13 Model Making I

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M.S Ramaiah School of Advanced Studies - Bangalore 1

PEMP- PDN 511

Session 13

Model Making-I

Session Speaker

Sukanta Majumdar


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Session Objectives

At the end of the session the delegates

will be able to understand the use of card and

paper model for model making and be able toconvey the purpose of model making


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Session Topics

1. Introduction to model making.

2. Card and paper modeling.

3. Appearance models

4. Modeling in foam and thermocol5. Examples on cardboard/paper models


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Introduction to Model Making


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Structuralrepresentation

Structural andfunctional

Functionalrepresentation

Physical size, shapeand appearance(but not function)

Appearancemodel

Physical size, shape(but not functionand appearance)

Form and fit model

As manufacturedMaterials and

process

Productionprototype

Mock-up of

Manufactured product(Size,shape and function)

Pre-productionprototype

Key functions(but not sizeand shape)

Working principles

prototypeSpecific functions

(but not size and shape)

Test Prototype

Types of MODELS used in the DESIGN PROCESS


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The termsprototype and model

model to describe a non-functional representation and

prototype to describe a functional item.

An appearance model is a full-scale, non-functional, representation

that looks, as closely as possible, identical to the prospective newproduct.

Form and Fit models are ideal for ergonomic analysis of handheld

electronic devices, medical equipment and computer input devices

SLA, SLS, CNC,etc


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Introduction

Cardboard and paper have been used for many years in

model making.

From the simple paper aeroplane to the most complexarchitectural models

card and paper as modeling materials are extremely cost

efficient

simple to use and Require few tools with little experience

needed to produce high quality models

Card and Paper Modeling


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Tools

It should also be remembered that all knives and scissors

are dangerous and should always be used with extreme

care.

Adhesives should only be used in a well ventilated room.

Always avoid inhaling any adhesive vapour as this is

likely to be harmful. Always wash well any spills in contact with the skin.

Always follow the directions on the container.

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Knife - The best modeling knives are surgical scalpels. They are

extremely strong and can be purchased in a variety of styles withvarious blade types. Dissection knives and other specific modeling

knives are preferably used precise and blunt cutting. The most

important fact is that the knife is comfortable to use and strong enough

not to slip. Remember to always wear safety glasses when using sharp

instruments, and to cut away from you. All craft and surgical knives are

extremely sharp!

Straight Edge - A simple but essential tool to ensure clean straight

lines are cut in a controlled manner. When using any form of

model/craft knife, always use a steel straight edge to prevent the bladecutting into the straight edge. A variety of sizes are useful from 15cm

to 100cm depending on the work. Safety straight edges are an

advantage as the 'holding' fingers are protected from the blade.

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Scissors - Good quality straight and curve blade scissors are

often overlooked by model makers but they can save time

when cutting irregular shapes. For accurate intricate work

use scissors with a small blade and long handles eg surgical

scissors, available in a variety of types. A pair of qualitylong blade straight scissors allows for neater straight cuts if a

knife cannot be used

Retaining Tools - Basically anything that holds the items in

place whilst the adhesive sets. Useful items include staplers,

paper clips and paper weights. Masking tape or similar can be

useful to hold the model while it sets or as a temporary fixwhen checking. Drawing pins can be invaluable

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Adhesives

Adhesives should only be used in a well ventilated room. Always

avoid inhaling any adhesive vapour as this is likely to be harmful.

Always wash well any spills in contact with the skin. Always follow

the directions on the container.

A wide variety of adhesives can be used on cardboard and gluedepending upon the thickness/quality of material and the required

finish. Some of the most popular types are listed as follows:

'All Purpose Adhesives' - These adhesives include glue stick, gums

and fevicol All Purpose Clear. They are designed for use on most

materials but are quick setting when used on card and paper.

Generally clear and relatively thick they are most suited to stickingthin surfaces together as a strong rapid bond is formed. They are

however a little thick in consistency and expensive for use on large

surface areas.

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Super Glue - A recent essential addition to the modellers tool box.

Super glue has its uses with most modelling materials and therefore hasa place in card and paper modelling. Super glue is ideal where holding

the subject may be difficult and a rapid bond is required. It is also

useful for adding detail to card and paper models. Do not purchase an

expensive super glue as it is not necessary. The fevi-quick, range is

recommended for our requirement.

Techniques - Hints & Tips

Techniques/hints and tips are very simple with card and paper.

One of the most important tips is to remember that paper blunts blades

rapidly! As soon as you feel the blade 'drag', replace it as ragged cuts

will spoil the appearance of a model.When making pre-coloured card kits, painting the edges using acrylic

or water based paints improves the appearance.

