International Journal of JOURNAL OF MECHANICAL ENGINEERING
INTERNATIONALMechanical Engineering and Technology (IJMET), ISSN 0976 –
 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME
                         AND TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 4, Issue 2, March - April (2013), pp. 21-31                        IJMET
Journal Impact Factor (2013): 5.7731 (Calculated by GISI)                                                     ©IAEME


           Raju B S 1, Chandra Sekhar U 2, Drakshayani D N 3, Chockalingam K 4
           Associate Professor, Mechanical Engineering, Reva Institute of Technology and
                     Management, Yelahanka, Bangalore: 560064, Karnataka.
                  Scientist G, GTRE, C.V.Raman Nagar, DRDO, Bangalore: 560093
                Professor, Mechanical Engineering, Sir.M.VIT, Bangalore, Karnataka.
                    Professor, Mechanical Engineering, TCE, Madurai, Tamil nadu.


           The paper presents an overview of new approaches in rapid product development
  from the design point of view. Due to the advances in mechanical, electronics and
  computers components, there has been significant growth in communication, information
  technology and worldwide networking, which leads to globalization and opening of
  markets, hence increases in worldwide competition among industries. The evolution of
  the market necessitated the reduction of time to market mainly because the product life
  cycle is shorter and also because it is very important to proceed more rapidly from an
  initial conception to mass production object. In product development, Rapid Prototyping
  has turned out to be the instrument to save time and money and also develop innovative
  products. RP has evolved as a frontier and emerging technology in which every individual
  can see the goal, the product and can relate to the customer, which tremendously reduces
  the lead-time to produce physical prototypes. RP is useful in the fast production of
  physicals prototypes and therefore constitutes a key element in the optimization and
  abbreviation of product development processes. Thus the paper gives the information,
  that how the product development time can be reduced by using RP with an aid of gas
  turbine engine component as an intended study , which aims to emphasize as time
  compression engineering.

  Key Words: Rapid prototyping, Time compression Engineering, Lead time, Rapid
  Product development, Centralizing spring.

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME


          The field of product development, particularly product modeling [1], has become
quite critical in industrial performance improvement. The art of managing rapid product
development depends on making good tradeoffs between four possible objectives in any
product development cycle: (a) development speed, (b) Product cost, (c) product
performance, and (d) development program expenses. Prior to the 1980s, product cost &
performance were the dominating factors. During 1980’s, quality became the focal point,
with the proliferation of techniques such as SQC, TQM, the Taguchi method and the Kaizen
method [13]. Since the 1990’s, the emphasis has shifted to the time-to-market race in order to
survive and compete in the global competitive market. This shift in emphasis, of course,
should not be at the expense of performance, cost, quality and reliability. Indeed, when all the
major players in the field are able to satisfy all the above criteria, a new competitive &
cutting edge strategy should appear, comprised of tools and techniques for rapid product
development (RPD).


        Introducing new products at ever increasing rates is crucial for remaining successful
in a competitive global economy; decreasing product development cycle times and increasing
product complexity require new ways to realize innovative ideas. In response to these
challenges, industry and academia have invented a spectrum of technologies that help to
develop new products and to broaden the number of product alternatives. Examples of these
technologies include feature-based design, design for manufacturability analysis, simulation,
computational prototyping, and virtual and physical prototyping. Most designers agree that
“getting physical fast” is critical in exploring novel design concepts. The sooner designers
experiment with new products, the faster they gain inspiration for further design changes [2].
        Rapid prototyping (RP) refers to a class of technologies that can produce physical
objects directly from 3D CAD or other 3D data sources. RP is characterised by an ‘additive’
or ‘layer-by-layer’ approach due to which it is also called as layered manufacturing. Uses of
RP models cover the wide range of fit, form and functional activities in a variety of industries
consisting of but not limited to aeronautical, automotive, biomedical, consumer goods,
foundry, electronics, MEMS, space research and tooling industries [3]. The first
commercially packaged RP technique ‘Stereolithography’ [4] was launched by 3D Systems,
USA during 1986 and since then different RP techniques such as FDM, laser sintering, 3D
printing, laminated object manufacturing, solid ground curing, laser engineered net shaping
(LENS), electron beam melting etc., have become commercially available. These RP systems
produce parts in a variety of materials including thermoplastics, laminated paper, starch
powder, polymer wax, metals, alloys and composites. Ceramics [5] with unique mechanical
and electrical properties have also been successfully inducted into RP process. 3D printing
systems developed by Z Corp, USA have led a revolution in RP industry by virtue of their
prolific applications in industrial design activities. These systems prepare prototypes in starch
like materials in a wide array of colors. LENS system produced by Optomec, USA facilitates
production of parts in a range of engineering materials including titanium and nickel based
super alloys [4] which in turn led to the induction of RP in repair and refurbishment of gas
turbine engine components. Combined use of reverse engineering and RP tooling has been
attempted in producing limited series castings from worn out parts [6].
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME

