Prototyping and Digital Manufacturing: 3D Printing, Plastics and Moulding Processes

Prototypes and Digital Manufacturing

• A prototype is an early example of an object that is manufactured to evaluate certain aspects during the construction phase of a technical project. It can cover anything from a specific element to the entire project.

• Digital manufacturing is a manufacturing process where data from a digital design is transferred to computer-aided manufacturing tools that execute the prototype manufacturing process without the need for human interaction.

• CAD (computer-aided design)

3D Printing

A 3D printer is a machine that can print three-dimensional figures from a computer design.

• Extruder: the part that takes the filament from the coil and deposits the exact amount on the print bed.
• Electronics: these control all the processes in the printer.
• Mechanics: these parts include the motors and mechanisms that move the material and deposit it in the selected spot.

The plastics used in 3D printing are generally ABS (for industrial use) and PLA (for domestic use).

There are three distinct phases in three-dimensional printing: design, slicing and printing.

Types of Plastics

Thermosets

Thermosets are plastics that can be shaped with heat once they have been formed; they cannot be remelted to create different forms.

• Melamine: for wooden boards
• Bakelite: for handles of kitchen utensils
• Polyester resins: for domestic swimming pools

Thermoplastics

Thermoplastics can be melted and formed as many times as needed.

• PET (polyethylene terephthalate): water bottles
• HDPE (high-density polyethylene): containers
• PVC (polyvinyl chloride): windows, pipes
• LDPE (low-density polyethylene): bags, packaging film
• PP (polypropylene): folders, toys
• PS (polystyrene): food packaging
• Others: nylon

Elastomers

Elastomers are very flexible materials that recover their shape and dimensions when external forces stop acting on them. They degrade easily with heat and cannot be remelted once they have been formed.

• Rubber: tyres, football pitches
• Neoprene: immersion suits, orthopedic devices
• Silicones: medical prostheses, joint sealing

Plastic Forming Processes

• Extrusion: used with thermoplastics to obtain long products (pipes, profiles, etc.).
• Injection moulding: melted plastic is injected into a mould. After it is cooled, the mould is opened and the object is removed.
• Compression moulding: used with thermoset plastics. The plastic is placed between two moulds with pressure and heat; the plastic melts and adopts the desired shape.
• Blow moulding: starts with a tube formed by extrusion. Air is blown inside the tube until it dilates and adopts the shape of the mould.
• Vacuum forming: used with thermoplastic sheets that are heated and placed on a mould. The vacuum is then turned on, forcing the sheet to adapt to the shape of the mould.