Reinforce card kits and structures using triangular corner pieces

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Some basic tips for paper modeling

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Basic folds

Mountain folds (fold the sides back) are

indicated with a dashed line (- - - - - - -)

Valley folds (fold the sides forward) are

indicated with a dotted line (. . . . . . . . .).

Cut out individual pieces along the black line

around their edges. Some pieces may require

cutting slots toward the center of the piece:look for a small scissors symbol or a fine

white line indicating the length and width of

the slot.

Mountain folds

Valley folds

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To get a crisp fold, particularly on the smaller pieces, score the

paper along the fold lines with a hobby knife before cutting outthe pieces entirely.

For valley folds, score the

reverse side of the paper. First,mark the ends of the dotted lines

by carefully pushing a pin or the

tip of your knife through thecard. Flip the card over and

connect the dots in order to score

the fold line.

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Have a chopstick or blunt toothpick ready to

move small pieces into their correct positions

while the glue is still tacky.

This technique is quite useful when pushing theroof pieces inside the small cylindrical sections of

the Tower like structures so that they are level

and correctly inset from the top of the cylinder.

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More advanced tips to improve your models

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You can strengthen the tiny, thin pieces by touching a drop of

super glue to the back of the paper. Make sure you touch the glueto the back of the piece so that it does not leave an unsightly

glossy blob on the front. Just a tiny drop will soak into the piece

and stiffen the paper. Just be careful not to touch the piece or getit dirty while the super-glue is drying.

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When making round cylinders,

you may want to modify themodel to make a smoother,

rounder cylinder. Here is how

most cylinders are made, withthe tab glued under the end of

the cylinder:

You can make a smoother

cylinder by cutting off the taband gluing a scrap of paper

behind the end in its place.

Then you can match the twosides of the cylinder to make a

smooth seam.

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If you are scoring each fold of your model,

you may want to hide the white interior ofthe paper that shows through at each corner

by coloring the edges of the folds and sides

of the pieces. Do not use water color paintsor markers on the models.The matte paper

our postcards are printed on will soak up the

ink too quickly and ruin your model.

Colored pencils work much better,

especially soft watercolor pencils. Before

you have glued the piece onto the model,

fold it back to expose the inside of thepaper, then carefully run the side of the

pencil along the edge to color it.

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N 5

Appearance models are approximate 3 dimensional models. One

can think of an appearance model as a 3-dimensional sketch,

sometimes referred to as a sketch model. The models are used

just like concept sketches--to both explore and gain insight into

preliminary ideas, and to communicate ideas. Specifically, theyfacilitate the exploration of aspects not accessible through 2-

dimensional paper sketches. They can be used to demonstrate

primary elements in a product and perform simple experiments.They can be made very quickly and are quite cheap. Typically,

such models are made in the process of developing a product.

This lecture presents a variety of techniques that will be helpfulwhen you make appearance models of your designs.

The lecture begins by briefly introducing some common

materials used to make appearance models. Then, techniques for

working with the materials are outlined.

Appearance models

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This model uses all of the common modeling materials described

in this lecture--foam, cardboard, foam core and honeycomb

board. The model was built to demonstrate modeling techniques.This example is a highly finished appearance model that could

be used to get feedback from potential customer. However, the

higher level of finish comes with a price. It is in terms of time.

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If you are going to bring models to potential users, the realism ofthe model can be enhanced by carefully detailing the areas where

the customers interact closely with the product. This instrument

panel is made of paper.

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The displays and controls can be quickly modeledusing everyday objects. In this instance many of the

buttons are from everyday seen objects, tablets etc..

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This concept sketch presents a 'boom box' like image for the stereo

LCD television.How to model it?

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The model for the concept is made of foam and foam core. Itallows the designers to explore and communicate the

concept when stored ...

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and demonstrate possible design features.

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Again, the process begins with concept sketches. This is a

concept for a stereo LCD television.

Note: time is very important. The goal of sketching andmodeling is to explore and obtain the necessary answers to

questions as quickly as possible. A model created demands

for concentration and time .else purpose is not solved.

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This is an early stage model based upon the 2D sketch that allowedthe designer to explore size, form and kinematics aspects of the

idea. It is made from foam core, foam, and some copper and PVC

tubing for the handle and pivot pins.

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This picture shows a visual mockup/visual model of the TV

concept. This is NOT a model. However, the slide gives an

indication of what follows in the mockup and detailing phases of thedevelopment process. When taking photographs, placing a relevant

object in the vicinity of the model provides information about both

scale and intended use.

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Another sketch for a TV concept using colour LCD technology.

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The first model, made mostly of foam and

foam core, illustrates the user features of the

concept.

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This is a later and more carefully detailed model for the

same idea. It took 3 days to make. the value to the model is

added by efficient use of time.

