Polymer Processes Flashcards
Calendering process
Pallets of thermoplastics are heated so that it melts to form a like consistency.
It is then extruded between a series of heated rollers so that it becomes squashed and stretched to make it thinner.
It is then finished on calling rollers.
It is then chopped into standard stock sheet sizes, all rolled up for storage.
Extrusion process
Polymer granules are loaded into the hopper.
The arcomedian screw moves the polymer granules past heaters.
The heat is soften the polymer.
When sufficient polymer has melted, the hydraulic ram pushes the Archimedean screw forcing the polymer through still die. The shape of the diet terms the shape of the extrusion.
The extrusion may be supported by rollers as it leaves the die and is called by cold water air.
The extrusion is then cut to the desired length.
Rotational moulding process
Polymer powder or granules are loaded into a mould which is clamped and sealed.
The mould is transferred to an oven where it is heated and the mould is rotated slowly around two axis and as the polymer is heated it coats the inside of the mould.
Once the polymer has achieved the correct thickness, the mould is called Usually a fan or water is used to line when the polymer has solidified. The part will shrink slightly allowing it to be removed.
Blow moulding process
The polymer is fed in into the hopper.
An arch comedian screw pull the polymer through a heated section which melts it.
The melted polymer is extruded as a tube which is called a parson.
The mould sites close around the parson and air is injected into the mould forcing polymer to the side.
The polymer is allowed to call for a few seconds the mould open and the finished bottle is ejected
Vacuum forming process
The mode is placed on the bed of the machine which is called the Platton. The Platton is lower to the bottom of the machine.
Polymer sheet is pumped over the mould and a heater is pulled over the polymer sheet.
When the polymer sheet has softened. Platton is raised into the polymer and the heat is removed.
The vacuum pump is switched on which sucks the polymer into the mould.
Once the polymer has called and returned to a solidified state the plate is lowered and vacuum switched off.
The mould is removed and, excess polymer is trimmed off
Thermoforming process
Very similar process to vacuum forming except there is an additional mould that is pressed into the surface of the polymer sheet at the same time as the vacuum is applied stuck in the polymer down on the mould below. The two moles trap the softened polymer in between them giving extra detail to the moulding.
Injection moulding process
Thermoplastic granules according to the hopper.
A screw thread is rotated by motor which pulls the granules through the chamber and past electric heaters.
The heat has melt the polymer.
When sufficient charge of polymer has melted and formed at the end of the screw, a hydraulic ram forces the screw thread forward. This injects the polymer into the mould.
The mould is water cold which enables the molten polymer hard and quickly.
The mould opens and ejector pins push morning out.
Excess mat trimmed off the moulding. Warmers or may be used to maintain the dimensional accuracy of the moulding while it calls and hardens
Compression moulding process
A slug of pre-weed thermostat polymer is inserted into preheated malt.
The moles are closed and hydraulic pressure is applied. The pressure insures that the polymer takes shape of the mould.
The mould remain closed while cross-linking takes place and the thermostat.
When the moulding has cured, the machine opens and the product is removed.
Access polymer known as flash is removed.
Lamination process
A mould or former in the shape of the product is prepared this may be made from timber manufactured for such as plywood or high density foam.
The mould or form is coated with a release agent such as rack or PVA or is covered with parcel tape
A top layer of gelcoat is applied. The gelcoat is coated of polyester resin offered mixed with a pigment to give to the moulding. The resin might also have additives included to prevent degradation from UV. It using CRP when curing takes place in a specialist oven known as an auto cave.
Bible matting is cutter size and laid over the former. Polyester region is brushed into the matting and a small roller is used to push out any air bubbles that may form and to smooth out the matting. The matting is available in a range of stock forms including chop strand woven and tissue which is a fine grade matting for covering the surface. This is repeated until the thickness is achieved and matting is used on the top layers. Then the GRP is allowed to set
Vacuum forming scale
Small scale batch as time required to make the moulds makes it not cost-effective for one of manufacture
Thermoforming scale
Industrial
Calendering scale
Continuous
Line bending scale
One off or limited batch
Injection moulding scale
Large scale mass or continuous production
Blow moulding scale
Continuous
