This document discusses rapid prototyping, including its definition, historical development, standard terminology, principles, applications, advantages/disadvantages, and process. Rapid prototyping is defined as building a prototype in one step using additive layer manufacturing without tools. It has expanded from prototype modeling to manufacturing parts for various applications. The standard terminology includes terms like additive manufacturing, layer-based, and digital fabrication. The process involves CAD modeling, STL formatting, data validation, orientation, support generation, parameter setting, slicing, layer construction, and finishing.

1. BAHIR DAR UNIVERSITY
BAHIR DAR INSTITUTE OF TECHNOLOGY (BiT)
FACULTY OF MECHANICAL AND INDUSTRIAL
ENGINEERING
Rapid Prototyping & Reverse Engineering
[MEng6123]
Rapid Prototyping

2. Rapid prototyping (RP)
Definition
• Rapid prototyping is a layer based automated fabrication process for
making scaled 3-dimentional (3D) physical objects directly from 3D
computer-aided design (CAD) data without using part depending tools.
• More concisely, it is a process of building a prototype in one step.
• Construction of the part or assembly is usually done using 3D printing
or “additive layer manufacturing” technology.

3. Historical development
• The first method for rapid prototyping became
available in the late 1980s and was used to
produce models and prototype parts.

4. • In today’s industry, RP exceeding the scope of prototype model
creation, expands the possibility of the layered manufacturing, into the
next level, where parts for real-world engineering applications are
fabricated.
Historical development

5. • Titanium powder-based 3D printing
technology is reported recently with
many successful stories.
• For example, a 3D-printed bike has
been fabricated with the Titanium
powder.
Historical development

6. • RP&M technology is used in a biomedical
application, especially for those areas
where customized design is required.
• For instance, an RP-machined knee joint
is produced to replace the injured knee
for a patient.
Historical development

7. • Another exciting area of application is 3D-manufactured building
construction, also known as “Contour Crafting.”
• Using this process, a single house or a colony of houses, each with
possibly a different design, may be automatically constructed in a
single run, embedded with all the conduits for electrical, plumbing, and
air-conditioning.
Historical development

8. • Recently, RP&M has become the “best practice” and the acceptable
approach to “one-off” parts.
• RP&M used for a wide range of applications
Historical development

9. • Over seventy percent (70 %) of the total uses of RP in the following
areas of manufacturing
Historical development

10. • RP&M is becoming more popular in today’s industry
• For example in US, RP market revenue, compound annual growth rate
(CAGR) is about 12.91%
Historical development

11. Standard Terminology
• During the period of its first invention it was called “Rapid
Prototyping” or “Generative Manufacturing”, both terms are still in
use.
• Many different names have been presented based on special view point
of its creator.
Historical development

12. Standard Terminology
• Most commonly used terms according to a few family key words includes
Rapid
• Rapid Prototyping (RP)
• Rapid Manufacturing (RM)
• Rapid Tooling (RT)
• Rapid Technology
Layer
• Layer Based Manufacturing
• Layer Oriented Manufacturing
• Layer Manufacturing
Additive
• Additive Manufacturing (AM)
• Additive Layer Manufacturing (ALM)
• Additive Digital Manufacturing (ADM)
Direct
• Direct Manufacturing
• Direct Tooling
Digital
• Digital Fabrication
• Digital Mock-Up
Historical development

13. Standard Terminology
• There were almost no efforts for standardization of RP for many years, other
than some preliminary work in Germany in the early 1990s.
• In 2007, a special recommendation dedicated to Rapid Prototyping [VDI3404]
was created under the supervision of the German Society of Mechanical
Engineers, VDI.
• In 2009, the American Society of Mechanical Engineers (ASME) in cooperation
with the American Society for testing and Materials (ASTM) started the
development of their own standards.
• ASME & ASTM have developed “Standard Terminology for Additive
Manufacturing Technologies” [F2794-09e1/F2792]
• According to this standard, among other naming, the name “Additive
Manufacturing” was accepted.
Historical development

14. Additive Manufacturing
The Principles of Layer-Based Technology
• The term additive manufacturing, like generative manufacturing covers
any imaginable way of adding material in order to create a 3D physical
part.
• The technical realization of AM is based solely on layers and therefore
called “Layer-Based Technology”, “Layer-Oriented Technology”, or even
“Layered Technology”.
• Consequently, today the terms, additive manufacturing, generative
manufacturing, and layer-based technology are used synonymously.

15. The Principles of Layer-Based Technology
• The Principles of Layer-Based Technology is to compose a 3D physical
object from many layers.
• Each layer is contoured according to the corresponding 3D data set &
put on the top of the preceding one.
Additive Manufacturing

16. APPLICATIONS OF RP
• Applications of rapid prototyping can be classified into four categories:
1. Design
2. Engineering analysis and planning
3. Tooling
4. Manufacturing

17. 1. DESIGN APPLICATIONS 
• Designers are able to confirm their design by building a real
physical model in minimum time using RP
Design benefits of RP:
• Reduced lead times to produce prototypes
• Improved ability to visualize part geometry
• Early detection of design errors
• Increased capability to compute mass properties
APPLICATIONS OF RP

18. 2. ENGINEERING ANALYSIS AND PLANNING
• Existence of part allows certain engineering analysis and planning activities
to be accomplished that would be more difficult without the physical
entity
• Comparison of different shapes and styles to determine aesthetic appeal
Examples
• Stress analysis of physical model
• Fabrication of pre-production parts for process planning and tool design
APPLICATIONS OF RP

