modelmaking guides

If your elevations are on paper it is best to spray mount them onto the foam board. Spray a light even coating onto the back of the design, let the glue become tacky then apply the paper to the foam board working from one end smoothing out any trapped air. For a very strong adhesion of the paper to the board use the spray mount as a contact adhesive by spraying both the paper and the board allowing the glue to become touch dry before sticking together.

You can either draw your template directly onto stiff card or draw your design on a computer, print out the design and glue it onto the card.

f gluing the template onto the card spray glue is usually the easiest method of gluing. Spray a light even coating onto the back of the design and onto the card, let the glue become touch dry then apply the paper to the card working from one end smoothing out any trapped air. Using spray glue as a contact adhesive will give a very strong adhesion of the paper to the card.

Before you start you need to check the hot wire cutter is set up correctly.

• Make sure that the wire is under tension and not loose.
• Make sure that the wire is set at right angles to the cutting bed.
• Set the temperature control to the correct setting for the thickness of the material you are cutting.

Then using the guide on the hot wire cutter cut the styrofoam to width, length and height required.

Now pin your cardboard template onto the foam and cut out the details of the design.

note: When cutting the foam try and make sure that you use one smooth movement as you pass the wire through the foam. The temperature of the wire will determine the speed that you can cut through the foam, you need to find the optimum cutting speed.
Cutting slowly will melt the foam too much causing uneven edges, where trying to cut too fast will distort the wire and could also cause it to break.
Use some scrap pieces to get the feel of the cutter before start.

suitable metals:

• Brass
• Copper
• Zinc
• Tin (tin plate)
• Steel (not stainless)
• Nickel Silver

Standard solder 60/40 will do for most jobs. There are specialist solders for particular jobs, such as Easy Flowing for long seams or Low Melting Solder for white metal.

The latter should only be used with an iron with an adjustment for temperature.

For electrical connections use Non Corrosive Resin Cored Solder.

Fluxes - helps the solder flow & stick to the metal (key) Acid Flux will serve most purposes but it will be necessary to wash the joint after construction otherwise it will corrode. Different fluxes are available for different metals (see Carr’s Range).

Large soldering jobs require large irons, but for most small model making joints use either a 25 or 40 watt iron.

Preparation of the tip is vital: with Tin Plated Tips (Weller) clean with sandpaper or a file. Iron Plated Tips (Antex) should only be wire brushed. When the tip is clean, dip in flux then apply a little solder to tin* the tip.

*Tinning - coating a base metal with a thin coat of solder

Make sure that the joint surfaces are clean, then add flux and then solder using the iron so each joint surface has a layer of solder. Put the joint together then apply the soldering iron tip to melt and unite the solder layers to make the joint.

On long joints, start at one end and work your way along to the other end rather than spot joint.

Styrene: Flexible but rigid extruded plastic from the polystyrene family

Users: Cladding for architectural models, vac forming and quick builds

Colours: White, Black, Grey & Clear and now, red, blue, orange, purple, yellow, cream and green

Thicknesses: 0.25, 0.38, 0.5, 1.0, 1.5, 2.0, 2.5, 3.2

Sheet size: 457x 508mm upto 660 x 1370mm

Accessories: White styrene strip, shapes, ladders, spiral staircases et

'As if by Magic'

The advantages of styrene over other building materials is speed:
>>score
>>snap
>>glue!

Four tools required:

• Scalpel
• rule
• paintbrush
• liquid solvent adhesive

Measure your shape out, score the surface, snap apart, pare the edge to tidy, hold together and then using the liquid solvent apply to the joint.

Capillary action: The adhesive is a solvent that will melt a small part of the styrene, drying in air the melted styrene will solidify and seal the joint

If you don't like it, peel apart, pare the surplus melted styrene off and start again.

Don't like it much later, score the surface, snap apart, and again and off you go!

Contact us if you would like a sample of Finnboard

Suitable moulding materials

Choosing the mould material will depend on a number of factors:

• Original artwork (master) material and shape

If there are a lot of overhangs/undercuts on the master then a flexible mould will be needed. However, on larger, simpler shapes a rigid moulding material may be more suitable, such as resin/fibre glass.