       The RP technology is increasingly being used to accelerate the preparation of
prototypes. The figure 1 Calls for the acceleration of all tasks required for the creation of

                Figure 1. Acceleration Potentials through use of CAD & RP

2.1. Rapid Prototyping Process Chains for Product Development.

        Prototypes for product development can be differentiated into design, functional and
technical prototypes [10]. Design prototypes are used for verification of haptic, aesthetic and
dimensional requirements, for functional verification and optimization, functional prototypes
are required during product design. Technical prototypes are produced using the production
material and where possible by means of the actual production process [3].
        In general, RP process chain in product development comprises the elements as
shown in fig 2 are process planning, production, quality inspection, digitization and geometry
modifications. For the continuous and uninterrupted support of RP process chains, an RP
toolkit has been developed comprising components for the following process steps as shown
in fig 2a.
    • Modeling of virtual products
    • Data exchange and model preparation
    • Technological planning and
    • Reverse engineering.
The rest of components enable the required information – technological linkage of individual
components for the implementation of a STEP based integration. [2]. For the modeling of
virtual products, systems were developed for styling and feature based design. The styling
process is supported using the virtual cal modeling approach based on Voxell modeler. The
VCM (Virtual Clay Modeling) system developed is an adequate tool for design conception,
enabling the provision of the conceived shape base on 3D model data representation at being
of the entire process. The VCM system is based on a modeling kernel, which oriented around
the real counter parts in the model building and which provides computer internal tools such
as scrapers, templates and true sweeps for the manipulation or editing of computer-internal
design models. The components for model preparation provide for automatic error detection
and repair of surface and facetted models. The measurement planning component is used for

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME

planning of inspection and digitization processes on coordinate measurement machines,
which comprises the determination of measurement operations, definition of measurement
strategies, selection and configuration of measurements probes and N/C path generation [2].
For the support of reverse engineering, concepts related to Voxel and feature based local
shape modification are under development. For Voxel based capture and update, the modified
work piece area is first digitized. The set of points captured is converted into a Voxel
representation and the original prototype adapted using a best fit procedure. Using the
measurement planning components for CMM, digitization strategies are assigned to the
modified features that make it possible to determine the current feature parameters based on a
small number of measurement points.

2.2. Rapid Product Development Process
       Today’s global environment can enable people to go “from Object to object” as
shown in fig 3 through 3D digitizing and reverse engineering. Part modeling and Rapid
manufacturing of parts, both directly and indirectly using rapid tooling. Knowledge and
know-how regarding new technologies should also be accessible for integration in the
product process during the design stage. In the course of Rapid product development, the
nature of data changes. Consequently, the numerical reference model should coherently
support different data formats, depending on the technologies and the design process stages.
The new technology initiative based on the STEP (Standard for Exchange of Product Model
Data) format which is used to define heterogeneous and multi-material object data
management [7].

