F R A U N H O F E R I N S T I T U T E F O R M A C H I N E T O O L S A N D F O R M I N G T E C H N O L O G Y I W U

Fraunhofer Institute for

Machine Tools and

Forming Technology IWU

Reichenhainer Strasse 88

09126 Chemnitz, Germany

Department

Hydroforming and Die Concepts

Dipl.-Ing. Markus Werner

Phone +49 371 5397-1863

markus.werner@iwu.fraunhofer.de

www.iwu.fraunhofer.de

www.greencarbody.de

STABIFÜ® – ECONOMICAL AND FLEXIBLE MANUFACTURING OF STRUCTURE SHEET METAL PARTS

Motivation and aims

The increasing model variety in car produc-

tion leads to decreasing quantities of a part‘s

variant. But the manufacturing of structural

components via multi stage deep drawing

is often uneconomical at less than 50 000

sheet metal parts per year because of high

tool costs.

Within the Innovation Alliance ”Green

Carbody Technologies” (InnoCaT®), a new

manufacturing method was developed to

solve this problem. Here, small changes in

a part’s design – and the coherent simpli-

fication of the technology chain – result in

significantly reduced tool costs. Multi stage

deep drawing tools were reduced to a single

stage and combined with the profitable

processing on flexible sheet metal working

systems. Beside the tool cost savings, the

focus of the developed technology lies on

the resource efficiency. This is ensured by

the reduced usage of sheet metal material

and process energy which shall contribute

to decreased CO2 emissions in automobile

production.

Benefit and potential

The innovative manufacturing method has

the potential to increase the flexibility of the

production and to reduce ramp-up times.

Furthermore it allows a profitable produc-

tion of structural sheet metal parts at low

to mid-size quantities.

On the example of the seat cross member

the feasibility of the technology was verified

and a reduction of the necessary tool mate-

rial by 90 percent, of process energy by 50

percent and an increase of the blank utiliza-

tion from 60 to 77 percent was achieved.

1 Flexible manufactured demon-

strator (material: DP600, sheet

thickness: 1.5 mm)

2 Process chain of the flexible

manufacturing method on the

example of a seat cross member

21

© F

raun

hofe

r IW

U, 2

015

#1 - blank cutting

#2 - crash forming

#3 - final cutting

#4 - free bending

3 Cavity of the only remaining

forming stage – a crash forming

tool

4 Optical measuremant of the

crash-formed semi-finished blank

Results of the research project

Within the InnoCaT subproject 2.1.5 the

new manufacturing technique was devel-

oped and tested on a demonstrator. This

seat cross member was originally produced

with a six stage drawing process and has

been successfully modified for a remaining

single crash forming stage. All additional

forming operations were performed on and

optimized for flexible sheet metal working

systems. The necessary geometrical chang-

es were minimal and the part can now be

produced profitable in small to medium

series up to 50 000 parts per year.

Because of the significant material and

energy savings, the resource efficiency is

drastically improved. Due to a close cooper-

ation with the InnoCaT subproject 2.1.4

”Formschlagen“ the only remaining forming

stage could be designed as a crash forming

process.

The machining of a test tool allowed the

manufacturing of real size demonstrator

seat cross members. Their structural

equivalence to the original parts can be

ensured by crash tests in a drop tower.

Additionally, a remodelling catalogue was

developed that shows for typical deep

3 4

drawing features the equivalent StaBiFü®

solution and gives modelling advice.

Profitable manufacturing

On the example of the seat cross member

demonstrator is shown that tools are an

important cost factor in a part’s price,

especially when using multi stage deep

drawing for small quantities, where they

may become overwhelmingly dominant.

Even if the new flexible manufacturing

strategy may cause higher manufacturing

process efforts, savings in the part’s cost

can be achieved by a reduction of the

number of part specific tools and therewith

the tool cost. These savings grow with a

falling yearly production quantity of the

part. In the case of the seat cross member

at a yearly production rate of 20 000 parts

per year the potential manufacturing cost

savings when changing from deep drawing

to StaBiFü® are 30 percent.

Acknowledgment

This research project was financed by the

BMBF within the Framework ”Forschung

für die Produktion von morgen“ (registered

under: 02PO2250 ff) and controlled by

the PTKA. The author is responsibe for the

content of this publication.

Cost comparison flexible manufacturing vs. deep drawing

Cost structure flexible manufacturing

TEuro/a

0 10 000 20 000 30 000 40 000 50 000 60 000 70 000 parts/a

500

400

300

200

100

0

TEuro/a

0 35 000 70 000 parts/a

500

400

300

200

100

0

Cost structure deep drawing

TEuro/a

0 35 000 70 000 parts/a

500

400

300

200

100

0

manufacturing material tool

flexible manufacturing favorable not definite deep drawing favorable

deep drawing flexible manufacturing