Unitized Structural Body Repair Questions and Answers

Unitized Structural Body Repair Questions and Answers Unibody Lightweight stamped sheet metal components that are welded to each other to create a single unit. Space Frame Body panels can be made from plastic are steel. Steel may be Mild, Intermediate, or HSS. Panels may hide damage to frame or structure. Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0:08 / 0:15 Full screen Brainpower Read More Crush Zones Structural components such as rails are designed to collapse and bend at specific points. Collision Energy Management Goal is passenger protection. Front and rear structures act as crush-able energy absorbers. Direct Damage POI. Easily located and diagnosed. Indirect Damage transmission of collision energy beyond the area of immediate impact. Examples; Split seam sealers, pulled spot welds, misaligned panels, buckles in steel, cracked glass, and cracked or chipped paint. Passive Restraint Systems Must have service manual. No two are alike. Datum Imaginary plane or line beneath the vehicle. Measures height. Centerline Vertical plane that passes from the front of the vehicle to the rear. Measures Width. May have stamped marks on vehicle body structure. Is confirmed by referencing at last 3 width measurements in the undamaged portion of the vehicle. Zero Planes Vertical plane that passes from side to side. Confirmed by measuring 3 length measurements from the undamaged portion of the vehicle. Symmetry Equal on each side of the vehicle. Asymmetrical Unequal on each side of the vehicle. (spare tire well) Reference Points Bolts or nuts, Holes, Mechanical attachment points, Edges of panels, Door strikers, Corner of openings. Common tolerance is =/.3mm (1/8) or all the way to 1mm (1.32). Loaded Measurements Drivetrain In Unloaded Measurements Drivetrain out Point to Point Measurements shortest distance between 2 reference points. AKA "as the crow flies". Uses tram or steel tape measure. Datum Measurements Taken at Datum plane, height differences between reference points. Laser measuring system Computerized Measuring System compare data stored in a software program or a central database. Get hard copy of measurements. Can watch while pulling. Steel Cannot know what kind by visible. Must check service manual. Tensile Strength Amount of pressure/force necessary to fracture or tear steel. Yield Strength Amount of force/pressure necessary to deform steel permanently. PSI Pounds per inch /// tensile and yield strengths are expressed. Higher the number the stronger the steel. Mild Steel Cosmetic, used on Space frames, May be stressed relieved with heat, tears can be welded without a loss of strength. Yield strength 30,000 PSI Intermediate Steel Yield strength 30,000-70,000 PSI, structural and cosmetic, may be affected by excessive heat, small tears can be welded w/o loss of strength. High Strength Steel (HSS) Yield strength between 30,000-100,000 PSI, used in cosmetic and structural, is destroyed by exceeding temperature or time limits, should be replaced if kinked or torn excess of 1/4 inch, should be straightened cold whenever possible. Ultra High Strength Steel (UHSS) Very high yield strength exceeding 100,000 PSI, must never be repaired, door intrusion beams and re-bars. MIG/GMAW Welding Stick-Arc, and Oxy-Acetylene Are not recommended for unibody repair. They heat up to large of an area that is not needed. you want to weld the smallest area possible. Compression Spot Welding Used by manufactures, but is not recommended for collision repair. Our equipment makes welds 70-80%of the strength of manufactures. Manufactures may have technicians use but must follow service manual and special procedures. MIG Welding Wire (Electrode) AWS ER70S-6 AWS ER70S-7 AWS American Welding Society Standard E Type of standard-ELECTRODE R Electrode Type-ROD (MIG Wire) 70 Tensile strength Expresses in Thousands of PSI (70,000) S Electrode Type-SOLID 6 Chemical Make-up / Higher the number, better wire .023 Wire Most commonly recommended wire size Flux Cored Wires Recommended for steel thicker than 18 Gauge, Galvanized Steel, but burn through on 20 Gauge and thinner steel. Shielding Gases Recommend on steel. Mixture of argon and carbon dioxide. (Aluminum you use pure argon) C-25 Shield Gas, 25% Carbon Dioxide and 75% Argon Types of MIG Welders 110/120 and 220/240 // Determined by two factors Output Amp and Duty Cycle Output Amp Min 90-100 Duty Cycle Amount of actual welding time. Corrosion Protection Zinc based coatings. Zinc rich weld thru primers, Acid based metal cleaners and etchers, conversion coatings that form a zinc poshpate layer, Paint Finishers-sealers, color and clear coats, seam sealers at panel joints and seams, petroleum and paraffin based compounds. Restoring Corrosion Protection Soap and Water, wax and Grease remover, Metal Conditioners, Conversion Coatings, Epoxy Primers, Self Etching Primers, Weld Thru Primers, Seam Sealers, Wax and Petroleum Based Anti-Corrosion Compounds. Soap and Water First material that should be used. water soluble contaminants are washed away and the surface is rinsed clean. Wax and Grease Remover Used after soap and water. Removes tar, wax, silicones, and other petroleum based contaminants. Clean cotton rag and wipe dry with a second rag. Metal Conditioners Acid clean and etch the surface for the best possible adhesion of conversion coatings and primers. Do NOT use in enclosed areas where they can not be washed away. Conversion Coatings Follows the metal conditioners and lays down a zinc phosphate layer that maximizes primer adhesion as well as preventing rust "creep" under the painted surface. Not to be used in enclosed sections. Epoxy Primers Provides a level of corrosion protection closest to that of the original E-Coat primer. Must be applied soon after the cleaning, etching and conversion steps. Induction Period Some epoxy primers need to sit for a time after mixing. Self Etching Eliminates the need for conditioners and conversion coatings. Must be top coated with a paint finish or anti corrosion compound.