TPR: 3ºESO. Departamento de Tecnología. IES Nuestra Señora de la Almudena Mª Jesús Saiz

UNIT 4: PLASTICS. 3D DESIGN AND PRINTINGPLASTICS OR POLYMERS

Plastics, also called polymers, are chemical substances that can be molded by heat or pressure and whose main component is carbon. These polymers are large clusters of molecules called monomers and that repeat and bind together.

They come from oil and natural gas.

1. FeaturesWhen they are heated they are elastic and flexible, which allows them to shape. Resistant to corrosion and chemical compounds. Thermal, electrical and acoustic insulators. Easy to work and mold. Low density. They are usually waterproof.

2. Main components of plasticsBase matter: the monomers or base molecules are mainly composed of carbon and come from petroleum or natural gas. Loads and additives: they are mineral or vegetable substances that are added to modify and improve the properties (textile fibers, glass fibers, etc.) Dyes and pigments: they are mineral or vegetable substances that give color to the base material. Accelerators: accelerate the process of formation of plastics.

3. Types of plastics:Thermoplastics: are plastics that are softened by heating and can be formed and melted (reshaped) as many times as we like. This is because their polymers have weak bonds. They are, therefore, recyclable plastics.

Thermoset: the polymer chains of thermoset plastics criss-cross to form networks. Because of this bond, the plastics can be shaped using heat; however, once they have formed, they cannot be re-melted to create different forms.

Elastomers: are very flexible materials that recover their shape and dimensions when external forces stop acting on them (elasticity). They degrade easily with the heat and cannot be re-melted once they have been formed.

The molecules form a network that can contract and stretch in countless.

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C

TPR: 3ºESO. Departamento de Tecnología. IES Nuestra Señora de la Almudena Mª Jesús Saiz

4. Most important plastics:Thermoplastics:

Considering separation and recycling, plastics are classified from number 1 to 7, (indicated in the lower part of the object); This classification allows to identify, separate, reprocess and form plastic objects.

NameRecycling

number Featured properties Image

PET: polyethylene terephthalate

Light, fall resistant, transparent

PE: polyethylene

HDPE: high density Rigid, transparent

LDPE: low density Soft and light

PVC: polyvinyl chloride Waterproof

PP: polypropylene Flexible, chemical resistance

PS: Expanded polystyrene (porexpan)

Chemical, mechanical and electrical resistance

Methacrylate Transparent

Teflon Non-stick, sliding

Naylon Waterproof, flexible

Cellophane Adherent, transparent

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TPR: 3ºESO. Departamento de Tecnología. IES Nuestra Señora de la Almudena Mª Jesús Saiz

Thermoset:

Elastomers:

5. Environmental Impacts and Contamination Plastics are not biodegradable, which means they do not degrade as time passes by. Each plastic object may remain in the environment for up to 1000 years. 280 million tons of plastic are thrown in the trash each year. This is a problem, as the recycling process can be expensive and releases greenhouse gases. When recycling, plastics are separated by different groups, and they are washed, crushed, melted, and form new pieces.

Recommendations:

Reduce plastic consumption

Reutilize plastic bags and objects

Separate plastics and put them in the yellow containers

Improve existing recycling program

6. Polymer Molding:Plastic materials are placed in dust or granulated form. Depending of what its application will be, the plastic is submitted to different molding techniques.

Name Featured properties Image

Bakelite Mechanical resistance, insulating, moisture resistant

Melamine Insoluble, chemical resistance

Polyester resins Resistant to moisture and solvents

Polyurethane Chemical resistance, and wear

Name Featured properties Image

Rubber Elastic, insulating

Neoprene Hard and tough

Silicone Moldable and ductile

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TPR: 3ºESO. Departamento de Tecnología. IES Nuestra Señora de la Almudena Mª Jesús Saiz

Pressing: granulated plastic is introduced into the bottom part of a mold. The mold clamps shut and heat is applied. The hardened shape is now removed from the mold.

