Abstract
The idea presented in this chapter is an innovative welding machine electrode force system. The operation, advantages of the new solution and the optimisation of the welding process were illustrated by the welding of aluminium bars (5182) (ø 4 mm). The solution involves controlling the force and/or displacement of welding machine electrodes. The modulation of electrode force significantly improves welding, particularly as regards aluminium alloys (requiring a very short welding process). The tests involved the numerical analysis of two electrode force systems, i.e. a conventional Pneumatic Force System (PFS) and an Electromechanical (Servomechanical Force) System (EFS). The numerical tests were performed using SORPAS software. FEM calculation results were verified experimentally. The technological welding tests were conducted using inverter welding machines (1 kHz) equipped with various electrode force systems. The research included metallographic and strength (peeling) tests and measurements of characteristic parameters. The welding process optimisation based on the EFS and the hybrid algorithm of force control resulted in i) more favourable space distribution of welding power, ii) energy concentration in the central weld zone, iii) favourable melting of the material within the entire weld transcrystallisation zone, iv) obtainment of the full weld nugget and v) longer weld nugget diameter.
Highlights
Force constitutes one of the most important parameters in the resistance welding process
The crosswise projection welding of aluminium bars (Al 5182) performed using the pneumatic force system (PFS) was subjected to numerical analysis verified experimentally and aimed to subsequently optimise the welding process performed using the electromechanical (servomechanical) force system (EFS) system
Risk of expulsion was accompanied by the lowest value of electrode force and the higher value of welding current (Table 8e, parameter field 7)
Summary
Force constitutes one of the most important parameters in the resistance welding process. During cross-wire projection welding ( of aluminium alloys) involving the use of a conventional application, i.e. the pneumatic force system (PFS), it is very difficult, nearly impossible, to make a weld containing the full weld nugget. Aluminium, when subjected to welding, gets plasticised very quickly, which is responsible for the formation of the excessively large area of contact between welded elements and, results in a rapid decrease in current density. These are not favourable conditions for the melting of materials. The PFS is characterised by high inertia and the impossibility of performing fast changes
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