Manufacturing Technical Objects Flashcards
When manufacturing objects, we must consider many aspects.
What constraints will the object be subject to?
(Constraints are stresses than an object must endure)
Will it deform in any way?
Do the materials used need to have specific properties?
(depending on the intended use of the object)
Do we need to condition the materials so they survive longer?
Types of constraints
Deflection, Compression, Tension, Torsion and Shearing
Compression
A material subjected to forces that tend to crush it is undergoing compression.
Symbol: –> <–
Compression ex.
- hands squeezing a wet sponge
- a foot crushing a can
Tension
A material subjected to forces that tend to stretch it is undergoing tension
Symbol: <—– ——>
Tension ex
Copper stretched into wire
Two teams in a tug of war
Torsion
A material subjected to forces that tend to twist it is undergoing torsion
Symbol: recycle circle
Torsion ex
An earthquake twisting a bridge
Hands wringing a wet towel
Deflection
A material subjected to forces that tend to bend it undergoing deflection
small arrow down BIG ARROW UP small arrow down
Deflection ex
A fish bending a fishing rod
Clothes weighing down a clothesline
Shearing
A material subjected to forces that tend to cut it is undergoing shearing
half arrows towards eachother
Shearing ex
Scissors cutting paper
metal cutters trimming shapes from metal
Deformation
Deformation - can happen when constraints are strong, or the object is weak against a specific constraint
Types of deformation
Plastic, Elastic, fRACTUre
Elastic
Elastic - returns to original shape ( squeezing a plastic water bottle)
The constraint leads to a temporary change in the shape or dimensions of the material. When the constraint is removed, the material returns to its original form.
Plastic
Plastic - deformation is permanent (squeezing an aluminum pop can)
The constraint leads to a permanent change in the shape or dimensions of the material. When the constraint is removed, the material returns to its original form.
Fracture
Fracture - material breaks (applying deflection to a pencil)
The constraint is so intense that the material breaks
Hardness
Ability to resist indentation or abrasion
Elasticity
Ability to return to their original shape after undergoing a constraint
Resilience
Ability to resist shocks without breaking
Ductility
Ability to be stretched without breaking
Malleability
Ability to be flattened or bent without breaking
Stiffness
Ability to retain their shapes when subjected to various constraints
Resistance to corrosion
Ability to resist the effects of corrosive substances (such as water, various salts, and some components of fumes) which cause the formation of rust, for example.
Electrical conductivity
Ability to carry and electric current
Thermal conductivity
Ability to transmit heat
Degradation
Some materials degrade (may depend on the environment the material is placed in ), and will require protection to survive long-term use.
Degradation: the decline of the properties of a material due to the effects of the surrounding environment
(Ex: rust, plastic discoloration, etc)
Protection of a material
Protection of a material: is the application of procedures that prevent or delay its degradation.
(Ex: rustproofing, additives in plastic, etc)
Fragility
Opposite of resilience, breaks/shatters easily
Lightness
Lightness - material that is not heavy (low density), important for large constructions
3) Categories of Materials
You must know:
-Wood and modified wood
-Ceramics
-Nonferrous metals and alloys (main component not Fe)
-Ferrous alloys (main component Fe)
-Plastics
-Composite materials
Modified wood
Modified wood: treated wood (processed or chemically treated), or material made from wood mixed with other substances (glues or plastics).
Ex: plywood, particleboard, fibreboard
Since wood is biological in nature, it degrades easily via fungi, microorganisms and insects.
Function of categories of materials
Knowing categories of materials we can make the best choices of materials when planning or designing an object (toy vehicle, backyard deck, can opener, etc).
How to protect wood
To protect the wood, treatments are possible:
-dipping the wood in an alkaline copper solution (gives greenish color)
-heating to a high temperature to remove moisture
-paints & varnishes
Ceramics
Ceramic is a solid material obtained by heating inorganic matter containing various compounds (usually oxides).
Useful material properties:
-low electrical conductivity (insulator)
-high hardness, useful in building materials (bricks, tiles)
-heat resistance (useful for dishes, oven pieces)
-resistant to corrosion (useful for water ducts)
-fragile (not resilient)
Generally resistant to corrosion, but certain acids and bases can have a degrading effect on ceramics.
Ceramics ex
-Glass
-Bricks
-Pottery (clay)
Metals
Metal: material extracted from a mineral ore. Usually shiny and are good conductors of electricity and heat.
ALloy
Alloy: mixture of a metal with one or more other substances, which may be metallic or nonmetallic.
