Introduction
For
the week of May 17 to 21, we received a visit from Oliver
Bayley, who conducted a prototyping and interaction design workshop
with us, drawing from his experience doing everything from model
making to interaction design. This document summarizes some of the
techniques and knowledge we gained from the workshop.
Photo gallery
Authors
Everyone
in attendance contributed to this document, including Oliver Bayley,
Erin Austen, Mario Enriquez, Jason Harrison, Lewis Johnson, Jocelyn
Smith, and Colin Swindells. Joseph Luk was responsible for editing
and publishing.
Idea
Process
We tried a "hands-on"
design methology to achieve fast results: realize the design as
rapidly as possible, experiment, test, and iterate the design. Prototypes
need not be fully polished designs -- in fact it helps sometimes
to have a "rough-looking" prototype because it encourages
users to give feedback on the important parts of the design rather
than minutia, colours, etc.
Purpose
of Prototype
Before you start,
you should know what you're trying to accomplish with the prototype,
and who will be seeing or using it.
Some possible
roles of a prototype are:
- Instantiate
a concept that exists in your hand (you think it should be cool,
but making it physical will confirm or deny this, or clarify problems
/ features).
- Brainstorm
with your hands (i.e. generate new ideas)
- Demonstrate
that a technical concept works (or figure out how
to make it work)
- Generate
usability feedback (e.g. run some user studies)
- Communicate
or sell a concept to others (e.g. a focus group, your boss, the
venture capitalist you're trying to get to fund your company...)
Very broadly,
your prototype could take two different forms:
- Engineering
/ functional model: it may not look right in most - or any - respects,
but it works. These often take more time and resources to build,
although sometimes you can pick out a small enough component of
the functionality to do quickly.
- Conceptual
/ appearance model: it may not work in most - or any - respects,
but it looks right in at least some key way. Time taken is likely
related to degree of polish. Often it's actually more useful to
have a rough polish in earlier stages.
At
early stages, you usually don't try to do these two things at the
same time since that would go against the quick-and-dirty brainstorming
ethic. One useful approach is to do them in parallel or in alternation:
generate a few quick conceptual models, then build one that works.
the one that works may be the wrong size / shape to accommodate
motors and other guts, it may have a tether when you expect it to
be wireless eventually, etc; but it could still give a different
idea of experience. You may adjust your design based on what you
learn from it, then go back to the concept prototyping stage, etc.
Machining
Machining
involves using precise, powered tools to cut, drill, or otherwise
reduce the amount of material. The following tools are available
in the SPIN lab:
- A
milling machine
- A
lathe
- A
small rotary tool (similar to a Dremel)
Always
use caution and wear safety goggles when operating these tools.
After use, clean and vacuum the area immediately and put away any
bits and other materials used.
MILLING:
The mill is similar to a drill press, except it has high-precision
cranks that move the cutting blade or object in each of the X, Y,
Z axes. While a mill can cut straight into a material like a drill,
it is also optimized for cutting across (i.e., perpendicular
to the bit). Using the sides of the bit means precise holes and
cuts can be made. Right angles, square holes, thin surfaces, etc.
are particularly convenient to create on a mill.
 CHOOSING
THE PROPER BIT: In our facility, two types of bits are available:
slot drills and end mills, shown in the diagram at right. The ones
with the flat top have four cutting surfaces, so they are more efficient,
but they must only be used for cutting across the
material (not down into the material, like a drill). Use
slot drills when cutting down into the material.
SECURING
THE MATERIAL: Clamps are available on the mill, and can be adjusted
by loosening the four hex screws on each clamp. However, for precision
milling on small surfaces such as acrylic, double-sided tape is
recommended. Choose a piece of scrap acrylic as the base, and securely
apply double-sided tape across the entire surface to anchor the
acrylic base to the mill's bed, and the material to be cut to the
acrylic base. When removing the material, gently pry with a chisel
pressed flat onto the base and be very careful not to break the
machined part. Lighter fluid may be used to loosen the tape (Goo-off
can cause damage to plastics such as acrylic).
PRECISION
MILLING AND BACKLASH: The X, Y, Z cranks are fitted with precision
scales, and a "floating" ring that can be rotated to zero
the scale. One revolution is 1/4th of an inch on the lower cranks,
and 1/2 of an inch on the upper one. Be careful -- the scales are
different! When milling using the crank scales, be aware of "play"
in the mechanism. This is called backlash. A point, approached
clockwise, will likely be in a different location than the same
point approached counter-clockwise, so always perform your measurements
rotating the cranks in the same direction (overshoot and wind backwards
if necessary and possible).
FEED
RATE: With the rotational speed set at 1,600 rpm, operate the cranks
with a smooth, controlled motion to get an accurate cut. Do not
rush the operation as you may shear a bit (particularly important
for small, sharp-end bits). When it doubt, go slow.
