AS - Graphics / Resistant Materials - Welding

This covers welding:

  • Plastic
  • Metal
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AS-Level ­ Resistant Materials ­
Welding
Plastic Welding
Plastic Welding or heat sealing as it is also known as is the process of placing 2 or more parts
together via melting of the 2 plastic. It is one of the primary processes of joining plastics.
How Is It Done?
There are many different types:
Hot Gas Welding:
A specifically designed heat gun called a hot air welder produces a jet of hot air that softens both
parts to be joined and a plastic filler rod, all of which must be the same or a very similar plastic BUT
when welding PVS to acrylic that is the only exception. This is commonly used for manufacturing
smaller items such as water tanks and heat exchanged.
Freehand Welding
The jet of hot air from the welder is played on the weld area and the tip of the weld rod at the same
time. While the rod softens its pushed into the join and fuses the parts, this process may be slower
than the others but it can be used in almost any situation
Speed Tip Welding
The plastic welding, which is similar to an soldering iron in appearance is fitter with a feed tube for
the plastic weld rod. The speed tip heats the rod and the substrate, while at the same time it presses
the molten weld rod into position. With some types of plastic such as polypropylene, the melted
welding rod must be "mixed" with the semi-melted base material being fabricated or repaired.
Speed tip welding method is a much faster welding technique and with practice can be used in tight
corners.
Extrusion Welding:
This allows the application of bigger welds in a single weld pass. It is preferred technique when
joining material over 6mm thick. Welding rod is drawn into a miniature hand held plastic extruder,
plasticized, and forced out of the extruder against the parts being joined, which are softened with a
jet of hot air to allow bonding to take place.
Made By Richard Francis - http://getrevising.co.uk/members/richard_francis1

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Contact Welding:
Basically the same as spot welding except the heat is supplied with conduction of the pincher tips
instead of electric conduction. Two plastic parts are brought together where heated tips pinch them,
melting and joining the parts in the process.
Hot Plate Welding:
This technique is used to weld larger parts, or parts that have a complex weld joint. The two parts to
be welded are placed in the tooling attached to the two opposing platens of a press.…read more

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This technique requires one part to be transmissive to a laser beam and either the other part
absorptive or a coating at the interface to be absorptive to the beam. The two parts are put under
pressure while the laser beam moves along the joining line. The beam passes through the first part
and is absorbed by the other one or the coating to generate enough heat to soften the interface
creating a permanent weld.…read more

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