Module 6 Flashcards
Wood is mainly used for packaging applications in the form of
crates, cases, wire-bound containers, pallets, and pallet boxes.
the single biggest use of wood in packaging is for
the manufacture of pallets.
pallets can be made of
plastic, steel, aluminum, and other materials, including corrugated board
was an early form of shipping container.
bilged cask
were used to handle liquid and dry products on trains and on ships and wagons
Casks
first modern shipping containers
wooden boxes and crates
primary packaging materials in most developing countries
wood
an indigenous raw material and is readily available.
wood
the major uses of wood can be classified as:
Fuel
Raw material for the manufacture of paper and paper products
Raw material for the extraction of useful chemicals
Structural and other applications that employ wood in its solid and largely unmodified state. Wood used for packaging applications is included in this last category.
The grain of wood results from
its fibrous structural formation in the tree.
Wood fibers are arranged in
concentric rings, parallel to the long (vertical) axis of a tree trunk
In compression and tension, wood is strongest ______ and weakest at ______
along the grain; right angles to the grain
In shear, wood is strongest at ______.
right angles to the grain
Wood may be cut and worked into various shapes with the aid of
simple hand tools or by power-driven machinery
Wood can be joined by means of ______
nails, screws, bolts, or other mechanical connectors
Decay and insect damage can be largely eliminated by
following sound methods of design and using properly seasoned wood.
Wood materials are not well suited for
high-speed mechanized packaging operations.
Wood is generally classified into two categories:
Softwood and Hardwood
The major use of softwood is
building construction
Examples of softwoods include
pine, fir, cedar, redwood
A major use of hardwood is
furniture manufacturing
Examples of hardwoods include
oak, maple, birch, walnut, cherry
In packaging, softwoods are used to make
crates and boxes
In packaging, hardwood is used to make
pallets, crates, boxes, barrels, and slats for wire-bound containers
refers to any irregularity or deviation from the qualities that make wood suitable for a particular purpose.
Defect
Defects can be separated into two categories:
(1) natural defects and
(2) defects due to seasoning and machining
are imperfections in the wood of living trees
Natural defects
arise from growth and environment.
Natural defects
occurs when the fiber alignment in a piece of wood is not parallel with
the longitudinal axis of the piece.
Cross grain
The irregular forms of cross grain
curly, wavy, or interlocked
reduce the tensile, compressive, and bending strengths of wood, as well as the stiffness.
The irregular forms of cross grain
is the base of a branch that is embedded in the wood of a tree trunk or of a larger limb or branch
knot
harder, more dense, often more resinous, and shrinks in a different manner than surrounding wood tissue.
knot
Sometimes increases the compression strength and shear strength of the wood
presence of sound, tight knots
there is a loss of bending strength associated with the grain distortion in the wood around the
knot
occurs when a tree produces greater growth on one side than the other.
Reaction wood
Is related to the process of straightening trees that are leaning
Reaction wood
are internal stresses that are created by a slight shrinkage in cell length at the end of the period of cell development.
Growth stresses
is an abnormal condition that causes the wood to break suddenly arid completely across the grain at stress levels lower than expected.
Brashness
The most objectionable feature of brash wood is
the sudden failure without previous warning, especially when shock loaded.
Pieces of brash wood can be distinguished from normal wood of the same species by the
unusually light weight
a consequence of a decrease in the amount of cell wall material.
unusually light weight,
are those defects that appear in the wood after a tree is cut.
Defects due to seasoning and machining
Defects due to seasoning and machining results from
changes in the moisture content of the wood or from improper machining
are ruptures in wood, which develop along the grain during seasoning
Checks
Checks develop because of:
(1) a difference in radial and tangential shrinkage, resulting in stresses of sufficient magnitude to cause the failure of the wood along the planes of greatest weakness;
(2) differences in shrinkage of the tissue and development of stresses of different magnitude in adjacent portions of the wood, occasioned by varying moisture content.
is any distortion from the true plane that occurs in a piece of wood.
