KEY CONCEPTS OF TEXTILES

Both natural and synthetic fibres can be woven to make a variety of textiles.

Natural fibres may come from animal sources (wool, silk), plant sources (cotton, linen, esparto, bamboo) and mineral sources (gold, siver, and cooper wires).

Stnthetic fibres, such as nylon, polyester, rayon and Licra, are plastic materials.

KEY CONCEPTS OF MODIFICATION TECHNIQUES

MODIFICATION TECHNIQUES use tools and machines to make changes to prefabricated materials, such as sheets, bars or mouldings.

Examples of these techniques include: MEASURING  ⇒ DRAWING MARKS AND LINES ⇒ CUTTING ⇒ DRILLING ⇒ FILING AND SANDING ⇒ JOINING

KEY CONCEPTS OF PLASTIC FORMING TECHNIQUES

Various industrial techniques can be used to manufacture plastic products, such as: EXTURSION, CALENDERING, VACUUM FORMING and MOULDING.

The main techniques for using moulds are as follows: BLOW MOULDING, INJECTION MOULDING and COMPRESSION MOULDING.

KEY CONCEPTS OF THE CLASSIFICATION OF PLASTICS

1. THERMOPLASTICS are usually made from petroleum products. The most common are:
- Polyethylene terephthalate
- High-density polyethylene
- Polyvynyl chloride
- Low-density polyethylene
- Ploypropylene
- Moulded polystyrene
- Expanded polystyrene

2. THERMOSETTING PLASTICS are made from petroleum products. They include:
- Polyurethane
- Bakelite
- Melamine
- Polyester resins

3. Typical ELASTOMERS include rubber and neoprene.

KEY CONCEPTS OF PLASTIC MATERIALS

1. Plastics consist of long chains of atoms which are mostly composed of carbon.

2. Plastics can be classified into natural and synthetic.

3. The process of manufacturing plastic is called polymerisation.

4. Plastic materials are resistant, insulating, ductile, malleable, impermeable and light.

5. There are three types of plastic recycling processes: chemical and mechanical recycling and energy recovery.

8. ELECTRONICS (8.1)

Electronics involves the study of circuits that modify the intensity, direction or properties of electric currents.

8.1. ELECTRIC COMPONENTS

Here, we'll analyse the most common electronic components.

Fixed resistance or resistor 

A fixed resistance or resistor opposes the flow of electric currents. Its value, which we measure in ohms is indicated by a code of colours and numbers.
The first two stripes are replaced by two numbers, according to their colour.The third stripe indicates the number of zeroes that we must add to the previous figure.The fourth stripe indicates the tolerance or the maximum deviation from the theorical value.

Variable resistance or potentiometer
The value of a variable resistance or potentiometer can be adjusted between zero and the maximum value specified by the manufacturer.
Resistance that depends on a physical factor
There are two types of resistances that depend on a physical factor:
  -Resistance that depends on temperature, that is called a thermistor. There are  two types of thermistors:
-Negative temperature coefficient (NTC):The resistance decreases as the temperature rises.
-Positive temperature coefficient (PTC): The resistance increases as the temperature rises.
-LDR: Resistance that varies according to the amount of ligth received.The resistance decreases as the amount of ligth increases. These devices ,like potentiometers, are often used in security systems, where they are parts of sensors.
Capacitors
A capcitor can store electrical energy from a battery and then use it to power a ligth bulb until the charge is totally depleted.
Capacitors are componets that can store an electrical charge.
The value of a capacitor indicates the charge in volts that it can store.This is measured in farads (F).
Diodes
A diode is an electronic component made from semiconductor materials.It only allows electric current to flow in one direction. A diode has two electrodes: an anode(A) and a cathode (K).
A LED (ligth emitting diode) only gives off ligth when an electric current flows through it.

7. ELECTROMAGNETIC CONTROL SYSTEMS

An electromagnetic control system activates the various parts of a machine, at the right moment and for the right amount of time, ensuring that the machine functions properly.

7.1. Cam switch controller

The device on the side of the pulley in the picture abovee is a cam. The shape of this device allows us to control the moment and duration of an activity.

 

7.2. Limit switches

There are two types of switches:

-Normally open
-Normally closed