DT Mini Test

3D Drawings

- Allows designers to represent more realistically

- Allows them to think about every angle

- Normally used to develop

Freehand Sketching:

Drawing done without tools like rulers or compasses.

Used for quick idea generation in early design stages.

Can be rough or detailed, depending on the purpose. :

One-Point Perspective:

All lines converge to a single vanishing point on the horizon.

Used for simple 3D views like roads, hallways, and interiors.

Objects appear to get smaller as they move into the distance.

Two-Point Perspective:

Uses two vanishing points instead of one.

Provides a more realistic 3D representation.

Commonly used for buildings, product designs, and landscapes.:

Exploded View:

Shows how the product would look if it were to be disassembled

Used in assembly instructions, engineering, and product manuals.

Helps visualize components and their connections.

Orthographic Projection:

A 2D representation of a 3D object, showing multiple views (Front, Side, Top).

Used in technical drawings and manufacturing to show precise measurements.

Helps engineers and manufacturers create accurate products.

Butt Joint

- Easy to make/use

- No mechanical strength just glue

- Not aesthetically pleasing

Dowel Joint

- Neat/Simple Joint

- Strong if glued properly

- Hard to accurately make by hand

Lap Joint

- Easy to make/use

- Can be strengthened with dowels

- Not very strong can be easily broken

Housing Joint

- Reasonably strong

- Relatively easy to make

- Hard to make when making shelves

- Can be tricky to cut on a wide board

Mitre Joint

- Look good as no grain shows

- Weak as its a butt joint at 45 degrees

Mortise and tenon joint

- Strong joints

- Hidden joint

- Time consuming to cut by hand

- Poor resistance to tension

Dovetail joint

- Very strong joint

- Attractive joint

- Tricky and time consuming to cut

Joints what is needed

- Aesthetically pleasing

- Strength

- Ease of producing

- Reversible can be dismantled

Finishes why is it needed

- To make product look better

- Makes wood water resistant and easy to wipe and clean

- Wood is porous and can look dirty easily

Painting

- Coloured pigment in liquid that dries out

- Available in range of colours

- Covers up natural wood grain

Staining

- Coloured liquid that soaks into the wood surface

- Makes cheaper wood mimic expensive wood (pine to oak)

- Grain still shows so doesn't not completely look different

Varnishing

- Clear coating that dries to a shine

- Hardwearing finish that shows the grain of the wood

- Can be high gloss or matt finish

- Can scratch/chip/expose the wood

Wax

- Soft solid that is rubbed into the surface with cloth

- Easy to apply and plain natural look

- Rubs away

- Need reapplying not a glossy finish

Oil

- Rubbed into the surface and soaks in

- Good waterproofing for timber

- vegetable oil is non toxic on kitchenware

- Surface feels oily

Shellac

- Cloudy liquid made from resin by a beetle

- Layers are rubbed to make a french polish

- Used on expensive furniture for its glossy lustre

- Easily damaged by water or heat

Veneering

- Thin layer of wood glued onto the surface

- Expensive wood can be put onto a cheaper wood

- Veneer is natural wood so it still need a finish

Gear

A toothed wheel fixed to a shaft that connects meshes with other gears to change the speed or direction of rotation of a driving mechanism.

Simpler Gear Trains

- Two spur gears are meshes and fixed on parallel shafts

- Driven gear goes in the opposite direction of the driver gear

- More of fewer teeth means speed can be increased or decreased

Velocity ratio simple gear

VR = No of teeth on driven / No of teeth on driver gear

Compound gear trains

- More than one gear on the shaft

- Gears are in pairs (mating gears)

- Driven gear goes in the opposite direction of the driver gear

Velocity ratio compound gear

Total VR = VR of gear train 1 (A to B) x VR of gear train 2 (C to D)

Idler Gear

- Driver and riven gears rotate in the same direction

- No impact on output speed

- Velocity ratio is still based on gears

Calculating output of a gear system

Output speed = input speed/gear ratio

Bevel gears

- Transmits rotary motion through 90 degrees (Hand drill)

- Bevel gears vary in size to achieve different ratios

- Mitre gears are same sized but input and output speeds are equal

Rack and pinion

- Uses a gear wheel and rack to change rotary motion to linear motion or vice versa (pillar drill or car steering)

- Rack movement is determined by the no of teeth on pinion gear and the no of teeth per meter on the rack

Calculating output of a rack and pinion

No of teeth on pinion/No of teeth on rack per meter x x meters (depends on revolutions)

Paper

Thin flat material made from natural fibres weighting less than 200gsm

Copier Paper

- lightweight cheap bright white paper 80gsm

- writing,printing

- Takes colour well,cheap,available in many colours

- Can jam printers , flimsy

Cartridge Paper

- Creamy thick heavyweight paper 90-150 gsm

- Drawing,printing,watercolour painting

- Opaque,accepts most drawing media

- Costs more than copier paper

Tracing Paper

- Thin smooth translucent paper 60-90gsm

- Art , making copies,overlays

- Strong ,translucent

- Expensive,limited ink absorption,longer drying

Board

Thick paper or layers of paper more than 220gsm

Folding Boxboard

• Cereal boxes,food and healthcare packaging

• Inexpensive,prints well,excellent for scoring and bending without splitting

• Lower strength than solid white board

Corrugated Board

• Protective packaging

• Impact resistance,inexpensive,recyclable

• Deforms under pressure,not water resistant

Solid white board

• Books covers,good,cosmetics,medicine packaging

• Strong,rigid,prints well

• Expensive

Mechanical Properties

elements of a material that resist deformation from external forces or loads

Physical properties

elements of a material that can be defined and measured such as colour size or weight

Ferrous metals

Metals that contain iron, known for their strength and magnetic properties, commonly used in construction and manufacturing. Vunerable to rust except stainless steel and wrought iron

Non Ferrous Metals

Metals that do not contain iron, typically resistant to corrosion. Not magnetic and tend to be more malleable than ferrous metals.

Alloy

A mixture of two or more metals or a metal and another element which has improved properties and characteristics.