1.4. processes Flashcards
press forming
sheet metal is clamped over a die of the the product that will determine the final shape of the pressing
a hydraulic press pushes the die into the sheet metal, cutting blades may be included to punch holes into the sheet and trim excess from the edges
the hydraulic die is lowered and the pressed sheet component is removed
the sheet may be placed into further press forming machines for additional pressing where the shape is complex
spinning
a former called a mandrel is put into the chuck
the sheet metal blank is held in place between the mandrel and the tail stock
the roller tool is moved into the blank and rotated with the mandrel, this starts to stretch the metal over the mandrel
the roller tool is moved along the mandrel as pressure is maintained against the rotating blank
the roller tool is moved to the end of the mandrel while still maintaining contact with the blank
this finishes the shape of the product and the product is then removed from the mandrel
drop forging
a die is made from cast tool steel and this is secured to the top of an anvil
a ram is also equipped with a die that resembles a mould
the metal billet to be forged is heated
using tongs the heated billet is placed by an operator into the anvil die and the hydraulic ram is brought down with a force
this makes the hot billed spread around the shape of the die
the ram is lifted and the completed product removed for cooling and finishing
bending
stock metal gets clamped between a matching punch and die
a hydraulic pneumatic or mechanical break holds the sheet
the punch is lowered to bend the material to shape
rolling
stock metal is passed through sets of rollers to reduce the thickness of the material
sand casting
a pattern is made
this is placed in a steel box called a drag
the drag is then filled with sand which is packed in tight around the pattern and levelled
the drag is turned over and a second box called the coper is clamped into position over the top of the drag
the top half of the pattern is placed in with the bottom half
sand is packed into the cope around the runner, riser and pattern
a small depression is made on the surface around the sprue to make a pouring basin
the cope and drag are separated and the stakes and patterns are carefully removed
connecting channels are cut to join the sprue to the pattern cavity and from this to the riser
small metal spikes may be inserted and removed to make vent holes, allowing gases to escape
the molten metal is poured into the pouring basin
it flows down the runner into the cavity, when the cavity is full the molten metal flows up the riser
once cool the sand is removed to reveal the casting and the runner and riser are cut off
die casting
the metal is melted and poured into the mould
this relies on gravity to help to metal flow through the mould
gravity die casting is generally used to make parts that have a thicker or heavies section than pressure or die casting
mig welding
an electric arc is used to create heat which then melts the joint area
a wire electrode also melts and fills the gap between the two pieces being joined
the operator swirls the welding gun as it is moved over the joint to form a continuous bead of weld
tig welding
the electrode does not melt in the process, instead a separate filler rod is used
a gas shield of argon or helium is used to protect the weld area from oxidation
brazing
material to be joined is cleaned and degreased
the two pieces are clamped together and a flux is applied
the joint is heated using an oxy-acetylene torch to a temp of approximately 850 degrees
the brazing rod is applied to the joint area
the brazing spelter will flow along the joint by capillary action to the hottest part
soldering
the metal is cleaned and degreased
the joint area is wired up or clamped
the metal is heated up to the melting point of solder
the solder is then added to the metal
the solder will flow along the joint using capillary action
the metal is cleaned to remove any flux residue
die cutting and creasing
the creasing channel are a raised part on the bed of the machine
these combined with the creasing rule will make a line where the material will be bent
the cutting dies are sharp and will cut out the outline of the net
rubber pads are fixed to the press to help prevent the paper or card sticking as the press moves up or down
vacuum forming
the mould is placed on the bed of the machine, the platen
the platen is lowered to the bottom of the machine
polymer sheet is clamped over the mould and a heater is pulled over the polymer sheet
when the polymer sheet has softened the platen is raised onto the polymer and the heat is removed
the vacuum pump is switched on which sucks the polymer onto the mould
when the polymer is cooled and solidified the platen is lowered and the vacuum is switched off
calendering
heating pellets of thermoplastic so that it melts into a dough like consistency
then extruded between a series of heated rollers so that it becomes squashed and stretched to make it thinner
then finished on the cooling rollers before being chopped into a standard stock sheet size
lamination
a mould or former in the shape of the product is prepared
the mould is coated with a release agent
a top layer of gel coat is applied
fibreglass matting is cut to size and laid over the former
polyester resin is brushed onto the matting and a small roller is used to push out any air bubbles, stippling
these steps are repeated until the desired thickness is achieved
