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Personalised 3D Printed Sneakers
Nevan Nicholas Johnson (19BME0358), Pratham Shrivastava (19BME0367), Rudra
Nath (19BME0390), Rahul Kar (19BPI0016)
J-Component Review: RAPID MANUFACTURING TECHNOLOGIES
Vellore Institute of Technology Vellore, Tamil Nadu, India
Abstract : 3D scanning is a very potential technology for creating personalised products. It
is used in various fields such as medicine, aerospace, automobile, clothing, footwear
manufacture, etc. The last-mentioned field has gained a lot of popularity in recent years.
Footwear fit is one of the fundamental factors for the consumer on buying shoes. Designing
footwear is a very complex process. Traditional footwear design begins with a plan to sketch
patterns and designs in scale drawings.
Nowadays, due to technological advancements, various scanning frameworks are developed
and implemented to allow the users to extract accurate 3D surface data of the foot shape by 3D
scanning. Utilizing these frameworks alongside specialized software programs, it will be
possible to integrate parameters like shoe fit, shoe performance, into the design and
manufacturing processes. This technology is mainly based on active methods such as laser
scanning. From a wide variety of 3D scanning systems, 3D low-cost scanning systems have
been developed and adapted for foot and shoe lasts digitalization. 3D models of the customer’s
feet taken by 3D scanners are converted in 3D software for shoes designing.
The main objective of this paper is to present a full cycle of personalised footwear production,
starting from 3D foot scanning, to custom 3D shoe designing, to 2D patterns extraction and
finally the production of the custom shoes by 3D printing.
1.Introduction :
Rapid manufacturing technology also known as direct manufacturing or direct fabrication is
the new area of manufacturing technology developed from the family of rapid prototyping.
The processes involved have already had the effect of improvising the fabricated parts and
reducing the manufacturing time and hence resulted in advancements of new technologies
like rapid tooling which uses these techniques for its own processes. Rapid manufacturing
today has revolutionised the manufacturing industries by eliminating the tooling time
required for the final part. This advantage of rapid manufacturing has made the
manufacturing processes more cost-efficient and far more flexible compared to the
conventional manufacturing.
In the modern world, RM technology finds application in a variety of fields including
Aerospace, Architecture, Military, Medicine, Fashion etc. RM is widely utilized for both large
and small scale components and products. For mold makers specifically, rapid manufacturing
encompasses more than just moulding. This Manufacturing automation is also applied to other
systems like 3D printing, CNC machining and more.
3D data capture of the human body is used in various application, such as clothing and footwear
industry. Taking the real form of the human body means taking accurate anthropometric data
and manufacturing garments and footwear with the right fit.
Various scanning systems are developed and executed to allow the users acquiring precise 3D
surface data of the foot shape, which can be used to obtain anthropometric data of the human
foot. The high costs are a disadvantage of scanning systems to be utilized for various
application. The Low-cost scanning systems are another great opportunity for foot scanning
and digitalization and have been introduced as an application for the footwear industry. A
prediction technique to model foot shapes through scaling a standard foot by utilizing restricted
parameter can be used at a retail shop to obtain 3D foot shape information.
Low-cost scanning systems utilizing laser technology has been invented to capture 3D foot
model. Additionally, the low-cost scanning system is created as a key part in producing custom
footwear. These scanning systems are based on hardware components that are easily available
like a camera and a video projector. You can also reconstruct accurate 3D foot model by using
pictures taken with a regular smartphone. The traditional technique for footwear designing is
tedious and time-consuming and requires the application of different graphical stages for
footwear designing. 3D CAD programs for footwear designing follow almost the same steps
as the conventional one.
2.Methodology:
Designing the footwear on the scanned foot, meaning the custom shoe will provide an
extremely good fit. The main aim of our work is to demonstrate the implementation of 3D
scanning of the foot and using it to produce custom footwear.
