tecnología

Composition of Wood
  • Cellulose
  • Hemicellulose
  • lignin
  • Mineral elements
  • water

Origin of Wood
    Wood comes from trees, generally from
  • the trunk, but also from
  • the branches and
  • roots

The cross-section of the tree trunk:
  • Bark
    • Outer bark
    • Inner bark or phloem
  • Cambium
  • Sapwood
  • Heartwood or duramen
  • Pitch
    • Others:
    • Growth rings
    • Rays
    • Knots

Classification of wood
    Natural wood (directly from trees)
  • Softwoods
    • Generally come from evergreen trees(coniferous)
      • They do not lose their leaves
    • They are Gymnosperms
      • Seeds without any covering
    • Needle-liked or scale-liked leaves
    • Grow faster than most hardwoods
    • They are usually lighter and less dense than hardwoods
    • Most of them contain more resin
    • They are cheaper
  • Hardwoods
    • Generally come from broad-leafed(deciduous) trees
    • They are Angiosperms
      • Flowering plants that produce fruits that contain the seeds
    • Balsa is one of the least dense and hence softest woods of all

    Forms of natural or solid wood:
  • Veneer, beam, plank, narrow board, board, strip, moulding
    Engineered wood products or artificial boards (from Sheets, chips, fibres, planks, pressed and glued)
  • Plywood
    • Sheets (veneer) of wood
    • One on top of another
    • Direction of the grain in each sheet perpendicular to the one below it
    • Gluing them together
    • Number of sheets must be odd
  • Chipboard or Particle board
    • Shavings (chips) or leftover wood
    • Glued and pressed
  • Fibreboard
    • Wood fibre and synthetic or wood resin compressed under high pressure
    • - Medium density fibreboard(MDF)
    • - Tablex or Hardboard(HDF)
  • Blockboard
    • Planks (strips of wood or flat board) glued together
Natural wood or plastic veneer is often used as a finish

The conversión of wood into timber (process of wood taken from the forest)
  • Tree felling
    • Selecting the trees in the woods:from single-tree selection to clearcutting
    • Cutting tree trunk and remove the bark and branches (pruning) with chainsaw or treedozers
  • Transport
    • Transport logs from the forest to the sawmill using: road (lorries), rail or waterway
  • Sawing
    • Strip off the bark and cut and process the timber,usually with a bandsaw or a circular saw.
  • Washing
  • Drying
    • Natural or artificial. To eliminates moisture
  • Planing
    • Make the wood smooth

Working with wood
  • Selecting the material
    • solid wood,chipboard,plywood...
  • Measuring and marking
    • Determine the dimensions
    • Tracing de profile (drawing the shape of a piece)
    • Tools: carpenter's ruler, measuring tape, carpenter's square,protractor,carpenter
  • Bracing
    • Held in place
    • Tools: bench vices, c-clamps,bar clamps, ring clamps, saw suports
  • Sawing
    • Cutting de pieces lossing material(sawdust)
    • Tools:handsaw,backsaw, tenon saw, coping saw,hacksaw. Electric saws: jigsaw or fretsaw and circular saw, bench saw
  • Drilling
    • Making holes with drill bits
    • Tools: gimlet, hand drill, portable electric drill column drill
  • Carving and levelling
    • Make smooth and shape
    • Tools: chisel, gouge
  • Planing
    • Eliminate excess of material
    • Tools: rasp, file, teasel brush, hand plane, electric planer
  • Sanding and polishing
    • Smooth finish
    • Tools:Sandpaper(coarse-grain and fine-grain),Grinder,electric sanders,belt sanders,orbital sanders
  • Joining
    • Joints using adhesives: Contact adhesive, wood glue, glue gun
    • Joints using nails or tacks
    • Joints using wood screws or self-tapping screws, bolts and nuts
    • Joints using hinges
    • Joints using assembly o joinery
      • Shaping pieces of wood that fits perfectly with another piece of wood
      • Mortise and tenon,box or tongue and groove,dowel,dovetail,half lap,full dado or housing,
    • Tools for nailing and screwing: hammers, pincers, pliers, screwdriver, spanner, electric screwdriver
  • Finishes
    • Protect the wood from external agents like sunlight, rain, insects, etc. and decorate (make the piece look nicer)
    • Opaque finish: paints (oil or acrylic), anamels and lacquers
    • Transparent finish:stains,varnishes and dyes
  • Industrial woodworking techniques
    • Conventional machines
      • circular saws, belts saws, sanders, lathes, milling machinesdriven by an electric motor and automated
    • Digital fabrication methods
      • drawings are directly transferred to computer numerically controlled(CNC)tools
      • Tools:CNC Milling, CNC Routing, CNC Waterjet, Laser cutters
  • Properties of wood
    • Density (lightweight: most wood is less dense than water, so it floats)
    • Electrical insulation (dry wood)
    • Thermal insulation
    • Porosity
    • Mechanical resistance (tension,compression and bending)
    • Colour and grain
    • Ecological properties(Environmentally friendly: Renewable raw material, biodegradable, recyclable)
    • Cleavability (the degree of ease with which a material can be split)
    • Hygroscopicity (a material's ability to absorb or release water -it picks up or gives off moisture; wood shrinks when dry or swells when wet-)
    • Flexible

    Cellulose materials: Paper
      Process of making paper
    • Cut trees
    • Remove the bark
    • Grind the wood
    • Mix with water and chemical products to make cellulose paste
    • Wash and bleach
    • Suction and remove water
    • Press with rollers
    • Dry with hot rollers
    • Smooth with rollers
    • Roll up and cut
      Grammage
    • paper: less than 140 g/m2(grams per square metre of paper)
    • card: between 140 and 400g/m2
    • cardboard: more than 400 g/m2