Development of a Design Feature Database to support Design for Additive Manufacturing Shajahan Bin Maidin and Dr R. I. Campbell Department of Design & Technology, Loughborough University, Loughborough, United Kingdom Abstract This paper introduces a method to aid the conceptual design of additive manufactured product or part particularly for the Selective Laser Sintering (SLS) system to enable the achievement of improved design concepts by implementing the tool in the form of additive manufactured design feature database. A taxonomy has been developed as a guide for the development of the tool that comprises four taxons of reasons for additive manufacturing (AM) utilisations. These are user fit requirements, improved product functionality, parts consolidation and improvement of aesthetics (or form). Each of these requirements has been expanded into thirteen sub categories of application that contains various examples of design features that are only possible to manufacture using AM technology. The collected and grouped design features will be presented in a form of a database as a method to aid designing for AM by enabling industrial designers to visualise and gather design feature information that could be incorporated into their own design work. Finally, the results from the user trial and the validation of the tool are presented. Keywords Additive Manufacturing, Laser Sintering, Design Support Tool, Design Feature Taxonomy & Design Feature Database Correspondence Details
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Development of a Design Feature Database to support Design for Additive Manufacturing
Shajahan Bin Maidin and Dr R. I. CampbellDepartment of Design & Technology, Loughborough University,
Loughborough, United Kingdom
Abstract
This paper introduces a method to aid the conceptual design of additive manufactured product or part particularly for the Selective Laser Sintering (SLS) system to enable the achievement of improved design concepts by implementing the tool in the form of additive manufactured design feature database. A taxonomy has been developed as a guide for the development of the tool that comprises four taxons of reasons for additive manufacturing (AM) utilisations. These are user fit requirements, improved product functionality, parts consolidation and improvement of aesthetics (or form). Each of these requirements has been expanded into thirteen sub categories of application that contains various examples of design features that are only possible to manufacture using AM technology. The collected and grouped design features will be presented in a form of a database as a method to aid designing for AM by enabling industrial designers to visualise and gather design feature information that could be incorporated into their own design work. Finally, the results from the user trial and the validation of the tool are presented.
features, multiple version features, instant assembly features, fasteners removal
features, multiple functional parts, over moulding, embossed features, surface
features, visual features and customised form.
A “rapid prototyping” software approach has been utilised where a “quick and dirty”
version of the tool has been developed to enable rapid user testing and
improvement of the system. The tool have been implemented within a Ms Access
database known as the DfAM design feature database. A series of forms have been
created to enable designers to interact, guide, search or browse through the feature
categories. The database enables industrial designers to visualise and gather
design feature information from examples in the database that could be incorporated
into their own design work. Figure 8 shows the welcome screen and Figure 9 shows
the general information screen where the user is requested to provide the users
general information.
Figure 8: Screen shot of the welcome page of the DfAM feature database
Figure 9: General Information Screen
Before a user proceeds to the concept profile generation stage the feasibility for
additive manufacture of a certain part has to be evaluated. As shown in Figure 10
there are four AM feasibility evaluation criteria. The first question is regarding the
number of targeted production unit. If the given answer to this question is more than
100,000 units, then a message informing that AM is not suitable will appear (Figure
11). If the production unit is less than 10,000 units the user may proceed to provide
answer to the next three general questions which evaluate the overall surface finish,
overall mechanical property and the importance of the tolerance and accuracy of the
part or the product.
Figure 1: AM feasibility validation screen
Figure 21: Message showing AM is not suitable for production volume more than 100,000 units
For question about the overall surface finish, overall mechanical property and the
importance of the tolerance and accuracy of a part or product, a scoring technique is
used to evaluate the feasibility of AM. Figure 12 showing AM is not suitable if the
general mechanical property, surface finish and tolerance are very important for a
certain application.