LATHE:
The small lathe in our lab can be used to produce objects with rotational
symmetry (for example, knobs). It works by spinning the object while
a cutter is precisely positioned on the surface. Because our lathe
was not fully functional during the workshop, we did not learn how
to use it at this time.
ROTARY
TOOL: A variable-speed rotary tool is located on the main bench
closest to LCI. There is a power switch on the back of the motor,
and a pedal is used to control the speed. Always wear safety goggles
when operating the tool.
A
variety of bits are available for the rotary tool, including tiny
drill bits and Dremel-style cutoff wheels. Stone type bits can be
used for sharpening or delicate grinding. Use the chuck key (with
a large black plastic handle) to attach and detach bits. Be careful
when reaching into the bit case, and always put away bits immediately
after use, because they are sharp.
The
rotary tool operates at a high speed, which can cause local heating
in the material. Go slowly but use a controlled motion when drilling
plastics to avoid the problem shown at right, which can cause the
intended hole to expand as material melts and can not be removed.
Foam
Shaping
Definition:
Shaping a solid 3-D piece of medium- or high-density foam (e.g.,
closed cell polyurethane foam) into a more 'organic' form.
Sources:
See section below.
Cutting:
Usually cut foam with:
- matte knife (aka utility knife)
- razor saw
- hack saw
Shaping
- Usually shape foam with:
- coarse (e.g., ~80 grit) wet-grade sandpaper (usually black)
- custom made sanding blocks or forms
(e.g., attach sandpaper to a block using double sided sticky tape,
and use as a sanding tool)
- lathe or milling machine
(e.g., treat a high-density foam like balsa wood)
Tips:
- when sanding to remove material, sand toward yourself with a smooth,
sweeping motion.
- it's easy to remove too much or too little material near the edges
of a piece of foam. So, cut the foam to size _after_ forming the
majority of your piece. For example, when forming a right-angle
prism into a right-angle cylinder, form the cylinder first, then
cut the ends to your desired length.
- before forming, you can use double-sided sticky tape to several
pieces of foam together into a larger piece of foam.
Bonding:
Usually bond foam with:
- high-quality double-sided sticky tape (usually the thin, non-foam
type)
- glue gun
- some super glues will melt the
foam! (usually avoid these glues)
Example:
(see diagram above)
1) Add sandpaper, using double-sided sticky tape, to the surface
of foam shape 'A'
2) Rub the base of foam shape 'B' back and forth along 'A' to create
a groove in 'B' that fits snuggly into 'A'
3) Remove the sandpaper and double-sided sticky tape from 'A'
4) Add fresh double-sided sticky to the groove in 'B', or use glue;
then, attach 'A' and 'B' together to create 'C'
Sanding
Forms:
Description:
Sanding forms are different shapes that are coated in sandpaper
(e.g, sanding block). The sanding forms discussed below are those
that are custom made for the project at hand.
Uses:
Custom sanding forms are useful for sanding oddly shaped pieces,
or for sanding with precision.
Making
a sanding form: There are a variety of materials that are appropriate
for making a sanding form (e.g., block of wood, sheet of plastic,
rod). The key is to make a sanding form from a shape that suits
the needs of the project at hand (e.g., take into account the
shape and size of project). Additionally, if you have to join
two awkwardly shaped pieces, you can drape a sheet of sandpaper
over one piece, and place the other piece on top and sand it until
it takes on the shape of the first pieces making them easier to
join.
Examples: To make a thin rectangular sanding form, take a material
that already has that shape (e.g., wood, plastic), and attach
columns of double-sided tape to one side (taking up the area that
you need but leaving room for a handle on the material), then
fix the grit of sandpaper that you need. The same can be done
with the other side of the material using a different grit of
sandpaper.
The
above can also be done with a rounded piece of material to make
a sanding form that is useful for sanding round objects. These
forms can be as big or as small as your project needs.
Making
Shapes with Foam Core
 Foam
Core Definition: Sheets of hard foam with thick paper glued to both
faces of the sheets. The edges of the foam core had exposed foam.
(see diagram on right)
Sourcing:
Available at many office supply and craft stores (e.g., Staples,
Office Depot, and Michael's)
Cutting:
Can cut with a sharp matte knife (aka utility knife). Can clean
edges with a wood chisel.
Joining:
Glue guns work well for joining foam core together. Some super glues
may melt the foam core.
Folding:
Example
1: A box
- Measure
the inside and outside dimensions of the box taking careful consideration
of foam to be removed.
- At
one edge of the sheet of foam core, make a perpendicular cut with
a knife through the foam core down to the lower paper. Remove
this foam and discard.