The main steps to produce custom 3D printed footwear include:
1. Data Acquisition (3D foot scanning)
2. Creation of the 3D foot model
3. 3D data analysing (to ensure accuracy)
4. Shoe design
5. Simulation and Testing
6. Production
3.Literature Review:
The use of 3D surface scanning technologies to produce digitised representations of parts of
the human anatomy has the potential to help change the way a wide range of products are
designed and fabricated. Until recently, the anthropometric databases that are used by designers
and manufacturers to guide the ergonomic form of their products have primarily been based on
1D and 2D measurements, for example, leg length or instep height. Databases that draw upon
3D scans can offer far more detailed information on the contours of the feet and potentially
provide an insight into changes in anthropometric measurements associated with dynamic
movement. 3D surface scanning has the potential to play an important role in the development
of customised products, i.e. devices and apparel that are designed for the individual using their
precise anthropometric measurements.
In the case of the foot, quantitative description of its shape is important for a number of different
applications relating to the ergonomic design of footwear, foot orthotics and insoles.
Additionally, because the foot is a flexible and complex structure, a better understanding of
how its shape changes in different situations, for example in the different loading phases of the
gait cycle, may lead to improvements in the overall comfort and functionality of the footwear
and devices that are been produced.
There are a few different methods to scan objects for the purpose of creating a 3D model.
I. Time of flight cameras:
It is also known as laser pulse scanning produces a 3D model scan by timing how long
it takes a laser’s beam to reach the object and bounce off, travelling back to the laser’s
source. The known value of the speed of light is what makes this method of calculating
distance possible. The technique is often used in range imaging camera systems or 3D
cameras. Time-of-flight technology is highly sophisticated in terms of quality but can
be an expensive option usually reserved for scanning large environments and buildings.
II. 3D laser scanner :
The most popular kind of scanner for consumer use is the 3D laser scanner. Laser
scanning combines two sets of information to create a point cloud of an object’s surface:
data from a laser being shone on the object, and data from another sensor (typically a
moving camera, or two stationary ones). 3D scanning software stitches these data sets
together using the known distance between the camera’s position and the laser’s source
to generate a model’s points. Building 3D geometry from a laser scan requires detecting
where the laser line falls in the images captured by the camera during scanning. The
laser line is usually the brightest pixel of an image, but sometimes there can be other
light sources captured. A stationary scanner can tell the laser line from everything else
by cycling the laser on/off, creating a trackable difference between it and other lights
captured during scanning.
Thousands of individual points are captured during a 3D scan. Like a regular camera, a
laser scanner can only capture what is in its field of view. The captured points record
everything from surface detail and texture to colour, creating a direct representation of
the scanned object. A captured point cloud is not a watertight digital object until its
points are meshed into surfaces. The meshing process calculates how the points relate
to each other in order to join them together into surfaces
III. Stereo visioning:
It is a cost-effective, but typically lower quality method of 3D capture. No lasers,
projectors, or extra hardware beyond a camera are needed. Stereo Vision creates a 3D
model using images of an object from two camera positions, mimicking the stereo
vision of human eyes. During this process, images are captured of the same scene from
two different angles. The images are then corrected to remove any lens distortion, so
any straight lines in a scene that appear straight in the image. Next, a filter is applied to
the image that finds the edges of objects. Pixels are then matched between the two
image sets to produce 3D depth. Matching points between the images rely on texture
variation to find edges and distinguishing features, which can cause problems when the
surfaces in a scene aren’t high contrast enough or are too much alike.
Photogrammetry adds more camera positions to the regular stereo vision routine,
making it a more robust 3D digitizer. Often, photogrammetry involves a large rig of
multiple cameras surrounding the scan object. A camera rig can be calibrated very
precisely and remain so for a long period of time, making the point matching needed to
create 3D geometry very consistent within the setup.
IV. Structured light 3D scanning:
This technology makes use of the pattern of light deformation on an object for
understanding its 3-dimensional geometry. The scanners use trigonometric
triangulation method instead of LASER. It works by projecting a series of light in linear
patterns onto an object. The system then examines edges of each line in the pattern and
indirectly calculates the distance from the scanner to the object’s surface. The structured
light used generally are of colours white or blue. The light is generated with the use of
various types of projectors such as the DLP technology (Digital Light Processing). The
projected light ray is generally either in a series pattern or it could be a random dot
matrix too.
