| As low-end commercial vehicle, mini-car has to be made undermass-production and low-cost mode to meet market demand, front door assembly,and as one of the critical parts to BIW, front door assembly quality directlydecide the quality and efficiency of BIW assembling. With welding, sealing andhemming as its main process, welding quality takes the biggest portion inimpacting door assembling reworking. The main problems in the certain modelmini-car front door welding are: improper welding spatter with inner panel,spot deformation and unacceptable spot depth, welding access problem with outerpanel, weld spatter with CO2welding at door rim, improper spot size, sport tier,spot displacing, dry joint or burn out, spot deformation at window rim, etc,which result in door reworking and production cost increasing and efficiencyreducing. Thus, it is of significant meaning to improve and stabilize productquality via process upgrading as well as enhance work efficiency and minimizeproduction cost and escalate product competitiveness via minimize reworking.Aiming at improving welding quality, production efficiency and reducinglabor work intensity, this thesis looks into following researches based onanalysis to front door of a certain present mini-car with combining resistantspot welding theory:1) the conclusion of manual welding is the most applicablewelding method to front door inner subassembly is get through analysis toproduct structure and welding spot deployment and research to welding processimprovement through spot distribution, welding parameters and welding gunstructure solutions by analysis of welding defect causes with verificationmethod from all the factors incl. process, specification and artificial.2)Research on transferring spots welding station of front door outer subassemblythrough product structure improvement by process verification through analyzing welding access from product structure, welding method and processlayout.3) Research on replacing CO2welding for door rim with power resistantspot welding through analyzing product structure and characteristics of CO2welding with the conclusion that CO2welding is improper to door rim welding.4)Research on upgrading welding gun structure and adopting multi-spotauto-welding for window rim by analyzing welding defect causes from processand artificial aspects.5) Analyze importance of the3welding qualityinspection methods incl. non-destructive test, destructive test andultra-sonic check to welding middle course supervision for welding defectspreventionBelonging to engineering application type, this subject has solved theresistant spot welding problems such as improper welding spatter, spotdeformation, unacceptable spot depth and the co2welding problems such as weldspatter, improper spot size, sport tier, spot displacing, dry joint or burnout. This subject obviously improved welding quality of front door assemblyesp. front door rim, reworking rate of front door assembly has been reducedcritically, through which production efficiency has been enhanced and cost hasbeen cut down after process upgrading. Nevertheless, process improvement itselfis a long procedure which still needs further detailed research for continuousupgrading to provide stronger support to process development in followingmodel. |
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