Ableitung von Kennzahlen für die Prozessqualität und Prozesskenngrößen abhängige Regelung beim Laser-MSG-Hybridschweißverfahren

Sha, Peng; Dilthey, Ulrich (Thesis advisor); Murrenhoff, Hubertus (Thesis advisor)

Aachen (2017) [Dissertation / PhD Thesis]

Page(s): 1 Online-Ressource (III, 256 Seiten) : Illustrationen, Diagramme

Abstract

Monitoring indices SSI, ASI and PR deduced from [99Ogu] were applied to CO2-Laser-GMA (gas metal arc) Hybrid welding. The indices are statistical values which come from voltage and current of the arc. The indices serve for as indicators for the stability of the arc. Therefore the indices are used for quality control of the process. Because of the interaction between laser and arc in the hybrid process, changes of the indices are correlated to changes in the laser power.Process distance and the welding direction may affect the efficiency of laser power as well as the indices. The index SSI at 3 mm process distance and with GMA leading is used for the closed-loop control of the process, because at this process distance and in this welding direction, SSI reacts most sensitively to changes in laser power.A closed-loop control with PID-controller is established. The control interval of 100 ms is optimal. The difference between measured process variable and designed setpoint of SSI determines the actual laser power via PID-controller. The controlled laser power can thus regulate the arc.The controlled laser power in a hybrid process has the following strongponits: fewer short circuits, fewer open circuits, more stable welding voltage, and more stable welding current.The closed-loop control is robust against changes in welding speed. It compensates for changes in the energy input per unit length and reduces laser induced plasma. As for changes in the He-percentage of the shielding gas, the closed-loop control is robust within a certain range. Because of the controlled laser power, plasma is reduced. This closed-loop control is also robust within a certain rage against sudden and gradual changes in the welding gap.The range of the function of the closed-loop control always depends on the value of the setpont. Each sepoint is correspondent with a desired amount of laser power. The value of the setpoint depends on the welding task, such as the thickness of the base metal. The setpoint must be known in advance.

Identifier

  • REPORT NUMBER: RWTH-2017-04365