How to Make a Toy? - instruction by Sangyun Han

The brief:

The set of instructions will include step-by-step images illustrating how a person should construct the case and put together the electronic components. There will also be instructions on air-brush painting techniques and ways in which individuals can use the final product to have fun.

The object will focus on a shell casing, painting and assembly of the casing. The casing must include mounting bosses for assembly. The casing must encompass an electronic, mechanical, or electrical component. The finished object will be a toy. The choice of target user is an important aspect that influence materials, color, complexity, and safety aspects of the assembly.

The design should be innovative and playful. The design will be created using Solidworks and produced, mainly, by using the 3D Printer. The parts produced will then be hardened, sanded, painted, and detailed prior to assembly. Paint will be applied using an airbrush to simulate a plastic finish to the prototype. The finished product will be a functioning prototype.

Target User:

People who want to create unexpectedly funny situations for others.

About the Toy:

The toy surprises people with fun sounds. A ghost made using a 3D-printer. When people cross in front of the ghost, the ghost’s sensor will detect them and begin to make sounds.


- 1 x Infra-red Motion sensor module kit – $2.99 from Radioshack electronics store or Sharp GP2D15, and the datasheet is available here.

- 1 x New Horizon’s sounds and lights module kit – $14.99 from Radioshack electronics store.

- 1 x 2pin mini Speaker – $3.99 from Radioshack electronics store.

- 1 role x Electric wire for small electronics device – $4.99 from Radioshack electronics store.

- 3 x LED for small electronics device (any color / regular ) – $4.99 from Radioshack electronics store.

- 3 x 1.5volts AAA Batteries

- 1 set x Z-Max bond and hardner

- 2 x Enamel paints 1/4fl oz – $2.99 each from Da Vinci Arts Supply.

- 1 x Primer for Enamel paints – $3.99 each from Da Vinci Arts Supply.

- 1 x Enamel Thinner – $4.99 each from Da Vinci Arts Supply.

- 2 x Empty Mixing Containers – $4.99 each from Da Vinci Arts Supply.

- 1 x Airbrush Jar Adaptor – $4.99 each from Da Vinci Arts Supply.

- 1 x Enamel Thinner – $4.99 each from Da Vinci Arts Supply.

Hardware Tools:

- Nipper

- Soldering iron & solder

- Air brush gun

- 3D printer

- Masking Tape and Burnisher

- Wet Sand Paper

Software Tools:

- Solidworks

- Zprint

How does it work?

Bring this toy to public rooms. When people cross in front of the ghost, the ghost’s sensor will detect them and begin to make sounds; the people will be surprised because of the sounds from the ghost. It’s fun!

Here’s how to build your own.

Step1: Design a cap part for the toy’s face.

Here is the Solidworks parts file. Download toy SLDPRT –

Model the exterior body.
Split and shell the exterior body.

Step2: Design a base part for casing the batteries and the module kits.

Model the internal components.
Create the support structure for the internal component.
Create any buttons, parts that extrude through the exterior shell.
Create the mounting and screw boss.

Step3: Export STL files from the design for 3D printing

To use 3D-printer for building a case kit. Here is the STL file you need. Download Base STL –, Cap STL –

The standard data interface between CAD software and the machines is the STL file format. An STL file approximates the shape of a part or assembly using triangular facets. Smaller facets produce a higher quality surface.

Here is a PDF guide how to use 3D printer Download PDF –

3D printing is a category of rapid prototyping technology. A three dimensional object is created by layering and connecting successive cross sections of material. 3D printers are generally faster, more affordable and easier to use than other additive fabrication technologies.

One variation of 3D printing consists of an inkjet printing system. Layers of a fine powder (plaster, corn starch, or resins) are selectively bonded by “printing” an adhesive from the inkjet printhead in the shape of each cross-section as determined by a CAD file. This technology is the only one that allows for the printing of full color prototypes. It is also recognized as the fastest method. This approach is a selective fusing of print media in a granular bed. In this variation, the unfused media serves to support overhangs and thin walls in the part being produced, reducing the need for auxiliary temporary supports for the workpiece.

Each technology has its advantages and drawbacks, and consequently some companies offer a choice between powder and polymer as the material from which the object emerges. Generally, the main considerations are speed, cost of the printed prototype, cost of the 3D printer, choice of materials, color capabilities, etc.

Unlike “traditional” additive systems such as stereolithography, 3D printing is optimized for speed, low cost, and ease-of-use, making it suitable for visualizing during the conceptual stages of engineering design when dimensional accuracy and mechanical strength of prototypes are less important. No toxic chemicals like those used in stereolithography are required, and minimal post printing finish work is needed. One need only brush off surrounding powder after the printing process. Bonded powder prints can be further strengthened by wax or thermoset polymer impregnation. -Marin, Dave. The Modelshop guide. 2009.

Step4: Sanding – Surface Preparation.

After the 3D printed parts come out, infiltrate the printouts with Z-Max. Sand the parts.

