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UBC Materials Engineering MTRL 466/467 Final Design Project Report
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 2
Design Report
Executive Summary (In one page summarize the salient points of your work)
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 3
Design Report
Problem Definition (general background to the project which must identify customers or users, the need for
the design and any applicable constraints. This section should not exceed 2 pages.)
Introduction
This report details the benefits and constraints of a new thermoforming design process project, where heated air is used to form a
pattern into a thermoplastic sheet. An architect, Blair Satterfield, along with colleges have determined a way to improve the
functionality of a thermoplastic sheet by creating specific patterns within the sheet itself. Blair seeks outside consultation to
improve upon his teams’ initial design processes (See: Background for further details) in terms of variability and precision of design,
portability, and costs. The process must uphold certain specifications.
The goal of this project is to compare Blair’s previous design process to this proposed Heated-Air-Compressor method. This section
provides a background to the project, process specifications and project goals. The report continues on to summarized research of
the advantages and disadvantages of using a thermoforming process to form a thermoplastic to form a better understanding of the
material being worked with as well as provide a wider array of ideas for a design. The next step involved brainstorming design
options and singling out the best option for this specific project. Next, rough parameters are given through thermal and mechanical
modelling to prove the chosen design is feasible. A comparison is then measured through environmental impact and economic
(costs of process, materials and equipment) means.
Background
Blair Satterfield is an architect and assistant professor of architecture at the University of British Columbia. Blair’s professional
practice (along with Marc Swackhammer), named HouMinn Practice[11], focuses on research-based design seeking collaboration with
experts outside the field of architecture. HouMinn strives to utilise digital production and fabrication techniques in housing and
urban landscapes.
Blair’s idea began with expanding the function of walls. Can we give walls extra functions that are difficult to obtain with traditional
building materials? A program was created to place patterns within these wall patterns to provide a specified function. The theory
behind the pattern formation relies on the basic drawing techniques: stippling and cross-hatching (See Appendix A – Figure 1),
where stippling relies on points for image formation, and cross-hatching relies on lines. Hence sheet designs would revolve around
these basic techniques. Lines and/or points (or bubbles) developed varying in geometries and positions within a thermoplastic
sheet. Note, this report will refer to the formation of a line/bubble within a sheet as a deformation.
Blair and his team began experiments to test the viability of the concept. The VarVac (Variable Vacuum forming) project (See Figure
1 below) involved forming wall panels with the ability to sound dampen a busy office. This design relied on the deformations of both
bubbles and lines in a polystyrene sheet (See Figure 1 below). The program specified the geometries and positions of the shapes for
multiple wall panels to create the noise-dampening wall. In the Core77 2014 Design Awards Program, VarVac won The Professional
Runner-Up Award – gaining attention from all around the world [10].
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 4
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Figure 1 – The finished VarVac project: this wall is composed of many wall panels (left); One wall panel: the original flat polystyrene sheet has been molded to form
deformations of lines and bubbles [Note: after drying the bubbles have been cut] (right).
Descriptions of the processes Blair and his team used to create these wall panels can be found in the Technical Review Section of the
report. The advantages and disadvantages to each process form a better idea of the aspects of the process that will need
optimizing, described in Proposal Specifications and Project Scope.
Proposal Specifications and Project Scope
In first understanding the goal at hand, it was important to define the scope of the project in terms of (1) the responsibilities of the
team, (2) the project constraints and specifications, and (3) a reasonable scope of accomplishment for the three month duration of
the project.
(1) The process proposed in this report focus’ on the ability to create a wall panel, allowing variability in design as specified by
the customer, Blair Satterfield. However, this project will not cover the functions of the designs in the wall panel, and will
focus solely on the designs of a specified thermoforming process. The team makes the assumption that Blair is able to
create functions in the wall panels via specified deformation geometry and positions of the pattern using this
thermoforming process.
(2) In this project, the customer requires an optimized and simplified manufacturing process to mold a thermoplastic sheet
through thermoforming. Optimizations of the process will be measured through time it takes to form the pattern in the
sheet as well as economic and environmental comparisons to Blair’s vacuum forming process. The vacuum forming
process is used as a comparison because Blair emphasized it as his main process. The process should be simplified to the
extent it is portable and easy to operate (minimal training necessary). Molding geometries of the sheet should be able to
deform the thermoplastic to the shape of a line. A line is the simplest form of deformation to model to prove the viability
of the process. This line is to have as much variability in geometry and position on the sheet as possible. (picture)
(3) Provided a short time-line with such a large task, this project focuses on proving the viability of the proposed process and
whether this process is an improvement to the vacuum forming process Blair’s team used (Stage 1). Take note,
reasonable assumptions have been made in order to thermally and mechanically model the process in this short time
frame. Recommendations are provided at the end of the report to detail the next Stages the project requires given
further time and resources.
