Manufacturing

Engineering Year 1

SECTION

4 RAPID
PROTOTYPING

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DESIGN AND PROTOTYPING

Rapid Prototyping

Introduction
In this section, we shall learn about rapid prototyping as a form of prototyping technique
used for product development. You will also be introduced briefly to conventional
prototyping techniques to give you a good basis to understand rapid prototyping. The
principles behind rapid prototyping, the process, the advantages and disadvantages
and its applications in product development will be thoroughly discussed. At the end
of this section, you will be equipped with practical skills that will enable you to make
prototypes of your design ideas. You will be exposed to hands-on activities to help
you practice how to make prototypes using rapid prototyping techniques such as 3D
printing

At the end of this section, you will be able to:

• Explain the fundamental difference between conventional prototyping and rapid

prototyping
• Discuss the principles and processes of rapid prototyping.
• Explain the advantages and disadvantages of rapid prototyping
• Discuss the applications of rapid prototyping in manufacturing

Key Ideas
• Prototypes are smaller versions of actual designs that allow manufacturers to test the
performance of their designs, correct design flaws and redesign before producing in full
scale.
• Conventional prototyping refers to the process of creating physical models or
prototypes using established, non-digital manufacturing techniques and tools such as
machining, injection moulding, sheet metal fabrication, woodworking, handcrafting
and many more.
• Rapid prototype involves the automated fabrication of intricate shapes from computer-
aided design (CAD) data using a layer-by-layer principle

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THE FUNDAMENTAL DIFFERENCE BETWEEN

CONVENTIONAL PROTOTYPING AND RAPID
PROTOTYPING
Prototyping is an essential part of the manufacturing process. Prototypes are smaller
versions of actual designs that allow manufacturers to test the performance of their
designs, correct design flaws and redesign before producing in full scale. Prototypes
of products can be made using conventional or rapid prototyping techniques. This
section discusses the major differences between conventional prototyping and rapid
prototyping techniques.

Conventional Prototyping
Over the years, manufacturers have used conventional prototyping methods to create
models of their designs for performance assessment. Conventional prototyping refers
to the process of creating physical models or prototypes using established, non-digital
manufacturing techniques and tools such as machining, injection moulding, sheet
metal fabrication, woodworking, handcrafting and many more. These processes can be
labour-intensive, time-consuming and expensive, prompting the need for easier, faster
and cheaper prototyping techniques to enhance the work of manufacturers.

Rapid Prototyping
In recent years, rapid prototyping techniques have been proposed to enhance the
manufacturing process. Rapid prototyping is a modern and innovative approach to
creating prototypes and physical models quickly and cost-effectively using computer-
aided design (CAD) software and additive manufacturing approaches. Examples
of rapid prototyping techniques include but are not limited to fused deposition
modelling, stereolithography, selective laser sintering, poljes technology, 3D printing
and bioprinting.

Differences between Conventional Prototyping and

Rapid Prototyping
Conventional prototyping and rapid prototyping are two distinct approaches to
developing prototypes in the product design and development process. They differ
in various aspects, including their processes, speed, cost and application. The key
differences between conventional prototyping and rapid prototyping are presented in
Table 4.1.

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Table 4.1: Differences between conventional prototyping and rapid prototyping.

Item Conventional Prototyping Rapid Prototyping

Process and Uses traditional manufacturing Involves creating prototypes layer

Technique methods such as machining, by layer using computer-aided
milling, or handcrafting. This design (CAD) data. It relies on
process is time-consuming and digital models and specialised
may require skilled artisans or machines to build physical
machinists to produce detailed prototypes quickly
models.

