Chapter 12 Observatory Grade 10 Science Text Notes

1. The Technological
World
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2.  Humans have always invented and
produced objects that have helped them
survive and live more comfortably.
 Today, technology is fundamental to the
entire process of designing,
manufacturing, maintaining, and repairing
objects and systems.
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3. Chapter 12
Manufacturing Technical Objects
 There have been many inventions that have
improved the quality of our lives. We will refer
to these inventions as technical objects.
 A number of issues must be considered when
designing and manufacturing these technical
objects.
 In this chapter we will look at:
1. Materials and their properties
2. Technical Drawings
3. Manufacturing of the objects
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4. 1. Materials
 All technical objects are made of
materials
 A technical object to be must be designed
to withstand the constraints and
deformations that it experiences during its
normal use.
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5. 1.1 Constraints and Deformations
 Constraints are the different types of
stresses that a material experiences as a
result of the forces applied to it.
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7.  Depending on the constraint, the material
can undergo three types of deformation.
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8. 1.2 Properties
 The mechanical properties of a material
determine how it will deform when
subjected to one or more restraints.
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9.  Other properties of a material are listed
below
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10. 1.3 Degradation and Protection
 The degradation of a material is the
decline in some of its properties due to the
effects of the surrounding environment.
 The protection of a material is the
application of procedures that prevent or
delay its degradation.
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11. Checkup
 Observatory: The Environment
Page 418, Questions 1 and 2
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12. 2. Categories of Materials and
their Properties
 Let’s have a closer look at the following
materials and their properties:
1. Wood and Modified Wood
2. Ceramics
3. Metals and Alloys
4. Plastics
5. Composites
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13. 2.1 Wood and Modified Wood
 Wood is a material obtained by harvesting
and processing trees.
 Hardwood comes from deciduous trees
such as maple, oak, and birch
 Softwood comes from coniferous trees
such as spuce, pine and fir.
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14. Properties of Wood
 The mechanical properties depend on the type
of wood and vary due to:
1. The species of tree
2. The speed of growth
3. The water content of the wood
 Other properties of wood that may influence
the choice of this material include:
1. Aesthetic appeal
2. Hardness, elasticity, resilience, and toughness
3. Low thermal and electrical conductivity
4. Ease with which it can be worked
5. Its colours
6. Its lightness relative to its strength
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15. Modified Wood
 Modified wood is treated wood or wood
made from wood mixed with other
substances.
 Common products include plywood,
particle board and fibreboard
 These are sheets, chips, or fibres of wood
that are glued together in sheets.
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16. Degradation and Protection of Wood
 Unprotected wood can degrade swiftly.
 Since wood is an organic substance, many fungi,
microorganisms, and insects can infest the wood, feed
off it and cause it to rot.
 Wood can be painted, stained, varnished or treated with
other protective coatings to help prevent its deterioration.
 Treated wood is made resistant to rot by:
 Dipping it in an alkaline solution containing copper. This
wood usually has a greenish colour.
 Heating it to a high temperature.
 Some woods, such a cedar, have a nature resistance
to rot.
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17. 2.2 Ceramics
 A ceramic is a solid material obtained by
heating inorganic matter containing
various compounds, usually oxides.
 When the raw material is heated, the
water evapourates, and the bonds
between the constituent compounds are
rearranged. A ceramic is always solid at
room temperature.
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18.  Traditionally, most ceramic objects were
made out of clay and sand. Sand is used
for making glass.
 Although other materials are now used,
clay and sand are still widely used as they
are both plentiful and inexpensive.
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19. Properties of Ceramics
 The properties of ceramic objects vary with the
raw material and the method of baking.
 The following properties make ceramics a good
choice for many objects:
 Low electrical conductivity – used as insulators
 High degree of hardness – used as building materials
and cutting tools
 Heat resistance and low thermal conductivity – dishes
and cookware as well as thermal insulators
 Resistance to corrosion – used in ducts for fumes or
water
 Fragility – most are very fragile, but some can be
made so resilient they are used in engines
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20. The Degradation and Protection of
Ceramics
 Although ceramics are generally very durable,
some acids and bases can have a degrading
effect on them
 Archeologists have found ceramic pieces that
are thousands of years old and are still in
remarkably good condition.
