Rugby School Thailand Design & Technology Senior School

1.4.5 Fabrication in polymers / fittings / glues

Fabrication in polymers

Because polymers are more commonly formed into the shapes, they are needed they are not generally fabricated but they can be welded together (P) using a heat gun or plastic welding.

To glue polymers together you can use Tensol Cement or Polystyrene Cement both of which lightly melt the surfaces of the plastics being joined.

Heat gun

Tensol cement

Fixtures and Fittings

A variety of fixtures and fittings can be used to join materials.

Nails (P)

are meant to reinforce a joint or to join wood together in a quick and crude way such as nailing together a wooden frame. They cannot be used on metal and are likely to crack plastic. Nails come in a variety of shapes and sizes from tiny veneer pins just 1cm long to 30cm for heavy duty applications. They are hammered in but can also be applied with an electrical or pneumatic (air powered) nail gun.

Screws (T)

are meant to pass through one material and screw into another acting like a clamp to pull the two together. There are many different types of screw, but they are either classified as wood screws or self tapping screws which cut their own thread into metal or plastic.

Additionally, machinery and industrial products are often joined together with machine screws which look like bolts with a screw head.

Screws can have countersunk heads, dome and pan heads and come in a variety of lengths and gauges.

Nuts and Bolts (T)

can be used to join any materials together as they simply pass through a hole in the materials and clamp them together when screwed tight. Washers are generally used on either side to protect the surface of the materials from scratching when the bolts are tightened.

Bolts come in a variety of lengths, gauges and styles for different applications. They can be used with most materials including glass and concrete.

Rivets (P)

act like a nut and bolt in terms of clamping the materials together but, because of the way they work, removal is only possible by drilling or boring them out so they are classed as permanent.

Traditionally they were made of Iron and would be heated until red hot before being placed in a hole through sheets of metal. The flat end would then be hammered down and when the rivets cooled they would contract leaving a very tight fit. Nowadays they have been replaced with Aluminium pop rivets in a variety of applications.

Hinges (T&P)

can be used to join any materials together as they simply allow the two parts to hinge or swing. They still need to be attached to a material either through gluing or welding (permanent) or using screw or bolts (temporary).

Knock Down (KD) Fittings (T)

are a relatively modern invention created to meet the demands of the flat pack furniture industry. Products which use these are not intended to be assembled and dismantled repeatedly but they are a temporary fixing.

Other adhesives (P)

When gluing unlike materials together a variety of glues are available including Araldite. For gluing large sheets of laminates to wood, contact adhesive is commonly used. A thin layer of this adhesive is applied to two surfaces and left until tacky. When the two surfaces come into contact, they instantly form a strong and permanent bond.

Multi Purpose Adhesives (P)

There are numerous different types and brand of glue that are designed to glue any type of material to another. As well as Araldite and Gorilla Glue there are all purpose glues such as Bostick and UHU as well as Superglues while Copydex is a rubber glue used with fabrics and paper etc.

Adhesive compatibility

Summary of processes

Summary

Fabrication techniques are those which join materials together permanently or temporarily.

Different methods are used to join like or unlike materials.

Unless parts are moulded or cut into the shape necessary, fabrication will be required to join different parts together.

Fabrication techniques are commonly used to manufacture wood and metal-based products but less so with plastic products which are easily moulded to the required shape.

Many furniture-based products rely on flat pack fittings (KD fittings) for assembly.

Wood joints are a common way of joining wooden components such as frames and boxes.

Welding and brazing are commonly used to join metal pieces permanently.

Revision Notes

For each material group, you need to be familiar with a range of forming, redistribution and addition techniques.

In these units we refer to wasting, deforming, reforming and fabrication but they correspond with those same groups.

If you change shape by force/heat it is deforming (forming/redistribution)

If you change shape by changing state, it is reforming (redistribution)

If you join pieces together it is considered fabrication (also additive)

This is just terminology and categorization, what it important is that you understand which processes are possible and effective with each material group.

Prep 21

L20-21-Fabrication.ppsx

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