Figure 3: Message showing that AM is not suitable if the general mechanical property, surface finish and tolerance is very important
Figure 13 shows the concept profile generation screen. There are 11 options that
can be selected individually. These questions have been grouped under the four AM
reasons of utilisation and its sub categories of application as shown in Table 7. For
example if a user select the first option (need custom fitting for individual user), then
by clicking the generate concept profile button, the customised profile feature button
and the customised form button will be enabled (Figure 14). This will assist the user
in selecting the appropriate features to be applied in their concept design.
Figure 13: AM Concept Profile Generation Screen
Figure 14: Buttons that has been enabled base on the concept profile selection
Table 7 shows which feature buttons will be enabled base on the concept profile
button that has been selected. Figure 15 shows a quick search function that enable
a user to find a specific features or information from the database.
Selected Options Enabled Button Reasons for AM
Does the product need custom fitting that conform to individual user?
Customised Profiles Features
User fit requirement
Does the product need to be light lightweight?
Weight Reduction Features
Improve functionality
Does the product subjected to hand held?
Increase surface friction features
Does the product have internal structures?
Internal structural features
Does the product benefit from being made available in a range of sizes or shapes to fit different users?
Multiple version features
Does the product benefit from number of parts reduction?
Instant assembly features
Parts consolidation
Does the product need to attach to other components?
Fasteners removal features
Does the product benefit from having several other functions?
Multiple functions parts
Does the product require over moulding?
Over moulding
Does the product need to be aesthetically pleasing?
Embossed features
Aesthetics
Surface features
Visual features
Does creative and innovative shape or geometry an important factor for the product?
Customised form features
Table 1: Result of concept profile selection
Figure 45: Quick search screen
The images currently used in the database have been sourced from various
websites, literatures and personal contact with the designers. Therefore, permission
would need to be sought from the owners of the images before the system be made
available online. The feature database contains macros and visual basic scripts that
could not be made available online at the time of writing.
4. DfAM Feature Database Appraisal and Validation
The implementation of the DfAM tool into the Ms Access as a prototype software
took place over a period of several months, during which time a number of revisions
and improvements were made. Prior to the user trial a series of pilot trials were
performed to establish a suitable format and test procedure before testing a finalized
system. The pilot trial was conducted with two groups of participants which are the
final year undergraduate student designers and the professional industrial
designers.
An exercise was devised for the trials in which both groups of participants were
asked to sketch a redesign of a familiar product of their choice for AM using the
DfAM tool. The students’ pilot trial was conducted in a room at the Design School.
Due to work commitment and travel distances the professional designers trials was
done by sending the database in a CD format accompanied with the design brief
and feedback questionnaire. Although the number of participant in this trial is small,
it provides an initial feedback of the usefulness of the tool prior to a more formal
validation.
4.1 Student Designer Pilot Trial
To ascertain user perceptions and verify its overall feasibility and to gather
suggestions for the improvement of the DfAM feature database, six final year
undergraduate students on the Industrial Design programme at Loughborough
University and two postgraduate students were recruited for the design trial. These
students were regarded as being competent industrial designers. In general, most of
these students have had some exposure to product design and had used AM
technology in their project due to the nature of the engineering and design courses
they were undertaking.
The basic idea behind the trial was that the students should develop sketches of
redesign concepts of a product of their choice with and without the use of the DfAM
tool and the results of doing so could be compared. Therefore, the trial was divided
into two concept sketching exercise sessions for each student, one using the
repository, one not. As shown in Table 8, students 1 to 4 were given access to the
DfAM feature database for their first sketching exercise, students 5 to 8 were given
access for their second sketching exercise. The students were given access to the
websites to get ideas and to help them in the conceptual sketch when they were not
using the repository. Table 8 shows the products that were sketched for the trial by
the students.
