wood
Content
Furniture Technology
Materials and Technologies of the
Wood and Furniture Industry
Part I - Wood!
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Introduction"
n
Wood is a complex material of plant origin and the primary constituent of trees. Timber is the name
given to wood used for building constructions.
n
Wood is used as construction material considering its good properties: low density, workability,
mechanical properties, insulating properties, etc.
n
The wood market represents one of the ten sectors of the global economy.
n
Wood consumption (2006) can be estimated around 3,5 billions cubic metres.
n
Wood is primarily used as raw material in the paper industry, but the majority (more than 65 %) is
used in the production of wood based panels or in the building sector as construction material. The
use of wood as energy source is growing.
n
There are around 3.7 billions hectares of forest in the world the majority of spontaneous type.
Plantations cover the 5 % of the total forested area
n
The production of wood products will continue to grow along the next years, but international trade of
wood products is expected to grow much faster"
Wood and Environment"
•
Renewable material
•
Wood as carbon sink"
"
Ref. EPF
Wood and Environment"
Ref. EPF
EU Regulation 995/2010
Laiyng down the obligations of operators who
Place timber and timber products on the market
(the “Illegal Timber Regulation” into force in 2013)
“illegal logging is a pervasive problem of major international concern. It poses a
significant threat to forests as it contributes to the process of deforestation and
forest degradation, which is responsible for about 20 % of global CO2
emissions, threatens biodiversity, and undermines sustainable forest
management and development including the commercial viability of operators
acting in accordance with applicable legislation. It also contributes to
desertification and soil erosion and can exacerbate extreme weather events
and flooding. In addition, it has social, political and economic implications”
Obligation
for timber operators
!
Importing companies will be required to apply the so-called “Due
Diligence” system by making available information on:
• trade name of the product;
• Country of origin;
• quantity of imported material;
• documents establishing the conformity of the products to the EU
Regulation.
They shall also carry out an assessment on wood and derived products
about the risk they are illegally marketed.
Moreover, retailers have the obligation to maintain adequate
documentation about suppliers and clients to whom they sell the material
for a minimum period of five years.
Wood certification
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Terminology
•
Anatomy = the science dealing with the structure of
animals and plants
•
Morphology = the branch of biology dealing with the form
of organisms.
•
Physiology = the branch of biology dealing with the
functions and activities of living organisms
The trunk section
Heartwood
Sapwood
Pith
Cambium
Bark
Wood (xilem)"
Heartwood
Sapwood
Cellular structure. Cell function
• providing support to the plant structure;
• enabling sap transport from the roots to the leaves;
• storing substances, including waste products, like sugars,
starches and fats;
• metabolising special substances used by the tree for
different biological functions;
• The cellular structure differs between the two groups of
trees: softwood and hardwoods (botanical distinction).
Softwoods
Hardwoods
Earlywood
Latewood
Ray
Parenchyma rays"
Beech
Oak
Resin and latex
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Wood. Chemical composition"
Macromulecolar
substances
{
Low molecular weight
substances
n
Cellulose "
n
Hemicellulose"
n
Lignin"
n
Extractives"
Cellulose
HO
O
H
H
HO
H
OH
OH
HO
H
H
Glucose (monomer)
HO
HO
O
H
HO
O
H
O
H
H
O
OH
HO
H
H
O
H
H
OH
HO
H
O
H
H
H
Cellulose (polimer)
H
O
OH
HO
H
H
Hemicellulose
• hemicellulose is a branched copolymer
consisting of different types of sugars
• hemicellulose can be considered a kind of
glue between the cellulose and lignin.
Lignin"
• thermoplastic polymer containing several aromatic groups
responsible for:
CH2CHCH2OH
H3 CO
- stiffness
- water repellency
H
HOH2CHCH2C
H
H
OCH3
CH2CHOH
H3 CO
CH2CH
CHCH2OH
H
O
- plasticity (when heated)
H3 CO
H H
CH2CHCH2OH
CH2CHCH2OH
H H
- sensitivity to sunlight
H
OCH3
OCH3
OH
O
OCH3
O
Wood bending"
Wood welding
Plastic from wood
Images: Tecnaro Gmbh
Low molecular weight substances
(extractives)"
• Inorganic (minerals)
• Organic
Inorganic Extractives (minerals)
• They are not real extractives, sometimes they are insoluble
• Mineral deposits can derive from the nutrients
• May lead to a fast tool wear
• May cause appearance defects after coating
Organic Extractives
Aliphatic derivatives (alcohols, waxes and fats)
Waxes and fats may confer some woods a natural water
repellency and became suitable for use in outdoor
environments (such as teak). However these substances
may be an obstacle to bonding and coating processes
Organic Extractives
Terpenes
Isoprene derivatives are particularly present in softwoods.