- For
the remaining three edges of the box, make three sets of 45 degree
cuts through the foam core down to the lower paper. Use a ruler
or special razor mitre tool to help make a clean 45 degree cut.
Be careful _not_ to cut the lower paper.
- Clean
the 45 degree cuts by scraping the foam smooth with a wood chisel.
- Fold
the box and glue the edge with a glue gun
Example
2: a curve
- Measure
the inside and outside dimensions of the curve taking careful
consideration of foam to be removed. For a large radius, little
or no foam core should be removed. For a small radius, more foam
core should be removed.
- Peel
the top paper from the foam core using your fingers and possibly
a matte knife to help you get started.
-
At one edge of the sheet of foam core, make a perpendicular cut
with a knife through the foam core down to the lower paper. Remove
this foam and discard.
- Make
a series of thin perpendicular cuts through the foam core down
to the lower paper. Be careful _not_ to cut the lower paper.
- Clean
and remove enough material so the foam core can be shaped into
your desired form (if needed). Use a matte knife or scrape with
a wood chisel.
- Form
the curve and glue the edge with a glue gun
- Finishing:
Paint the foam core, attach sticky labels, write on it with pens,
glue gun additional media, etc.
Mold-Making
and Casting
Molding:
(by Mario)
I have found a couple of sites that best explain how to make molds:
http://www.hirstarts.com/moldmake/moldmaking.html
http://www.garlic.com/~blufrogg/dolls/mold.htm
We
made 3 molds during Olly's visit. Two of them using silicone rubber
and one using an aluminum lamp shell and a rubber ball (my own).
In the case of the silicone rubber molds, you must affix the part
to the bottom (or side) of a container to be used to hold the mold
material. In olly's case, he used two acrylic sticks to hold the
piece in place. These acrylic sticks had another function, when
removed from the hardened mold, they leave two vents (one for filling
the mold and another to allow air to escape from the mold being
filled). Olly talked about how to design your mold to allow the
part to be extracted once the mold has hardened.
When
we need to make a 2 piece mold, we need to make sure that the mold
halves will be put together in the proper orientation. To do this,
you must leave some alignment marks (irregular cuts, stubs, etc)
in the two halves of the mold.
As
for the mold made for the plaster hemisphere, I used a lamp shell
and a rubber ball. In order to get a hollow hemisphere, I cut a
few wood sticks to the length of the required thickness of the piece.
These sticks were glued (with ca) to the outside part of the mold
(the lamp shell). They held the ball in place after pouring the
plaster into the mold.
In
order to have the lamp shell form a good hemisphere, I used plasticine.
Casting
with Plaster:
We
used Plaster of Paris to make the hard hemisphere for my vibrotactile
display. You have to mix the Plaster at a 1.5 to 1 ratio with water.
You must mix the plaster and place it in the mold rather quickly.
The consistency of the plaster is about the same as oatmeal. (and
just as gross)
Casting
with Bondo:
Autobody
filler, aka Bondo, is a multipurpose building material for prototyping.
It can be used to fill in contours in some other material, smoothing
out contours in acrylic for example, and as a building material
on it's own for molding and machining. The set filler is fairly
hard and can be painted for a nicer finish.
Auto
body filler comes as a paste and a catalyst or hardener. The hardener
will need to be mixed evenly with the paste before you can use the
filler. The ratio of catalyst to paste is roughly about 1 to 20,
but read the directions on your supplies for directions. The amount
of catalyst controls how long the filler will take to set. More
catalyst will result in a faster setting time, but too much will
cause heating and possibly cracking of the filler.
Autobody
filler should be used with good ventilation.
There
are very few solvents to dissolve it, so clean up must be done mechanically,
by scraping and wiping the filler off.
To
make a contoured grove or fillet corner, first find or make a disposable
tool that fits the contour you want. Then mix enough filler to fill
the empty space between the tool and the part. Dab filler into space
to be filled and use tool to smooth it. It may take several passes
to smooth out the contour. A second application of filler may be
used if the surface is bumpy.
Molding
autobody filler is fairly easy. It can be molded in any form that
you can squish it into and remove it from. A disposable mold is
likely best in case your molded piece gets stuck and you have to
break it free. You will need to use some mold release agent, such
as petroleum jelly (Vaseline), because the filler will stick to
almost any thing. Oil will also work as a releasing agent, but it
doesn't work as well. The steps to molding autobody filler are:
Make the mold Check that all parts of the mold fit when any covering
has been added Apply mold release to inside of mold and edges of
mold Mix enough filler to fill mold Put filler in mold Clean up
any spills, drips or extra filler Allow to set.
Sculpting
Sculpting
an object from a pliable material like clay is possible, but one
should be aware of its limited accuracy, which can cause the process
to become more time- and labour-intensive than machining or forming
methods. Sculpting can be useful for creating highly organic shapes
not otherwise possible -- for instance, hand grips.
