Vac-Formed Buildings and Terrain by David Drage

Diarama featuring vac-formed earthworks and medieval tents produced for Model, Design & Craft. The earthwork has been modelled up to show three different ways of using it,basic earthwork, Roman and stone wall (suitable for historical, fantasy or SF).

Vacuum formed items are seen all over the place. Sandwich cartons, chocolate box liners and Easter Egg boxes are just a few examples. Vacuum forming is a process that can produce high quality items very rapidly. It is not however very practical to consider it for home based modelmaking. Although I have seen home-made vacuum forming machines, I have found that these are not very efficient and do not form very well at all.

Another view of the diarama produced for Model, Design & Craft.

The basic process involves making a tool, I usually use MDF and car body filler. The tool must be finished to a high quality and the smoother the surface the easier the tool will release from the formed plastic. It is very important that the piece to be formed is designed properly. If there are any under-cuts on the tool it will be virtually impossible to remove the tool from the formed plastic. Also vertical sides must be kept to a minimum. It is best that side walls are kept at least two or three degrees off of vertical.

Vac-formed craters produced for Model, Design & Craft. These will be produced on a sheet with four sizes of crater on it.

Once you have your tool, you place it into the forming machine. The tool is usually placed on a plate which is lowered down into the machine. The plastic that is to be formed is then clamped into the machine and a heater (very similar to a grill on a cooker) is brought over the plastic.

Vac-formed tents produced for Model, Design & Craft. These tents are ideal for Colonial (Darkest Africa, Zulu, North-west frontier) or ACW games amongst others.

Once the plastic has softened the heater is removed and the tool is pushed up into the plastic. Then the vacuum is applied, which pulls the plastic tight over the tool. The plastic is allowed to cool and then the vacuum is turned off. The plastic can then be removed from the machine and trimmed of the excess around the edge. There are several types of plastic that can be formed. Polystyrene sheet (plasticard), ABS sheet, PVC and Acrylic sheet . Different plastics have different properties. I prefer to use polystyrene sheet( this is not the expanded stuff ) for most jobs as it seems to for very easily. I usually use PVC if I want clear pieces, but the PVC is much more elastic than styrene and so tends to web much more. PVC is also quite tricky to stick to things. In industry it is usually welded. Styrene, on the other hand, can be stuck with any modelling glue usually dichloromethane based, such as Tensol).

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