Organic Extractives
Phenol derivatives
•
•
•
•
•
are more present in Heartwood
are mainly responsible for the dark color of some woods.
give the wood a greater ability to resist biological attack.
Stilbenes darken when exposed to light
Flavanoids flavonoids are the most important substances
for the color of the wood.
Acidic Substances
The acidity of wood may interfere with the alkaline pH of
some coating materials and can be responsible for any
oxidation of metal parts in contact with wood.
The chemistry of wood
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
EN 13556:2003 Round and sawn timber.
Nomenclature of timbers used in Europe
SPECIE BOTANICA
"
ORIGINE
Prunus serotina Ehrh.
!
!
Quercus ilex L.
"
NOME ITALIANO
AMERICA (Nord)
Pericopsis elata (Harms)
Quercus cerris L.
"
!
!
AFRICA
!
EUROPA!
!
leccio!
EUROPA
Quercus spp., incluse
Q. alba L. e altre specie
AMERICA(Nord)
!
Quercus spp., incluse
Q. rubra L. e altre specie
Intsia bijuga (Colebr.)
!
!
!
!
afrormosia
holm oak
!
"
american cherry
NOME
FRANCESE
!
merisier
d’Amerique
afrormosia
!
chêne vert
!
quercia bianca
americana
American white oak
!
quercia rossa
americana
American red oak
!
!
!
merbau
!
merbau
!
!
Amerikanische
r Kirschbaum
!
!
afrormosia!
!
!
!
Steineiche !
Zerreiche
!
chêne blanc
Européen
Eiche
chêne blanc
d’Amérique
Amerikanische
Weißeiche
chêne rouge
d’Amérique
Roteiche
!
!
"
!
chêne chevelu
!
European oak
NOME
TEDESCO
"
!
Turkey oak
rovere
farnia
AMERICA(Nord)
ASIA
!
cerro
Quercus petraea (Matt.)
Liebl.,
Q. robur L.
!
!
ciliegio americano
afrormosia
EUROPA
!
!
NOME INGLESE
!
!
merbau
!
!
!
Merbau
!
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Porosity"
• Low
density
• Acoustic and thermal insulation properties.
• Higher density = improved mechanical properties (e.g.
hardness)
• Absorption (directional) of liquids
39
Density"
Density is defined (ISO 3131) as the ratio at a given moisture
content, between the apparent mass of wood and its volume
(kg/m3).
Basic Density is the ratio between the minimum weight
(anydrous wood) and maximum volume (moisture content
above the saturation point)
Fibrous structure
The mechanical properties of wood element depend on
the following factors:
• the species, generally the higher is the density,
and the higher is the mechanical strength;
• the direction and regularity of fibres;
• the moisture content as water acts as a
"plasticizer" for wood by reducing its mechanical
strength;
• the direction of the applied force to the fibres
orientation;
• the presence of defects such as knots, cracks
etc.
Mechanical properties
• Modulus of elasticity: the mathematical description of the
tendency to be deformed elastically (non-permanently)
• Flexural strength (modulus of rupture): a mechanical
parameter defined as the ability to resist deformation
under load
• Hardness: the resistance to a permanent shape change
when a force is applied.
Anisotropy"
1. Transverse
2. Radial
3. Tangential
• Appearance
• Permeability
• Movements
Sensitivity to water
Free water and bound water
“Fresh” wood
Fibre saturation point
Dynamic equilibrium
Wood and water
Figura da Stefano Berti - CNR (FI)
Moisture content"
MC (%) = 100 x Ww - Wd
Wd
MC = Moisture Content
Ww = Wet Weight
Wd = Dry Weight
Equilibrium moisture content"
Wood movements"
Movements"
• during all the working process moisture content should
be as close as possible to that determined by the
environmental conditions of its final use. By following
this simple rule, it is possible to minimise the
dimensional variations that are harmful for the product
both as functionality and appearance;
Movements"
• the dimensional variations of wood are
different along the three spatial
dimensions
1.