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Materials:

In this section we will introduce four common modeling

materials and describe their properties. These materials are

foam,thermocol cardboard, foam core and Honeycomb board,

mount board.

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Foam is a lay term for the family of PU foams. Depending

on the manufacturer and requirements it varies in density.In most cases the higher density blue material is easier to

work with but it may not always be available.

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Thermocol is a good material to use when you need to make

sculptural forms or models that need to be solid. The material is

easy to cut and shape with hand tools and is fairly inexpensive

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Corrugated board is a paper product comprising of a medium (the

inner fluted part) sandwiched between linerboards (the outer

paper faces). It is available in a variety of thicknesses and

numbers of plys. It is very good for creating strong structuresthrough folding. It is also a very cost effective way to build large

scale models. Used boxes or clean sheets sold in art supply stores

are good sources for the material.

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Cardboard is quite anisotropic, so planning is required to correctly

orient the grain to obtain desired structural characteristics in amodel. Additionally, it can only be bent in two dimensions.

Cardboard is not suitable for creating surfaces that are curved in 3

dimensions.

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Foam core is also a sheet material, like cardboard. It is available inthickness from 1/8" to 1". The inner medium is foam and the outer

liner is a filled, high quality paper board. Foam core can be

purchased at art supply stores and it is fairly expensive comparedto cardboard. It is usually reserved for applications which demand

a higher degree of finish or refinement than corrugated cardboard

can accommodate.

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Foam core can be bent and worked much like cardboard.

However, it is much less anisotropic than cardboard.

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Compared to both cardboard and foam core, it is quite expensive.

However, it has good structural characteristics. If parts of a model are

going to be heavily loaded (such as stood on by potential users) this

may be the material to use. However, the bending and forming

capabilities of the material are very limited.

Honeycomb board is a

sheet material in which themedium is made from a

paperboard honeycomb.

The medium is sandwichedbetween paperboard liners.

The material is available in

thickness of 1/2" to 3".

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Cutting

This section described the basic cutting techniques when usingthermocol. Warning: cutting thermocol with a long knife can be

quite dangerous. Friction between the blade and thermocol

tempts one to force the knife, causing the material to tear out

and the knife to slip, sometimes resulting in severe cuts. The

cutting technique described in this section using a hot wire

cutter is a safe way to cut thermocol and usually provides a

higher quality cut.

Modeling in Foam and Thermocol

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Hot wire cutters come in many forms. It is very simple to

construct. A 20 Amp, 12V battery charger is connected to a nickel-

chromium wire which warms when current passes through it. The

wire is held in tension to create a vertical cutting blade. The main

drawback of the hot wire cutter is that fumes are created. The

vapors are not toxic, but they are a mild irritant. There is therefore

a need of ventilation duct near the hot wire cutter.

A hot element can be used tocut the Thermocol by melting

through it.

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G id


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A jig is a figure that holds a

part in a particular

orientation and can also

help control or restrict the

motion of the work-piece.

In the picture above,

cardboard has beenconstructed to help orient

part of the dashboard

Guides:

Obtaining really smooth cuts on the hot wire cutter requires someskill. A fence is good for straight cuts. However, for more complex

shapes it is often worth making simple jigs or templates.

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The jig takes about few minutes to build but without it, it wouldnot be possible to cut the part with sufficient precision.

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Paper templates are useful for complex

details such as grills. Templates can be cut

from heavy paper or any material that will

not melt when in contact with the hot

wire.

Once the templates are attached to thefoam block, the shape can be cut using the

hot wire, making sure that the wire

follows the template edges.

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F t i


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Double sided tape is a simple and reliable way to join thermocol. It isfast, surprisingly strong and, removable (with care). Clamping is not

required.The main disadvantage is that the double sided tape does not

cut well on the hot wire.

Fastening :

One of the easiest

ways to build

thermocol appearance

models is todecompose the object

into easy- to-make

shapes and thenassemble them to form

the complete artifact.

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You can also attach thermocol


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You can also attach thermocol

using spray glue (we can useindustrial grade chloroform ).Put

a moderate coating of spray glue

on the faces to be joined and then

clamp them together for at least

15 minutes.

This will form a permanent bond

because the spray glue chemicallydissolves the foam. This is not an

intended use for spray glue.

The advantage of this method is that it creates a very tight permanentjoint that cuts very well on the hot wire. The disadvantages are that it

requires clamping, time to dry and is suitable only for smaller objects.

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Water-based bonding gums also can


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The pieces will now be permanently joined. The

advantages of this adhesive is that it adheres on contact without

clamping and that it is good for joining large surfaces. The

disadvantages are that you have only one shot at positioning the

pieces as they adhere immediately and that the glue layer cuts

poorly on the hot wire.

g g

be used for joining foam.NEVER

use organic solvent base gluesbecause they will dissolve the foam.