            Figure.2. Integration of Rapid prototyping into product development


        For initiating the Stereolithography process, the CAD model of the desired object is to
be created. Though water-tight surface models can be acceptable, the most preferred file
input is the 3D CAD solid model. Interface between the CAD model and Stereolithography
system is the STL file (tessellated file format). The slicing phase follows the STL file
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME

generation and in this phase, the input file is mathematically sliced into a series of horizontal
planes through special software. The result is the SLI file that represents a series of closely
spaced two-dimensional cross-sections of the three-dimensional object, each at a slightly
different Z coordinate value. The most important build parameter that is frozen in the slicing
phase is the layer thickness. On the SLA 5000 system, layer thickness can be fixed between
the limits of 50 and 250 µm. The models used in the present research are built with 100
micron thickness layers [8]. Before initiating the build process, supports are created for
holding the layers during the build process and also securing isolated segments. Throughout
the part building phase, galvanometer-driven micro mirrors receive commands from the
process computer and direct the laser beam downward onto the free surface of the liquid
photopolymer. The short wavelength of the UV radiation and the weak focusing employed,
result in sufficient focus depth to provide acceptable beam diameter over the entire surface of
the photopolymer. During the scanning phase, the laser beam firstly traces the boundaries of
the particular cross-section and subsequently solidifies the internal areas through hatching.
The system automatically adjusts the laser exposure to ensure that the border and hatch
vectors are cured to adequate depth that in turn facilitates adhering of the current layer to the
previously formed layer. The process continues without any human intervention until the
entire physical object has been generated. After the completion of the build process, the
platform along with part and supports is transferred to a cleaning station. [14].

            Figure 2a. Integration of Rapid prototyping into product development

 Uncured residual liquid resin is cleaned off the part with a solvent like acetone or isopropyl
alcohol. Supports are removed with due care as to avoid damage to the down facing surfaces.

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME

The object in this condition is said to be in ‘green’ state as a small amount of uncured resin
still remains trapped among the hatch lines. The cleaned object is placed in a post cure
apparatus (PCA), where it is flooded with ultraviolet radiation of an appropriate wavelength
to complete the curing. After post curing, the object may be subjected to a variety of finishing
steps such as glass bead blasting, sanding, milling, drilling, tapping, polishing, painting,
electroplating, etc for further improvement in surface quality or functionality [9]. If the part
size is bigger than the build envelope of a Stereolithography system, the part can be built in a
modular manner and bonded with epoxy resin to form the assembly as shown in the fig 4.
But the Size limitation is up to 500mm X 500mm X 500mm, if the prototypes are Larger size
then the parts builds with different sections and then it will be glued to get the prototype.

                        Figure 3. Rapid product development process

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME

                      Figure 4. Schematic of Stereolithography process


        The rotor damper bracket (fig 5) of a gas turbine engine performs very crucial role in
ensuring appropriate rotor dynamic performance of the fan module. Stringent stiffness
requirements, assembly limitation and weight restrictions render the process of designing the
bracket very challenging with inevitable iterative studies. The regular method of
manufacturing an epoxy bracket model consists of the fabrication of a metallic master
pattern, silicone rubber moulding (fig 6) and casting with room temperature setting epoxy
resins. These labor-intensive procedures consume about 25 days to prepare every damper
bracket model. In conventional scenario, manufacturing of each new candidate design entails
manufacturing of new pattern and subsequent silicone rubber moulding. The optimization of
rotor bracket involves studying of 6 to 8 design, which in turn extends the manufacturing
cycle time to about 150 days. The present study uses Stereolithography (Building parameters:
Layer thickness -0.01mm , HX –orientation, Post curing time- 60 min , Hatch spacing
between layers – 0.0015mm) though which a similar model is produced from the CAD data
in just 3 days (fig 7). Different design options of the rotor bracket that have modified values
of axial web length, number of slots and radial thickness of the web are made through CAD
data modifications. It takes less than 30days to manufacture the full range of the models that
incorporate all the intended design changes. Effective time saving s in this case study is about
120 days and this ensures competitiveness of experimental procedures vis-à-vis analytical

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME

               Figure 5. CAD Model of Rotor Bracket (Centralizing Spring)

 Figure 6. Master pattern and silicone rubber moulds         Figure 7. Prototype pattern
 used for conventional manufacture of rotor bracket.             produced by SLA

Hence conventional machining procedures are fraught with several debilitating features that
prolong the manufacturing time frame to as high [table1].The present works uses a
methodology which is totally devoid of tooling, casting and residual stress related problems
that in turn leads to notable compression [table 2] in manufacturing time frame[15].

