Reengineering automotive parts.
Bondrea, Ioan ; Simion, Carmen ; Pirvu, Bogdan 等
The goal to design, manufacture and sell a product with the highest
efficiency possible is the common target of all companies. Time
shortages regarding the product's development can be obtained by
starting from an existing model, and changing its characteristics to
match future trends. Product reengineering fulfils all these major tasks
in order to build fast, precise and at a lower cost as a conventional
approach. Product reengineering is linked with modern tools like: Rapid
Prototyping, 3D Scanning and state of the art C.A.D. Software, in order
to obtain conclusive results. In this research we present a complete
flow of a product's design makeover, from existing model to a new
one and also manufacturing aspects.
Key words: reengineering, 3D scan, computer aided design, rapid
prototyping
1. INTRODUCTION
The reengineering term was first launched by Hammer, one of the
co-authors of the book "Reengineering the Corporation" (Hammer
& Champy, 1993)--considered to be the "bible" of
reengineering, into one article of the Harvard Business Review named
"Reengineering Work: Don't Automate, Obliterate".
Business reengineering is defined as a fundamental rethinking and
radical redesign of the business processes, in order to obtain
spectacular improvements of indicators, considered today to be critical
in evaluating the performances, like costs, quality, service and speed
(Bondrea & Simion, 2004).
2. CAR DESIGN REENGINEERING
The goal of this work is to design an updated body shape of the
model that is new and at the same time keeps a strong bound with its
predecessor.
The first step towards reengineering or redesigning a model is to
choose an existing one. We focused our attention on the Porsche 959
(Ludvigsen, 2003). The input for the design came from a scale model
1:17.
2.1 3D Scan
The second step of the reengineering flow is the 3D scan. Before
starting the actual scale model scan, some preparations have to be made
regarding the target surface and alignment points.
The surface that is being scanned must not reflect the scanner
laser beams. Therefore the model was covered with a thin layer of
powder. This enabled to receive a better quality of the scan.
The software needs to have at least three common pins placed on two
different scanned sequences to build the complete virtual model.
Because the goal is to export the scanned model into CAD software,
we have to improve the surface quality. Creating a waterproof surface
(using the FUSE command) ulfils that, allowing to approximate later the
model by a certain number of surfaces or to extract splines that cut the
model at a certain increment (defined by user). These last elements
(surfaces/splines) could be saved as *.iges file.
Usually for relatively big models before using the Fuse command it
is recommended to optimize the assembled model. Without this
optimization in some cases the system cannot calculate the waterproof
surface (often a message that warns about low RAM is shown).
2.2 Model redesign
We started by importing the *.iges file into Catia V5 R17
environment. As already mentioned before, the goal is to improve the car
shape by the aesthetical and functional criteria. For this purpose we
used the Generative Shape Design Workbench (GSD). The model imported
from the 3D scan usually is not at a very good quality. In order to
improve the existing design, a good quality input model is needed first.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
The first step was to rebuild the missing elements. We focused to
have a complete half.
Now having as a complete reference the old model, the new shape is
ready to be built.
Following improvements were done on the existing model:
* Improved front air intake.
* Front bumper improvement.
* New fender air outtake.
* Lowered center of gravity.
* Reduced air friction coefficient.
* Rear bumper improvement.
Before deciding upon the final shape, the model was printed on a 3D
printer (Zcorp ZPrinter 310) to see if the design looks good also in
reality. After using this rapid prototyping tool we decided that the
design does not need further changes in the car body shape design
(Gebhardt, 2008).
3. VIRTUAL FABRICATION FLOW
Fabrication of one of the outer shape components was another goal
of our research. The bonnet (the exterior metal sheet) was the element
that we set out to fabricate:
* Roughing
* Sweeping
* Finishing sweep
* Biax finishing
The first step was to extract the shape of the bonnet from the
virtual 3D model and the scale was modified to be at the real
dimensions. The shape was optimized to have the best quality possible.
The second step was to find the best production solution for our part.
Taking into account that the shape is relatively complex, we decided
that the tangential stretch forming method is most suited.
