Rotation moulding:
Rotation moulding is a process mainly to create hollow shaped products such as balls. The machine works by having 3 separate arms that rotate around a central point, these stop at different stages, otherwise known as processing points. Moulds are attached to these arms and are rotated throughout the moulding process. The only times in which they are not being rotated is the first stage (where the moulds are filled with the plastic granules) and the final stage (where the product is removed).

The stages of Rotational moulding:
1- The first stage of rotational moulding is simply filling the mould with thermoplastic granules/pellets
2- The second stage would consist of transferring the mould into an oven chamber where the plastic is heated to mould to the shape of the cavity
3- The machine then rotates with heat, after this the mould is put in to a cooling chamber where it is cooled by cold air or jets of cold water.
4- The final stage is when the product has been cooled; it is removed from the mould as a complete product.

Extrusion moulding:
This product can be compared to toothpaste being squeezed from the tube. It is a continuous process that can be used to create solid and hollow products that have the same cross section throughout. It cannot create a shape with an alternating cross section as the die is one solid shape.

The stages of Extrusion moulding:
1- Thermoplastic granules are put into a hopper which are then fed through the machine by a rotating screw that runs throughout the whole machine, this runs through the heating area, where when the plastic granules run through it, are melted down into liquid.
2- The plastic granules are given a plasticiser after being heated, which adds a flow property making it easier to flow through the die
3- As the plastic flows through the mould; it is cooled by water coolers so that it comes out the other side as a hard, solid shape.

Injection moulding

Injection moulding is a manufacturing process for producing parts by injecting material into a mould. Injection molding can be performed with a number of different materials, including metals, glasses and most commonly thermoplastic and thermosettingplastics. Material for the part is put into a heated barrel, mixed, and forced into a mould  where it cools and hardens to the shape of the mould. 
What is a 'jig' and what is the purpose of one?
A jig is a type of custom-made tool used to control the location and/or motion of another tool. A jig's main purpose is to provide a stable working envrionment for the product making them able to accurately repeat a product. A jig is often confused with a fixture; a fixture holds the work in a fixed location. A device that does both functions (holding the work and guiding a tool) is called a jig.

Thermoplastics:
There are no links inbetween the polymer chains of thermoplastics, this means they can be recycled as they can be heated and re-moulded over and over

Thermosetting plastics: They can not be re-heated and re-moulded because the polymer chains have links in between each one making it a rigid structure


Properties of plastics 
Good thermal and electrical insulators 
Good straight against weight ratio 
Good resistance against chemical and atmospheric erosion (doesn't decompose)
Low melting point
Available in wide range of colours and transparency
Two main categories thermoplastic and thermosetting plastics


Ways to improve properties of plastics
Fillers: fillers are used to bulk up plastics and means that they can get a more plastic without using up loads of crude oil
Flame retardants: This is used to help reduce the risk of combustion
Anti static agents: Reduces the effects of static charges (Can be used in carpets)
Plasticisers: makes material less brittle and improves the flow properties
Stablisers: reduce the effect the ultra violet light has upon the object so that the colour of the plastic isn't lost (Outdoor benches or Window frames)


Types of thermoplastics
ABS -  Acrylonitrile butadiene styrine
CA - Cellulose acetate
NYLON - Polyamide
PMMA - Acrylic
PP - Polypropylene
HIPS - High impact polystyrene
PS - Polystyrene
LDPE - Low density polyethylene 
HDPE - High density polyethylene
uPVC - Polyvynal chloride 
PVC - Unplasticated flexible polyvynal chloride 
PET - Polyetheylene terepheluate
PC - Polycarbonate 

Types of thermosetting plastics

Epoxy resins: surface coating, adhesives
Malamine formaldehyde: table ware, laminate 
Polyester resins: castings
Urea formaldehyde: electrical fittings, adhesives

Closed loop recycling:

Closed loop recycling is where a waste or byproduct of a process or product is used in making another product. E.g., recycling waste newspaper to make paper-board or other types of paper.

I should never have purchased... Assignment 1

A few weeks ago my dad bought two airsoft rifles off of a website, designed by a company called G&G, as a present for my 16th birthday and for him to use when he goes airsofting.

It was reviewed as a 'new revolutionary piece of kit that every airsoft player will want on the field' and 'is considered perfect for indoor and outdoor encounters'. admittedly the weapon has a short body with a long outer barrel for accuracy, but the long barrel hinders movement within close quarter environments and just isn't what was advertised on the website.


This weapon is a replica of the American armed forces M4/M16 and is aesthetically pleasing in the sense that it looks exactly like the real fire arm, but with it being aesthetically pleasing, there comes a lack of function and ergonomics some of which make the gun unsuitable for certain people.
Every time I come to use the gun, it is extremely uncomfortable as the grip you use to operate the gun is really small and doesn't have any finger grips. Also when using the gun in competitions I've either dropped the gun or I have had to hold it in a way which wasn't comfortable for me.
Another disadvantage of this gun is that is it not suitable for left handed shooters, the magazine release is only on the right side and so is the trigger safety. This means that a left handed shooter would not be able to access these parts of the gun without putting it down and using them, which shouldn't happen as it means when on the battlefield the shooter would take a lot longer than someone who was a right handed shooter, using this exact gun.
One thing the designer should have done is make this a little more ergonomically friendly!