Development of concrete pipe molding machine with topology optimization.
Park, Hong Seok ; Dahal, Prakash
1. Introduction
SPC is a new emerging material which is a mixture of sulfur, binder
and variety of aggregates. Sulfur concrete is manufactured by allowing
mixtures of the aggregates and molten sulfur to cool, whereupon the
mixture solidifies to give products of hardness comparable to concrete.
This concrete has unique properties including fast setting
characteristics, high ultimate strength, low permeability, and
resistance to acids and saline solutions. Although Portland cement
concrete is widely used from the past but the strength deterioration is
rapid due to the reaction of various chemical, mechanical and biological
processes. owing to this fact, sulfur concrete is rapidly increasing its
demand due to its vast range of advantages. Sewer pipe made of sulfur
concrete is inexpensive during construction, and after manufacturing it
will provide better sewer systems and conduit extremely durable in most
of the environments. owing to this fact, this research is focused to
develop the molding machine which will be able to manufacture the SPC
sewage pipes. From the various experiments, it was found that there are
several factors which are used to manufacture all concrete pipes as:
strength at early age, surface texture and density, permeability,
sulfate resistance, and consistency. Superior strength is generated due
to fast curing time of material property whereas density and consistency
of product will be obtained from manufacturing process. To obtain denser
and consistent product, the die of molding machine is made to perform
multi functions to provide compressibility and removing air voids during
the manufacturing phase.
Corrosion of concrete sewer pipe is an existing problem that faces
sewer systems all over the world. Sewer pipes are attacked by sulfuric
acid that is derived from the biogenic activity or by direct oxidation
of hydrogen sulfide from sewerage. Corrosion in sewage pipes leads to
costly replacement of concrete structures therefore if the sewer pipes
manufacturing process are not efficient and quality of pipe will not
perform good function for a long period. The pipe manufacturing machines
popular in now days are mostly horizontal spun type. Although concrete
pipe manufacturing processes have changed throughout the years, each
process ensured a durable product. Concrete pipe that is manufactured
today is dense, strong and durable. As the demand for concrete pipe
continued to grow, so did the need to increase output and productivity
with uniformity of concrete particle distribution. Equipment
manufacturers are interested to produce high quality pipe with faster
rate. (OCPA) Therefore new material with new manufacturing method is
necessary to develop to cope of the requirement of pipe manufacturing
company.
2. Problem Description
There are a lot of technologies to produce pipes of different shape
and size including spun technology, center core vibration, and packer
head etc. Until now spun technology is dominating in most of the
industries to produce the concrete pipe which works on the principle by
incorporating mechanism of outer core rotation in horizontal centrifugal
machine. This machine operates on high speed RPM where concrete is feed
into the rotating mold. This manufacturing operation is time consuming
and efficiency is very low, in addition physical strength of the product
quality is not good and thickness is not uniformly distributed.
[FIGURE 1 OMITTED]
To improve the product quality following points must be considered
for the new system:
1. Centrifugal force of conventional molding techniques must be
replaced to develop new product of SPC.
2. Manufacturing facility must be more efficient which makes very
less time to manufacture
In the current study, based on the existing horizontal centrifugal
molding technology high frequency vibration is added and layout will be
changed into vertical to ensure quality product. This process will
improve the dimensional accuracy of the products and also enhances the
manufacturing time. So, there is a great change in effectiveness of
product when the manufacturing process changed to high frequency
vibration with centrifugal force in vertical alignment. To complete this
research task engineering design is done with systematic planning,
following the scientific and practical ideas to meet the stated
objectives.
3. Development of Vertical Type Machine
3.1. Design Specification
Design specification for the new machine was obtained from the
existing pipe manufacturing company in South Korea. From the discussion
with company a prototype machine will be developed which can manufacture
the pipe of size shown in Fig 2.
[FIGURE 2 OMITTED]
Design requirements are the set of terminologies which are used to
develop the final approach of a system. They can be classified into
physical, structural, functional, cost requirements. Considering those
requirements target prototype must fulfill the following requirements
1. Homogenous compaction of material
2. No cosmetic cracking at surface
3. No leakage
4. Able to produce product varieties
5. Can be easily operated
Therefore to have a chance of reliable durable product to be
manufactured, system must be long lasting, requiring low maintenance,
low cost and designed by sequential design process is preferred.