 Glazes can be used to protect the ceramics
 A thermal shock (a sudden change in
temperature) can cause damage to a ceramic
object.
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21. 2.3 Metals and Alloys
 A metal is a material extracted from a
mineral ore. Metals are usually shiny in
appearance and are good conductors of
heat and electricity.
 The pure metal is rarely used.
 An alloy is a mixture of a metal with one
or more other substances, which may be
metallic or nonmetallic. The mixture of
materials results in more desirable
properties.
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22.  There are two main types of alloys:
Ferrous alloys whose main component is
iron.
Nonferrous alloys whose main component is
a metal other than iron
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24. The Degradation and Protection of Metals
and Alloys
 The main cause for metal and alloy degradation
is oxidation, where the material reacts with
oxygen. This is commonly referred to as rusting.
 The material can be protected by coating it with
a substance that isolates it from the oxygen in
the air:
 Metallic coatings: zinc, chrome, gold, silver, nickel,
aluminum, lead
 Other coatings: paint, enamel, grease, resin
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25. Techniques That Enhance the Properties of
Metals and Alloys
 Steel heat treatments are methods of
enhancing certain mechnical properties of steel
through periods of heating.
 These methods include:
 Quench hardening – hardens the steel
 Tempering – hardens the steel
 Annealing – returns the original properties by
removing the stress created by deforming (welding)
 All of these methods work by rearranging the
crystals within the material
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27. 2.4 Plastics
 Plastics are made from fossil fuels
(petroleum and natural gas)
 Monomers are extracted from the fossil
fuels and are arranged into long chains
called polymers.
 Plastic is a material made of polymers, to
which other substances may be added to
obtain certain desirable properties.
 The invention of plastics lead to a
revolution in world of materials
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28. Types of Plastics
 A thermoplastic is a plastic that becomes soft
enough when heated to be moulded or
remoulded and that hardens enough when
cooled to hold its shape.
 Most plastic objects are made of this type.
 Most thermoplastics can be recycled
 A thermosetting plastic is a plastic that
remains permanently hard, even when heated.
 Often harder and more resilient than thermoplastics
 Include melamine and polyesters
 Cannot be recycled in Quebec
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29. The Degradation and Protection of Plastics
 Plastics tend to degrade over time. This
process is usually slow, but can be
detected as cracks and changes in colour
appear.
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30. 2.5 Composites
 A composite is formed by combining materials
from different categories to obtain a material
with enhanced properties.
 A composite has two main parts: the matrix and
the reinforcement.
 The matrix is the body of the material. It
surrounds and supports the reinforcement and
gives the object its shape.
 The reinforcement is inserted into the matrix to
strengthen the object.
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32. The Degradation and Protection of
Compsites
 The degradation of composites usually
takes one of two forms:
1. The deformation or fracture of the matrix or the
reinforcement.
2. The loss of adherence between the matrix and
the reinforcement.
 The speed of degradation depends on
the type of matrix and reinforcement and
the conditions of use.
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33. Checkup
 Observatory: The Environment
Page 418, Questions 3 to 6
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34. 3. Technical Drafting
 Before a technical object can be
manufactured, its shape and dimensions
must be determined. A technical drawing
must be created.
 Technical drawings can be made by hand
or on a computer.
 To understand these drawings, we must
be able to recognize and analyze different
projections.
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35. 3.1 Projections
 A projection is the representation of a
three-dimensional object on a two-
dimensional surface.
 Two of the most commonly used
projections are:
1. isometric
2. multiview.
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36. Isometric Projections
 A drawing is an isometric projection if the
lines representing the length, width, and
height make angles of 60° or 120°.
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37. Multiview Projections
 In a multiview projection, each face of the
object is drawn separately looking at it
from straigh on. Usually only the top, front
and right side of the object are illustrated.
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38.  Isometric projections show the object in
perspective. It represents the three
dimensions of the object in a single
drawing.
 Multiview projections usually provide
greater detail without distortion.
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39. 3.2 Engineering Drawings
 A general arrangement is a technical
drawing representing the overall
appearance on an object.
 It usually includes the top, front, and right
side multiviews as well as an isometric
projection drawn to scale.
