0.125 mm
Machines usually have a repeatability of 0.025mm
Comparatively, traditional machining centers can hold tolerances 0f 0.02mm with similar repeatability.
WaterJet tolerance range is sufficient for many applications.
When is it practical to use Water-jet cutting?
Practical to use it to cut any kind of material.
In waterjet cutting, there is no heat generated. This is especially useful for cutting tool steel and other metals where excessive heat may change the properties of the
material.
Waterjet cutting does not leave a burr or a rough edge, and eliminates other machining operations such as finish sanding and grinding.
Can be easily automated for production use.
Identifyt the advantages of Water-jet Cutting
- Cheaper than other processes.
- Cut virtually any material. (pre hardened steel, mild steel, copper, brass, aluminum etc. brittle materials like glass, ceramic, quartz, stone)
- Cut thin or thick materials
- Make all sorts of shapes with only one tool.
- No heat generated.
• Leaves a satin smooth finish, thus reducing secondary
operations.
- Clean cutting process without gasses or oils.
- Modern systems are now very easy to learn.
- Safe manufacturing process
- Machine stacks of thin parts all at once.
- Unlike machining or grinding, waterjet cutting does not produce any dust or particles that are harmful if inhaled.
- The width in waterjet cutting is very small, and very little material is wasted.
- Waterjet cutting can be easily used to produce prototype parts very efficiently.
- Program the dimensions of the part into the CNC controller and the waterjet will cut the part out exactly as programmed.
- Waterjets are much lighter than equivalent laser cutters, and can be mounted on an automated robot arm.
No heat in machining process:
Abrasivejets cut material at room temperatures. As a result, there are no heat-effected areas or structural changes in materials. Abrasivejets can also machine hardened metals and materials with low melting points.
Environmentally friendly:
Abrasivejets use garnet as an abrasive. Garnet is an envirmentally- safe, naturally-occuring, hard crystal. No noxious gases or liquids are used in abrasivejet machining, nor are there any oils used in the machining process.
No tool changing:
A wide range of conventional processes can be performed with this single tool.
Identify the Disadvantages of Water-jet cutting.
- Disadvantage is that very thick parts cannot be cut with waterjet cutting and still hold dimensional accuracy.
- If the part is too thick, the jet may dissipate and cause it to cut on a diagonal, or to have a wider cut at the bottom of the part than the top – Taper.
- It can also cause a rough wave pattern on the cut surface.
Discuss the arguement of using Water-jets verus the use of Lasers.
• Abrasive waterjets can cut many materials that lasers
cannot. (Reflective materials in particular, such as Aluminum and Copper.
• Uniformity of material is not important to a waterjet.
• Waterjets do not heat your part. There is 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).
- Waterjets are safer.
- Maintenance on the abrasive jet nozzle is simpler than that of a laser.
Discuss the argument of using Water-jets versus the use of EDM (Electric discharge Machining).
- Waterjets are much faster than EDM.
- Waterjets machine a wider variety of materials (virtually any material).
- Uniformity of material is not very important to a waterjet.
- Waterjets make their own pierce holes.
- Waterjets do not heat the surface of what the machine.
- Waterjets require less setup.
- Many EDM shops are also buying waterjets.
•Waterjets can be considered to be like super-fast EDM
machines with less precision.
Discuss the argument of using Water-jets versus the use of Plasma Cutting.
- Waterjets provide a nicer edge finish.
- Waterjets don’t heat the part.
- Waterjets can cut virtually any material.
- Waterjets are more precise.
- Plasma is typically faster.
- Waterjets would make a great compliment to a plasma shop where more precision or higher quality is required, or for parts where heating is not good, or where there is a need to cut a wider range of materials.
Discuss the arguement of using Water-jets verus the use of Flame cutting, Milling and Punch press operations.
Flame Cutting:
Waterjets would make a great compliment to a flame cutting where more precision or higher quality is required, or for parts where heating is not good, or where there is a need to cut a wider range of materials.
Milling:
Waterjets are used a lot for complimenting or replacing milling operations. They are used for roughing out parts prior to milling, for replacing milling entirely, or for providing secondary machining on parts that just came off the mill. For this reason, many traditional machine shops are adding waterjet capability to provide a competitive edge.
Punch Press:
Some stamping houses are using waterjets for fast turn-around, or for low quantity or prototyping work. Waterjets make a great complimentary tool for punch presses and the like because they offer a wider range of capability for similar parts.