4. Design Procedure
[FIGURE 3 OMITTED]
The practical design of molding machine starts with collection of
necessary parameters, study of design specification. In this phase,
several existing technologies and patents are reviewed to omit the
patents and getting review of technology. Conceptual designs are created
and realized by means of 3 dimensional CAD model to verify the
functionalities of generated concepts. Concepts are designed in terms of
performance, cost and ease of manufacturability. Generated conceptual
designs are visualized to verify the kinematic behavior and production
steps of SPC pipe. Similarly, all of the innovative concepts are
evaluated by means of evaluation criteria for selection of the best
design. Detail design was carried out from selected conceptual design
which includes detail drawings of each components and 3D CAD model of
machine. After making detail design, prototype will be built for
validation in real environment.
5. Conceptual Design
In order to develop the high quality pipe, systematic procedure is
followed, TRIZ methodology is employed to assist the way to get new
models which in turn used to resolve the encountered problems of old
machine.
TRIZ is a powerful methodology which can provide the conceptual
solutions. TRIZ can offer competitive innovation ideas. (SOUCHKOV, 1988)
This approach is based on the four steps: Identifying problems,
Formulate the problem, the Prism of TRIZ, Search for Previously
Well-Solved Problem, Look for Analogous Solutions and Adapt to Solution.
According to this principle, technical uncertainties during the design
are eliminated and focus on the target objective is considered.
Product's appearances as well as aesthetics are also considered in
first stage of conceptual phase. Concept design is aimed to give number
of reliable models that satisfies the requirements. Conceptual model
generation is based on the four steps of TRIZ design parameters which
are focused in manufacturability of machine, durability, reliability and
shape of product (Serban et al., 1988). Number of patents and TRIZ
technology is studied to avoid the patents and to generate robust
conceptual design. Based on the inventive principles of TRIZ, specific
solutions are established for generating efficient machine (Serban et
al., 1988).
By considering TRIZ principles concepts are generated via CAD model
where each machine satisfies the design requirement.
[FIGURE 4 OMITTED]
Concept 1 shows the model of machine having vibration base to give
the vibration energy on the freshly inserted concrete. Vibration table
is equipped with motor which is able to change the desired amplitudes,
frequencies, and vibration during change in pipe size. Therefore, it is
important to keep the concrete mixture in constant proportion regardless
of the pipe sizes. Rotation is carried by the electric motors mounted at
the top to provide more compaction and shaping of concrete. Inner die
system is movable in up down motion during shaping of pipe.
Concept 2: This unique concept is used to make circular as well as
rectangular pipes. The positioning of the pipe is vertical mount system
where the vibration is given from the base which is alike to the
vibration as mentioned in concept 1. This machine is able to provide not
only vibration but also rotation. outer die is fixed in the vibration
table and inner die is movable which can move by means of rotation of
shaft coupled with electric motor mounted at the top. In the inner die
there are slots to couple the shaft with inner die so that when the
shaft rotates the torque is transmitted to the inner die. So the product
is speculated to perform better than existing products till now.
Concept 3: This model looks similar as model1 but the difference is
inner core is equipped with vibration motor inside. Inner part
consisting of two parts can be assembled and disassembled easily in the
different steps of manufacturing as shown in Fig 4. During the first two
steps the inner part generates vibration to remove air voids and
compaction by rotation; whereas in the last two steps vibration is
stopped and only small inner die portion is be rotated to give the
smooth surface finish to the inner part. The smooth surface finish is
given at last step to ensure low water permeability from the inner part
of sewage pipe. The motion of inner core is provided by hydraulic
mechanism whereas the rotation of inner part is provided by means of
electric motor.
Concept 4: The vibration system for the concrete pipe making
machine utilizes a precisely manufactured inner core that contains
spiral shaped screw to generate pressure in the concrete of the inner
mold. This setup consists of vibration table where preferably arranged
electric vibrators are mounted at the frame of table. Vibration table is
designed in the way that different size of pipe can be manufactured in
the same table. To manufacture different sized pipe, only the changeable
part is the upper plate of vibration table. The outer die and spigot end
is fixed on the table at the first step then inner part is moved to its
position and concrete is fed into the inner zone. Core starts to move in
upward direction by compacting concrete. The core part can be adjusted
to slide up and down from the small clearance hole at the center of
table. The novel benefit of this machine is that it has vibration,
compaction and centrifugal rotation mechanism by means of vibratory
table and screw core respectively. The uniform distribution of vibration
allows the concrete consolidation in the optimum manner and distribution
of particles will be uniform.
