Methods of Joining materials
For a variety of reasons it can be advantageous to produce a component in a number of parts and then join them together.
The mould tool for injection moulding or casting can be significantly simplified.
weight savings.
Much of the material removal associated with wasting can be avoided.
Standard components can be incorporated into the design.
Permanent Methods:
Welding
Permanent method of joining a wide range of materials, welding is the joining of two materials usually metal in their liquid form, which solidifies to form a joint that is as strong as the parent metal. This process can be repetitive and so is ideal for using robots. The materials are joined by melting them and allowing the molten material to mingle and then cool to become a solid. The molten material is protected by gas (to prevent impurities being absorbed) produced by the vaporisation of a powdered coating around the welding rod.
Very high melting point around 3000- 3500 degrees which produces a very strong joint which is used to join wide thicknesses of materials.
Brazing
Is very similar to soldering and with appropriate filler materials, it can be used on nearly all metals and many ceramics. The melting temperature is much higher than those used in soldering, this makes the filler alloys much stronger.
Very clean joint performed with better tolerances. Weaker hold than welding. Temperature is above 600 degrees- 900 degrees.
Soldering
Is a quick method of joining most metals such as brass, copper, tin plate and steel. An exception is aluminium. This process is best confined to light fabrication where joints are not subjected to heat and vibration.
Low melting point around 200 degrees, used for thin metal and has a weak joint.
Rivets
Riveting is a quick and convenient method of fixing 2 or more pieces of material together in a permanent fashion. It is a cheaper alternative to threading. Rivets are used in sheet metal and are available in a wide range of materials such as iron, aluminium, copper as well as low carbon steel and stainless steel.
Adhesives
Gluing is rapidly taking the place of other methods of joining. Technological advances continue but no single adhesive will join all materials.
Drying Adhesives
These adhesives are a mixture of ingredients dissolved in a solvent. white glue and rubber cements are members of the drying adhesive family. As the solvent evaporates, the adhesive hardens. These adhesives are typically weak and are used for household applications.
Contact Adhesives
Contact adhesives must be applied to both surfaces and allowed some time to dry before the two surfaces are pushed together. Some contact adhesives require as long as 24 hours to dry before the surfaces are to be held together. Once the surfaces are pushed together, the bond forms very quickly. contact adhesives are used in strong bonds with high sheer-resistance.
Hot Adhesives
E.g. a hot glue gun
Hot adhesives, also known as hot melt adhesives, are simply thermoplastics applied in molten form which solidify on cooling to form strong bonds between a wide range of materials. These adhesives are popular for crafts because of their ease of use and the wide range of common materials they can join.
Semi-Permanent Methods:
Machine Screws
Machine screws, nuts & bolts provide a convenient method of securing parts. Easily un-done, this temporary method of fixing is suitable for all kinds and combinations of materials.
Self tapping Screws
Are only suitable for thin sheet metal but also plastic. Made from hardened steel, they cut their own thread as they are screwed in.
Knock Down fittings
This type of fastening offers opportunities to make self assembly products, especially large items such as kitchens, bedrooms and other furniture. For such products assembly is through flat pack. This allows:
Easy assembly and dismantling
Fittings can be used with most modern materials.
Can create varied solutions.