Speed Takes a considerable amount of Significantly faster

time, especially for complex and
intricate designs

Cost Can be costly, primarily due to Initial investment is relatively high.

labour, material and machine However, it can be cost-effective
costs. Skilled machinists and in the long run. It reduces labour
artisans are often required, which costs, minimises material wastage,
adds to the expense. and enables quicker design
iterations

Complexity Better suited for certain types of Well-suited for creating complex,
materials and complex, large-scale intricate and detailed prototypes. It
prototypes. They are versatile but excels in producing prototypes with
may have limitations in intricate intricate geometries that would be
and highly detailed designs challenging or impossible to create
using traditional methods

Iterative Due to the time and cost involved, Facilitates iterative design, allowing
designs conventional prototyping may limit designers to quickly modify and
the number of design iterations test multiple design variations.
possible during the development This accelerates the product
process. development cycle

Materials Offers a wide range of material Material selection may be more

choices, including metals, plastics limited compared to conventional
and composites, depending on methods. It primarily uses various
the machining or manufacturing types of plastics and resins
process.

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Activity 3.1

Making a prototype of a miniature shaft, nameplate or signage using available

conventional prototyping and rapid prototyping techniques.
A: Conventional Prototype of a miniature nameplate
Conventional prototyping involves more manual and hands-on processes. Let us
follow the steps below:
1. Design the nameplate manually with a detailed sketch considering the
dimensions, font, and any other design elements.
2. Selection appropriate material for your prototype. .Basic materials such
as wood, plastic, metal, or even cardboard can be used, depending on the
purpose.
3. Cut the material to shape using basic tools like a saw, knife, or scissors, to
the desired dimensions of the nameplate. Use files or sandpaper to remove
all shape edges.
4. Apply the required design by either
a. Engraving (hand-engrave the text and design using engraving tools).
b. Hand Painting (paint the text and details by hand using fine brushes)
c. Printing Print the text and design on a sticker and apply it to the
nameplate.
4. Assemble components using glue, screws or rivets if the nameplate has
multiple layers or pieces,
5. Give the prototype (nameplate) a finish by using sandpaper, polish, or paint
the prototype to make it attractive and protect the surface.
6. Present your nameplate prototype for inspection and comments.

B: Rapid Prototype of a miniature nameplate.

For miniature nameplate using rapid prototyping follow the steps below:
1. Create a digital 3D model of the nameplate using CAD software like
AutoCAD, Fusion 360, and ensure that the design is detailed, including text,
logos, and other elements.
2. Scale the model down to the desired miniature size while maintaining the
proportions and details.
3. Select appropriate prototyping method to print the miniature nameplate.
a. Convert the 3D model into a format compatible with 3D printers, such
as an STL file. (Remember to choose the appropriate material and
print the miniature nameplate)
b. Laser Cutting and Engraving: If you’re using materials like acrylic or
wood, prepare vector files for laser cutting. The machine will cut the
shape and engrave the text or design onto the material.

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4. Set up the 3D printer or laser cutter and the type of prototyping process.
Calibrate it, and load the chosen material.
a. For 3D printing, print the scaled model.
b. For Laser cutting, cut and engrave the design on the material.
5. Review the prototype for accuracy and detail. For 3D-printed prototypes,
clean up the model by removing supports, sanding, and possibly painting.
For laser-cut prototypes, remove any burn marks, and assemble any parts if
necessary.

Activity 3.2

In a group organised by your teacher discuss and make presentations on the

major differences associated with the use of conventional and rapid prototyping
techniques, with emphasis on the processes, complexities, production speed,
time involved, needed skill sets, and cost implications.

Activity 3.3

Now, think about any product you may want to design to help your class or school
and use rapid prototyping to design a prototype of it.

PRINCIPLES AND PROCESSES OF RAPID

PROTOTYPING
This is one of the main ways we approach product development. Rapid prototyping is a
technique that allows us to create physical prototypes quickly and efficiently, providing
invaluable insights into the design and functionality of a product before it goes into
full-scale production. However, to effectively utilise this technique, it’s crucial to
understand its underlying principles and processes.

The Principles of Rapid Prototyping

In rapid prototyping (RP), a solid object with a prescribed shape, dimension and finish
can be directly produced from a CAD-based geometric model data stored in a computer
without human intervention. The parts obtained by RP technology can be used directly
as the prototype or as a mould for casting the prototype component. The principle
of RP technology is based on speed, efficiency, and the layer-by-layer construction of
physical models from digital designs.