 The general arrangement will also include
a title block showing important
information about the object
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41. Exploded Views
 An exploded view is a drawing in which
the various parts of the object are
separated from one another so as to more
easily visualize the componet parts of the
object.
 The drawing will use an isometric
projection drawn to scale.
 The is accompanied by a list of parts
indicating their names and the number of
each part required.
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43. Detail Drawings
 A detail drawing is a drawing specifying
all of the relevant information for
manufacturing a part. It is almost always
drawn to scale.
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44. Dimensional Tolerances
 Since machines, tools, instruments, and
the operators of machines are not perfect,
the manufactured parts may be slightly
different from the dimensions indicated on
the drawing.
 A dimensional tolerance is an indicator
of the maximum acceptable difference
between a specified measurement and the
actual measurement on the finished
object.
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45.  If the dimensional tolerance applies to all
of the parts on a diagram, it may be
indicated in the title block.
 It can also be applied to a single part and
indicated as shown in the diagram.
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46. Functional Dimensioning
 The functional dimensioning of a
drawing specifies the information required
for the object to work.
 For example, the play required for a blade
to slide freely in a utility knife is shown as
the space between the blade and the
guide.
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48. Developments
 A development is the representation of
the surface area required to make a part
by bending.
 Sheet metal is often used to manufacture
a technical object. The development
shows the surface area of the material as
well as the lines where the sheet will be
bent.
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50. 3.3 Diagrammatic Representations
 A diagram is a simplified representation of an
object, a part of an object, or a system.
 Diagrams are used to help explain an object’s
operating principals as well as any other
characteristics that must considered during the
manufacturing process.
 Depending on the type of information that a
drafter wishes to display, one of the following
common diagrams will be chosen:
 Design Plan
 Technical Diagram
 Circuit Diagram
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51. The Most Common Types of Diagrams
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55. Standardized Symbols In Diagrams
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56. Checkup
 Observatory: The Environment
Page 419, Questions 7 to 10
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57. 4. Manufacturing: Tools and
Techniques
 Once the materials have been choosen and the
plans have been drawn, the object must be
manufactured.
 Manufacturing is a series of operations
resulting in the creation of a technical object.
 The various steps in the manufacturing of an
object require the use of various instuments.
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58.  A tool is and instrument used in the
manufacture of an object.
 A hand tool is powered by human force.
 A machine tool is powered by forces
other than human.
 The manufacturing process is usually
divided into three parts:
1. Measuring and laying out the parts
2. Machining the parts
3. Assembling and finishing the parts
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59. 4.1 Measuring and Laying Out
 The information needed for the
manufacturing of an object can be found
in the detailed drawings of the object, or
on its manufacturing process sheet.
 The manufacturing process sheet is a
document describing a series of operation
to perform in the manufacturing of a given
part and listing the materials and tools
required.
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60.  Measuring out is the act of determining
the size or position of a marking.
 Laying out is the act of tracing markings
or reference points onto a material.
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61. 4.2 Machining
 Machining consists of shaping a material
into a desired configuration.
 The first step in machining a part is to cut
it out roughly into its approximate shape.
 The most commons techniques used in
this step are cutting, drilling, tapping,
threading, and bending.
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62.  Cutting consists of giving a material a desired
shape.
 Drilling consist of making a hole in a material.
 Tapping is a machining technique in which
screw threads are formed inside holes drilled
into a material.
 Threading is a machining technique in which
screw threads are formed around a rod.
 Bending is a machining technique in which a
material is curved into a certain shape.
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63. Inspection
 Throughout the machining phase, the
parts are measured and inspected to
ensure that they match the required
specifications.
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64. 4.3 Assembling and Finishing
 Assembling is a set of techniques by which
various parts are united to form a complete
technical object. Techniques used for
assembling include: nailing, screwing, bonding,
riveting, bolting, and welding.
 Finishing is a set of techniques that complete
the manufacture of the parts of a technical
object. The finish protects the materials from
the elements and enhances the appearance of
the object. Finishing techniques include:
painting, vanishing, staining, and polishing.
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65. Checkup
 Observatory: The Environment
Page 420, Questions 11 to 14

66. Review
 Observatory: The Environment
Page 421, Review Questions A to D
Credits
 All images are from:
Observatory: The Environment
Editions du Renouveau Pedagogique Inc