For a shoe to fit a person's foot, a good understanding of the 3D foot shape is necessary. A
good fitting shoe should be free of any high-pressure points, and at the same time should have
the right ‘feel’ and support. A meaningful way to evaluate footwear compatibility would be to
determine the dimensional difference between the foot and shoe. If guidelines or standards can
be established for these dimensional differences, then footwear selection can be made much
simpler. If a shoe is tight, the pressure or force will produce undue tissue compression making
it uncomfortable for the wearer. When the shoe is loose, there will be slippage between the foot
and shoe resulting in damage or injury to soft tissue. Both these situations are undesirable as
they may cause discomfort, pain or even injury to the wearer. Thus, for the right fit, the
desirable clearance between feet and shoes should be present in addition to having the foot
supported in the most appropriate locations. Since footwear fit is one of the most important
considerations when purchasing footwear, it has to be understood when manufacturing
footwear. A fit metric can be useful in the design and development of good-fitting footwear.
Based on the customer’s feet and the type of shoe he requires, the CAD system will design the
customized shoe. Visual C++ and OpenGL have been used for the system development, and
the system consists of three main modules: (i) automatic extraction of 18 important foot
features from a scan of the customer’s foot; (ii) a global grading together with a local
deformation approach that can deform the base shoe last of the customer’s chosen style to the
customized shoe last based on the extracted foot features without altering the style of the base
shoe last; and a colour-coded map for the final evaluation of the fit/match between the
reconstructed customized shoe and the customer’s foot.
For 3D printing shoes, you need a good flexible material that is also strong enough to withstand
load. Thermoplastic elastomers (TPEs) are polymers that exhibit elasticity similar to that of a
cross-linked rubber. The degree of elasticity in the material depends on the type of TPE and
the chemical structure of the grade. Thermoplastic polyurethane (TPU) is a type of TPE. TPU
3D printing offers unique possibilities that are otherwise unachievable with other 3D printing
materials like ABS, PLA or nylon. Combining the properties of both plastic and rubber, TPU
can produce elastic, highly durable parts that can be easily bent or compressed.
Pros
Cons
Applications
Elastic and soft material
Hygroscopic
Sporting goods
Low warpage and shrinkage
Prone to stringing and clogging
Protective cases
Chemical – resistant
Needs to be printed at low
temperatures
Automobile
bushings
Good impact – resistance
Difficult to post - process
Vibration – damping
components
Good vibration damping and shock
absorption
Available in a range of colours
There are two main technologies with which you can print using TPU : Selective Laser
Sintering (SLS) and Fused Deposition Modelling (FDM). Selective Laser Sintering (SLS) is a
powder bed fusion 3D printing technology that uses a laser beam to selectively melt and fuse
powdered material. SLS offers many advantages for industrial manufacturing, as the
technology is capable of producing functional parts with great mechanical properties.
Furthermore, SLS requires no support structures, allowing free-form parts without any support
removal marks. However, parts will require some form of post-processing to achieve a better
surface finish.
FDM technology can also be used with TPU filaments. There are two major benefits of using
FDM instead of SLS when manufacturing TPU parts: firstly, FDM is less expensive and
secondly, it is typically faster to produce TPU parts with filaments rather than with powders.
On the other hand, 3D printing with TPU filaments using FDM will result in a less
dimensionally accurate part, with visible print layers that cannot be smoothed. Additionally,
since TPU is a soft material, particularly when compared to ABS and PLA thermoplastics, TPU
filaments can flex in the extruder mechanism, resulting in coiling of the filament and clogging
of an extruder. However, the softness of the material is what makes the layer to layer adhesion
in TPU prints strong and durable.
4.Design Process:
I. Data Acquisition
Custom printing custom shoes begins with a scanning of the customer’s feet.