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The Process of Rapid Prototyping

The rapid prototyping process is described in Fig. 4.1, and can be summarised as below:
1. Creation of the CAD model of the (part) design: A component is modelled on
a Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) system.
2. Conversion of CAD model into Standard Tessellation Language (STL)
Format: The solid or surface model to be built is next converted into a format
called the “STL” (Stereolithography) file format which originates from 3D systems.
The STL file format approximates the surface of the model using polygons. Highly
curved surfaces must employ many polygons, which means that STL files for curved
parts can be very large.
3. Slicing of STL file into thin sections: A computer program analyses an STL file
that defines the model to be fabricated and “slices” the model into cross sections.
4. Building part layer by layer: The software that operates RP systems generates
laser-scanning paths or material deposition paths. Information computed here is
used to deposit the part layer-by-layer on RP system platform. This step is different
for different RP processes and depends on the basic deposition principle used in the
rapid prototyping machine.
5. Post-processing/finishing/joining: At this stage, some manual operations are
generally performed to give the model a good surface finish. The post-processing and
surface finishing process can be done by sanding, polishing or painting. Also, excess
elements adhered to the part or support structures are removed when cleaning the
surface. A skilled operator is, therefore, required during the post-processing and
surface finishing stage.

Fig. 4.1: The rapid prototyping process

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Fig. 4.2: Flow chart to produce a 3D model

Activity 3.4 : Exploring 3D Modelling

Visit a nearby 3D model printing studio to be introduced to the 3D modelling

concept, for a hands on experience in creating your own 3D model
Write a summary of your experience at the 3D model printing studio in less than
two pages under the following headings
1. Introduction
2. Tools, machines, or equipment and soft wares
3. Practical session
4. Printing process
5. Conclusion

Activity 3.4

Watch the video on the processes of developing a 3D model of a shock absorber

of a car using a 3D printing process using the link below.
https://www.youtube.com/watch?v=qfmW6hdZupg

After the video, follow the steps below to design and make a 3D model of a shock
absorber of a car.

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1. Create a digital 3D model of the shock absorber of a car using Computer-

Aided Design/Computer-Aided Manufacturing (CAD/CAM) software like
AutoCAD, Fusion 360, and ensure that the design is detailed, including text,
logos, and other elements. Save your design in the Standard Tessellation
Language (STL) format.
2. Scale the model down to the desired size while maintaining the proportions
and details. Use slicing software to slice your 3D model into thin cross
sections. This step prepares your model for the 3D printing process.
3. Set up the 3D printer and choose the appropriate material and print your
prototype. Where you do not have a 3D printer, visit a nearby centre and
print your prototype or watch videos, to understand how the printer builds
the model layer by layer
4. Review the prototype for accuracy and detail. Clean up the model by
removing supports, sanding, and possibly painting.

Activity 3.5

Prepare a presentation of the RP prototyping process, using the 3D printing

process in Activity 2 as a case study.

ADVANTAGES AND DISADVANTAGES OF RAPID

PROTOTYPING
Here we discuss the advantages and disadvantages of rapid prototyping. Innovation
has become an integral part of the manufacturing process. Rapid prototyping provides
a faster and cost-effective means of creatively making physical prototypes during
product development. However, rapid prototyping has several disadvantages that need
to be understood to help in making decisions when selecting a prototyping technique.

Advantages of Rapid Prototyping

Rapid prototyping has many advantages including:
1. Faster Product Development: Rapid prototyping significantly speeds up the
product development process by allowing teams to iterate designs and concepts
quickly.
2. Reduced Costs: Rapid prototyping allows designers to detect and address design
flaws early in the development cycle. This helps to save substantial costs compared
with making changes later in the process or after production has begun.
3. Improved Communication: Prototypes made using rapid prototyping techniques
provide a tangible representation of the product. This makes it easier for stakeholders,