2.
3.
Beech
negligible along the axial direction;
significant in the radial direction;
considerable in the tangential direction;
Movement (%)
Humidity
Movements and Anisotropy"
Longitudinal movement for Radial movement for each Tangential movement
each moisture unit
moisture unit absorbed or for each moisture unit
absorbed or released.
released.
absorbed or released.
(%)
(%)
(%)
Negligible
0,1 ÷ 0,2
0,2 ÷ 0,3
Movements"
• the drying processes and the following phases
(transport, storage) are determining factors for all
subsequent production processes and thus the
final result;
Dry
Normal
Moisture content
Wet
Movements"
• dimensional variations are
different between wood species.
Denser woods normally take up
more water due to the higher
wood mass.
beech
teak
Movements"
• coating films are not able to completely prevent wood
from moisture changes.
• adequate dimensional tolerances should be allowed in
the designing and production of wood products.
Movements"
Sensitivity to fire
The biological sensitivity
The biological sensitivity
Type of biological
aggression
Area
Effects
Damage
Sapwood
Holes
Structural
Blue Stain Fungi
Influence
of
wood
moisture
Depends
on
the
insect
> 20 %
Sapwood
Colour
Decay Fungi
> 20 %
Sapwood
Lignin
Cellulose
degradation
Porosity
Increment
Structural
Soft Decay Fungi
> 30 %
Sapwood
Moulds
Surface
humidity
Surface
Cellulose
Degradation
Colour, Spots
Insect
and
Structural
Appearance
Wood appearance"
• Texture
• Grain
• Figure
• Colour
Texture"
Texture is a term used to classify the relative
size of wood elements. Woods are
considered fine-textured when individual
elements are so small that they cannot be
distinguished individually with a hand lens.
Coarse textured woods have large individual
elements that often can be observed without
magnification.
Grain"
Grain is a term used to describe the alignment of
wood elements to the longitudinal axis.
Grain
Direction
Straight
Grain which runs in a single direction, parallel to
the axis of the t r e e
Spiral
Grain which spirals around the axis of the tree
Interlocked
Grain which spirals around the axis of the tree, but
reverses its direction regularly, alternating,
interlockin g
Immagini prof. S. Berti - CNR (FI)
Figure"
Figure is a term applied to certain patterns formed
naturally in wood
Wood Colour"
Wood Colour"
Wood colour can rapidly change in consequence of the
following factors:
• light;
• kiln changes;
• enzymes (e.g. from fungal attack);
• metal;
• alkaline solutions;
• acids.
Acids in wood
Acids in wood
Sensitivity to light
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Wood defects (anomalies)"
- Knots
- Reaction wood
- Checks, Splits
- Ring shake
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Classification
Wood is traditionally classified on the basis of its visual
appearance, mainly considering the presence of defects,
which are defined as type and quantity.
In addition to those criteria, also mechanical properties
can be evaluated, especially in the case of softwoods
Classification
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Solid wood use"
Primary woodworking. Sawing
Type
Chain Saw
Main futures
The "blade" is made up of a mobile chain rotating by
means of an engine. The chain saws are generally
suitable for transport and then cut the trees in the
forests or plantati o n s .
Circular (disk)
Saw
Circular saw is a metal disc or blade sometimes with
saw teeth on the edge as well as the machine that
causes the disk to spin
Band S a w
A band saw uses a blade consisting of a continuous
metal band with teeth along one edge. The band
usually rides on two wheels rotating in the same
plane. Band sawing produces uniform cutting action
as a result of an evenly distributed tooth load.
Reciprocating
(Oscillating)
Saw
Reciprocating saw is a type of saw in which the
cutting action is achieved through a push and pull
reciprocating motion of the blade. Usually the cutting
machines are equipped with a series of
reciprocating saws (multiblade system s ) .
