Optimized Prototyping for the Increasing [611984]

Optimized Prototyping for the Increasing
of Performances of a Design Process
Daniel-Constantin Anghel , Maria-Luiza Be șliu-Gherghescu,
and Nicolae-Doru St ănescu(&)
University of Pite ști, 110040 Pite ști, Romania
[anonimizat]
Abstract. The level of production quality is established by the technological
solutions adopted by designers during the design stage. In order to realize a
product which responds to diverse customer requirements, the designers use alot of methods and resources. One of them is the prototyping method. Thedesigners use the prototype to propose, test and develop their theories and
solutions. This paper presents a method to optimize the prototyping process for a
product in order to increase the performances of the design process. The studywas conducted at University of Pite ști. Two design experiments were conducted
for the same product. The first experiment used conventional methods of pro-
totyping and the second one used the rapid prototyping. We followed theevolution of parameters: cost, duration, number of iterations needed to quantify
the impact of the two methods. In order to represent and analyze the perfor-
mance of studied experiments there were used instruments as: DSM (DesignStructure Matrix), Manhattan distance, a graphical representation tool based on
the model proposed by Pahl and Beitz.
Keywords: Rapid prototyping
/C1DSM/C1Manhattan distance
1 State of the Art
Product design is a dynamic and complex process. It can be de fined as the idea
creation, concept development, prototyping, testing and manufacturing of an artifact.The designers conceptualize and evaluate ideas, making them tangible through prod-ucts in a more systematic approach [ 1].
A prescriptive model of design process was proposed by Pahl and Beitz [ 2], Fig. 1.
It is almost impossible to have a once through execution of tasks in a design process.One or more repetition of the tasks is necessary to obtain the expected results. These
repetitions are called iterations. Iteration is an activity that occurs in all design projects.
Iterations are fundamental for the design process and several authors underlined theirimportance; however, this subject is still not well tackled in the literature. Iteration canbe de fined as the repetition of design tasks in order to improve the design solution
being performed. Figure 2shows an iteration process between three design tasks. In
this example, task “B”needs the result of task “A”, task “C”needs the one of task “B”,
and task “A”the one provided by task “C”. This type of design problems could only be
©Springer Nature Switzerland AG 2019
N. Burnete and B. O. Varga (Eds.): AMMA 2018, PAE, pp. 1 –9, 2019.
https://doi.org/10.1007/978-3-319-94409-8_52

resolved through an iteration process, which starts with a rough or a preliminary
information of one of the results “x”,“y”or“z”.
Pahl and Beitz, in their work [ 2]d efine iterations as a process by which a solution is
approximated step by step. Smith and Eppinger [ 3] state that design iteration is the
repetition of design tasks due to the arrival or discovery of new information. Yassine
et al. [ 5]a ffirm that iteration is a typical characteristic of any complex engineering
development project due to the coupling and interdependency between the develop-
ment tasks. Osborne [ 1] has observed that iteration is a signi ficant component of the
product development cycle time and represent about one third to two thirds of project
effort. It is then important to consider the iteration aspects of design tasks when
developing a design process model. We present below some models that consider the
iterative aspect of design. One of the most important model families is based on the
Design Structure Matrix (DSM). Design Structure Matrix (DSM) based models [ 3–5]
have been extensively used to capture and display the iterative structure of engineering
design.
DSM uses a matrix representation of the design process, Fig. 3. The DSM matrix is
square with one task by column and by row. Information flows between tasks are
indicated in the off-diagonal elements of the matrix. Two types of information flows are
distinguished: feed forward (lower diagonal elements) and feedback (upper diagonal
elements). With this representation, cyclic information flows are easily captured and the
need for iterations is identi fied.
Fig. 1. Pahl and Beitz ’s model of design.
Fig. 2. Design iteration.447 D.-C. Anghel et al.

Matrix elements are manipulated in an attempt to eliminate or minimize the number
of upper diagonal elements. This process is known as partitioning. Figure 4represents
the reordered elements of the DSM shown in Fig. 3.
By this method we analyze the dependencies between tasks of the two experiments.
In order to find the distance between two points, we use the Manhattan distance
algorithm. The Manhattan distance function computes the distance that would be traveled
to get from one data point to the other if a grid-like path is followed. The Manhattan
distance between two items is the sum of the differences of their correspondingABCDEFGH I JK
A XX
B XXX
CX X
D X
E XX X
FX X
GX XX X
HXXX X
IX X XX
JX
KX
Fig. 3. A DSM representation.
ACFDJ BEGH I K
A XX
CX X
FXX
D X
J X
B X X X
EX X X
GX X XX
HX X X X
IX X X X
K X X
Fig. 4. Rearranged DSM matrix.Optimized Prototyping for the Increasing of Performances 448

components. For example, if xa ;bðȚ andyc ;dðȚ , the Manhattan distance between xandyis
a/C0c jj țb/C0d jj |, Fig. 5.
2 The Rapid Prototyping Process
Rapid Prototyping can be de fined as a group of techniques used to quickly fabricate a
scale model of a part or assembly using three-dimensional computer aided design.
The prototyping soft takes virtual designs from computer aided design, transforms
them into thin horizontal cross-sections and then creates each cross-section in physical
space, one after the next until the model is finished. The Zprinter machine reads the data
from a CAD drawing and lays down successive layers of liquid and powder and in this
way builds up the model from a series of cross sections. These layers, which correspond to
the virtual cross section from the CAD model, are joined together to create the final shape.
The standard data interface between CAD software and the machines is the STL file
format. An STL file approximates the shape of a part or assembly using triangular facets.
Smaller facets produce a higher quality surface. To make the part presented in Fig. 6,w e
have used a composite powder (ZP131) and an epoxy binder. The soft used by Zprinter
Fig. 5. Manhattan distance.
Fig. 6. The 3D part in Catia V5.449 D.-C. Anghel et al.