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 5
Design Report
Technical Review (Review the prior art relevant to the design task, provide relevant scientific background
information, and critical assessment of the literature. This section should not exceed 5 pages.)
The customer, Blair Satterfield, has requested a thermoforming process using thermoplastics. To fulfill Blair’s request (See Problem
Definition), technical understanding of the properties of thermoplastics and thermoforming process is necessary. Technical
understanding of the properties describes the limitations of the forming process or materials.
This section is split into the main categories of Processes and Materials. First, researching an array of thermoforming processes will
aid in brainstorming ideas that can optimize Blair and his team’s initial experiments. Next, researching thermoplastics properties will
provide an understanding to the benefits and restrictions of the material being deformed.
Processes: Various Plastic Forming Methods
A wide variety of heating and molding methods are used to form different shapes and patterns for polymers.[6] A few are described
below:
Vacuum Forming (See Appendix A – Figure 2) – A sheet of thermoplastic is clamped over a mold, softened by heating, and a vacuum
removes the air between the sheet and the mold. This causes the heated sheet to be sucked down onto the mold, taking up the
shape of the mold. Molds are generally expensive, allow for poor variability and aren’t portable.
Blow molding (See Appendix A – Figure 2) – Polymer blanks are heated and expanded with compressed air, like a balloon, inside a
mold to create the finished product. This process is generally used to create hollow shapes such as soda bottles, milk cartons, and
gasoline containers.
Press forming (See Appendix A – Figure 2) – Involves the use of a large, 2-sided die to press the material into the desired shape. This
process is generally used to make storage containers, small packaging containers, etc.
Extrusion molding (See Appendix A – Figure 2) – Polymer (in the form of pellets) is heated to a viscous state, and pushed with
pressure through a small die. This process is continuous and is used to make things like piping (See Appendix A – Figure 2).
Narrowing the forming processes using basic constraints given by the Customer, all large-scale and fixed-mold processes are
eliminated (a portable, variable process is required). Only vacuum forming is left on this list (Note: although vacuum forming has a
fixed mold shape, it can be pre-manufactured in any design at a relatively low cost).
Processes: Initial Experimentation
After reviewing the various forming techniques, the next step involves further understanding the thermoforming processes that Blair
and his team undertook. Thermoforming is a manufacturing process where a thermoplastic is heated above a specific temperature
and molded to a desired shape (See Materials: Why thermoplastic?). Understanding the advantages and disadvantages for the
processes that already achieved the project goal will make it easier to understand what can be optimized in order to create a new
and improved thermoforming process. To create designs in the panels, Blair’s team used various methods to heat and deform the
polystyrene thermoplastic. Note that most of this section references Blair himself through presentation, discussion and email.
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 6
Design Report
Vacuum Forming
Vacuum forming (See Appendix A – Figure 2) was one of the initial forming techniques used. This method involves heating the
sheet, placing it over a pre-manufactured mold, and removing the air from between the sheet and mold.[6] By removing the air, the
heated sheet is forced to form to the details of the mold. Some disadvantages included vacuum leaks (leading to imprecise forming),
bulky equipment (decreasing mobility at job sites), and pre-manufacturing molds (decreasing variability of shape and increasing
costs).
As Blair explained, in an attempt to improve on the last process, the mold was redesigned. Hexagonal shaped bars stacked side to
side, in a vertical orientation each able to vary in height allowed for more variation in shapes (See Figure 2). This method provided
higher resolution of shapes and less material waste. Unfortunately it was slow, could only be efficiently controlled with one sheet
thickness, and required specialized equipment available only in their machine shop.
Wire and Gravity Forming Process
To simplify the process, Blair and his team tried to eliminate the mold altogether. A wooden support was constructed upon which
wires were laid out in the desired pattern (See Figure 2). The polystyrene was heated and allowed to droop through the holes
formed by the wires –imposed forces were due to gravity only.
Blair and his team found a few difficulties with this process:
Understanding how long to apply heat with the sheet underneath the heater took much trial and error. There was a very small
margin of error between no deformation at all and a ripped sheet. Many parameters needed to be controlled for heating (i.e. the
distance the heater is from the sheet, the relative intensity of the radiation, forming environment, etc.).
During forming, the edges of the sheet deformed and further separated from the plywood mold. It appeared that as the sheet
stretched after heating, the sides pulled in and away from the edge of the mold. This created a non-uniform border. Without the
ability of an adequate clamping system, the customer mitigated the issue by using larger sheets and trimming the formed sheet back
to square however, this isn’t as cost effective as it could be.