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including clients, engineers and designers, to understand and discuss the design
and functionality.
4. User Feedback: Rapid prototypes can be tested with end-users, providing valuable
feedback that helps refine the design and align it with user needs and expectations.
5. Elimination or Reduction of risk: Rapid prototyping helps identify potential
issues and risks early, enabling designers and manufacturers to address them before
they become critical problems.
6. Enhanced Creativity: Rapid prototyping provides the freedom to quickly exper-
iment with ideas. This can stimulate creativity and innovation among designers.
7. Improvement in Iterations: Rapid prototyping allows for multiple iterations,
enabling continuous improvement until the final product meets the desired
standards.
8. Customisation: Prototypes made with rapid prototyping techniques can be cus-
tomised to focus on specific aspects of a product, allowing for the testing of individ-
ual features or components.

Disadvantages of Rapid Prototyping

Rapid prototyping has several disadvantages, including:
1. Limited Functionality: Prototypes may lack full functionality, which can lead to
misconceptions about the final product’s capabilities.
2. 2. Time and Resource Intensive: Creating prototypes requires time and resources,
and the rapid iteration process can be demanding for the team.
3. Potential for Scope Creep: Frequent changes during the prototyping phase can
lead to scope creep, causing delays and increased costs.
4. Quality Concerns: Rapid prototyping may prioritise speed over quality, potentially
leading to the development of unstable or inefficient solutions.
5. Overemphasis on Aesthetics: Prototypes can sometimes focus too much on
visual design, neglecting underlying functionality and performance.
6. Resistance to Change: Teams or stakeholders may resist making significant
changes based on prototype feedback, especially if they are attached to a particular
design or concept.
7. Risk of Misinterpretation: Stakeholders may misinterpret the purpose of a
prototype, thinking it represents the final product, which can lead to unrealistic
expectations.
8. Cost of Tools and Equipment: Utilising advanced prototyping tools and equip-
ment can be expensive, especially for small businesses or start-ups.
9. Material Problems: Most rapid prototyping techniques have a limited material
range. Prototypes may also exhibit reduced material properties like surface finish
and strength.
10. Skilled labour: Rapid prototyping requires skilled labour.

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Activity 3.6

Making a diamond-nine arrangement of the advantages and disadvantages of

rapid prototyping. To arrange cards of the advantages and disadvantages of rapid
prototyping in a diamond-nine shape follow the steps given below.
1. Write down the advantages and disadvantages of rapid prototyping on
separate cards
2. Arrange the cards in a diamond shape. Ensure that he most significant
points should be at the top and bottom, and the least significant points
should be towards the middle.
3. Start with the most significant advantage and disadvantage. Place these
cards at the top and bottom of your diamond
4. Identify the next two most significant advantages or disadvantages. Place
them on the second row of your diamond.
5. Adding more cards to each row as you move towards the middle of the
diamond.
6. Start reducing the number of cards per row as you move towards the bottom
of the diamond
7. Note that there is no right answer for this activity. It only encourages critical
thinking and skills.
NB: Figure 4.3 represents a diamond-nine activity for the advantages of a rapid
prototyping and figure 4.4 represents a diamond-nine activity for the disadvantages
of a rapid prototyping

Faster Product
Development

Improved
Reduced Costs Communication

Elimination or Enhanced
User Feedback Reduction of Risk Creativity

Improvement Customisation
Iterations

Overemphasis or
Aesthetics

Fig. 4.3: Advantages of rapid prototyping on a diamond-nine

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Limited
Functionality

Time and Potential for

Resource Scope Creep
Intensive

Overemphasis or Resistance to
Quality Concerns Aesthetics Change

Risks of Cost of Tools and

Misinterpretation Equipment

Skilled Labour

Fig. 4.4: Disadvantages of rapid prototyping on a diamond-nine

Now, make a diamond-nine activity on the advantages and disadvantages of rapid

prototyping used in manufacturing on your own.