Concept 5: This machine serves to cast pipes of concrete in
horizontal pattern. Machine includes inner mold part, outer mold part.
The inner core is displaced in horizontal axis after the production of
pipe and outer die, finished pipe along with spigot end are taken to
next place for storage. After the solidification of concrete, outer
cover is taken to another place and finished pipe is taken out from die.
Manufacturing steps of this embodiment is concrete is fed from the upper
part of the die where there are holes to inject the pressurized
concrete. Several holes are made to reduce the manufacturing time and
for uniformity of concrete flow throughout the pipe cavity. Tiny air
holes are also made at the upper part to remove the trapped air inside
the cavity.
6. Concept Selection
Concept selection is the activity in which the generated concepts
are analyzed and sequentially eliminated to identify the most promising
concepts. A reference design is existing machine which is considered as
the datum. Selection criteria are generated based on design
requirements, which includes the customers' requirements and
designers' intentions. For purpose of concept selection, the weight
of the criteria can be determined subjectively by team consensus or
through a designer's rational intent. A percentage is normally used
to assign the weight.
Design concepts are rated through a comparison to the datum design.
Representative ratings are valued from 1 to 5, indicating from much
worse to much better designs than the reference. (Xiao et al) once all
the concepts are rated, a total score for each design is calculated
using this formula. Sj = [summation]ln [rij wi] where, n is the number
of selection criteria, rij is the rating of concept j for ith criterion,
and wi is the rating of the ith criteria. The overall performances of
the alternative designs are ranked based on their total score. The
relative strengths and weaknesses of alternative concepts can be
identified by investigating the concept scoring matrix which can be seen
in table 2. The concept scoring method can help designers to identify
the strengths and weaknesses of alternative designs; and, by combining
of the advantages of different designs, a designer can achieve an
improved design to fulfill functional requirements. This technique is
efficient, because when functional requirements are changed, only the
weighting information needs to be adjusted to reflect the change; and,
most of the scoring information can still be used. (Xiao et al) Best
concept is selected and design improvement of the selected concept is
done to improve the functionality of concept after concept scoring.
Design improvement includes making machine components which are able to
perform mechanical functionality when machine is functional. It can be
tested by means of analysis of mechanisms, linkages, collision between
the parts and realization of production process. Comparison is done in
machines that can make different product varieties, ease in
manufacturing, uniform density and durable product weight is given for
each criterias; and by using the selection formula concept 4 is applied
for further improvement.
7. System Improvement and Realization
The target specifications set earlier in the process are revisited
after a concept has been selected and tested. At this point, the whole
system is reanalyzed with mechanical behavior for the realization of
product concept for practicing to reality. Drive system of motor and
linkages are fixed. Size of system is fixed to make the prototype pipe
shown in Fig 5. Vibration table, inner die, outer die and support
structures are made in CAD environment to realize the system workable
for production of prototype pipe.
[FIGURE 5 OMITTED]
8. Topology Optimization of Inner Die
8.1 Introduction
Ribs of inner die are used as a component for this study. Inner die
being main component for rotation driven by rotation powered motor;
therefore weight of inner die should be put as minimum as possible.
Weight reduction will give substantial impact to fuel efficiency,
efforts to reduce emissions and therefore, save environment. Weight can
be reduced through several types of technological improvements, such as
advances in materials, design and analysis methods, fabrication
processes and optimization techniques, etc. These weight reducing
strategies in industrial field can be achieved by means of different
tools by performing optimization procedure. (Zurofi, 2004 l). Components
must be designed to meet the requirements for strength and safety.
optimization methods were developed to have lighter, less cost and may
have better strength too. There are four disciplines for optimization
process in structural optimization strategy topology optimization, shape
optimization, size optimization and topography. (Kojima, 2000) This
optimization research aims to contribute to the development of
structural design and weight reduction of inner die using topology
optimization by the density method. optimization process for this work
was conducted using OptiStruct solver in order to reduce the weight of
the existing component.
8.2 Methodology
optimization process used in current research is followed by
several design steps firstly by making design domain of CAD model in
CATIA. Next, Hyper mesh was used to import model for finite element
modeling where loads and constraints are applied. Furthermore, Hyper
view and Hyper graph were used to display and plot the data for results
interpretation. Results of optimization runs performed with individual
loads applied separately help to identify preferred load path with
respect to the type of load applied.(Forcier & Joncas, 2010, (Hsu,
2005) Finite element analysis is used in first stage before performing
optimization to analyze the initially generated design. optimization is
performed and generated optimal model is further compared with initial
model for verification of new design.