Seasoning"
The purpose of seasoning is to get wood elements to
the appropriate moisture content for the intended end
use. It is therefore necessary to bring wood, in a
controlled manner, from the high moisture contents of
newly felled wood, to the average equilibrium
conditions that will be required in service, drying also
prevents the onset of deterioration due to biological
attacks to which the wood is prone.
Seasoning (or drying) is defined as the process by
which water is removed from wood after felling the tree
and the execution of the first cutting of the trunk.
Artificial drying"
Plant Type
Main features
Hot air
Wood is heated and consequently dried by hot air
flow. Air removes moisture from the wood surface,
which is then expelled from the oven.
Heat pump
This method is similar to the above, in this case,
however, the air expelled is dehumidified before
recirculating inside the oven.
(dehumidification)
Vacuum
Wood elements are placed into an autoclave,
which is practiced in a severe depression.
Depression favours the release of moisture from
wood. With these systems it is possible to dry
wood at low temperatures, reducing the risk of
defects.
Wood drying. Defects"
• Over drying
• Gradients
• Cracking
• Discolouration
• Case-hardening (crust)
• Collapse
Secondary processing
• Wood turning
• Wood bending
• Wood moulding
• Wood drilling
• Sanding
• Clamping
Turning"
Bending"
Bending"
Moulding. Splindle moulder"
cnc
Drilling"
Sanding"
Clamping. Joint systems"
Butt Joint
Tenon and Mortise
Dovetail joint
Joint systems"
Dowel joint
Finger joint
Reversible joint
Defects of joining processes
•
Wood moisture
•
Preparation and sizing
•
Bonding process
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Safety"
• There are some woods that can cause allergic reactions
and other effects (eg epistaxis) to workers on the basis of
their extractives
• The powder of some wood species can be carcinogenic.
Bibliography
F. Bulian, Materials and Technologies of the furniture
Industry, Goliardica Editrice, 2012
This presentation contains material (text, pictures, tables and figures) protected by
copyright.
Any partial or total reproduction is strictly forbidden.
Materials and Technologies of the
Wood and Furniture Industry
Part I - Wood!
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Introduction"
n
Wood is a complex material of plant origin and the primary constituent of trees. Timber is the name
given to wood used for building constructions.
n
Wood is used as construction material considering its good properties: low density, workability,
mechanical properties, insulating properties, etc.
n
The wood market represents one of the ten sectors of the global economy.
n
Wood consumption (2006) can be estimated around 3,5 billions cubic metres.
n
Wood is primarily used as raw material in the paper industry, but the majority (more than 65 %) is
used in the production of wood based panels or in the building sector as construction material. The
use of wood as energy source is growing.
n
There are around 3.7 billions hectares of forest in the world the majority of spontaneous type.
Plantations cover the 5 % of the total forested area
n
The production of wood products will continue to grow along the next years, but international trade of
wood products is expected to grow much faster"
Wood and Environment"
•
Renewable material
•
Wood as carbon sink"
"
Ref. EPF
Wood and Environment"
Ref. EPF
EU Regulation 995/2010
Laiyng down the obligations of operators who
Place timber and timber products on the market
(the “Illegal Timber Regulation” into force in 2013)
“illegal logging is a pervasive problem of major international concern. It poses a
significant threat to forests as it contributes to the process of deforestation and
forest degradation, which is responsible for about 20 % of global CO2
emissions, threatens biodiversity, and undermines sustainable forest
management and development including the commercial viability of operators
acting in accordance with applicable legislation. It also contributes to
desertification and soil erosion and can exacerbate extreme weather events
and flooding. In addition, it has social, political and economic implications”
Obligation
for timber operators
!
Importing companies will be required to apply the so-called “Due
Diligence” system by making available information on:
• trade name of the product;
• Country of origin;
• quantity of imported material;
• documents establishing the conformity of the products to the EU
Regulation.
They shall also carry out an assessment on wood and derived products
about the risk they are illegally marketed.
Moreover, retailers have the obligation to maintain adequate
documentation about suppliers and clients to whom they sell the material
for a minimum period of five years.
