• Spots to be loaded in Shear • The Material Thickness (All included) < ~4.00mm • The Difference between the Thickness of welding panels : < 25% • Check Distance between Two Consecutive spots • Panel to be designed to have Max. Stretching. • Thinning of Panels : ~10% • Part to be designed to have minimum number of Dies. • Panels to split in a manner to utilize maximum Steel • Generally for big panels 60% utilization is Good
BIW Design Do’s and Don’ts
• Sufficient provision of Holes and Cutouts for Air Escape and Paint Drain. • Weight Reduction Cutouts should be clubbed with the Access holes / Cutouts and Drains. • Add Bird Beaks, Ribs to contain Spring back • Avoid Stretch Flanges • Corner Radii Min 2.5 * Depth (e.g. IngressEgress issue for Body Side)
Panel Design Guidelines Should not be odd and big in shape and size; handling issues. Size as per manufacturing facility available. Panel Split for maximum utilization of material, criticality of the area and manufacturing facility available. Generally for bigger panels 60% of material utilization is good. Sufficiently stretched – Load Considerations. No area left un-stretched In areas which are mostly of geometrical continuity, Stiffener beads to be provided.
Panel Design Guidelines
A maximum of 15% stretching is allowed in steel sheet drawing. Thinning < 10%. Depth of draw can be achieved by providing steps. Internal features (Local depressions) should have radius as big as possible. For deep draw panels, the number of draw should be as per manufacturing guidelines. Avoid providing any feature, in other than die tip angle, as this may lead to cam operation. If possible the trim edges of internal features should have some radius. (Sharp edge tools get damage soon)
Panel Design Guidelines Thickness of panels should be chosen as per the application. Do not increase the thickness of complete panel. Local reinforcement to be added as an when required. Latest trend is of Tailored blank.
To reduce the part weight, areas of least stress should be trimmed (Pockets created).
The weight reduction pockets should be tried and clubbed for Tooling Access Holes, Air vent and Paint drain.
Panel Joinery Guidelines
Load on Spot weld to be in Sheer. Flange width to be as per manufacturing requirements (Tooling). For general purpose, 18mm flat is considered OK. There should not be more than three panel thickness stack for spot weld. CO2 weld and Brazing to be avoided. Joinery should be designed in a manner where no spot is on the A- class Surface. The joinery should be such that it counters the tolerance stack. Joinery should have sliding contact i.e. No joinery to be in locking condition.
Panel Joinery Guidelines
For bigger assemblies in docking - design gap should be kept. For Example between Side assembly and Underbody assembly, 1.00mm design gap is OK. The joinery to be sequenced to avoid any locking situation. There should not be a difference of more than 50% between two joining panels. To get better Spot strength, total material stack should be 4 to 4.5mm. The Serviceability aspects should be kept in consideration.
BIW Manufacturing Process Press Shop Form the panels Presses Dies Checking Fixtures
Body Shop Assemble the panels Fixtures Welding Guns Checking Fixtures Metal Finishing tools Conveyers
Paint Shop
Trim Line
Painting Body
Body Trimming
Pre-treatment
I/P Fitment
Oven Baking
Seat Fitment
Finishing
Glasses
Painting
Trim
Oven Baking
Carpets
Inspection
Final Assy Vehicle Rolldown Power Train Suspension Steering Fuel System Brakes Alignments
Testing Inspection
Formability Problems in Panels
• • • • •
Fracturing Buckling and Wrinkling Shape Distortion Oil Canning Undesirable Surface Textures (Orange Peel, Luder Lines or Stretcher Lines, Spangles etc)
Properties affecting the formability of material
• • • • • • • • • • •
‘r’ value – Work Hardening Coefficient ‘n’ value – Resistance to thinning UTS Yield Point Elongation Uniform Elongation Total Elongation Yield Strength Hardness Punch Velocity Lubrication Chemistry
Steel used in BIW
Properties vary for the same material
• • • • • •
From Supplier to Supplier From heat to heat From coil to coil From angle to angle with the rolling direction From one end of coil to other end of coil From one edge of coil to other
Design-Manufacture
Design-Manufacture
Exploded View of Automobile Body Panels Door Inner Panel
