Chapter 7IT 2081 Thermal and Other Methods of Material Removal Chapter 7

IT Competency Describe the process of oxy-fuel cutting and laser cutting

Chapter 7 IT Thermal Methods of Material Removal Hot Wire Cutting Used to cut foamed thermoplastic material (Thermoplastic - Soften repeatedly when heated) Requires good ventilation Cannot cut thermosetting polymers, insulation materials or polyurethane foam (Thermosetting -When hardened cannot melt again )

Chapter 7 IT Thermal Methods of Material Removal Oxy-Fuel Gas Cutting A cutting torch uses a circle of oxy-fuel jets to bring the material to its melting point then compressed oxygen is released in a center nozzle to “blow away” the molten metal. Typical oxy-fuel is oxygen-acetylene or oxygen- hydrogen It is a fast, inexpensive process that requires fairly little operator training. Plates as thick as 12 inches may be cut Industry often uses computer controlled machines with multiple cutting torches to produce multiple parts simultaneously.

Chapter 7 IT Thermal Methods of Material Removal LASER Cutting - source of energy is a light -Light Amplification by Stimulated Emission of Radiation Uses a highly focused light source as energy Removes metal by melting and then vaporizing the workpiece, gas blows liquid and vapor away Reflectivity and thermal conductivity of materials are important (dull materials preferred) A gas stream helps to clear the path for beam Small holes with deep depth can be made the size of the laser beam (blind holes cannot be made to exact depth) Never look into a laser – can cause major damage to retina

Chapter 7 IT Thermal Methods of Material Removal Advantages Material savings from very narrow kerf Minimum heat effected zone Fine finishes on thin pieces Cut complicated shapes Can cut material of any hardness Can produce short runs quickly and efficiently Disadvantages Cost of machine can be as high as $2 million and more Cost of maintenance can be $4,000 per machine per month

Chapter 7 IT Thermal Methods of Material Removal Water Saw (Waterjet) Water that has been filtered for minerals and debris is increased in pressure from 20,000 to 60,000 psi and forced through a small orifice (0.003” to 0.023”) to cut through material Electron Beam Machining - high velocity electrons strike work piece causing heat and melt the work piece Voltages of 50, ,000 V Must be done in a vacuum or loss of power results Makes cuts accurately on smaller size work pieces

Chapter 7 IT Thermal Methods of Material Removal AdvantagesDisadvantages Oxy-Acetylene Flame Fast; can be used on large cuts Rougher cut surface Workpiece surface oxidized Electron Beamclean; good precisionExpensive; requires vacuum Water SawGood on hard materials Relatively fast Expensive equipment