Wood certification
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Terminology
•
Anatomy = the science dealing with the structure of
animals and plants
•
Morphology = the branch of biology dealing with the form
of organisms.
•
Physiology = the branch of biology dealing with the
functions and activities of living organisms
The trunk section
Heartwood
Sapwood
Pith
Cambium
Bark
Wood (xilem)"
Heartwood
Sapwood
Cellular structure. Cell function
• providing support to the plant structure;
• enabling sap transport from the roots to the leaves;
• storing substances, including waste products, like sugars,
starches and fats;
• metabolising special substances used by the tree for
different biological functions;
• The cellular structure differs between the two groups of
trees: softwood and hardwoods (botanical distinction).
Softwoods
Hardwoods
Earlywood
Latewood
Ray
Parenchyma rays"
Beech
Oak
Resin and latex
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Wood. Chemical composition"
Macromulecolar
substances
{
Low molecular weight
substances
n
Cellulose "
n
Hemicellulose"
n
Lignin"
n
Extractives"
Cellulose
HO
O
H
H
HO
H
OH
OH
HO
H
H
Glucose (monomer)
HO
HO
O
H
HO
O
H
O
H
H
O
OH
HO
H
H
O
H
H
OH
HO
H
O
H
H
H
Cellulose (polimer)
H
O
OH
HO
H
H
Hemicellulose
• hemicellulose is a branched copolymer
consisting of different types of sugars
• hemicellulose can be considered a kind of
glue between the cellulose and lignin.
Lignin"
• thermoplastic polymer containing several aromatic groups
responsible for:
CH2CHCH2OH
H3 CO
- stiffness
- water repellency
H
HOH2CHCH2C
H
H
OCH3
CH2CHOH
H3 CO
CH2CH
CHCH2OH
H
O
- plasticity (when heated)
H3 CO
H H
CH2CHCH2OH
CH2CHCH2OH
H H
- sensitivity to sunlight
H
OCH3
OCH3
OH
O
OCH3
O
Wood bending"
Wood welding
Plastic from wood
Images: Tecnaro Gmbh
Low molecular weight substances
(extractives)"
• Inorganic (minerals)
• Organic
Inorganic Extractives (minerals)
• They are not real extractives, sometimes they are insoluble
• Mineral deposits can derive from the nutrients
• May lead to a fast tool wear
• May cause appearance defects after coating
Organic Extractives
Aliphatic derivatives (alcohols, waxes and fats)
Waxes and fats may confer some woods a natural water
repellency and became suitable for use in outdoor
environments (such as teak). However these substances
may be an obstacle to bonding and coating processes
Organic Extractives
Terpenes
Isoprene derivatives are particularly present in softwoods.
Organic Extractives
Phenol derivatives
•
•
•
•
•
are more present in Heartwood
are mainly responsible for the dark color of some woods.
give the wood a greater ability to resist biological attack.
Stilbenes darken when exposed to light
Flavanoids flavonoids are the most important substances
for the color of the wood.
Acidic Substances
The acidity of wood may interfere with the alkaline pH of
some coating materials and can be responsible for any
oxidation of metal parts in contact with wood.
The chemistry of wood
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
EN 13556:2003 Round and sawn timber.
Nomenclature of timbers used in Europe
SPECIE BOTANICA
"
ORIGINE
Prunus serotina Ehrh.
!
!
Quercus ilex L.
"
NOME ITALIANO
AMERICA (Nord)
Pericopsis elata (Harms)
Quercus cerris L.
"
!
!
AFRICA
!
EUROPA!
!
leccio!
EUROPA
Quercus spp., incluse
Q. alba L. e altre specie
AMERICA(Nord)
!
Quercus spp., incluse
Q. rubra L. e altre specie
Intsia bijuga (Colebr.)
!
!
!
!
afrormosia
holm oak
!
"
american cherry
NOME
FRANCESE
!
merisier
d’Amerique
afrormosia
!
chêne vert
!
quercia bianca
americana
American white oak
!
quercia rossa
americana
American red oak
!
!
!
merbau
!
merbau
!
!
Amerikanische
r Kirschbaum
!
!
afrormosia!
!
!
!
Steineiche !