19. 2. ENGINEERING ANALYSIS AND PLANNING
Examples
• Wind tunnel testing of streamline shapes
APPLICATIONS OF RP

20. 3. TOOLING APPLICATIONS
• When RP is used to fabricate production tooling called rapid tool
making (RTM)
• Two approaches for tool-making: Direct & In direct RTM
Direct RTM method
• RP is used to make the tool itself
Example:
• 3DP to create a die of metal powders followed by sintering and
infiltration to complete the die
APPLICATIONS OF RP

21. 3. TOOLING APPLICATIONS
Indirect RTM method
• Pattern is created by RP and the pattern is used to fabricate
the tool
Examples:
• Patterns for sand casting and investment casting
APPLICATIONS OF RP

22. 3. TOOLING APPLICATIONS
Indirect RTM method
• Pattern is created by RP and the pattern is used to fabricate
the tool
Examples:
• Electrodes for EDM
APPLICATIONS OF RP

23. 4. Manufacturing
• Small batches of plastic parts that could not be economically
injection molded because of the high mold cost
• Parts with complex internal geometries that could not be made
using conventional technologies without assembly
• One-of-a-kind parts such as bone replacements that must be made
to correct size for each user
APPLICATIONS OF RP

24. General advantages:
• Freedom of design: The production of complex parts is reduced to the
accumulation of layers.
• Well automated: No supervision is needed during the build process.
• Relative easy to employ: Only little preparation and postprocessing are
required.
• Avoiding the high cost of prototype tooling, allowing (more) design
iterations.
• Physical models are easy to check for errors.
General disadvantages:
• Accuracy generally >0.1 mm.
• Material properties: products can be very fragile, and some need
postprocessing before they can be handled (as with 3-DP).
• Staircasing effect. Because an inclined surface is constructed using
several layers, staircasing will occur.

25. Rapid Prototyping Process
• All RP systems have a common information workflow. The main stages
in preparing and pre-processing data for automated fabrication of 3D
objects are as follows:

26. Rapid Prototyping Process
• All RP systems have a common information workflow. The main stages
in preparing and pre-processing data for automated fabrication of 3D
objects are as follows:
1. Create 3D CAD model
• A 3D CAD package or 2D scanning device can be employed to create
geometric data.
• The object to be built is modeled (3D solid or surface) using a
Computer-Aided Design (CAD) software package or coordinate
measuring machine or laser scanner.

27. Rapid Prototyping Process
2. Conversion to STL Format:
• The valid 3D model is exported from the CAD package in
most cases is STL format.
• The STL format has been adopted as the standard of the RP
industry and acts as the interface between CAD software
and RP machines.
• This format represents a three-dimensional surface as an
assembly of planar triangular facets.
• STL files use planar elements, they cannot represent curved
surfaces exactly.
• Increasing the number of triangles improves the
approximation.

28. Rapid Prototyping Process
3. Data Validation and Repair
• The exported data is an approximation of the precise internal 3D
model. During this approximation process the model surfaces are
represented with simple geometrical entities in the form of triangles.
• Unfortunately, STL models created in this way can contain undesirable
geometrical errors such as holes and overlapping areas along surface
boundaries.
• Therefore, the generated files have to be validated before being
further processed.
• Some RP packages offer facilities for model repair, automatic and/or
manual.
• These packages include software tools that evaluate the STL models
and determine whether any triangles are missing.
• In case of errors, the gaps in the models are filled with new triangles.

29. Rapid Prototyping Process
4. Part Orientation and Scaling
• RP systems build parts along the Z axis of their STL models.
• Through reorientation of the parts relative to the model coordinate
systems, their accuracy, surface finish and build time can be
optimized.
• Some RP systems allow several parts to be nested in the system
chamber in order to be built simultaneously.
• In addition, the parts can be scaled to compensate for anticipated
anomalies that might be introduced by downstream processes such as
deformation, shrinkage, warpage and curling.

30. Rapid Prototyping Process
5. Support Structures Generation
• Liquid-based RP processes require support structures during
manufacturing
• Supports are useful for delicate features such as overhangs, internal
cavities, and thin-walled sections.
• These structures are usually generated automatically using specialized
software tools.
• The areas requiring support structures can be minimized by
appropriately selecting the part build direction.

31. Rapid Prototyping Process
6. Setting-up of Process Parameters
• Process-related parameters are entered to specify the build style and
desired system attributes.
• These parameters can be adjusted based on part requirements and the
RP material being used.

32. Rapid Prototyping Process
7. 2D Slice Data Generation.
• The pre-processing software slices the STL model into a number of
layers from 0.01 mm to 0.7 mm thick, depending on the build
technique.
• One cross-section will be built at a time during part building.

33. Rapid Prototyping Process
8. Layer by Layer Construction
• This step is the actual construction of the part.
• RP machines build one layer at a time from polymers, paper, or
powdered metal, etc.
• Most machines are fairly autonomous, needing little human
intervention.

34. Rapid Prototyping Process
9. Clean and Finish:
• The final step is post-processing.
• This involves removing the prototype from the machine and detaching
any supports.
• Some photosensitive materials need to be fully cured before use
• Prototypes may also require minor cleaning and surface treatment.
• Sanding, sealing, and/or painting the model will improve its appearance
and durability.