To join two pieces, spread a thin

layer over both surfaces to be joined.Allow the glue to dry to a light tack.

Then, press the pieces together

firmly to ensure contact between thetwo faces.

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This section describes techniques other than the hot wire that can


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The surform is a rasp-like tool.

The cutting surface isexpanded metal. It is very

effective for sculpting and

removing large quantities ofmaterials. The tool leaves a

rough finish that usually

requires additional sanding.

Care must be taken to avoid

tearing out chunks of foam.

This section describes techniques other than the hot wire that can

be used to shape thermocol,foam

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Riflers are rasp or file-like tools that come in a variety of shapes

and sizes. They are appropriate for making fine details such as

parting lines or small concave areas.

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Sand paper comes in variety of grits and should be used in a

sequence of increasingly finer grits. Gross shaping or the removal

of surform marks can be done in thermocol, foam with 80 gradepaper. The 100 and 200 can be used subsequently if a very

smoothly sanded foam model is desired. 150 grade is usually

sufficient to remove hot wire marks.

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When sanding it is quite easy to tear out pieces of the

foam. Take care to avoid digging the edges of the paperinto the foam. Practice a bit first before tackling a piece

you have invested your time in. Always wear a dust

mask when sanding.

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In many cases painting an


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In many cases painting an

sketch model is a waste of timeand can make the models look

worse. Before painting, think

carefully about whether thepaint will allow you to learn or

evaluate anything that is not

possible when unpainted. If

there is not a good reason to

paint, don't waste your time. If

you do paint, only use a water-

based latex or acrylic paint. DONOT use oil or lacquer-based

paints, If you do ...

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Examples on cardboard/paper models


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This section and figure outlines the key points for safely cuttingcardboard. The most important thing is to have a very sharp

knife. The best knives are those having blades with tips that can

be snapped off to give a new cutting point.

The techniques for cutting, bending and making shapes incardboard are described.

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As a rule of thumb, the cutting tip


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Cardboard is a material that works best when bending is used to make

shapes. If you find yourself gluing several pieces of flat cardboardtogether to make a shape you are probably not using the material

effectively. Sharp corners can be made by compressing the flutes at

the location you want to make a bend.

is too dull after cutting 10 feet of

cardboard. Cutting without glass

base will lead to quick decay of

your blade.Leaving your blade

exposed to moisture also blunts theedge. Use the blade at a slant angle

to get sharp cut.Select for the

thickness of blade in relation to thethickness of board.

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Dimensional tolerance is an issue

h b di db d Th


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when bending cardboard. The

following slides illustrate thispoint. For the best control of

where a bend occurs, place it

across the grain as shown in thepicture. The layout lines for the

bends are 10cm apart

A straight edge is then used to

crush the flutes under the bend

layout lines.

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Making gentle curves


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Cardboard can also be bent in

gradual curves by using relief

cuts. An example is shown above.

This technique works best whenbending along the grain, but is OK

across the grain.

Once the flutes are crushed thecardboard will bend in very crisp

and straight lines.

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To make the gentle curve, parallel layout lines are drawn between the

flutes (when bending along the grain) or roughly 1 cm apart when

bending across the grain. Then a series of scoring cuts along the layout

lines are made, cutting only through the top piece of linerboard. In the

areas of the relief cut the cardboard may be bent like a sheet of paper.

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Trying to cut holes in cardboard

f hi h i b


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for hinges or otherwise can be

frustrating when using the

wrong tool (i.e., a knife). A

leather punch is the tool to use

for such applications. Theycome in a wide variety of sizes

(from about 1/8" to 2").

Using the leather punch a hole is

created by giving the punch a

sharp tap with a mallet. Be surethe cardboard is supported by a

firm surface.

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Fastening


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Any of the glue works well with cardboard.SR gum glue is a

good solution for cardboard. Place a small bead of glue along the

joint and then hold the pieces together until the glue sets.It comes

in varieties with different melting points and strengths.

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When cardboard is folded into sections, strong and stiff structures

can be created. Note the grain orientation in this example. If the

grain had been longitudinally oriented the sides would be prone to

local buckling under load.

Structures

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Summary The session develops an ability to understandmaterials and their applications and apply them to

communicate the design. It helps in understanding the necessity of model

making in Product design cycle.

It gives insight to Fabricate and form models thatshow an understanding of technical skills and arehighly resolved and finished.

It guides to Capably present, exhibit and recordwork. It instructs to Demonstrate safe working practice

for Model Making.

13 Model Making I

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