3D scanning is a technology for creating extremely high-precision 3D models of real-world
articles. It generally works like this:- a 3D scanner takes numerous snapshots of the object. The
shots are then intertwined and fused to form a 3D model, an exact three-dimensional duplicate
of the object, which you can rotate and view from different angles on your PC.
Structured light 3D scanning (SLS) would be the most cost-effective method to get a good
quality 3D model for the foot. SLS is also safer compared to laser scanning as lasers are harmful
to the naked eyes. There are many softwares which support this 3D scanning technique. For
example, DAVID 3D Scanner, Solidworks, GOM Inspect, 3DF Zephyr, Metashape, Geomagic
Studio, etc.
Structured Light Scanning (SLS) uses a simple projector to project the required structured light
pattern onto the foot. Then film it with at least one camera (usually two cameras) to capture
the ways in which the foot deforms the light pattern. By triangulating multiple images of the
scan, you can calculate the dimensions of the object in all its complexity.
Fig. DAVID 3D Scanner Pro
II. Creation of the 3D foot model
The data obtained from the scanner is directly fed to the scanning software which visualizes
and produces the necessary 3D model of the foot. Importing 3D models for virtual design and
simulation in a 3D environment helps designers to quickly design a shoe according to the 3D
avatar after assessing the 3D model.
III. 3D data analysing
The precision of 3D image data is pivotal to getting the right custom shoes, whereby the
geometry of the foot needs to be accurately and carefully reconstructed in software. Compared
to generic data, 3D scanning of feet implies that subject-specific items can be designed that are
more comfortable and custom-fitted to the specific requirements of the wearer. Some of the
best outcomes originate from working with tools that allow 3D image data of feet to be easily
combined with CAD software, where designs can be immediately tested and tried out to decide
on the best approach for customers without the need for utilizing multiple software packages.
With the development of information technology, big data and data collection hardware
equipment data has significant value for footwear design at this stage. Particularly for wearable
products, data as the core of parameterization can meet the exercise habits of various users and
acknowledge personalized customization services. Two principle types of data are crucial to
the design of shoes: one is the 3D model of the user's feet, and the other is the pressure
distribution of the user's sole movement. The standard method of gathering user feet
information is using a 3D scanning device and collect the pressure distribution through the
pressure test board.
A 3D modelling software should be used for converting the 3D scanned feet and further use
the data for editing and altering the surfaces of the feet, fill gaps, surface smoothness, scans
overlap, spikes etc. These procedures are necessary to obtain a proper representation of the
feet.
IV. Shoe design
The shoe is then designed around the 3D model of the customer’s feet. This can be done by
certain software like Delcam Crispin Shoemaker, Romans CAD, Shoemaster, Fusion 360, etc.
According to the gcode of the 3D model of the feet, an automated software can be programmed
to automatically design the shoe with the exact dimensions and size.
The mid-sole of the shoe is the most important component of the shoe. Hence, you start to
design the shoe from the mid-sole. The mid-sole has to be designed carefully according to the
feet of the wearer. Pressure distribution on the feet is also an important factor.
The mid-sole is then placed over the lower sole of the shoe and then the rest of the shoe is
designed around the sole obtained keeping in mind the dimensions of the wearer’s feet.
V. Simulation and Testing
To check if the design is a success we have to use lattice tools in software such as Simpleware,
Rhinoceros 3D, Solidworks, etc. This involves increasing or decreasing lattice volume and
node thickness to add flexibility or increase support in certain areas, such as the heel or arch,
from pressure map data. Lattice structures are also ideal for testing out different types of
flexible TPU (thermoplastic polyurethane) and other elastomeric material, as they allow for
significant design freedoms when looking at areas from orthopaedic soles to running shoes and
everyday walking.
We can apply single or multiple loads to the topology optimization. For example, a mapped
pressure load can be used to represent static loading of an average human’s weight and a
bending load can be used to represent the resistance to push off. Optimizations are made to find
the maximized stiffness structure with a reduced weight target. Iteration by iteration, this
optimization yields intermediate relative density distributions. It is found that the maximum
density region in an optimum design does not always correspond to the maximum load location.