[FIGURE 6 OMITTED]
8.3 Optimization Problem
For selecting inner die to generate optimal shape rib, design
domain was considered. Keeping constant thickness of 5 mm from
traditional rib, design domain is created as shown in Fig 7. Design
domain is one portion of rib model among the six ribs from the whole
inner die rib structure. Feasible optimal design topology is created by
satisfying the optimization function. General optimization problem for
topology optimization can be derived by
Minimize f(x)
Subject to (x)- 0 j = 1, 2,....m i = 1, 2,....n
Where, f(x) represents the objective function, (x) and represents
the j-th constraint response and its upper bound respectively. M is
number of constraint. is normalized material density of i-th element.
Lower and upper bound of ith elements are between 0 and 1. To enforce
the design to be close to a 0/1 solution, a penalty is introduced to
introduce intermediate densities. For the SIMP approach the penalization
is achieved by the following power law:
Ei = (xi)p E0
Where, and are actual and original densities. Ei and E0 are actual
young's modulus and original young's modulus; p is
penalization power. For practical applications it is important to
support a variety of common analysis responses. In this research
OptiStruct is used to get wide range responses for topology optimization
including compliance and displacement response analysis. (Bendsoe &
Sigmund, 2004), (Altair OptiStruct) The optimization problem in this
research is
Minimize Compliance (C) = FTU
Subject to V= f.VO = eve
stress 2.5e8 N/m2 and Displacement 0.0357mm
where, the values are obtained from the material yield stress and
results from the FE analysis. Finite element analysis is performed in
consideration of loading condition during manufacturing process of SPC
pipe. During the analysis maximum loading process is considered for
worst case scenario.
Forces acting on the inner core are due to frictional force during
the up down movement of core, centrifugal effect during rotation,
pressure loads in concrete walls, drag force due to concrete during
vertical movement of core in Z direction and frictional force during
rotation. These forces are summarized as, FR1, FR2, FD3, FD4 where FR1 =
sum of Pressure force at area 1 due to load of concrete + fricitional
force at area 1 during rotation. FR2 is also same as FR1 however area is
different.
FD3 and FD4 are drag force during inner die upward movement given
by FD = 0.5 Cd [rho]A V2 Where, p = Density of the fluid, V = speed of
the object relative to the fluid, Cd = Drag coeff, A= Reference area. In
the above expressions 1, 2, 3 and 4 are areas that are determined with
respect to geometry of the consecutive areas (Fig.7). In this research
force acting on the particle and particle interaction is not considered
because target is to reduce the material in the inner die.
To perform optimization the structure of geometry is necessary to
be minimized for reducing iteration time. Therefore one part of rib
design domain was considered. Upper part of design domain is connected
with shaft therefore is fixed during optimization.
[FIGURE 7 OMITTED]
The CAD geometry of the traditional joint was generated by removing
features such as fillets and other excessive details to facilitate
meshing. From this geometry a design space was created. This design
space was obtained by expanding the existing traditional geometry to
create a very simplified envelope within which the final design must
reside. This design envelope is determined by the maximum size of design
domain.
The first stage in pre-processing was the definition of materials
and element properties in HyperMesh. Once these were created with the
appropriate qualities the model was meshed. A 3D tetramesh was created
for the rib design space. The last input parameter required before
implementation of the topology optimization study is the material
identification. In the case of the inner core, the material was
specified as steel; as a result, the material was defined as linear
isotropic (MAT1) and the values for Young's modulus and
Poisson's ratio were entered. These values used for the study were
2.1e5 (N/mm2) and 0.3 respectively.
The number of design variables is generally large in topology
optimization; we need to obtain the design sensitivity with respect to
each design variable to accurately and quickly find a local minimum
design. In this case, the objective function is compliance when volume
is minimized and the design variable is the normalized density so that
we can easily obtain the numerical design sensitivity as follows:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]
It can be written in another form as
-[u.sub.i.sup.T][[partial derivative][k.sub.i]/[partial
derivative][[rho].sub.i]][u.sub.i]
[Where.sup.[phi]] is compliance, K is the global stiffness matrix,
ui is the ith element displacement vector, and ki is the ith element
stiffness matrix. (Kim et al., 2012)
From the sensitivities formula we can check the convergence of the
optimal topology as
[absolute value of [C.sub.k+1]] - [C.sub.k]/[C.sub.k]] <
[epsilon] [absolute value of max([x.sub.K+1]) -
max([x.sub.k])/max([x.sub.k])] < [epsilon]
The relative difference of the design variable and objective can be
used as the judgment condition of a convergent result. (Zuo et al.,
2007) After the optimization has processed, model is adjusted for a
series of steps until the convergence is reached. The resulting geometry
proposal obtained from optimization process can be seen in Fig 8. The
graph shows the convergence value in each level of iterations to
determine the maximum allowable limit of volume contained in the
material under boundary conditions. When the value tries to become
stable for several iterations then the convergence criteria is
considered as fulfilled and the target is accomplished.