Zerreiche
!
chêne blanc
Européen
Eiche
chêne blanc
d’Amérique
Amerikanische
Weißeiche
chêne rouge
d’Amérique
Roteiche
!
!
"
!
chêne chevelu
!
European oak
NOME
TEDESCO
"
!
Turkey oak
rovere
farnia
AMERICA(Nord)
ASIA
!
cerro
Quercus petraea (Matt.)
Liebl.,
Q. robur L.
!
!
ciliegio americano
afrormosia
EUROPA
!
!
NOME INGLESE
!
!
merbau
!
!
!
Merbau
!
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Porosity"
• Low
density
• Acoustic and thermal insulation properties.
• Higher density = improved mechanical properties (e.g.
hardness)
• Absorption (directional) of liquids
39
Density"
Density is defined (ISO 3131) as the ratio at a given moisture
content, between the apparent mass of wood and its volume
(kg/m3).
Basic Density is the ratio between the minimum weight
(anydrous wood) and maximum volume (moisture content
above the saturation point)
Fibrous structure
The mechanical properties of wood element depend on
the following factors:
• the species, generally the higher is the density,
and the higher is the mechanical strength;
• the direction and regularity of fibres;
• the moisture content as water acts as a
"plasticizer" for wood by reducing its mechanical
strength;
• the direction of the applied force to the fibres
orientation;
• the presence of defects such as knots, cracks
etc.
Mechanical properties
• Modulus of elasticity: the mathematical description of the
tendency to be deformed elastically (non-permanently)
• Flexural strength (modulus of rupture): a mechanical
parameter defined as the ability to resist deformation
under load
• Hardness: the resistance to a permanent shape change
when a force is applied.
Anisotropy"
1. Transverse
2. Radial
3. Tangential
• Appearance
• Permeability
• Movements
Sensitivity to water
Free water and bound water
“Fresh” wood
Fibre saturation point
Dynamic equilibrium
Wood and water
Figura da Stefano Berti - CNR (FI)
Moisture content"
MC (%) = 100 x Ww - Wd
Wd
MC = Moisture Content
Ww = Wet Weight
Wd = Dry Weight
Equilibrium moisture content"
Wood movements"
Movements"
• during all the working process moisture content should
be as close as possible to that determined by the
environmental conditions of its final use. By following
this simple rule, it is possible to minimise the
dimensional variations that are harmful for the product
both as functionality and appearance;
Movements"
• the dimensional variations of wood are
different along the three spatial
dimensions
1.
2.
3.
Beech
negligible along the axial direction;
significant in the radial direction;
considerable in the tangential direction;
Movement (%)
Humidity
Movements and Anisotropy"
Longitudinal movement for Radial movement for each Tangential movement
each moisture unit
moisture unit absorbed or for each moisture unit
absorbed or released.
released.
absorbed or released.
(%)
(%)
(%)
Negligible
0,1 ÷ 0,2
0,2 ÷ 0,3
Movements"
• the drying processes and the following phases
(transport, storage) are determining factors for all
subsequent production processes and thus the
final result;
Dry
Normal
Moisture content
Wet
Movements"
• dimensional variations are
different between wood species.
Denser woods normally take up
more water due to the higher
wood mass.
beech
teak
Movements"
• coating films are not able to completely prevent wood
from moisture changes.
• adequate dimensional tolerances should be allowed in
the designing and production of wood products.
Movements"
Sensitivity to fire
The biological sensitivity
The biological sensitivity
Type of biological
aggression
Area
Effects
Damage
Sapwood
Holes
Structural
Blue Stain Fungi
Influence
of
wood
moisture
Depends
on
the
insect
> 20 %
Sapwood
Colour
Decay Fungi
> 20 %
Sapwood
Lignin
Cellulose
degradation
Porosity
Increment
Structural
Soft Decay Fungi
> 30 %
Sapwood
Moulds
Surface
humidity
Surface
Cellulose
Degradation
Colour, Spots
Insect
and
Structural
Appearance
Wood appearance"
• Texture
• Grain
• Figure
• Colour
Texture"
Texture is a term used to classify the relative
size of wood elements. Woods are
considered fine-textured when individual
elements are so small that they cannot be
distinguished individually with a hand lens.