You can’t lay down a good paint job unless the surface you are painting has been properly prepared. Things that look like a minor blemish on an unpainted surface, once covered with a few coats of paint, can become a major eyesore. To get a good paint job, the layers need to be as thin as possible; this will prevent small details being hidden. Spending time preparing the surface, making sure it is as smooth and as blemish free as possible will only help you to achieve a better paint finish.

Step5: Priming.

Use air brush gun and Primer.

After preparing the surface, it is recommended to prime the surface, this helps the paint to stick to the surface properly. For the paint to bind properly to the surface of the model, it must be free from oils, dust and other contaminants, to ensure this it is important to wash the model thoroughly with a mild detergent and warm water before painting. Be careful with the temperature of the water as hot water can cause the plastic to warp. Once the model is clean and dry, spray a thin coat of primer, this does two things, it gives the color coat a surface to adhere to, and helps to highlight any defects in the finish that may need correcting. Problems are generally easier to see with gray primer than they are with white primer. If you find any problems, fix them and respray with primer. If the model is going to be painted with a light color, then a thin coat of white primer over the gray primer is recommended. -Van, John. The Art of Painting Model Cars. 2002.
After priming, the model should be set aside to dry for at least 24 hours.

Step6: Painting.

Use air brush gun and enamel paints.

Enamel paints need to be mixed with Thinner.

The mixing ratio for Floquil Paint
Manufactured by Testors Mixture Ratio Paint 3:1 3 parts paint to 1 part airbrush thinner (Compressor Regulator Setting 16-25 PSI)

The mixing ratio for Model Master Paint
Manufactured by Testors Mixture Ratio Gloss Paint 3:2 3 parts paint to 2 parts airbrush thinner Mixture Ratio Flat Paint 3:1 3 parts paint to 1 part airbrush thinner (Compressor Regulator Setting 16-25 PSI)

Painting comes down to more than just laying down a layer of spray paint, getting a good color coat starts right at the point of preparing the paint before spraying. Preparing the paint involves mixing it for use in the airbrush. When it comes to preparing the paint for the airbrush, it usually involves mixing the paint with the relevant solvent to getting the paint to the correct consistency for spraying.
The general rule of thumb for airbrushing is to get the paint to about the consistency of milk. This will give you an idea of what to aim for when thinning the paint.When the trigger on the airbrush or nozzle on the rattle can is depressed, the paint is atomized; this means there are tiny droplets being shot through the air towards the model. Upon landing on the model they spread out and join together to form a uniform surface. The smaller the droplets, the thinner and more even the coat of paint. At the same time the droplets are spreading out, the solvent are evaporating, which stops the paint flowing as it dries, if the solvent evaporates too soon, it doesn’t have time to level properly and you will end up with orange peel effect, at worst it can evaporate before the paint reaches the surface and you up with a surface that looks like flat paint.
-Van, John. The Art of Painting Model Cars. 2002.

Coat gently multi times until the color comes out.

If you are constantly getting orange peel, it is likely that it is caused by one of two things, one is that the paint is too thick in the case of airbrushes, the other is that you are spraying from too far away. Trial and error will help you find the best distance to spray from and how thick the paint should be for your application.

When spraying, never start or stop the spray over the surface of the model, start the spray one side, spray over the model in a straight line keeping an equal distance from the model, and after you have passed the end of the model with the spray. This will prevent any drips that could possibly build up on the nozzle from landing on the model and potentially ruining a good paint job.

Use masking tape for separating the colors.

Allowing paint time to dry between coats is important, if the solvents don’t have enough time to evaporate between coats, the paint will remain soft longer, at worst it may even crack over time because of uneven drying. When it comes to paints and drying times, it is totally dependant on the paint type, enamels will take at least 7 days to be completely dry, lacquers will take at least 2 days and acrylics at least 4 days. Between mist coats the minimum drying times are; minimum 4 hours for enamels, minimum 20 minutes for lacquers and minimum 1 hour for acrylics. Remember that longer will always be better. It is mostly recommended to lay down several ‘mist’ coats before apply- ing a ‘wet’ coat to allow even build up of paint. Using a primer can help eliminate the need for too many mist coats. Once a good coverage is acquired with mist coats, it is time to lay down the final coats otherwise called the wet coats, this is when the paint creates the shine you are looking for. -Illsley, Geoff. Airbrush Painting Techniques. 2007. The basic rule is to spray until the paint looks about ready to run, this is really a practiced technique in many ways, I know it sounds risky, and I am sure the first couple of times you may end up with a run or two, but practice and time will help. Never expect paint to form a complete cover on the first coat, this is the way to run into any number of problems described, rather build up the paint layers gradually and evenly. Any defects you notice should be repaired between coats, you should never hope the next layer of paint would cover something up; paint hides nothing once it is dry. The most recommended method to repair paint blemishes is careful wet sanding, before sanding though, you should always allow the paint to dry completely for at least 24 hours.

Step7: Assembling.

Affix the module kits to the case. Insert the circuit board to the case inside, but make sure to test that the circuit functions before hiding it between the cases.

Step8: Have Fun!

Place it in a room. Enjoy it!

Cited from Marin, Dave. The Modelshop guide. 2009.