Student Designer
Product Sketched Using DfAM feature database
Product Sketched Without DfAM feature
database (Website Access)1 Table Lamp Toy
2 Toy Table Lamp
3 Chair Computer mouse
4 Computer mouse Chair
5 Salt Shaker Kettle
6 USB Stick Salt Shaker
7 Kettle Ice-cream scoop
8 Ice-cream scoop USB Stick
Table 8: Products that has been sketched by student designers
4.2 Student Designer Pilot Trial Discussion
Each student has produced six sketches in total, three concept sketches using the
website and three concept sketches using the feature database as an aid. In total
there are forty eight sketches that have been collected. A decision has been made
to evaluate the concept sketches and choose each best concept from each group
and compare them. There were eight criteria that have been evaluated: safety,
usability, manufacturability, functionality, ergonomics, durability and aesthetics.
Using pair wise comparison, the weight for each criteria has been assigned. Table 9
and Table 10 shows two examples of the selected concept sketches of products
with some text annotation developed by the student designers without using and
with using the DfAM features database.
Salt Shaker design without using DfAM feature database Salt Shaker design using DfAM feature database
Design Feature:1. Embossed Feature2. Snap fit feature
Design Feature:1. Weave Surface Feature2. Hock Clip Feature3. Spiral Element 4. Over moulding feature5. Hand grip contour
Table 9: Comparison of salt shaker sketched using and without using the DfAM feature database
Table 9 shows the comparison of the salt shaker sketched using and without using the DfAM feature database. Salt shaker sketched without using the DfAM feature database shows only two features such as embossed feature for its aesthetics and snap fit feature to open and close the lid. However, the salt shaker sketched using the DfAM feature database shows various features from the library such as weave surface feature, spiral element for enhanced aesthesis. The hand grip contour and over moulding feature for better ergonomics and the hook clip feature for improved functionality.
Ice-cream scoop design without using DfAM feature database Ice-cream scoop design using DfAM feature database
Design Feature:1. Press in mechanism load and unload the ice cream
Design Feature:1. Over moulding feature2. Transparent feature3. Hollow structure on the scoop4. Embossed pattern on the scoop
Table 20: Comparison of ice-cream scoop sketched using and without using the DfAM feature database
Table 10 shows the comparison of the ice-cream scoop sketched using and without using the DfAM feature database. Ice-cream scoop sketched without using the DfAM feature database shows just the press in mechanism load and unload the ice cream. However, the ice-cream scoop sketched using the DfAM feature database shows transparent feature that enhance its
aesthetics, over moulding feature for better ergonomic and hollow structure for reduced weight and embossed pattern for better functionality elements.
4.3 Student Designer Pilot Trial Results
The trial found that there are two factors that influence the results. Firstly, the skills
and creativity of the students designers and secondly, the number of features used
from the feature database. However, by analysing and comparing the sketches
produced by the student designers with using the DfAM feature database, it is found
that the tool provide ideas on how to incorporate various features to enhance and
improve aesthetics, ergonomics and functionality of a product or parts. The sketches
produced indicates that with using the DfAM tool, the student designer was able to
apply creative and innovative design features such as the variable wall thickness,
living hinge, over moulding, transparency and various surface features into the
concept sketches.
Table 11 shows the list of the features used from the repository extracted from all the
concept sketches using the DfAM feature database. An overall observation of the list
shows that the students had made used of the feature database and applied features
from twelve categories of applications with the exception of the multiple function
parts feature under the consolidation requirement. The weight reduction feature,
instant assembly features, embossed features, visual features, customised form
features has been applied in most of the conceptual sketches. The feature that was
mostly used from the feature database is the over moulding feature. As most of the
product is being hand held this is an important feature to be applied to the
conceptual sketches. However, only the hand grip contour feature has been applied
from the customised profile feature. As most of the design features in the user fit
requirement are collected from specific application areas such as medical, sport and
consumer product, this does not relevant to the student sketching exercise.
However, this is also depends to the students creativity to use the idea of the
features from the user fit requirements and apply it on other product. In summary,
Table 11 shows that the feature database is useful, relevant and helpful to support
conceptual design of parts and product for AM. The number of feature used from the
library would likely increase if the number of participants in the trial is increased.
