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Technological Innovations in Body in White Manufacturing of the BMW X6

Markus PfestorfBMW Group

Duane CopelandBMW MC

BMWGroup

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ContentBMWGroup

• Body in White Requirements for EfficientDynamics

• Body in White Materials

• Ultra High Strength Steel Grades

• Joining Technologies

• Conclusion

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BodyIn

White

EfficientDynamics

Axle and

KinematicsPower Train

Aero

dyna

mics

Weight and Axle

Load Distribution

Body in White RequirementsEfficient Dynamics

BMWGroup

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- Torsional Stiffness of 29.000Nm/°- Implementation of Ultra High Strength Steel Grades- Mixed Material Concept (Steel, Aluminum, Thermoplastic)- Cost Efficient Engineering using existing Panels with a maximum Design

Differentiation

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Body in White RequirementsCost Efficient Light Weight Design

Specific PanelsShared Panels

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Body in White MaterialsYield Strength

Deep Drawn Steel14%

180 MPa15%

200-220 MPa, 4 %

260 MPa7%

300 MPa18%

380-420 MPa, 25%680 MPa, 5%

950 MPa, 3%

6xxx Aluminum, 2%Others, 4%

550 MPa, 3%

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?

Body-In-White MaterialsAverage Minimum Yield Strength

BMWGroup

3´SeriesSedan5´Series

7´Series

1´Series

3´Series Sedan

7´Series 5´Series

5´SeriesSports Wagon

3´SeriesSports Wagon

5´SeriesSports Wagon

3´Series Sports W. 3´Series Coupé

3´SeriesCompact

Z4´Coupé

6´Series Coupé

3´SeriesCoupé

Z4

3´SeriesConvertible

6´Series Convertible

150

200

250

300

350

400

MPa475

500

1994 1996 1998 2000 2002 2004 2006 2008 20102008

Start of Production

Ave

rage

min

. Yie

ld S

tren

gth

Rp0

,2

Previous X5

Current X5X6

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Body-In-White MaterialsAverage Thickness

BMWGroup

7´Series

5´Series

Previous X5

3´Series Convertible

Z4

7´Series

6´Series Convertible

6´Series Coupé

5´Series Sports Wagon

1´Series

3´Series Sports Wagon

0,9

1,0

1,1

1,2

1,3

1,4

1,5

mm

1,7

1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

Start of Production

Ave

rage

Thi

ckne

ss

Without Advanced High Strength Steel

Current X5 X6

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t = 1.2 mm

t = 1.4 mm

t = 2.2 mm

t = 1.2 mm

Weight Savings: 2 kg/side(compared to a hot stamped part with a constant thickness)

Thickness (t)

Mechanical Values:Yield Strength Rp0,2: > 950 MPaTensile Strength Rm: > 1300 MPa

UHSS – Hot Stamped 22MnB5Side Crash

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BMWGroup

UHSS – CP800Rear Crash

Weight Savings for theLongitudinal Rear Member: 4,4 kg

Mechanical Values:Yield Strength Rp0,2: 680 - 830 MPaTensile Strength Rm: 800 - 980 MPaElongation A80: > 10%

(Complete Longitudinal rear memberincluding other steel grades)

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UHSS – CP800Rear Crash of a Prototype

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Tested profile

Specimen after Drop Test

Yield Strength Rp0,2

Tensile Strength Rm

Elong. after Fracture A80

Thickness

Mech. Properties(as delivered)692 MPa901 MPa11,40,99

Mech. Properties(180°C, 60 min.)796 MPa923 MPa10,80,99

± 118 mm

±88

mm

40

80

120

kN

200

Def

orm

atio

n Fo

rce

Deformation Time

157,37 kN (with Bake Hardening Response)155,84 kN (without Bake Hardening Response)

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UHSS – CP800Rear Crash

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Thickness of all Parts: 1,5 mm

UHSS – CP800X6 Part Application

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Phase 1 Phase 2 Phase 3

ab

d

a

c

UHSS – CP800Tool Realization Guidelines

Tool Change Content : a) Optimize the release of flange formb) Optimize the draw of the embossmentsc) Increase the radii if necessaryd) Optimize the trim

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Secure the part fastening assembly process in the Prototype Phase.• Testing the Series assembly Tools with the Prototype Parts and early

Optimization of the Clamping Technology. • Higher Measurement Stability in the BIW.

UHSS – CP800Clamping in Body in White

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Joining TechnologiesMaterials and Joining Technologies

Main Joining Technologies:• Resistant Spot Welding (6643 Spot Welds)• Adhesive Bonding (116999 mm)

Other Joining Technologies:• Self Pierce Riveting (82)• Clinching (53)• Mig Welding and Brazing (8053 mm)• Capacitance Discharge Welding

Adhesive Bonding

Spot Weld

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Local Static StiffnessUpper Control Arm

+ 12%

Static Torsional Stiffness + 2%

Dynamic Stiffness+ 0.1Hz

to+ 0.3Hz

Applied Adhesives

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Joining TechnologiesBenefit of Structural Adhesives

Local Static Transversal Stiffness ofthe Upper Control Arm

Difference of Displacements of theSpring Support with and without Adhesive Application

with Adhesivewithout Adhesive

Benefit on Stiffness

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BMWGroup

Joining TechnologiesAluminum Casted Front Shock Tower

- High Pressure VaccumCasting

- Heat Treated

- Machined

- Cataphoretic Painting

- Bonding (ca. 5.4 m)

- Self Pierce Rivets (82 times)

- PVC Sealant

Supplier Body In White Paint Shop

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Ø 52 mm

Ø 90 mm

BMWGroup

Joining TechnologiesCapacitance Discharge Welder

Cold Forged partMaterial: C15E2C

Advantages:- More economical Process- Less Weld Splatter- High local connection Stiffness- Smaller amount of Heat introduced in Parts during

the welding Process- No Process induced Material Structure Change.

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Force vs. Distance Relationships:1 Outer projection2 Inner projection

Distance (mm)

Internal Weld Seam Evaluation:- Small Fusion Zone- Small heat induced Zone- Continuous Material Connection

2

1

1,0 mm

200 µm

BMWGroup

Joining TechnologiesCapacitance Discharge Welder

Forc

e (k

N)

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Conclusion

• Mixed Material light weight Concept for the Body in White– 8% Ultra High Strength Steel Grade– 46% Advanced High Strength Steel Grade

• Significant Weight Savings by UHSS– Hot Formed B- Pillar Reinforcement with tailor rolled Blank– CP800 for Longitudinal Rear Member

• Capacitance Discharge Welding for Bushings– High local stiffness– Extreme short Process Time

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Thank You for Your Attention