Ferrous: iron is main component
Non-Ferrous: main component is not iron
Useful Material Properties (Metals):
Useful Material Properties (Metals):
-metals/alloys can be soft or hard, we can choose hard alloys for building materials, or soft ones that are easier to shape
-metals/alloys are good conductors of heat and electricity
-metals/alloys are malleable and ductile: we can make sheets and wires and cables from metals/alloys.
cause of metal degradation
Main cause of degradation:
Oxidation (exposure to air and water-based oxygens)
Solutions to metal degradation
Solutions: 1) coatings and surface treatments (“anti-rust” coatings, paint, oil, etc)
2) Steel can be enhanced with heat treatments like quenching (rapidly cooling, makes the metal hard but brittle) and tempering (slow heating and cooling, makes the metal
less brittle).
This improves the mechanical properties of steel.
Plastics
Mainly made from petroleum and natural gas (fossil fuels).
Most plastics are polymers (poly = many), which are small chemical units repeated and linked together into a chain.
Other substances may be added to the
polymers to enhance the material properties.
Types of plastic
Thermoplastic and thermosetting plastic
Thermoplastic
becomes soft enough when heated to be moulded or remoulded. Hardens enough when cooled to hold its shape.
Heat allows you to change its shape
Thermosetting plastic
tting plastic: remains permanently hard, even when heated.
Heat make the shape permanent, cannot soften to change shape.
Plastic degradation
Plastic degradation occurs over time: appearance of cracks and discoloration.
plastic degradation CAUSES
Causes: -liquids (water, acids, etc) can penetrate certain
plastics and cause them to degrade
-Oxidation
-UltraViolet rays
protections for plastic damage
Protections: -waterproof coating
Additives:
-addition of anti-oxidants (carbon black)
-addition of pigment that absorbs UV rays
Composites
A composite material is made up of a combination of different categories of basic materials.
The result is often a “best of both worlds” scenario.
Composites are usually made of two parts: matrices and reinforcements.
Matrices (singular matrix): the components that holds everything together; bulk of material is matrix
Reinforcements: added into the matrix to support and reinforce
Main matrices
Plastic matrices, metallic matrices, ceramic metraces, firbre glass, aramid fibres, carbon fibres
Plastic matrices
Thermosetting plastics are preferred for plastic matries, although thermoplastics are also used. Thermosetting plastic matrices are often called resins.
- DURABILITY, LIGHTNESS, RESILIENCE, LOW COST
Metallic matrices
Made from metals or alloys
- Ductility
- Thermal and electrical conductivity
- stiffness
Ceramic matrices
made from ceramics, often glass
DURABILITY, HEAT RESISTANCE
Fibreglass
Made of glass a ceramic in the form of fibres. Their length and dimaemeter as well as the type of glass used, may vary. STINESS CORROSION RESISTANT
Aramid fibres
Known by the trade name Kevlar and one of the few plastics used as a reinforcement
LOW DENSITY, RESILIENCE
Carbon fribres
Obtained by carbonizing ploymers, mostly polyacrynolinitriles
STIFFNESS
LOW DENSITY
ELECTRICAL CONDUCTIVITY
Degradation and Protection of composites
The matrix and reinforcement may degrade separately
Ex: -deformation / fracture of the matrix or reinforcement
-loss of adherence between the matrix and reinforcements
4) Technical Drafting
Types of projections and drawings
Projection: the representation of a 3D object onto a 2D surface (paper/page/screen
Isometric Projections
Good for presenting information/object, shows 3D aspect while maintaining proper proportions.
Isometric projections show the object in perspective (viewed from a single angle).
Uses angles of 120o
Multiview Projections
Shows many sides of an object simultaneously.
Minimum of 3 sides are necessary to represent the whole object:
(right-side/left-side; front/back; top/bottom)
General Arrangement Drawing
Technical drawing that represents the overall appearance of an object.
Usually drawn to scale (correct proportions).
This example includes both isometric and multiview projections.
May include some overall measurements, but not enough to machine and construct.
General arrangement drawings could be useful for marketing (size of object and box to hold it, etc)
Exploded View
Drawing where the various parts of an object are separated from one another.
Useful when planning or performing assembly of an object.
Detail Drawing
Detail drawings will include all the information needed to manufacture a part.
(measurements: angles, diameters, lengths, depths, etc)
Symbol for diameter is ⌀
Dimensional Tolerance
Dimensional Tolerance : the value of the acceptable manufacturing error in size.
Like resistors, tolerance here indicates how off the production measure is from the design measure.
Example: dowel diameter D = 5.0 cm +/- 5% or D = 5.0 cm +/- 0.3 cm
% is relative tolerance, just a number is absolute tolerance
Symbol for diameter may also be ⌀