Student Designers
AM Reason Application Design Features 1 2 3 4 5 6 7 8 Total
User Fit Requirement
Customised Profiles Features
Hand Grip Contour x x x x 4
Improve functionality
Weight Reduction Features
Undercut Feature x x 2
Thin Wall Feature x x 2
Variable Wall Thickness Feature x x x x 4
Hollow Feature x x 2
External Ribbing Feature x 1
Increase Surface Friction Features
Textured Surface Feature x 1Circular Array Feature x 1Honey Comb Feature x 1
Internal Shelving x 1Internal
structuring feature Internal cable support x 1
Multiple Version Features
Customised Thread Feature x 1
Consolidation Requirement
Instant Assemblies
Features
Living Joint Feature x x 2Torus Feature x 1
Interconnected Feature x 1Encapsulated Track & Ball
Featurex 1
Living Hinge Feature x x 2Integrated ball and socket
featurex 1
Multiple link feature x 1Encapsulated bearing x x 2Ball and socket feature x 1
Hook clip feature x x 2Slide opening & closing x 1
Snap fit hook x 1
Fasteners Removal Features
Hook clip x x 2Slide opening & closing x 1Internal cable support x 1
Snap fit hook x 1
Over Moulding Over Moulding x x x x x x x 7
Aesthetics or Form
Requirement
Embossed Features
Embossed Alphabets x x x x x 5Logo x x 2
Surface Features
Weave Element x 1Alphabet Element x 1
Spiral Element x 1Overlapping Element x x 2
Visual FeaturesNet Shadow Effect x 1
Transparent Feature x x x x x 5
Customised Form Features
Curve Feature x 1Swept Feature x x 2
Alphabet Feature x 1Freeform geometry x x 2Floating Elements x 1
Replicated Element x 1Bio- mimic feature x 1
Table 3: Range of features used from the DfAM feature database
5. Professional Designer Pilot Trial
In addition to the student designer’s trial, a second trial was conducted with
professional designers. Seven professional industrial designers who had
experienced in designing products for AM and variety of market sectors were invited
to take part in the user trial to generate feedback on the proposed DfAM feature
database. Generally these designers had at least three years of working experience
and involve in product design and development activities.
5.1 Professional Designer Trial Discussion
The focus of the trial with the professional designers is to design three conceptual
designs for a product of their choice, possibly a product that they have previously
worked on or one that has already been identified for potential manufacture using
AM that they think has a potential to have its functionality, aesthetics, ergonomics or
parts consolidation improved through the use of AM. Comparison of using and not
using the DfAM feature database was not conducted with the professional designer.
The aim of the trial is to test the DfAM feature database to see if it is relevant,
effective and applicable to aid the conceptual design of part or product that are to be
produced using AM processes from the professional designer’s point of view.
Twenty one conceptual sketches were produced by the professional designer for the
trial. The best conceptual sketches have been selected to show the range of the
features that have been selected and applied in their sketches. Table 12 shows the
product sketched by the professional designers and the concepts that have been
selected for each product.
Professional Designer
Product Sketched
1 Computer mouse
2 Sensor
3 Thermometer
4 Watch Bracket
5 Electric Fan
6 Chair
7 Flashlight, Mini fan & USB
5.2 Professional Designer Trial Analysis of Results
Figure 16 and Figure 17 shows the concepts that have been selected for each
product sketched by the professional designers. These figures illustrate the features
that the designers have selected and applied in their concept sketches. Figure 16
shows the concept of a computer mouse sketched by professional designer number
1. The features that can be seen from the sketch are transparent feature that shows
the internal element of the computer mouse. The blue light from the transparent
feature will enhance the aesthetics aspect of the computer mouse. Other features
that have been used are circular array and honey comb surface features that will
improve the ergonomic aspect and the surface friction for better gripping of the
computer mouse.
