Plastic Moulding

Injection Moulding-



Extrusion Moulding-
This process is a continuous process used to produce solid and hollow products that  have a constant cross-section.

• Thermoplastic granules are fed from a hopper through a heated cycinder by a rotational screw
• the tapered shape of the screw compacts the plastic as it travels through the the heated cylinder towards the die
• the die determineds the shape of the cross section of the plastic when it is extruded through the die opening
• Extrusion rates vary from 9 to 60 metres p/minute. The thinker the cross section the longer it will take to extrude
• as the extrusion is complete the product passes through a cooling trough which contains cold water
• after cooling the product is cut to specification/ requirements automatically

Vacuum Moulding-
This process is used to manufacture a wide range of thermoplastic products. these products vary in size from food trays to interior vehicle panels

• A desired mould is placed upon a platen (support plate)
• the platen and mould are lowered, Rigid thermoplastic sheet material is then clamped onto an air tight gasket and heated from above
• After the sheet has softened, air is blown uder the sheet to raise it into a bubble shape before the platen is raised bringing the mould into contact with the plastic
• Any trapped air is then removed using a vaccum pump which ensures that the plastic has taken complete shape of the mould
• Once the plastic sheet has cooled to below its freezing point, the air flow is reversed to remove the plastic from the mould
• Once completed the waste material is then cut from the plastic sheets and recycled

Rotational Moulding-
This process is mainly used to manufacture hollow objects such as footballs, road cones and storage tanks

• Moulds are mounted and rotated contnuously by three rotational arms
• Firstly, The moulds are filled with thermoplastic powder, which is measured only to coat the outer edges before closing the mould for the next stage
• whilst being rotated (both horizontal and vertically) the mould is subjected to 230°C - 400°C
• as tyhe mould rotates it's inner surfaces are coated with the powder which turns to plastic with the extreme heat applied. Producing an even thickness of plastic inside the mould
• Whilst still rotating the mould is then moved into a cooling area where it is cooled by air or water jets
• Once cooler enough to retain it's own shape, the products are removed from the moulds and in some cases to prevent distrosion to the shape during final cooling. A jig can be applied, this is often with flat surfaces (eg storage containers)

Polymers

Polymers are long chains made up of induvidual monomers. The raw material used to create polymers is found in crude oil therefore making them a finite resourse.

polymers are widely used from wiring insulator to window frames. This is because polymers have many different properties including

• Good Insulator to Electricity and Heat
• Good Strength to Weight ratio
• Good resistance to atmospheric and chemical erosion
• Low melting points
• Lightweight

There are two types of polymers, Thermosetting and Thermo

Theremosetting polymers

Thermosetting polymers cannot be remoulded once cooled, this is because of the molecular structure of them. This does make them ideal for saucepan handles and kettles ect.
Some examples of thermosetting plastics are.

• Epoxy Resin
• Melamini Formaldehyde
• Polyester Resin
• Urea Formaldehyde

Thermo- polymers

Thermo polymers can be remoulded repeatedly as the bonds in the molecular structure are weak, therfore applying heat to the material makes it maluable

ABS- Acrylonite Butadiene Styrene
CA- Cellulose Acetate
Nylon- Polyamide
PMMA- Poly Methyl Meth Acrylate (aka Acrylic)
PP- Poly Propylene
HIPS- High Impact PolyStyrene
PS- Poly Styrene
LDPE- Low Density PolyEthylene
HDPE- High Density PolyEthylene
uPVC- PolyVinyl Chloride
PVC- (un plasticised flexiable) PolyVinyl Chloride
PET- PolyEthylene Terephthulate
PC- Poly Carbonate

Plastic Additives

Fillers-

Flame Retardants-

Antistatic-

Plasticizer-

Stabilizer-

Mini Chair Project

I Should Never Have Purchased!

Late January I had a fair amount of my Christmas money remaining leaving me perplexed on what to spend my money on. I wanted to find something that was not too expensive, but at the same time something that would not be forsaken and left at the back of the cupboard after a week of use.

10 Inch Touchscreen Android Tablet

After searching the web I came across an android tablet. the tablet was a 10 Inch Touchscreen Epad tablet. On initial glance the aesthetics of the product looked familiar to the Apple tablet the Ipad. The functionality of the product also seemed pleasing as it was described as having a crisp touchscreen display, built in mic and quality sound for a tablet of its type. All of these features draw me away from the fact that I was buying a cheap copy of the Ipad running off of a poor quality Android Operating System.

When I received the product the aesthetics were simply of the quality I paid for...cheap. And as of the "crisp" touchscreen the device retained...well it was extremely resistive and had lost its crisp touch it was once described of having. Upon the issues with the display, the ergonomics of the device were not great either. Not the physical ergonomics but instead the practicality and how easy it was to operate. For example the battery life did not exactly allow you to use it often as it did not last any longer than 2hrs at most.

In my opinion the device was useless and within a month of getting it, it discovered the dark fate of the cupboard. Ultimately by trying to save money on a tablet I instead wasted money on a tablet that's functionality was of suitability for a child's toy.