Activity 3.7

Make a search on the internet, read the book or watch the video on the
advantages and disadvantages of rapid prototyping used in manufacturing using
the link and the book below. https://www.youtube.com/playlist?list=PLQmc-I2-
FO2Gnp2s74U5fBjfHDg1tUbOh
Gibson, I., Rosen, D.W., & Stucker, B. (2014). Additive Manufacturing Technolo-
gies: 3D Printing, Rapid Prototyping, and Direct Digital Manufacturing (2nd ed.).
Springer. Page 8
Steps:
1. Form research groups, in a mixed ability research groups, focus on either the
advantages or disadvantages of rapid prototyping.
2. Discussion after completing your research, discuss your findings within
your group. Make sure everyone understands the key points and address any
questions or confusion.
3. Presentation Preparation: prepare a presentation to share your findings
with the rest of the class. This could be a slide presentation, a poster, oral
presentation or even a short video

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4. Reflection: After all groups have presented, reflect as a class on what was
learned. Discuss the strengths of each group’s research and any new insights
gained about rapid prototyping.

APPLICATIONS OF RAPID PROTOTYPING IN

MANUFACTURING
Rapid prototyping helps validate the feasibility of a design and verifies that a
design meets the desired requirements and specifications. It is essential in product
development, customisation, concept modelling, production of end-use parts, reverse
engineering and rapid manufacturing. Here we will discuss the application of rapid
prototyping in product development.

Applications of Rapid Prototyping

Rapid prototyping has many applications, including;

1. Concept models and validation

Rapid prototyping allows for the development of physical concept models of future
products. These concept models allow engineers and designers to test and validate
their ideas. It also provides the opportunity for engineers and designers to explore the
functionality of their initial concepts and demonstrate their validity to stakeholders for
the approval of the development of the product.

2. Functional Prototyping
Engineers use rapid prototyping to produce prototypes of various designs. These
prototypes, which are closely related to the final products, help engineers and designers
accelerate their product development cycle through testing and evaluation.
This allows designers and engineers to refine their designs based on real-life performance
data to ensure better product performance. For example, automobile manufacturing
companies use rapid prototyping to create concept cars and test new designs and
features before going into full production; components like engine parts, interior
features and exterior panels can be rapidly prototyped to evaluate their performance
and fit.

3. Customisation and Personalisation of Products

Rapid prototyping helps in the production of customised and personalised products
specific to individual preferences and requirements.
This is extremely important in the medical, footwear and consumer goods industries
where products need to be designed specifically for an individual. For instance, surgeons
use rapid prototyping to create patient-specific implants for bone reconstruction,
craniofacial surgeries, dental procedures, prosthetic limbs and other medical devices

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that fit patients perfectly; shoe manufacturing companies can create prototypes of
different sole designs to evaluate comfort, support and performance and also create
footwear tailored to an individual’s foot shape and preferences.

4. Tooling and Jigs

Rapid prototyping is used to create specialised tools, jigs and fixtures that aid in the
manufacturing process. These tools can be produced quickly and cost-effectively,
enhancing production efficiency.

5. Iterative Design
Rapid prototyping helps designers to easily iterate and refine their designs multiple
times in a shorter span, leading to faster innovation and improvement of products.

6. Creation of Complex Geometries

Rapid prototyping allows for the creation of intricate and complex geometries that
would be challenging or impossible to produce using traditional methods. This is
particularly beneficial in industries like aerospace and medical devices.

7. Spare Parts Production

Maintenance and service industries such as the automotive and aerospace industries use
rapid prototyping to quickly and efficiently produce spare parts for their maintenance
and repair services.

8. Education and Training

Rapid prototyping is used in educational institutions and training programmes to
teach students about product design, manufacturing processes and hands-on problem-
solving.