The pattern of rib is completely different than the proposed design
at the first phase. The convergence graph shows below the objective
function as minimizing volume. In 31 iterations the volume is converged
from the single design domain to feasible geometry in design space. Main
objective is focused to minimize the geometry by considering stress and
displacement as a constraint. By applying the entire prerequisites
information convergence graph is obtained as follows.
Although the topology results appear reasonable, the design is not
ready to hand over to the machine shop for fabrication. The results of
the topology studies are merely rough geometric proposals, and some
interpretation is required to create the final design. OptiStruct has
the ability to export the topology results as an IGES file using an
export feature so that the geometry can be opened and traced over in a
cAD environment.
[FIGURE 8 OMITTED]
For the interpretation of the ribs of inner die, the optimized
shape was created using CATIAV5. To capture the shape of the proposed
design, sketch was done over the generated rough model for creation of
the CAD model, and the interpretation can be seen in Fig 9.
The design retains the features proposed by OptiStruct to get
better and efficient performance within the minimization of weight. The
obtained design was rotated in circular pattern in six places to support
the outer structure as same orientation with traditional design. The
generated model after the optimization was found to be 9.5 percent
lesser in weight than initial design.
[FIGURE 9 OMITTED]
Displacement analysis is also done to check the performance of
structure. Initial displacement result is 0.035 mm during the full
loading condition in whole structure whereas final displacement result
is 0.034 mm. The slight reduction in displacement verifies that although
significant weight is reduced; displacement can also be minimized by
proper distribution of material in given design space
[FIGURE 10 OMITTED]
This research introduced a procedure to apply topology optimization
to rib designs for an inner core of newly designed molding machine. The
rough configurations of ribs formed by solid elements are generated by
topology optimization within a specified design space.
Post-processing work based on the generated rib topology and some
engineering experience replaces the topology optimized structure to
feasible structure for manufacturing. The effect of topology
optimization is significant which does not only satisfies all
constraints but also weights much less than the structure obtained by
conventional methods as the weight is reduced to 6Kg from the research.
9. Conclusion
This research proposed a new concept molding machine capable of
performing conveying, mixing, compacting and surface finishing during
production of concrete pipes. Due to the new design concept and by
following proper design process, the proposed design can be a milestone
to satisfy the requirement of the pipe manufacturing companies. From the
optimization strategy it is mentioned that basic shape from traditional
design is changed to new shape. And the weight is less than compared
with the original design.
Therefore, it can be verified that application of topology
optimization in the conceptual design phase is reasonable for reducing
weight. This is a moving structure therefore some amount of energy can
be saved during manufacturing SPC pipe due to light weight design. The
performed optimization technique is a robust technique which has seen
small uses in particular research such as automotive and aerospace.
This research has shown that the same methods can be applied to
manufacturing areas. By using this approach rib structure weight is
reduced to 9.5 percent. The optimized design has been arrived
numerically through the number of iterations but verification is needed
as a future work. Although, the concept is generated but practical
validation is needed in application for the real use.
10. Acknowledgements
This work was supported by Research Grant University of Ulsan 2012.
11. References
Adrian Xiao, Simon S. Park, Theo Freiheit; "A Comparison of
Concept Selection in Concept Scoring and Axiomatic Design Methods",
University of Calgary, Canada Altair OptiStruct, HyperWorks 10.0,
User's manual. Altair Engineering, Inc D. Serban, E. Man, N.
Ionescu and T. Roche; 2004 "A TRIZ Approach to Design for
Environment", Product Engineering 89-100
Kojima, Y. 2000, "Mechanical CAE In Automotive Design",
R&D review of Toyota CRLD, Vol 35, no. 4
Kong-Tian Zuo, Li-Ping Chen, Yun-Qing Zhang. Jingzhou Yang, 2007,
"Study of key algorithms in topology optimization" Int J Adv
Manuf Technology 32: 787-796.