The whole process is conducted in five process steps:
* The sheet blank is clamped between two gripping jaws located
opposite to each. The grips are moved away from each other stressing the
blank,
* Without reducing this applied stress, the gripping jaws are moved
downwards
* The ramming punch is now moved downwards to produce the counter
pressure
* The punch is moved back to its original starting position
* The gripping jaws are opened and also moved to their original
starting position, enabling the shaped part to be removed
A stretch forming system was designed that can grab and stretch the
sheet metal in tangential directions to meet the bonnet shape
specifications.
The bonnet material is an aluminum alloy that allows the car to
keep a reduced mass (6016_T4) with the following characteristics:
[A.sub.6] = 0,22
[R.sub.m] = 226 daN/[mm.sup.2]
[[sigma].sub.0] = 117 N/[mm.sup.2]
[[epsilon].sub.0] = 0,816 %
To cut the final shape after the stretch forming we selected a
water jet cutting solution (with abrasive particles) as the fourth step.
The resulting dimensions are 1170x1178x882.
The following operations were made to machine the raw cast iron
stock part:
* Drilling and reaming: Tool--FRAISA Unicut 45332, [PSI]20, Z=3;
Tool-FRAISA Unicut 45362, [PSI]20, Z=6
* Roughing: Tool-Franken Time -S cut, IC= 12,5 mm, [PHI]80 x 45,5 x
21, R=1,5 mm, Z=6 with HPC inserts covered by TiA1N T13 (code 9589A)
* Sweeping: Tool-Franken Time -S cut, IC=8mm, [PHI]25 x 44 x 23,
R=1,5 mm, Z=3 with HPC inserts covered by TiA1N T13 (code 9589A)
* Finishing sweep: Tool-Ball End Franken [PHI]32, R=16 mm, Z=2 with
KP1 inserts covered by TiA1N T13 (code 9589A)
* Biax finishing
The program we used for the mold machining is Catia V5 R17 with its
Surface Machining Workbench. This environment offers a user friendly
interface and a very powerful tool for extremely complicated shapes.
The final step is the fabrication (surface machining) of the mold
on which the sheet blank is stretched.
The mold is made out of cast iron (globular) GGG40 DIN EN 1563.
To obtain the desired result from the sheet metal that is being
deformed sessions of testing are established and carried out. Usually
always some changes have to be made so that the mold reaches desired
results.
4. CONCLUSION
Product reengineering is defined as the study, capture, and
modification of the internal mechanisms or functionality of an existing
system or product in order to reconstitute it in a new form with new
features, often to take advantage of newly emerged technologies without
major change to the inherent functionality and purpose of the system.
Reengineering uses as a fundamental catalyst the information
technology (IT).
This approach in comparison with the traditional one has the
following advantages:
* Reduction of product developing period
* Reduction of fabrication period
* Reduction of production costs
* Better error avoidance
Reengineering in general has also its critics that are linking it
with massive reduction of employees.
Worth mentioning is the fact that everything that was needed to
complete this paper was located in the "Hermann Oberth"
Engineering Faculty and thus the whole cycle can be completed by
students with other products. It could serve as didactical guidance.
The companies should make out of the newest technologies usage one
of their main competencies if they want to succeed into an every
changing environment.
The ones who are capable to recognize and understand the potential
of the newest technologies will have a continuous and ever growing
advantage over the competition.
5. REFERENCES
Bondrea, I.; Simion, C. & Hermann, H. (2006). Product Lifecycle
Management in Stamping and Moulding Tool Manufacturing for the
Automotive Industry, Proceedings of the 10th WSEAS International
Conference on Systems'06, pp. 687-691, ISSN 1790-5117, ISBN 960-8457-47-5, Greece, Vouliagmeni Beach-Athens, 10-12 July 2006.
Bondrea, I. & Simion, C. (2004). The integration CAD/CAE/CAM
activities using CATIA v5, Book of extended abstracts of the 1st
International Conference on Computing and Solutions in Manufacturing
Engineering CoSME 2004, pp. 39-40, ISBN 973-635-372-9, Romania, Sinaia,
16-18 September 2004.
Gebhardt, A., (2008). Rapid Prototyping, Hanser Verlag, LLC,
Germany, Munchen.
Hammer, M. & Champy, J. (1993). Reengineering the Corporation:
A Manifesto for Business Revolution, Harper Business Books, Inc.,
U.S.A., New York, NY.
Ludvigsen, K. (2003). Porsche: Excellence Was Expected, Vol.3,
Bentley Publishers, Cambridge, MA.
*** (2007) CATIA v5, User guide.