Molding by Injection: the plastic material is introduced, heated and injected inside of a mold where it hardens and takes its form. When it cools, the mold is opened and the plastic figure is removed.

Extrusion Blow Molding: a heated polymer is introduced into the mold and pushed by hot air. The plastic then pushes against the walls and empty shapes are form. Ideals for things like bottles.

Thermoforming: Consists of heating a thermoplastic sheet until it becomes bland and placing it onto a mold. It then takes the shape of the mold.

Calendered: The plastic passes through different cylindrical wheels that flatten the plastic, and make it ideal for uses such as transparent film for storing foods.

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Mold

Air blows

Dose of plas2c Plas2c adap2ng

Interior presure in the plas2c

Crea2on of molded object

Precision mold

Feeding plas2c system

Injec2on

Hea2ng chamber

TPR: 3ºESO. Departamento de Tecnología. IES Nuestra Señora de la Almudena Mª Jesús Saiz

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3D PRINTING Thermoplastic materials can be utilized in 3D printing due to how easily they change their shape with heat. The plastic has the shape of wire and is deposited in layers.

7. Plastics used in 3D Printing:ABS (acrylonitrile butadiene styrene) It is a very hard, resistant, and rigid plastic. It results in high quality objects. Heating it may result in toxic gases, which is why it should be printed in ventilated rooms.

PLA (polylactic acid) A plastic created using natural materials such as corn or sugar cane. Does not emit harmful gases when being printed.

The quality of the plastic is inferior to ABS.

Filaflex A flexible plastic. Can print shoes, phone cases, etc.

8. 3D Printing ProcessThe steps we have to follow are:

3D Design: done using programs on the computer. We must always save or export our archive in a .stl format, which is the format the printer works with.

Laminate: the computer programs calculate the sheets of material that they must use to create the object. They change the file to the .gcode format which the printer understands. 3D Printing: the .gcode file is copied into a memory card and taken to the 3D printer.

9. Design Programs for 3D PrintingMost 3D design programs can be classified by two general groups which are:

CAD Program (Computer Assisted Design) These programs are utilized in industrial design, mechanical design, architecture, aerospace industry, and engineering. These programs create precise technical designs. These programs use solids (solid pieces) to create 3D models, which is different from animation programs that use surfaces. Some of the most important CAD programs are:

• AutoCAD • SolidWorks • Catia • FreeCAD

3D DESIGN LAMINATE 3D PRINTING

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Extrusor

TPR: 3ºESO. Departamento de Tecnología. IES Nuestra Señora de la Almudena Mª Jesús Saiz

3D Modelling Programs or Animation. Programs of artistic design used for animation and video games. In these softwares you work with surfaces. In other words, you design the exterior of objects with very thin layers or skins. To convert these surfaces into solids you must create groups or components. If this is not done, the objects will be hollow. Some of the programs include:

• SketchUp • Blender • 3D Studio Max

10.Laminate

We will use the program Repetier Host. This program will convert our .stl file to the .gcode format so the 3D printer will be able to print it.

The steps we should follow are:

Open the .stl file in Repetier-Host

Preparing the design for printing:

The limitation of 3D printers is that they can’t print into the air. When a design has areas in the air, we say it has overhangs and it needs support, brackets, or scaffolding in order to successfully print it. That is why we must place the object in the optimal position for printing. We will use the Rotate Object option in order to place the design in a position will there will be no parts in the air.

Defining the printing parameters:

We must select the option: Slicer

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TPR: 3ºESO. Departamento de Tecnología. IES Nuestra Señora de la Almudena Mª Jesús Saiz

Plastic type and color: in our example it is PLA plastic and black color

Density and Infill Pattern: We must decide on the density and the infill in percentage. We can also select the pattern it will be filled in.

Laminate or slice the 3D Model

We click on the Slice option with Slic3r. The program then creates a file with the extension .gcode We can then also see how the 3D printing process will go in the preview.

Save the .gcode file It is recommended to save the file in an SD card that can be used on the printer later.

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