After performing the simulation and validating the material selection topological optimisation
is to be performed. Topological optimisation is by definition an optimisation scheme based on
a mathematical method that optimizes the material layout within a given design space for a live
set of loads boundary conditions and constraints with the goal of maximizing the system
performance The topological optimisation scheme took into account the loads and constraints
defined in the previous numerical simulations. Therefore, topology optimization is useful to
determine the most effective material to use. The relative density/material stiffness distribution
can then be used to reconstruct optimum geometries with matching lattice patterns.
While few companies are able to 3D-printed custom shoes on the same day, this approach
frequently lacks the range of data and the design testing enabled by software design
optimisation and improvements and the use of lattices. An extremely quick process doesn’t
generally deliver the most accurate results, especially given the high risk of small errors
influencing the 3D printing process. Fast yet cautious design work with the client's data is,
therefore, an important part of avoiding any deformities and defects that might undermine the
value of a custom shoe.
VI. Production
Once the shoe is designed, simulated and tested, it can be sent to a 3D-printing process. First,
the 3D CAD model is converted to an STL file. Selective laser sintering (SLS) is frequently
utilized for its precision and suitability in working with TPU (Thermoplastic Polyurethane)
powder and polyurethane to create a finished product that is both durable and waterproof. TPU
is an industry-standard flexible, rubber-like material that is versatile and great for elastic end-
use products. TPU parts are durable and can incorporate interlocking features. The unique
particle bonding of this approach implies that energy may be more evenly dispersed throughout
the shoe and foot, and at a slower rate than with traditional manufacturing. This material is
great for FDM printers that at the same time can be used for ABS and PLA filaments. Printing
temperature range of these TPU filaments is 210°C – 245°C. The material has high flexibility
and brilliant abrasion resistance, as well as a consistent diameter and smooth feeding properties.
The Filament material easily sticks to the build platform and bonds between layers.
Flex PLA filaments are filaments that are mainly comprised of PLA but have added fillers and
plasticizers to make them more flexible and elastic. Generally, a lot easier to print than
TPE/TPUs, these materials are also harder and not as elastic and flexible. Though the TPE/TPU
materials easily find their original forms, this may be restricted with Flex PLAs. With Flex
PLAs you can utilize variations in infill structure and percentage to increase and decrease your
flexibility, similar to what was done with regular PLA material.
When it comes to 3D printed shoes, adaptable and flexible material is something consumers
will want. Additionally, there are also some mild issues that can come from using flexible
materials. Bowden tube-based systems have difficulty printing them because they can get stuck
or not be able to be squeezed through. However, most Bowden system will have issues, they
can be updated with specific extruders for flexible materials.
However, SLS printing methods can be really expensive and include post-processing demands,
as well as a relatively limited number of suitable materials. By comparison, fused deposition
modelling (FDM) is more affordable and achieves similar results without the requirement for
significant additional work subsequent to printing. Keeping the work process straightforward
for 3D printing custom shoes is crucial to make sure that the services and products are still
affordable. Resin-based systems could also eventually be a viable method, although for now
FDM and other approaches like fused filament fabrication production arguably represent the
most cost-effective solution for customizing soles.
The upper is a shoe component that covers the toes, the top of the foot, the sides of the foot and
the back of the heel. It is one of the two integral and indispensable shoe components alongside
soles. Uppers are generally made of textile, which can be challenging for polymer 3D printers
to produce. However, you can create uppers utilizing flexible, adaptable plastics like TPU. The
uppers are produced with the help of Solid Deposit Modeling (SDM), a process whereby a TPU
filament is melted and laid down in thin layers.
One advantage 3D-printed uppers have over customarily woven uppers is greater material
durability because the layers are fused together, eliminating any frictional resistance common
for a knit or woven textile.
Precautions to take while printing :
i. No retraction:
Make sure to turn off retraction for the whole print. Constant retracting and extruding
can cause your print to under-extrude from having to “refill” the hot-end with much
more filament after each retraction. In some cases, you could even grind a flat spot in
the filament preventing you from extruding filament at all. Despite turning off
retraction, unless you’re printing an incredibly complex part, you shouldn’t even notice
the difference.
ii. Keep it dry:
Use a vacuum oven to dry your filament for 30 to 60 minutes. Most flexible filaments
are hygroscopic to some degree and will pop and sizzle if you try extruding it wet.