Louis-Charles Forcier, Simon Joncas, 2010 "Development of a
structural optimization strategy for the design of next generation large
thermoplastic wind turbine blades" AIAA/ASME/ASCE/AHS/ASC
Structures, Structural Dynamics, and Materials Conference, Orlando, FL,
USA
M. P. Bendsoe, O. Sigmund. Topology Optimization--Theory, Methods
and Applications. Springer, Berlin, Heidelberg, New York, 2nd edition,
2004 MING-HSIU HSU, YEH-LIANG HSU "Generalization of two- and
three-dimensional structural topology optimization. Taylor &
Francis, Vol. 37, No. 1, January 2005, 83-102
OCPA concrete pipe design manual, Ontario Concrete pipe
association. SOUCHKOV V., 1988, "TRIZ: A Systematic Approach to
Conceptual Design", Ideal Design Solution, Netherlands
Sun Yong Kim, Yong Kim and Chris K. Mechefske; 2012, "A New
Efficient Convergence Criterion For Reducing Computational Expense In
Topology Optimization: Reducible Design Variable Method";
International Journal For Numerical Methods In Engineering, 90:752-783
Zurofi M., 2004 "Manufacturing Process Effects on Fatigue
Design and Optimization of Automotive Components--An Analytical and
Experimental Study", The University of Toledo
Authors' data: Univ.Prof. Dr.-Ing. Park, H[ong] S[eok] *;
Graduate Researcher Dahal, P[rakash] **, * Department of Mechanical
Engineering, University of Ulsan, Daehak-ro 93, Nam-gu, Ulsan, Republic
of Korea, ** Department of Mechanical Engineering, University of Ulsan,
Daehak-ro 93, Nam-gu, Ulsan, Republic of Korea,
[email protected],
[email protected]
This Publication has to be referred as: Park, H[ong] S[eok] &
Dahal, P[rakash] (2013) Development of concrete Pipe Molding Machine
with Topology Optimization, Chapter 45 in DAAAM International Scientific
Book 2013, pp. 751766, B. Katalinic & Z. Tekic (Eds.), Published by
DAAAM International, ISBN 978-3-901509-94-0, ISSN 1726-9687, Vienna,
Austria
DOI: 10.2507/daaam. scibook.2013.45
Tab. 1. Changing TRIZ principles to specific solution
Principle TRIZ principles Specific solution
No
4 Asymmetry -Stable design of product
-Flexibility in manufacturing
operations
5 Merging -Merging vibration and rotation
functions to get better design and
improved functionality.
8 Antiweight -Reduces energy consumption and less
material consumption.
14 Spheroidality -Make round smooth cylindrical shape
-Equal circulation of plastic
concrete in all parts
17 Another -Traditional horizontal machine is
dimension replaced by vertical type to reduce
manufacturing space
-For shortening manufacturing time
18 Mechanical -Mixing the concrete particles and
vibration removing unnecessary voids within
concrete, for making durable product
20 Continuity of -Can be able to produce varieties of
useful action products e.g circular pipe and
tetrapod.
28 Mechanical -Replacement of horizontal noisy
substitution system to vertical system with
noise minimization.
29 Pneumatics and -Use hydraulic or pneumatic damper
hydraulics for vibration table for Stable
operation
Tab. 2. Concept scoring table for identification of best concept
Concept 1 Concept 2
Selection Weignt Rating weighted Rating weighted
Criteria score score
Product 8 2 16 5 40
variety
No 9 4 36 4 36
peneteration
of liquids
Ease in 6 3 18 4 24
manufacturing
Uniform 7 3 21 3 21
density
product
Ease of 6 4 24 3 18
Handling
Durable 9 3 27 3 27
product
142 166
Continue? No No
Concepts
Concept 3 Concept 4
Selection Rating weighted Rating weighted
Criteria score score
Product 3 24 5 40
variety
No 4 36 4 36
peneteration
of liquids
Ease in 3 18 3 18
manufacturing
Uniform 4 28 5 35
density
product
Ease of 3 18 3 18
Handling
Durable 3 27 5 45
product
151 192
No Yes
Concepts
Concept 5
Selection Rating weighted
Criteria score
Product 3 24
variety
No 4 36
peneteration
of liquids
Ease in 5 30
manufacturing
Uniform 4 28
density
product
Ease of 5 30
Handling
Durable 4 36
product
184
No
