Machining Lab
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Transcript of Machining Lab
Prepared by Dr .K..Elangovan
Jet machining
Prepared by Dr .K..Elangovan
Jet machining
Consisting of:Consisting of:•• Abrasive Jet MachiningAbrasive Jet Machining
•• Water Jet MachiningWater Jet Machining
•• Abrasive water jet machiningAbrasive water jet machining
Prepared by Dr .K..Elangovan
Abrasive Jet MachiningAbrasive Jet Machining– High pressure air with fine powder, blended together to
form an abrasive mixture – This mixture is sent through a small, precisely machined
nozzle– The result is a highly accurate abrasive stream used for
cleaning, cutting, drilling, deburring
Prepared by Dr .K..Elangovan
Abrasive Jet MachiningAbrasive Jet Machining--Set upSet up
Prepared by Dr .K..Elangovan
Abrasive Jet MachiningAbrasive Jet Machining--Set up Set up (Schematic)(Schematic)
Prepared by Dr .K..Elangovan
Abrasive jet machining (AJM)– A high velocity stream of gas containing small abrasive particles– Pressure: 0.5 – 2 Mpa– Nozzle orifice diameter: 0.08 – 1 mm – Velocities: 150 - 300 m/s– Gases: dry air, nitrogen, carbon dioxide and helium– The process is usually carried out manually by an operator– AJM is normally used as a finishing process– Applications: deburring, trimming and deflashing, cleaning and
polishing– Applied on hard, brittle materials (glass, silicon, mica and
ceramics) that are in the form of thin flat stock– Typical abrasives: aluminum oxide (for aluminum and brass),
silicon carbide (for stainless steel and ceramics), and glass beads (for polishing)
Prepared by Dr .K..Elangovan
Abrasive Jet MachiningAbrasive Jet Machining
• Abrasive Machines are extremely versatile and have limitless applications.
• They have the power to cut and drill materials as hard as diamonds as well as the precision of delicate items like fabric and paper
• Grit sizes are small, 15-40µµµµm in diameter and must be very uniform in size for a given application
• No recycling of abrasives; abrasive grains are fractured, worn and contaminated
Prepared by Dr .K..Elangovan
Machining system• Relative motion between nozzle and work piece
– can be manual• Or automatically controlled using cam drives,
tracer mechanisms or using computer controlled according to the cut geometry required
• Masks of copper, glass or rubber – can be used to concentrate the jet stream of abrasives to a confined area on the work piece
• Intricate and precise shapes can be produced using masks with corresponding contours.
• Dust removal or collecting equipment must be incorporated to protect the environment
Prepared by Dr .K..Elangovan
Mechanism• The abrasive particles from the
nozzle follow parallel paths for a short distance
• Then the abrasive jet flares outward like a narrow cone
• When the sharp-edged abrasive particles of Al2O3 or SiC hit a brittle and fragile material at high speed, tiny brittle fractures are created from which small particles dislodge
• The dislodged particles are carried away by the air or gas
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Process Parameters• Carrier Gas (Non toxic, Cheap - Air, Carbondi-oxide,
Nitrogen)
• Type of abrasive( Aluminium oxide, Silicon carbide, sodium bicarbonate, Dolomite)
• Size of abrasive grain (coarse grains-cuttingFine grains- polishing and de burring)
• Work material (Glass, ceramics, refractories)
• Nozzle design( Circular, Rectangular- Mat: Wc, Sapphire)• Shape of cut (Not suitable to sharp corners) • Velocity of abrasive jet• Stand off distance
Prepared by Dr .K..Elangovan
Velocity of abrasive jet
Abrasive:Al2O3
Work Material: Glass
Abrasive:Al2O3
Work Material: Cemented Carbide
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Effect of process parameters
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Stand off distance-Accuracy
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Stand off distance-MRR
SOD, mm
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Advantages• No heat generation-Cool Process
(Heat-sensitive materials like glass, quartz, sapphire, and ceramics can be machined)
• No surface damage• Low capital investment& Power consumption• Ability to cut thin brittle materials (super alloys and refractory
materials)
Disadvantages
• Not suitable for ductile materials• The abrasive may get impeded in the work surface• Additional cleaning is required• Stray cuts &Poor accuracy(± 0.1 mm)• High nozzle wear rate• Environment hazard
Prepared by Dr .K..Elangovan
Applications• Drilling holes, cutting slots, cleaning hard surfaces• De burring of cross holes, slots, and threads in small
precision parts that require a burr-free finish, such as hydraulic valves, aircraft fuel systems, and medical appliances
• Removal of flash and parting lines in moulding parts• Deburring and polishing plastic, nylon components• Cutting thin sectioned fragile components• Cleaning mould cavities• Frosting glass plates and tubes• Marking on glass cylinders
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Cleaning of corroded surface
Before cleaning After cleaning
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Frosted Glass
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Casting cleaned by Abrasive Jet
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Abrasive Jet Cleaning Equipment
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Before cleaning
After cleaning