The mold itself also caused issues during forming as it was made of plywood. The mold starts to smolder if left in the radiant heat for
too long, and during heating, the screws holding up the metal wires began to come loose.
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 16
Design Report
When looking at this table it can be concluded that the original process will be lower in energy cost. When comparing the
total cost of energy to the cost of labour, it can be concluded that the cost of energy usage is much smaller than that of labour and
that it has virtually no impact on the final cost of forming the sheets. The cost of labour was taken to be the average hourly wage of
a general construction labourer in the Vancouver area.[13]
Other cost factors are the initial setup cost of the process. Blair’s process was fairly inexpensive to set up since heating
lamps of 250 W can be purchased for approximately 10 dollars. The start up cost for our process lies higher since both the
compressor and heating nozzle need to be bought. The compressor can range anywhere from $250 to $2000 dollars depending on
the quality, pressure output and volume of the compressor. Our process will work with at 1800 W, 4-gallon compressor that can be
bought for $285. For the nozzle, a quote from the manufacturer regarding the exact model that we will need was required. The
manufacturer came back with a price of $400 dollars. As can be seen from these prices, the original process used by Blair would have
a cheaper initial setup cost when it comes to machine setup.
Another advantage of the process developed by us is that the rental of a workshop is not necessary. The process takes place
on site, eliminating the midpoint used by Blair to develop the sheets. The cost to rent a workspace in or around Vancouver seems to
vary between $1500/month to $2000/month. Extra costs for the workshop would include heating, electricity, water and general
labour for clean up and maintenance. Eliminating these costs would make a process much more economical for Blair.
The rental of a workspace ties in to the next important factor in our socio-economic report, the difference in transportation
cost and environmental impact. The transportation of unformed sheets is much easier and more efficient than that of formed
sheets. Our method would allow the process to happen on site, allowing the material to be transported to the worksite as flat sheets
directly from the store or manufacturer. The old process used by Blair required the transportation of flat sheets to a workshop
where the sheets were formed. These sheets would then be moulded to the desired shape and sent off to the work site. These
formed sheets have a depth of up to 10 cm compared to the 3 mm thickness of the flat sheets. In the table below we compare the
efficiency of transporting flat sheets versus formed sheets. It will give us the amount of sheets that can be transported per cubic
meter of space.
When studying the overall life cycle, it is important to note that for both processes, the energy used and CO2 associated
with the production of the flat sheets is the same. This is also the case with the disposal of the formed sheets, therefore the
calculations performed for this section do not account for those aspects of the life cycle process.
The environmental impact is important to take into account when choosing what process is most suitable for this project.
This environmental impact includes everything from energy consumed during forming, to the CO2 emissions created during the
transportation of the products. When looking at the transportation of the products we can see a clear difference in the two
processes. As seen in the previous figure, the energy used to form 100 sheets using the old method is 4.265 kWh, while the energy
consumed in our process is 8.33 kWh. From this comparison we can see that it is much more economically and environmentally
depth 0.003 m depth 0.1 m
width 1 m width 1 m
length 1 m length 1 m
volume 0.003 m^3 volume 0.1 m^3
#sheets/m^3 333 #sheets/m^3 10
flatsheets formedsheets
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 17
Design Report
friendly to transport flat sheets compared to pre-formed sheets. These m3 values can be used to determine the size of vehicle or
amount of trips needed to transport the sheets to the worksite.
Safety is a very important factor in the design of any process. Safety to the worker needs to be guaranteed if the proper
instructions are followed. In this section we will set out some basic steps that need to be followed to avoid injury on the jobsite.
Always wear PPE (safety glasses, ear buds, gloves, steel toe boots, long sleeved shirts and pants)
Keep hand away from the front of the heating nozzle.
Never point the nozzle at anything you don’t want to melt.
Place compressor on stable and level surface.
Do not handle formed sheets with bare hands.
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 18
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Recommendations (in one page, summarize your findings and provide recommendations for future work)
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 19
Design Report
Project Planning (Describe the project planning process, task breakdown and specifically which student(s)
were responsible for each task. Discuss progress and provide details of challenges experienced in completing the project. Provide a Gantt chart for the project. This section should not exceed 2 pages.)
Thermoforming of Thermoplastic: Proposed Improvements to Design Variability and Socioeconomic Effects (Stage 1) 20
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References
[1] Callister, W. D. (2007). Materials Science and Engineering: Introduction (7th ed.). New York, NY: John Wiley & Sons Inc
[2] Cambridge University. CES Software. Cambridge, England.