Warping
principal types of warping are
bowing, crooking, cupping, twisting, and diamonding
come loose during drying, because they are not physically attached to the surrounding wood.
Fallen knots
The wood in the knot usually is more _____ than the surrounding wood.
dense
is a roughened condition of the surface of dressed lumber in which the hard summerwood is raised above the softer springwood, but not torn from it.
Raised grain
Deterioration of wood is caused by:
Decomposition produced by physical agents, including heat or moisture
Chemical decomposition
Mechanical wear
Activity of biological agents, such as fungi, bacteria, insects, and marine borers
is the ratio of the mass of water in the material to a reference wood mass
Moisture content of wood
Freshly cut (green) wood typically has a moisture content in the range of
30 to 60 percent
Wood for packaging should be well seasoned, either by
air drying or kiln drying
Well-seaoned wood should have moisture content of
around 15-20 percent
is an essential step in the preparation of all wood for use in packaging applications
Drying
Dry wood is also less subject to attacks from
microorganisms
Wood is _____ after the initial sawing operation
air dried
The drying area should have
reasonable air movement unobstructed by trees or buildings and a ground surface that is free from debris and vegetation.
A reduction from green to 20 percent MC can take anywhere from _____ for 1” thick material for air drying
20 to 300 days
is done in a dosed chamber at an elevated temperature with controlled humidity and air circulation.
Kiln drying
produces quicker reduction of moisture content to levels required, independent of weather conditions.
Kiln drying
A reduction of MC from green to 16 percent can usually be
accomplished in ______ for 1” thick material for kiln drying
2 to 50 days
Plywood panels are manufactured by
gluing one or more veneers (thin sheets of wood) to surfaces of other veneers or a solid wood core.
Usually, the total number of layers of plywood is
Odd (3, 5, 7)
There are many types and thicknesses of plywood. Common types are
marine plywood, furniture grade plywood, and construction grade plywood.
The use of the word “exterior” indicates that
glue has been used that will retain its bond even when wet.
is a mixture of wood particles and chips mixed into a resinous carrier and cured in a mold.
Particleboard
is similar to particleboard, but there are larger chips of wood in the mix.
Oriented strand board (OSB)
Particleboard is used for
pallet decks and similar applications.
The most common fastener is the
ordinary nail
In the United States, the size of nails is frequently designated by the term
penny
identifies a certain length and diameter of wire nail.
penny
are widely used and provide a strong and efficient means of constructing cases, crates, and pallets
Staples, straps, metal edges, and wire binding
An example of nonstructural construction is
attaching waterproof linings and cushioning material to the inside of a package for shipping industrial equipment.
is used for wooden boxes, crates, barrels, and cases and for unitizing palletized loads.
Tension strapping
There are three types of tension strapping.
Steel strapping
Weftless strapping
Thermoplastic strapping
is usually flat, but may, in some cases, have a round or oval cross section.
Steel strapping
is subject to corrosion, which weakens the material, but the effect is usually minimal because of the relatively short time that the strapping is in use
Steel strapping
is made up of continuous strands of parallel laid, adhesive-bonded, high-tensile textile. This material is often provided in the form of tape.
Weftless strapping
is made of flat strips of an appropriate plastic material, usually polypropylene. Straps are usually applied and tightened by semiautomatic or fully automatic equipment.
Thermoplastic strapping
Wooden containers can be classified into two general types
shipping containers and consumer packages
There are two basic pallet designs:
(1) stringer design and
(2) block design
is defined as a flat portable platform constructed to sustain a load and permit handling by mechanical equipment.
pallet
is well-known source of wooden box designs
USFS (United States Forest Service)
is probably the best-known example for wood can also be used to manufacture containers for the transport of liquids
wooden beer cask
The beer cask is made by
the wet cooperage method. The cask is soaked after manufacture so that the wood in the staves swells up, sealing the cracks between the staves.
A ____ is the name given to one of the arched vertical tapered boards or panels forming the walls or sides of a cask.
stave
