BIW Design

BIW Design Do’s and Don’ts

• 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. Ingress-

Egress 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.

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 Design Guidelines

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.

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.

Panel Joinery Guidelines

BIW Manufacturing Process

Body ShopPress Shop Paint Shop Trim Line Final Assy

Form the panels

Presses

Dies

Checking Fixtures

Assemble the panels

Fixtures

Welding Guns

Checking Fixtures

Metal Finishing tools

Conveyers

Painting Body

Pre-treatment

Oven Baking

Finishing

Painting

Oven Baking

Inspection

Body Trimming

I/P Fitment

Seat Fitment

Glasses

Trim Carpets

Vehicle Roll-down

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

Floor Panel Body Side Panel

Cowl Panel

Door Inner Panel

Rear Floor Panel

B pillar inner

Tail Gate panel

Rear Long Member

Bonnet Inner

Hinge reinforcement

Roof bow rear Roof bow middle

Panel A pillar Inner

Shot gun panel

Hinge Reinforcement

Sill Rear Inner

Thank You