  Table 1: Manufacturing of rotor bracket     Table 2: Rotor bracket model manufactured –
       model-Traditional approach                       New approach (RP-SLA)
                                    Time                                            Time
            Activity               Taken                   Activity                Taken
                                   (days)                                          (days)
  Casting of epoxy resin blanks      35          CAD data preparation,
                                                 translation and verification
 Tool development, process plan                        Pre-processing and
                                     48                                              05
          and Fixtures                             Stereolithography building
  Rough and finish machining         35             Post curing and finishing        05
    Inspection and approval           7             Inspection and approval          07

       Total time take = 125 Days                        Total time take = 25 Days

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME

The dimensional accuracy of the casting produced by the prototypes is measured by using
coordinate measuring machine and the results are summarized in the table 3. The results
reveled that the prototypes produced had close tolerance and accuracy and surface texture

              Table 3: Dimensional deviation of the spring (Rotor bracket model)

    Sl. No.      Drawing Dimensions          Actual Dimension
       1         Dia 256.25 / 256.000           Dia 256.24              0.19 Roundness
       2        Dia 218.007 / 217.987           Dia 218.470             0.25 Roundness
       3         Dia 208.35 / 208.00            Dia 208.37              0.21 Roundness
       4         Dia 167.25 / 167.00         Dia 166.79 /166.70         0.17 Roundness
       5         Dia 190.25 / 190.00         Dia 189.92 / 189.91        0.25 Roundness
       6        Dia 6.6 / 6.4 (12 holes)        Dia 6.20 / 6.4                  -
       7               5.1 / 5.0                 5.19 / 5.08                    -
       8              13.5 /13.4                13.42 / 13.24                   -
       9                   30                        30                         -
      10              237.0 PCD                 237.69 PCD              0.22 Roundness


        The case study gives the analysis of the above influential factors in the field of rapid
product development. The Gear Box casing is a component that was chosen for the purpose
of the study which involves intricate shape and complexity as shown in the fig 8.

                              Figure 8. CAD Model of Gear box

       The component was fabricated by the Stereolithography process to obtain a prototype.
The time taken to built a prototype and also for the production of the actual part is as shown
below [table 3].

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME

      Table 3: Comparison of a fabrication of actual part and prototype of a Gear Box
                  Prototype part                                      Actual part

                               CAD MODELLING TIME = 2 Months
                        PART ENVELOPE = 430 mm X 330 mm X 190 mm
                                                   Time taken to build actual metallic engine part =
                                                   12 months (Involves drawing, Designing of
       2 Days per one part + 3 months for
                                                   jigs and fixture, Process plan, fabrication &
        preparation moulds and castings
  Thus from the above it can understood that the product development can be reduced by using the
  Rapid prototyping technology.

                   RP MODEL                     ACTUAL METALLIC PART
                          A PICTURE IS WORTH 1000 WORDS


        RP has the potential to optimize product development if it is embedded into the
process chain., where the RP tool kit demonstrates the feasibility to achieve the continuous
and unint6errupted support of design model preparation, process planning and prototype
fabrication, which leads to a fast production of physical prototypes and thus to a shortening of
time required for product development in order to reduce the product time to market. Thus
the selected approach leads to a fast production of physical prototypes and parts by rapid
tooling by shortening of the time required for product development where a remarkable
reduction (in excess of 50%) in model preparation time is realized & reduction in the cost of
the product as illustrated in the case study.
        These models exhibit necessary mechanical strength, dimensional accuracy and
stress-strain linearity as demanded by photoelastic evaluation where the prototypes are
produced by epoxy resin which has brifreigent in nature. The presented study demonstrate the
suitability of rapid prototyping for the product development programme specifically in the
design development phase where quick manufacturing solutions are paramount for timely
completion of design iterative exercises.

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 2, March - April (2013) © IAEME


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