Additional Information I: Basic Paint Composition

In general, all paint products (whether water-based or solvent-based) are made up of four essential components (raw materials).

1 Binder (vehicle or resin)
2 Solvents
3 Pigments
4 Additives

1 The principal binder in most Testor / Model Master enamels is a specially modified alkyd. The binder is a polymer that forms the final dry film and “ binds ” the paint to the substrate and the other paint components.

2 Solvents in the enamels are a blend of various organic solvents. The blend chosen (different for gloss and flat colors) is one that maximizes desired evaporation rate, dry time, proper flow, level and anti-sag properties and also promotes excellent adhesion to polystyrene and other materials used in model construction.

3 Pigments include organic and inorganic. Organic pigments are primarily the bright and clean yellows, oranges, reds, blues and greens. Inorganic pigments are represented by white (Titanium Dioxide), black, yellow and red iron oxides, umbers, sienna’s and similar “dirty – shade” pigments.

4 Additives include many key components of paint such as driers, anti-skinning agents, plasticizers, viscosity modifiers, wetting agents, defoamers, anti-settle agents, and more. While, even when taken collectively, these additives comprise a small percentage of the final paint formulas by weight, they are critical components that will “make or break ” the final performance and appearance of the paint when put into the hands of the end user.

Additional Information II: Paint Compatibility Considerations

1. Most solvent-based hobby coatings are classified as either enamels or lacquers.

2. Enamels and lacquers should never be wet-mixed at any time.

3. All Model Master enamels (both pigmented and clear products) are wet-mix compatible. They can be combined in any ratio in order to produce a finish which produces the final color and gloss desired by the modeler.

4. When thinning solvent-based hobby finishing materials (for brushing or airbrushing application), it is essential to select and use correct thinners. In general, the best thinners for enamels are those which contain petroleum distillates. These thinners are primarily blends of aliphatic hydrocarbon solvents such as mineral spirits, naphtha, or Stoddard solvents. Occasionally these thinners also may contain small amounts of aromatic hydrocarbons (such as toluol or xylol) to enhance certain application and performance properties of the paint. Lacquers, on the other hand, usually contain little, if any, hydrocarbon solvents. Instead, they usually contain what is often referred to as “ active” or oxygenated solvents. These include ketones (such as acetone, MEK, and MIBK), esters ( isopropyl acetate, butyl acetate) and sometimes alcohols (isopropyl alcohol, butyl alcohol), and occasionally small amounts of aromatic hydrocarbons.

5. Most modelers are familiar with the general rule, “ Never apply lacquer over enamel.” This is generally a good rule of thumb. However, there are custom-formulated clear lacquers (available in gloss, satin semi gloss and flat) which are specifically designed to do just that. They may be brushed or airbrushed over our dry enamels or unpainted polystyrene surfaces to produce smooth, transparent overcoats. They will not lift or wrinkle previously enamel-painted surfaces or decals, nor will they craze clear polystyrene parts such as windshields or canopies.

6. When in doubt, always follow manufacturer’s directions when mixing or thinning any hobby finishing enamel or lacquer.

Additional Information III: Glossary of Paint Terms

Any one of a number of special chemicals added to paint to bring about special effects. Examples are plasticizers, driers, fungicides, anti-setting and ant skinning agents.

Merging of dispersed particles into aggregates that adversely affect smoothness, hiding, color and gloss.

Anti-Skinning Agents
Chemicals added to paint to help prevent the formation of a surface film.

Base Coat
A highly pigmented color coat applied prior to a clear coating that gives the system the desired color.

The paint material that forms the film. So called because it binds the pigment and any additive present into a solid durable film.

A defect in which pigment from a lower coat of paint diffuses into an upper coat and discolors the latter.

Formation of dome-shaped projections in paints or varnish films resulting from local loss of adhesion and lifting of the film from the underlying surface.

The undesirable sticking together of two painted surfaces when pressed together under normal conditions.

Usually caused by condensation of moisture during the drying period. The film becomes cloudy or translucent.

Formation of a pigment layer on the surface of weathered paint. Promotes self-cleaning of white paint but causes fading in colored paints.

Merging of latex particles to form the coating film as the latex or latex paint dries.

The formation of a surface crack, often as a fine network, which does not penetrate to the underlying surface. Crazing is sometimes caused by the softening effect of solvents from successive paint coats as in lacquer operations.

Combination of solvents for the purpose of removing grease and oil from the surface in preparation for painting.

Dispersing Agent
Additive that increases the stability of a suspension of pigments in a liquid medium.

A catalyst added to speed the cure of oil base paints. Driers are often metal salts of naphthenic acids obtained from petroleum.

If you want to learn more, visit these websites below.

Testors Corporation –
Tamiya –
Tower – Hobbies
MicroMark – http://www.micromark.comPaasche .
Paasche –

< Bibliography >

Illsley, Geoff. Airbrush Painting Techniques. London, UK: The Copendium Films, 2007.

Marin, Dave. The Modelshop guide. New York, NY: The New School, 2009.

Van, John. The Art of Painting Model Cars. Round Rock, TX: Pagewise, 2002.

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