*for life casts a non toxic and fast drying material is required: plaster, alginate, Smooth On Body Double, latex.

• Final casting material

Certain materials are only suitable for specific casts, for example aliginate is best only used with plaster casting. Planning your casting material is important before starting your mould.

• Level of detail required

Some reusable moulding compounds produce a lower level of detail compared to most silicone and resin moulds.

• Number of reproductions/casts required

It is important to determine how many casts you require from your mould, waste moulds (usually plaster) can be a cheap way to do a single cast. If multiple casts are required then silicone rubber is a better choice, as it can be used over and over again without deteriorating.

• Budget

Mould making can be an expensive process, understanding the requirements of the project is important before choosing materials.

Releases and Sealants

Most moulding materials will require a release agent, this is usually a spray/wax/vaseline that is applied to the surface of the master to ensure that the moulding material does not stick.

Depending on the material of your master and your choice of mould material, you may need a release agent and/or sealant. Careful consideration should be given to the surface of your master because any excess release agent or scratches on the surface will be transferred into the detail of your mould.

Depending on your moulding material most porous or slightly damp materials, ie plaster, wood and stone, will require a sealent before a release agent is applied. Any layers of sealant or release should be allowed to sufficiently dry before a further coat is added.

Layers of wax can be applied and polished onto the surface of your master to give a high gloss finish to your mould, as well as acting as a good release.

Making a rubber mould

This is only a basic guide, there are many ways to go about making a mould and through practise and experience you will develop your own methods.

Open mould

The simplist mould ia an open mould when the master onject has one flat side, it can be placed at the bottom odf a moulding box and the moulding material simply poured over the object. Once cured the mould can be removed from the box (ensuring the walls of the box have a release agent applied) leaving a cuboid mould with the negative space of the object within it.

Multiple part mould

On more complicated shapes it is necessary to make up the mould of two or more parts that join together.

To begin, cover the entire object with a thin layer of rubber (approx 2mm). Once this has cured you can build up the thickness to between 5-10mm, ensuring that where the edges of the mould meet has a thicker covering.

Fix keys (small rounded tubes of cured silicone) to the curved surface, these will hold the rubber skin in place when you make the mould jacket, see figure 5.

You now need to make a jacket for the mould, this will hold the flexible rubber skin in place when you are casting. With a silicone mould it is best to do this with fibre glass and laminating resin or Smooth On Plastipaste, however you can use plaster bandage although this will deteriorate over time.

Firstly mark out the lines you have decided to make for the seperate parts of your mould (see figure 4). The walls of your jacket should follow the lines you have made on the rubber. Accurately make a Clay Scrim* (see figure 6) along the line of your mould and build up the fibre glass walls against these.

As you layer up the different parts that make up the jacket (see figure 7) ensure you have a barrier or release agent on the previous piece so the two cannot stick together, these also should have registration or keys (see figure 6) on them so they can be taken apart and put back together accurately.

* Clay Scrim: a wall about 5cm in height that follows the line of your mould to stop the jacket spilling over to another section of the mould. The clay should have a release agent on it as well as registration points (the registration points can be simply made by making an indentation with your thumb).

Once the jacket has cured you can remove it. Make a scalpel cut along the seperation lines marked on the silicone underneath, the rubber will come away with the jacket as it will be fixed now with the keys. Take out the master.

Once you are ready to cast the mould, use wing nuts (see figure 8) to ensure the pieces of the mould remain firmly together while casting.

Casting

To cast the object turn the fastened together mould upside down and pour the casting material into the opening. On small moulds you may need air holes in your mould to allow air to escape as you pour in the casting material.

Other Moulding Materials

Alginate

• Usually used for life casting as non toxic
• Mixed with water
• Degrades after one or two casts
• Only for use with plaster

Moulding Compounds (Gelflex/Polymorph)

• Less detail will be picked up in the mould
• Reusable by melting down
• Is affected by heat so best used with plaster and waxes, can be used with polyester resins but the surface will be affected

Polyurethane Rubbers

• Needs a good release agent and sealant
• Very good detail obtained
• Long curing time
• Good for concrete casting

A basic guide to mould making (773kb .pdf)