We
tried several new sculpting materials, all commonly available at
crafts stores:
- Rubberized
clay: Sculpey Bake & Bend Clay and Eraser Clay are quite similar.
They both require baking in a low-temperature (250 degrees Farenheit)
oven. If the clay is not fully baked, it will be weak and break
easily. The Bake & Bend Clay produced a strong, pliable material,
while the Eraser Clay was somewhat more rigid after baking. It
was even possible to make quite reliable air bladders using the
materials. Neither material exhibited much shrinkage during baking.
- Crayola
Model Magic is best described as a marshmallow that isn't gooey.
It is amazingly lightweight for its volume, and has a foamy, flexible
texture. The material can be rapidly dried on the surface with
a heat gun (much like toasting a marshmallow). The material shrinks
significantly during curing, but remains flexible and squishy.
Good material for sculpting hand grips.
Adhesives
Also
available in PDF and Excel formats for printing:
Hot Glue:
Description:
Hard glue sticks may be inserted into the back of an electric
glue gun. The front end of the glue stick is heated, melts, and
can be used in controlled quantities by using the trigger.
Uses:
Hot glue can be used either as glue or as a gap filler. Depending
on the quality of the glue used, a sturdy bond can be formed between
a variety of materials. The glue can also be used in larger quantities
to fill gaps, and once dry, excess glue can be scraped away.
Where
to Buy: Glue guns and glue can be purchased at most hardware stores
(e.g., Dunbar Lumber), craft stores (e.g., Michaels) or dollar
stores (for the smaller glue guns). Glue guns may be purchased
in a variety of sizes. Smaller glue guns are useful for projects
that require more precision.
Cautions:
The glue is hot when it leaves the glue gun. The tip of the glue
gun is also hot. Hot glue may melt certain materials (e.g., some
varieties of foam).
Double-Sided
Tape:
Description:
As the name implies, this tape is sticky on both sides. It comes
in many sizes and strengths (e.g., carpet tape vs. poster tape).
The recommended type is shown below:
Uses:
This kind of tape has many functions. It can be used to adhere
two materials together (e.g., two thin sheets of plastic). It
can also be used to temporarily adhere a material to a surface
while the material is shaped, cut, soldered, etc. When finished,
the tape residue may then be removed from the surface and the
material using lighter fluid (note that this may not apply to
all materials).
Where
to Buy: There are a number of double-sided tapes on the market
that can be found just about anywhere. One of the better products
for smaller prototyping jobs is a double-sided tape from 3M (see
website for picture). See 3M Tapes.pdf
for a description of available 3M products.
Cautions:
Double-sided tape used in place of a clamp is only as good as
the tape itself. Make sure that the tape is strong enough to hold
the particular material used in place while it is manipulated.
Note also that this tape will not stick at temperatures that are
either too warm or too cold (read the packaging to determine optimal
temperatures).
Wiring,
Soldering, and Electrical
by
Jocelyn
Tips
I got from everyone while trying to solder
-
Don't use too much solder
-
When soldering to a board make sure you get a nice little circle
of solder around your wire
-
When soldering two wires together
- stick a little solder on each wire
- hold the wires together and use the solder on them to solder
them together
- works best if you secure one of the wires somehow (ex. tap it
to a scrap of something)
- If
your solder starts to get old and gross 'cause you keep screwing
up then take it off and start again
Parallel
port interface:
Basically I just used Andrew's code.
I did learn that there is some bit somewhere or other that needs
to be set/unset but I'm not even sure which one.
I will try to find out more about this and write something that
makes sense.
Parallel
port plug
To make a little voltage amplifier for the parallel port we needed
only some of the pins.
2-9 - the data pins
10-14 - not sure what for
19-23 - grounds
We
connected these pins to a board. Next we connected one side of a
little black amplifier thingy to the data pins. We could then connect
the other side to one of a motor's wires while connecting the other
motor wire to ground. To amplify we used a power source through
the first pin of the little black thingy. With this we could control
a motor and up to 7 other things through the parallel port.
LEDs
Rectangular LEDs only really omit light out the end. If you would
like the whole thing to light up you need to rough up the surface
so that light will refract though it. (At least that's my understanding)
I used the sandwet 600 grain paper. I would actually recommend a
slightly corser grain as I had to be pretty rough with this paper
to get the lights sufficiently "scratched up".
Materials
and Supplies
The
following is a list of the materials we used during the workshop.
For more details please see the respective sections in this document,
and refer to the Photo
Gallery for pictures. Reviewers please check this list.
Supplier Index
SPIN has compiled an index of suppliers for various types of materials. Most are local to the lower mainland area of BC.
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