has the possibility to simulate the printing process, step by step, and to make an esti-
mation of binder usage, number of layers necessary to make the prototype, of total time
etc., very ef ficiently for the designer in the process of decision making, Fig. 7.
3 Conventional Prototyping
The material of the conventional prototype is a polyamide. The properties of this
material are the same with the material for the final part, but different to the prototype
realized by the rapid method. We can make the mechanical or thermal tests and a lot of
other tests: geometrical tests, functional tests, technological tests, the quality of surfaces
etc.
In order to realize the conventional prototype, a CAD/CAM soft is necessary. For
our work, the soft Catia V5 was chosen. All the operations necessary was calculated
and simulated by Catia V5. In the NC Manufacturing, the milling operations were
conducted under “prismatic machining ”module. Three manufacturing programs were
made, in order to realize the process: Roughing, Contour driven and Pocketing . All of
the three programs were optimized and simulated by the appropriate tools and the NC
code was generated. In the Fig. 8we show a screenshot of the manufacturing module.
4 Presentation and Analysis of Experiments
The experiments analyzed in this paper were made at the University of Pite ști, in the
“Automotive Engineering Research Center ”, by a local team. The goal of the design
experiments was to design a part in CATIA V5 and to create two types of prototypes:
by the conventional method and by rapid prototyping method. Our intention in this
study is to observe the design activity performed by a team of designers. Video-based
observational techniques were used in this experiment to provide useful and reach
Fig. 7. Estimation report of printing by Zprinter soft.Optimized Prototyping for the Increasing of Performances 450

record of the design process that is then used by different researchers in different ways
to study different issues.
During the design process the designers cooperate in order to perform together the
design of the part, to set up the manufacturing parameters and the rapid prototyping
Fig. 8. The prototype manufacturing program in Catia V5.451 D.-C. Anghel et al.

parameters. In order to realize the rapid prototyping, the designers have made the tasks
presented into the Table 1. For the conventional prototyping, the tasks are presented
into the Table 2.
To illustrate the relationship between the tasks a DSM matrix was performed for
each case, Fig. 9.
The Manhattan distance for the rapid prototyping process is:
LRPP¼4/C00 ðȚ ț 5/C04 ðȚ ț 7/C06 ðȚ ț 12/C07 ðȚ ț 13/C012 ðȚ
ț14/C013 ðȚ ț 5/C04 ðȚ ¼ 14 :ð1Ț
The Manhattan distance for the conventional prototyping process is:
LRPP¼4/C00 ðȚ ț 6/C04 ðȚ ț 8/C06 ðȚ ț 10/C08 ðȚ ț 11/C010 ðȚ ț 12/C011 ðȚ
ț15/C014 ðȚ ț 17/C015 ðȚ ț 18/C017 ðȚ ț 11/C010 ðȚ ț 10/C08 ðȚ ț 6/C04 ðȚ ¼ 21 :
ð2Ț
We observed in case of the conventional prototyping process, a larger number of
elements on the right side of the main diagonal. This indicates a large number of
iterations. In our analysis, iterations are considered as the repetition of design tasks. So,
when a task is executed for the first time by the designers, each new switch to this task
will be considered as a new iteration.
In the iteration process, the rework may concern the entire task or just a part of it.
After conducting two tests for the two experiments, we find the following: (a) for the
case of conventional prototyping, the number of tasks required is higher, between tasks
A, Ba, Bb, Bc, C, D, there is a block independent of the other tasks; (b) we have
observed a large number of iterations needed to optimize the manufacturing program.
These iterations are necessary to obtain a product correct but, they have like effect the
increasing of the process duration; (c) the number of tasks is less for the case of rapid
prototyping, the links between them are in series, a single task could be made in
parallel with others, is the task E. However, the time for this process is inferior
compared with each other.Table 1. The task for the rapid prototyping process.
Tasks Time [units of time]
Modeling the part in Catia V5 4
Realize the prototyping program by the Zprint soft 1
Preparing printer 3D (Zprint) 1
Printing the part 1
Solidi fication the part 5
Removing the part on the printer and cleaning the part 1
Part painting 1Optimized Prototyping for the Increasing of Performances 452

5 Conclusions
The prototypes are an important role in the design process. It is used to aid the
designers to view the “characteristics ”of the product, to simulate the functions of the
product or to construct the injection mold.
The advantage of rapid prototyping is the reduction of manufacturing times. The
piece is more complex and the difference with a traditional production increase. In
addition, rapid prototyping provides new opportunities for manufacturing.
The bene fits to have and use a prototype are: detect design problems; testing
alternatives; validate the industrial feasibility; forms and optimize the cost of tooling;
minimize the risk of modi fication; re fine the operational characteristics; have a media
object; carry out mechanical and thermal tests etc.; have a media object and avoid
potential con flicts.Table 2. The task for the conventional prototyping process.
Tasks Time [units of time]
A. Modeling the part in Catia V5 4
B. Realize the manufacturing program in Catia V5 –
a. Roughing 2
b. Contour driven 2
c. Pocketing 2
C. Simulation and optimization the manufacturing programs 1
D. Realize the NC code 1
E. Preparing the NC for the manufacturing process 2
F. Preparing and install the blank on the NC 1
G. Part execution 2
H. Part painting 1
Fig. 9. DSM representation of the tasks for the rapid prototyping process (left) and for the
conventional prototyping process (right).453 D.-C. Anghel et al.

Acknowledgments. This work was supported by a grant of the Romanian Ministry of Research
and Innovation, CCCDI-UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017-0224 / 77
PCDI/2018 within PNCDI III.
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