Abrasive Water Jet Cutting (AWJC)

Abrasive Water Jet Cutting (AWJC)

• Abrasive particles (aluminum oxide, silicon dioxide) are added to the water jet stream.
• Grit sizes range between 60 and 120 μm.
• Grits are added to the water stream at about 0.25 kg/min.
• The orifice jewel may be ruby, sapphire, or diamond, with sapphire being the most common.
• Nozzle orifice diameter: 0.25 - 0.63 mm, which is slightly larger than in water jet cutting.
• Water pressures are about the same as in WJC (400 Mpa).
• Typical standoff distances are between 1/4 and 1/2 of those in WJC.

Abrasive Jet Machining (AJM)

• A material removal process caused by the action of a high-velocity stream of gas containing small abrasive particles.
• Pressure: 0.2 to 1.4 Mpa.
• Nozzle orifice diameter: 0.075 to 1.0mm.
• Velocities: 2.5 to 5.0 m/s.
• Gases: dry air, nitrogen, carbon dioxide, and helium.
• Typical abrasives: aluminum oxide (for aluminum and brass), silicon carbide (for stainless steel and ceramics), and glass beads (for polishing).
• Grit sizes are small, 15-40 μm in diameter and must be uniform in size for a given application.

Advantages of AJM

• Low cost.
• Less vibration.
• No heat is generated in the workpiece.
• Ability to cut complex holes.
• No burrs as in conventional machining.
• Low tool wear.
• Relatively high metal removal rates for hard and difficult metals.
• Capable of machining complex parts and hard materials.
• High production and high tolerances.

Electrochemical Deburring (ECD)

• Modification of ECM to remove burrs or round sharp corners on metal parts.
• The electrolyte flows through the hole to carry away the burr particles.
• Cycle times are much shorter, typically less than a minute.

Electrochemical Grinding (ECG)

• An improved electrochemical grinding wheel electrode consisting of electrically conductive abrasive grains bonded together with nonconductive bonding material.

Electrochemical Machining Processes

• Electrical energy is used in combination with chemical reactions to remove material.
• Reverse of electroplating in that it removes material instead of adding it.
• Work material must be a conductor.

Electrochemical Machining (ECM)

• Material removal from an electrically conductive workpiece using an electrode (tool) in close proximity to the work but separated by a rapidly flowing electrolyte.
• Material is removed from the anode workpiece (positive pole) and transported to the cathode tool (negative pole) in an electrolyte bath.
• Electrolyte carries off the material that has been removed from the workpiece.
• Electrolyte – salt solutions like sodium chloride (NaCl) or sodium nitrate (NaNO3) mixed in water.
• The flowing electrolyte also serves the function of removing heat and hydrogen bubbles created in the chemical reactions of the process.
• Electrode materials: Cu, brass, or stainless steel.
• Tool has the inverse shape of the part.
• Tool size and shape must allow for the gap.
• Die is gradually lowered into workpiece.
• Low voltage (5-25 V) and very high current (700 amps).

Advantages of ECM

• Does not cause any thermal damage to the parts.