Upload
suresh-kumar-nath
View
40
Download
9
Embed Size (px)
Citation preview
PLYWOOD
FWT - KU
In 1797 Samuel Bentham applied for patents covering several machines to produce veneers.
About fifty years later Immanuel Nobel, father of Alfred Nobel, realized that several thinner layers of wood bonded together would be stronger than one single thick layer of wood.
plywood manufacture was an established process in France in the 1860s.
Plywood was introduced into the United States in 1865.
In 1928, the first standard-sized 4 ft by 8 ft (1.2 m by 2.4 m) was produced
History of Plywood
Panels comprising of at least three layers of thin wood bonded together with an adhesive.
Each ply is usually orientated at a right angle to the adjacent layer in order to improve strength and reduce the probability of shrinkage.
Plywood is a manufactured wood equally panel from thin sheet of wood veneer. It is one of the mostly used wood products.
Definition
“Face & back” are commonly preferred for outer Layer of ply and graded according to their quality. The inner or intermediate layer are collectively known as “core”.
Plywood is flexible, inexpensive, workable & re-usable and usually can be manufactured locally, resistance to cracking, splitting, shrinkage, twisting and has high strength.
Definition (Cont’d)
These are thin sheets or slices of wood of superior quality.
Dimension:Usually 0.5 to 1.0 mm in thickness. Sometimes up to about 10mm.
Veneer
All species may be used for production for production of veneer.
Softwood and hardwood species with a uniform texture without large differences between early wood and latewood are used.
Tropical woods are extensively used due to absent of pronounced growth rings.
Sources of Veneer
Should have straight and round log
Should be defect free on log surface
Should have a centered pith, uniform color and growth rate
Should be free from mineral deposit.
Criteria of Veneer Trees
Decorative Veneer: It is used for surface furniture, interior plywood paneling and related products.
Utility veneer: It is used for partitions of furniture and cabinets and other structural uses or in products coated with paint or other materials.
Veneer Types
1. Sizing of veneer logs
2. Storage of veneer logs
3. Debarking
4. Pretreatment
5. Veneer cutting
6. Veneer handling and green clipping
7. Veneer Drying
Preparation of Veneer
Preparation of Veneer (Cont’d)
Step 1: Preparation of veneer
Step 2: Veneer Drying
Step 3: Jointing and Splicing of dry veneer
Step 4: Mixing and spreading of adhesive
Step 5: Pressing of Plywood
Step 6: Conditioning & finishing
Manufacturing Process of Plywood
Manufacturing Process of Plywood (Cont’d)
Manufacturing Process Flow Chart
Urea formaldehyde(UF)
Phenol Formaldehyde(PF)
Melamine formaldehyde(MF)
Isocyanides
Plywood Sizes and Thickness
General dimensions are 8x4, 8x3, 7x4, 7x3, 6x4 and 6x3 sq. feet.
The general thickness ranges are 1/4", 3/8", 1/2", 5/8", 3/4", 1" and sometimes higher.
Adhesives Used and Plywood Dimensions
Commercial plywood
Waterproof plywood
Marine plywood
Softwood plywood
Hardwood plywood
Tropical plywood
Flexo plywood
Aircraft plywood
Decorative plywood
Types of Plywood
•It is an interior grade plywood for indoor Use
•It has light colour shades.
Commercial Plywood
• Waterproof ply is mostly used• It has black collared shades• Due to chemical used in it , it don’ t get affected
by termite• Black colour is also due to chemicals used.
Waterproof Plywood
• It is flexible and is used for making curved
parts
• All the grains go in one direction.
Flexo Plywood
• It is a form of plywood that has been constructed using waterproof veneer to make it suitable for use in wet environments including a home built boat , and other structures.
• It may serve as underlayment of boat, deck cover, the wall and compartment overhead panels of boat.
Marine Plywood
• Softwood panel is usually made either of cedar , pine , redwood , and is used for construction and industrial purpose
• The most common dimension is 1.2 m x 2.4 m or large imperial 4’ x 8’
• Thickness is from 1.4 mm – 4.3 mm.
Softwood Plywood
• It is made from angiosperms trees and is used for demanding end uses
• Especially suitable for heavy duty floor and wall structures
• It has excellent surface hardness , damage and wear resistance.
Hardwood Plywood
• Tropical plywood is made from species of tropical wood• Originally from the Asian region , it is now also
manufactured in African and south American countries• Tropical plywood is superior to softwood plywood due
to its strength , density and high quality• Tropical plywood is used widely in UK, Japan, US,
Taiwan, Dubai and other countries.
Tropical Plywood
• High strength plywood is also known as aircraft plywood
• It is made from birch and mahogany and uses adhesive with increased resistance to heat and humidity
• It was used for several world war 2 fighter aircraft• Although the british built mosquito bomber nicknamed
“the wooden wonder”, it was constructed using plywood having indiviual veneers of birch, balsa.
Aircraft Plywood
• Usually faced with hardwood including ash, oak, red oak, birch, maple, mahogany, rose wood, teak and large number of other woods
• This plywood is lot easier to dye and draw on than any other plywood.
Decorative Plywood
• BWR : boiling water resistant
• BWP : boiling water proof
This grade is mostly used in kitchens.
• MR : moisture resistant
Plywood Grades
Dimensional stability
Uniform strength in along & across the board
Resistance to warping , cracking & twisting
Economical & affective utilization of wood
Use of fast growing & non durable species
Solid wood is 20 times stronger along the grain
than across. Plywood over 10mm thick is almost
equal in strength in both directions
Plywood can be formed or bent to make a curve.
Advantages of Plywood
Veneer Checking
Discoloration of plywood
The layering effect in plywood makes it porous and susceptible to water damage if exposed over time. Plywood becomes heavy when wet
Because plywood is fibrous, it will easily absorb water and water vapor, causing it to bubble or delaminate.
Disadvantages of Plywood
Floors, walls and roofs in house constructions
Furniture Structure panel Vehicle internal body
work Packages and boxes Fencing Floor base Container flooring
Uses of Plywood
Playground equipment Musical instruments Sports equipment High-end loud speakers Fences for demanding
outdoor advertising
Uses of Plywood (Cont’d)
Thanks to All for
Your Attention