Activity 3.8

Search the internet, read a book or watch the video on the application of rapid
prototyping used in manufacturing using the link and the book below.
https://www.youtube.com/playlist?list=PLQmc-I2-
FO2Gnp2s74U5fBjfHDg1tUbOh.
Follow the steps below for a group debate:
1. Form Research Groups In research groups, focus on the group
representing an industry (such as the automobile, engineering,
manufacturing, building, food and clothing industries
2. Discussion After completing your research in the application of rapid
prototyping, discuss your findings within your group. Make sure everyone
understands the key points and address any questions or confusion.
3. Presentation Preparation Prepare a presentation to share your findings
with the rest of the class. Each group chooses their preferred mode of

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presentation, such as oral presentation, webbings, mind maps, written

reports, video presentations, or PowerPoint presentations.
4. Presentation Each group presents their findings to the rest of the class.
This allows you and your peers to learn from each other and gain a broader
understanding of the applications of rapid prototyping across different
industries
5. Reflection After all groups have presented, reflect as a class on what was
learned. Discuss the strengths of each group’s research and any new insights
gained about applications of rapid prototyping.

Activity 3.9

Your teacher will provide you with components used in varying industries such
as the automobile, building, food, and clothing industries. (Car tyre, shock
absorbers, trowel, wooden float, tea cup, serving tray)
1. Form groups: Form a mixed ability group of 4-5 classmates to work
together on this task..
2. Selection of components: Your teacher will provide you with components
used in various industries such as car tyres, shock absorbers, trowels,
wooden floats, tea cups, serving trays, bottles, etc. Your group should select a
component from the given components.
3. Design of Prototype: You are tasked to design a prototype of your choice
based on your selected component. The applications of rapid prototyping in
your design process should be considered.
4. Creation of Prototype In your group cooperate to create your prototype
using 3D printing. Document the process used and any challenges
encountered during the prototyping creation processes.
5. Testing and Evaluation: Test your created prototype for its functionality
and evaluate its performance. Record your observations and findings.
6. Presentation Preparation: After testing and evaluation, prepare a
presentation on your prototype. The presentation should
7. Presentation: Then present your prototype and your findings to the rest of
the class, this should include the design process, the challenges faced, how
you overcame them, and your observations and findings from the testing
and evaluation process. This allows you to learn from each other and gain
a broader understanding of the applications of rapid prototyping across
different industries
8. Reflection After all groups have presented, reflect as a class on what was
learned. Discuss the strengths of each group’s project and any new insights
gained about applications of rapid prototyping.
Now, think about any product you may want to design to help your class or
community and use rapid prototyping to design and construct.

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Review Questions

1. What is the major difference between rapid prototyping and conventional

prototyping?
2. How does the use of conventional or rapid prototyping techniques affect the
duration of the development of a product?
3. How do the technologies used in conventional prototyping differ from those
used in rapid prototyping?
4. What are the steps involved in the rapid prototyping process?
5. What is the justification for slicing the STL file into thin layers for the design
of the models?
6. As a manufacturing engineer in your company, outline any three reasons
why rapid prototyping should be adopted in all the production sections of the
company.
7. Discuss any three reasons why rapid prototyping must not be over-encouraged
in industries.
8. Evaluate the economic impact of rapid prototyping on the local manufacturing
industry.
9. Discuss the benefits the local automotive and manufacturing industries can
derive from using rapid prototyping.

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Extended reading
1. Gibson, I., Rosen, D.W., & Stucker, B. (2014). Additive Manufacturing Technologies: 3D
Printing, Rapid Prototyping, and Direct Digital Manufacturing (2nd ed.). Springer.
2. Simpson, T.W., Yu, J., & Jiao, J. (2020). Design for Additive Manufacturing: Guidelines and
Applications for Industrial 3D Printing. CRC Press.
3. Chua, C. K., Leong, K. F., & Lim, C. S. (2010). Rapid Prototyping: Principles and Applications
(2nd Edition). World Scientific Publishing
4. Gibson, I., Rosen, D.W., & Stucker, B. (2014). Additive Manufacturing Technologies: 3D
Printing, Rapid Prototyping, and Direct Digital Manufacturing (2nd edition.). Springer.
(Page 8)

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ACKNOWLEDGEMENTS

LIST OF CONTRIBUTORS
Name Institution

Engr. Ali Morrow Fatormah Mfantsipim School, Cape Coast

Ebenezer Adusei Kumasi Technical University

Benjamin Atribawuni Asaaga Kwame Nkrumah University of Science and Technology

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