Joining Processes PDF - Cambridge Nationals

CAMBRIDGE NATIONALS TA1.2.5: Joining processes R014: Principles of engineering manufacture TA1: Manufacturing processes CAMBRIDGE NATIONALS R014, TA1.2.5 Joining processes Joining proces...

CAMBRIDGE NATIONALS TA1.2.5: Joining processes R014: Principles of engineering manufacture TA1: Manufacturing processes CAMBRIDGE NATIONALS R014, TA1.2.5 Joining processes Joining processes attach parts together Some product designs cannot be made as a single piece using conventional manufacturing processes Some materials may not easily be joined together Types of joint Why would a designer use Permanent: can only be taken apart by breaking the material a temporary joint rather Temporary: can be taken apart without damaging the material than a permanent one? Joining MIG/MAG welding MIG/MAG welding Brazing Brazing process Riveting Pop rivets Mechanical processes equipment fastenings CAMBRIDGE NATIONALS R014, TA1.2.5 MIG/MAG welding Used to make permanent joints between parts made from similar metals Heat from an electric arc melts the edges of the parts The arc is formed between a wire and the parts being joined – the wire melts to become part of the joint The weld is protected from the atmosphere by a shielding gas: in Metal Inert Gas (MIG) welding the gas is typically argon in Metal Active Gas (MAG) welding the gas may also contain carbon dioxide or even some oxygen Welding can give the strongest joints Joining MIG/MAG MIG/MAG welding Brazing Brazing process Riveting Pop rivets Mechanical processes welding equipment fastenings CAMBRIDGE NATIONALS R014, TA1.2.5 MIG/MAG welding equipment Spool of wire Regulator Hazards Arc light Hot metal Gas cylinder Welding fume Welding torch Electric shocks Power source Return What could be done to reduce health and lead safety risks? Joining MIG/MAG welding MIG/MAG welding Brazing Brazing process Riveting Pop rivets Mechanical processes equipment fastenings CAMBRIDGE NATIONALS R014, TA1.2.5 Brazing Used for metal parts, to make a permanent joint The metal parts being joined do not melt The joint is typically not as strong as a weld Brazing equipment Oxyfuel torch Gas supply, e.g. gas cylinders (oxygen, fuel gas) Forge/firebricks Consumables: Brazing rod Why would brazing be used Flux rather than welding? Joining MIG/MAG welding MIG/MAG welding Brazing Brazing process Riveting Pop rivets Mechanical processes equipment fastenings CAMBRIDGE NATIONALS R014, TA1.2.5 Brazing process The surfaces to be joined are thoroughly cleaned and any Hazards oxides (rust) removed Combustible gases Flux may be applied to prevent oxidization and help the braze Flames to flow Hot metal Flux chemicals The joint is heated with an oxyfuel flame The brazing rod is added and melts, flowing into the gap between the parts being joined When it cools, the braze solidifies, holding the parts together The braze might be a different colour to the parent metal What could be done to reduce health and safety risks? Joining MIG/MAG welding MIG/MAG welding Brazing Brazing process Riveting Pop rivets Mechanical processes equipment fastenings CAMBRIDGE NATIONALS R014, TA1.2.5 Riveting Used to permanently join overlapping sheets of metal Can join dissimilar materials Hole must be drilled through both sheets Rivet is pushed through the hole and the end hammered over The overlaps ‘pinch’ the sheets together Needs access to both side of the joint Hazards What could be done to Applied force reduce health and Impact noise safety risks? Joining MIG/MAG welding MIG/MAG welding Brazing Brazing process Riveting Pop rivets Mechanical processes equipment fastenings CAMBRIDGE NATIONALS R014, TA1.2.5 Pop rivets Special type of riveting – needs access to only one side of the joint Enlarged pop rivet Rivet gun Once the rivet us is pushed through the hole in the sheets, a rivet gun pulls on the central steel pin Pin Steel pin This causes the back of the rivet to breaks off deform, causing the pinch between the two sheets Completed rivet Pop riveting is often used to Hollow attach the metal ‘skin’ to aircraft rivet wings and bodies. Why do they body use this process rather than the alternatives? Joining MIG/MAG welding MIG/MAG welding Brazing Brazing process Riveting Pop rivets Mechanical processes equipment fastenings CAMBRIDGE NATIONALS R014, TA1.2.5 Mechanical fastenings Used to make temporary joints Can join dissimilar materials These use screw threads Available in a variety of metals and polymers Normally require a hole in the parts to be joined Put in place using screwdrivers or spanners Washers can be used to spread the force over a wider area Types of mechanical fasteners What applications of mechanical fastenings can you think of? Why were they used for Nuts and bolts, self-tapping screws these applications? Joining MIG/MAG welding MIG/MAG welding Brazing Brazing process Riveting Pop rivets Mechanical processes equipment fastenings