These are pockets of water that steam up instantly, leaving voids in your print.
iii. Printing speed:
30mm/s for infill should be set as the maximum speed.
iv. Getting the first layer right:
You need a good base material for your flexible filament to adhere to. Blue painter’s
tape or a heated glass bed with PVA glue are ideal surfaces for your print bed.
v. Filament temperature:
When working with a new roll of filament for the first time, you should generally like
to start printing at about 235°C and afterwards adjusting the temperature up or down by
5 degrees until you get a quality print.
If the temperature is too high, you will observe more strings between the different parts
of your print, similar to spider webs. In the event that this happens you should try to
gradually lower the temperature by 5 degrees until the extruder isn't leaking out so much
material.
If the temperature is too low, you will either observe that the filament is not adhering
to the previous layer and you are getting poor layer adhesion or you will get a part that
is not strong and can be pulled apart easily. In either case, you should increase the
temperature by 5 degrees and try again until you get good line segments on each and
every layer and have a strong part when done printing.
1.5 mm is the minimum wall thickness with which you can print when using TPU powder.
Shoes 3D printed with 1.5 mm walls will be very flexible but you can also make certain parts
of the Shoe more rigid by increasing the wall thickness to 3 mm.
VII. Recycling Materials and Future Challenges
By not needing to utilize molds to test out different designs, a virtual approach of employing
software and 3D printing is able to cut down on waste and only use the optimal amount of
materials. Another approach to save some time and money on the manufacturing process is to
swap out soles from existing old shoes to the new ones, whereby the upper sole can be fitted to
a shoe to help test outsole and midsole designs.
During manufacturing, it is also possible to use a vacuum bag as a low-cost alternative to a
hydraulic press; this method creates high-pressure contact on all sides for glueing. Soles can
then be combined with the rest of a shoe to create a unique product that is ready to be used by
the customer. Keeping these costs down and maintaining an economic process does, however,
mean having to keep an eye on potential problems with the printing process. For example,
when working with very precise designs, any small defects can upset the printing, adding more
costs to the overall work. While the hydraulic press is superior, it's also very costly and not
necessary. Vacuum bagging can be used to quickly adhere the upper to the printed sole in
prototyping.
The ongoing objective for 3D printing better-personalized shoes is to decrease the amount of
material waste as much as reasonably possible while exploring new and existing techniques for
quick customization of digital models for each and every consumer. Getting the shoes printed
within a day of the order is one ideal target, as are keeping defects in the manufacturing process
as minimal as possible to guarantee a quick turnaround from retrieving customer data to design,
optimization, production, and delivery to customers.
5.Conclusion :
3D technologies are of expanding interest to the shoe industry due to the opportunities offered
in terms of personalisation. Consumers are searching for a one of a kind final product, adapted
first and most importantly to their morphology but also to their necessities and style. Additive
manufacturing is proving to be an efficient new method of production to fulfil this trend.
Thanks to 3D scanning, companies can just scan the consumer’s foot, model it, comprehend
and understand its specificities and 3D print a completely personalised product, all in record
time. It is therefore not surprising to note that the industry is predicted to grow by 19.5%
annually.
Revenues from 3D printed footwear now represent about 0.3% of the worldwide shoe market’s
revenues. This figure, which incorporates materials, software, prototypes and tools, is predicted
to achieve about 1.5% of total market revenue by 2030. Considering all 3D printed consumer
goods, the footwear segment ought to represent the most significant and important segment,
followed closely by home products. At present, this is the only main segment where there are
instances of mass production utilizing additive manufacturing processes that have proven to be
feasible and profitable solutions.
Therefore, in this project, we have demonstrated how to use these Additive Manufacturing
Technologies to manufacture personalized Shoes in a cost-effective way.
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