14-04-2011, 12:31 PM
Abrasive Waterjet1.ppt (Size: 4.07 MB / Downloads: 541)
Abrasive Waterjet Machining
Introduction to Waterjet
Fastest growing machining process
One of the most versatile machining processes
Compliments other technologies such as milling, laser, EDM, plasma and routers
True cold cutting process – no HAZ, mechanical stresses or operator and environmental hazards
Not limited to machining – food industry applications
History
Dr. Franz in 1950’s first studied UHP water cutting for forestry and wood cutting (pure WJ)
1979 Dr. Mohamed Hashish added abrasive particles to increase cutting force and ability to cut hard materials including steel, glass and concrete (abrasive WJ)
First commercial use was in automotive industry to cut glass in 1983
Soon after, adopted by aerospace industry for cutting high-strength materials like Inconel, stainless steel and titanium as well as composites like carbon fiber
Pure WJ Cutting
Pure cuts soft materials – corrugated cardboard, disposable diapers, tissue papers, automotive interiors
Very thin stream (0.004-0.010 dia)
Extremely detailed geometry
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 at kerf line into small particles
Pure WJ Cutting cont.
Water inlet pressure between 20k-60k psi
Forced through hole in jewel 0.007-0.020” dia
Sapphires, Rubies with 50-100 hour life
Diamond with 800-2,000 hour life, but they are pricey
Abrasive WJ Cutting
Used to cut much harder materials
Water is not used directly to cut material as in Pure, instead water is used to accelerate abrasive particles which do the cutting
80-mesh garnet (sandpaper) is typically used though 50 and 120-mesh is also used
Standoff distance between mixing tube and workpart is typically 0.010-0.200 – important to keep to a minimum to keep a good surface finish
Abrasive WJ Cutting cont.
Evolution of mixing tube technology
Standard Tungsten Carbide lasts 4-6 hours (not used much anymore)
Premium Composite Carbide lasts 100-150 hours
Consumables include water, abrasive, orifice and mixing tube
Tolerances
Typically +/- 0.005 inch
Machines usually have repeatability of 0.001 inch
Comparatively traditional machining centers can hold tolerances 0f 0.0001 inch with similar repeatability
WJ tolerance range is good for many applications where critical tolerances are not crucial to workpart design
Setup
When is it Practical?
Advantages
Disadvantages
Waterjets vs. Lasers
Waterjets vs. EDM
Waterjets vs. Plasma
Waterjets vs. Other Processes
Future of Waterjet
Drilling wells
Drilling for oil
Radial tunnels
Practical Applications
Edge finishing
Radiusing
De-burring
Polishing
Conclusion
Relatively new technology has caught on quickly and is replacing century-old methods for manufacturing
Used not only in typical machining applications, but food and soft-goods industries
As material and pump technology advances faster cutting rates, longer component life and tighter tolerances will be achievable
Paves the way for new machining processes that embrace simplicity and have a small environmental impact