Table 42: Concept Sketches by Professional Designer
Figure 56: Concept of computer mouse sketched by professional designer number 1
Figure 17 shows the concept sketch that has been selected for the thermometer. In
this sketch the designer used the integrated ball and socket feature from the instant
assembly category. From the user fit requirement category the designer applied the
hand grip contour feature. From the customised form category the designer applied
the bio mimic feature (concept of a “humming bird”). From the weight reduction
category the non uniform wall thickness feature has been applied.
Figure 17: Concept of thermometer sketched by professional designer number 3
Range of features that have been used by the professional designers for each sub
category of applications for all three conceptual designs of the product are
summarised in Table 13. An overall observation of the list shows that the designers
had applied features from all the thirteen categories of applications from the feature
database. The weight reduction feature, instant assembly features, visual features,
customised form features, increase surface friction features, aesthetic requirement
surface feature, customise form feature and the fasteners removal features has been
applied in most of the conceptual sketches. Three specific features that was mostly
used from the feature database is the Internal selective reinforce feature under the
weight reduction application, mounting boss feature under the fasteners removal
application and the transparent feature under the aesthetics or form requirement
visual feature application. In summary, Table 13 shows that the feature database is
useful, relevant and helpful to support conceptual design of parts and product for AM
from the professional designers’ perspective.
5.3 Summary
The user trial conducted to see the usability and relevancy as a means of improving
the DfAM feature database developed in this research. The user trial was conducted
twice which involve the first trial with a group of student designers and the second
trial with a group of professional designers. Both trial shows that the DfAM feature
database provides ideas on how to incorporate various features to enhance and
improve part or products aesthetics, ergonomics and functionality.
Professional DesignersAM Reason Application Design Features 1 2 3 4 5 6 7 Total
User Fit Requirement
Customise Profiles
FeaturesHand Grip Contour x x 2
Improve functionality requirement
Weight Reduction Features
Thin Wall Feature x 1Variable Wall Thickness
Featurex x 2
Internal selective reinforce feature
x x x 3
Hollow Feature x 1Increase Surface Friction
Features
Textured Surface Feature x 1Circular Array Feature x x 2
Honey Comb Feature x 1
Internal structuring
feature
Internal cable support x 1
Internal shelving x x 2
Multiple version feature
Size variations x 1
Consolidation Requirement
Instant Assemblies
Features
Living Hinge Feature x x 2Integrated ball and socket
featurex 1
Internal Hinge Button Feature
x x 2
Enclosed Volume Feature x 1Fasteners Removal Features
Internal cable support x x 2Mounting Boss Feature x x x 3
Snap fit cap x 1Multiple
Functional Part
Multiple Elements x 1
Over Moulding
Over Moulding x x 2
Aesthetics or Form
Requirement
Embossed Features
Embossed Alphabets x x 2
Surface feature
Double Mesh Feature x 1Fingerprint Feature x 1Perforated Feature x x 2
Visual Features
Transparent Feature x x x 3
Customise form feature
Replicated Element x 1Bio- mimic feature x 1
Table 53: Range of features used by the professional designers
6. Conclusions
The objective of the DfAM design feature database is to enable industrial designers
to access and reuse design knowledge accumulated over the years, specifically the
features designed for laser sintered additive manufactured parts or products. It
allows designers to visualize and retrieve AM design feature information and
knowledge at the conceptual design stage. By providing four reasons for utilization of
AM with various design feature examples that fall under thirteen sub-categories of
applications, the DfAM feature database provides an innovative way to approach AM
part or product conceptual design. The tool enables fast conceptual idea generation
and to demonstrate AM design freedom to novice designers.
The AM design features taxonomy is seen as a useful aid for industrial designers to
understand the design freedom associated with AM. The classification of four taxons
that were further expanded into sub-categories of various design features is
anticipated to help designers to visualize and extract design feature information to
assist the AM design process.
This research has shown that the DfAM method of providing designers with
examples of design features from the database is a suitable strategy to aiding the
conceptual design of additive manufactured part or product. The next stages of the
research are to improve and validate the repository with responses from professional
industrial designers and to create a web based system to gather, present and to
exploit the prominence of design for AM.
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