Coarse textured woods have large individual
elements that often can be observed without
magnification.
Grain"
Grain is a term used to describe the alignment of
wood elements to the longitudinal axis.
Grain
Direction
Straight
Grain which runs in a single direction, parallel to
the axis of the t r e e
Spiral
Grain which spirals around the axis of the tree
Interlocked
Grain which spirals around the axis of the tree, but
reverses its direction regularly, alternating,
interlockin g
Immagini prof. S. Berti - CNR (FI)
Figure"
Figure is a term applied to certain patterns formed
naturally in wood
Wood Colour"
Wood Colour"
Wood colour can rapidly change in consequence of the
following factors:
• light;
• kiln changes;
• enzymes (e.g. from fungal attack);
• metal;
• alkaline solutions;
• acids.
Acids in wood
Acids in wood
Sensitivity to light
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Wood defects (anomalies)"
- Knots
- Reaction wood
- Checks, Splits
- Ring shake
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Classification
Wood is traditionally classified on the basis of its visual
appearance, mainly considering the presence of defects,
which are defined as type and quantity.
In addition to those criteria, also mechanical properties
can be evaluated, especially in the case of softwoods
Classification
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Solid wood use"
Primary woodworking. Sawing
Type
Chain Saw
Main futures
The "blade" is made up of a mobile chain rotating by
means of an engine. The chain saws are generally
suitable for transport and then cut the trees in the
forests or plantati o n s .
Circular (disk)
Saw
Circular saw is a metal disc or blade sometimes with
saw teeth on the edge as well as the machine that
causes the disk to spin
Band S a w
A band saw uses a blade consisting of a continuous
metal band with teeth along one edge. The band
usually rides on two wheels rotating in the same
plane. Band sawing produces uniform cutting action
as a result of an evenly distributed tooth load.
Reciprocating
(Oscillating)
Saw
Reciprocating saw is a type of saw in which the
cutting action is achieved through a push and pull
reciprocating motion of the blade. Usually the cutting
machines are equipped with a series of
reciprocating saws (multiblade system s ) .
Seasoning"
The purpose of seasoning is to get wood elements to
the appropriate moisture content for the intended end
use. It is therefore necessary to bring wood, in a
controlled manner, from the high moisture contents of
newly felled wood, to the average equilibrium
conditions that will be required in service, drying also
prevents the onset of deterioration due to biological
attacks to which the wood is prone.
Seasoning (or drying) is defined as the process by
which water is removed from wood after felling the tree
and the execution of the first cutting of the trunk.
Artificial drying"
Plant Type
Main features
Hot air
Wood is heated and consequently dried by hot air
flow. Air removes moisture from the wood surface,
which is then expelled from the oven.
Heat pump
This method is similar to the above, in this case,
however, the air expelled is dehumidified before
recirculating inside the oven.
(dehumidification)
Vacuum
Wood elements are placed into an autoclave,
which is practiced in a severe depression.
Depression favours the release of moisture from
wood. With these systems it is possible to dry
wood at low temperatures, reducing the risk of
defects.
Wood drying. Defects"
• Over drying
• Gradients
• Cracking
• Discolouration
• Case-hardening (crust)
• Collapse
Secondary processing
• Wood turning
• Wood bending
• Wood moulding
• Wood drilling
• Sanding
• Clamping
Turning"
Bending"
Bending"
Moulding. Splindle moulder"
cnc
Drilling"
Sanding"
Clamping. Joint systems"
Butt Joint
Tenon and Mortise
Dovetail joint
Joint systems"
Dowel joint
Finger joint
Reversible joint
Defects of joining processes
•
Wood moisture
•
Preparation and sizing
•
Bonding process
Summary
1.
2.
3.
4.
5.
6.
7.
8.
9.
Appendix
Introduction
Anatomy and Morphology
Chemical composition
Wood nomenclature
Wood properties
Wood defects
Classification
Woodworking
Safety
Modified wood
Safety"
• There are some woods that can cause allergic reactions
and other effects (eg epistaxis) to workers on the basis of
their extractives
• The powder of some wood species can be carcinogenic.
Bibliography
F. Bulian, Materials and Technologies of the furniture
Industry, Goliardica Editrice, 2012
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