Laminated Wood
Defination:
The word laminated from the word lamina means layer. Laminated wood is one kind of manufactured product where two or more parallel- grained layers of planks are joined together by adhesives or other fastener.
Manufacture:
Due to manufacture of laminated wood the individual planks or veneers are dried in dry klin or veneer dryer respectively to a MC between 3-5% and 10-12% depending on adhesive and pressing method. The difference between the laminae not exceeding 5%. L arge differences results is delamination & warping in laminetes due to considerable strees on glued joints.
Picees with case hardening , warp, cheeks, & splits are discarded or defective portion cut out. Wood board is surfaced by machines. Final surfacing is done just before gluing. Short pieces are joints end to end with adhesive for producing longer laminates. Narrow board are glued edge to edge.
The laminae are arranged in the proper order and are spread with adhesives, preferably with a glue spreader.Brushes may be used for spreading glue on some types of lamination, for example, badminton rackets. The glued laminae are assembled ina jig or form and pressure is a applied by clamps fixed at regular intervals. For proper distribution of pressure, caul plates of heavy wood boards are placed on both faces of the assembly for straight laminates. For curved laminates two or more thin cauls are used.
Thin laminates are suitable for curved laminates because it retain shape better after realeasing the preesure. When laminates are made from thin laminae then higher pressure is required because it tends to spring back after removing the pressure and removal from the jag. The pressure is applied by the screw press, clamps or with hydraulic or pneumatic presses. Nailing is also used for applying the pressure but is not recommended because of indifferent results. The dense wood requires more pressure for ensuring intimate contact of the glue and the lamination.
Generally pressures between 10.5 and 17.5kp/cm are required for dense wood and 7.0 and 14.0kp/cm are required for light wood. High pressures are applied for large and heavy laminates and curved assemblies. Small laminates and thin laminaes may be successfully bonded with low pressure.
Due to adhesives requiring high temperature for setting, hot presses may be used to laminate straight assemblies. For curved assemblies, the glued laminations after alamping is put in an oven or a heated chamber. Alternatively radio-frequency heating or low voltage heating meathods may be used. The compitability of the preservatives and the adhesive must be taken into consideration when laminations are treated before gluing and the adhesives should be of highly water-resistant type. The treated laminae should be resurfaced just before gluing to reduce interference by oily solvents or other exudations of preservative materials. Preservative treatment should be applied after lamination. Highly water resistants are also applied in this time too.
For protection against fire, either laminae or laminates are impregnated with fire retardant chemicals, or fire-retardant coatings are applied on all surfaces of the laminate.
Advantages:
1:Huge number of laminated product is produced from smaller pieces of wood.
2:More complete utilization of wood is achieved.
3:Very large load-bearing structural members, difficult to produce from a single piece, can be manufactured.
4:Curved and variously shaped laminates with beautiful architectural designs normally not otherwise available, can be made.
5:Structural members varying in cross-section along their length in accordance with the requirement of strength can be made.
6:Large one-piece wood members take considerable time to dry and develop checking and other seasoning defects which are eliminated by the use of thinner lamination which can be thoroughly seasoned throughout the pieces in less time at lower cost.
7: Forest are conserved and the technology may be considered environment-friendly.
Disadvantages:
1:The careful processing of wood is necessary for gluing, the gluing operations.
2:Extra equipment is necessary for gluing operations.
3:Skilled manpower is essential for the manufacture of laminated wood.
4:Plant machineries are needed for this activities.
5:Curved and large structural laminates are difficult to transport.
Uses:
1:One of the greatest use is the making the core of the core plywood or core boards.
2:Laminated wood furniture parts , cores of plywood, sports goods, such as rackets of badminton and tennis , heads of golf clubs etc are made for along time.
3:Most important uses as structural members.
4:Glued laminated timber, glulam, is being used as beams, straight or curved, and other farming member of buildings, bridges etc.
5:Laminated veneer lumber made with thick knife-cut veneer glued together, is another innovative use.
The word laminated from the word lamina means layer. Laminated wood is one kind of manufactured product where two or more parallel- grained layers of planks are joined together by adhesives or other fastener.
Manufacture:
Due to manufacture of laminated wood the individual planks or veneers are dried in dry klin or veneer dryer respectively to a MC between 3-5% and 10-12% depending on adhesive and pressing method. The difference between the laminae not exceeding 5%. L arge differences results is delamination & warping in laminetes due to considerable strees on glued joints.
Picees with case hardening , warp, cheeks, & splits are discarded or defective portion cut out. Wood board is surfaced by machines. Final surfacing is done just before gluing. Short pieces are joints end to end with adhesive for producing longer laminates. Narrow board are glued edge to edge.
The laminae are arranged in the proper order and are spread with adhesives, preferably with a glue spreader.Brushes may be used for spreading glue on some types of lamination, for example, badminton rackets. The glued laminae are assembled ina jig or form and pressure is a applied by clamps fixed at regular intervals. For proper distribution of pressure, caul plates of heavy wood boards are placed on both faces of the assembly for straight laminates. For curved laminates two or more thin cauls are used.
Thin laminates are suitable for curved laminates because it retain shape better after realeasing the preesure. When laminates are made from thin laminae then higher pressure is required because it tends to spring back after removing the pressure and removal from the jag. The pressure is applied by the screw press, clamps or with hydraulic or pneumatic presses. Nailing is also used for applying the pressure but is not recommended because of indifferent results. The dense wood requires more pressure for ensuring intimate contact of the glue and the lamination.
Generally pressures between 10.5 and 17.5kp/cm are required for dense wood and 7.0 and 14.0kp/cm are required for light wood. High pressures are applied for large and heavy laminates and curved assemblies. Small laminates and thin laminaes may be successfully bonded with low pressure.
Due to adhesives requiring high temperature for setting, hot presses may be used to laminate straight assemblies. For curved assemblies, the glued laminations after alamping is put in an oven or a heated chamber. Alternatively radio-frequency heating or low voltage heating meathods may be used. The compitability of the preservatives and the adhesive must be taken into consideration when laminations are treated before gluing and the adhesives should be of highly water-resistant type. The treated laminae should be resurfaced just before gluing to reduce interference by oily solvents or other exudations of preservative materials. Preservative treatment should be applied after lamination. Highly water resistants are also applied in this time too.
For protection against fire, either laminae or laminates are impregnated with fire retardant chemicals, or fire-retardant coatings are applied on all surfaces of the laminate.
Advantages:
1:Huge number of laminated product is produced from smaller pieces of wood.
2:More complete utilization of wood is achieved.
3:Very large load-bearing structural members, difficult to produce from a single piece, can be manufactured.
4:Curved and variously shaped laminates with beautiful architectural designs normally not otherwise available, can be made.
5:Structural members varying in cross-section along their length in accordance with the requirement of strength can be made.
6:Large one-piece wood members take considerable time to dry and develop checking and other seasoning defects which are eliminated by the use of thinner lamination which can be thoroughly seasoned throughout the pieces in less time at lower cost.
7: Forest are conserved and the technology may be considered environment-friendly.
Disadvantages:
1:The careful processing of wood is necessary for gluing, the gluing operations.
2:Extra equipment is necessary for gluing operations.
3:Skilled manpower is essential for the manufacture of laminated wood.
4:Plant machineries are needed for this activities.
5:Curved and large structural laminates are difficult to transport.
Uses:
1:One of the greatest use is the making the core of the core plywood or core boards.
2:Laminated wood furniture parts , cores of plywood, sports goods, such as rackets of badminton and tennis , heads of golf clubs etc are made for along time.
3:Most important uses as structural members.
4:Glued laminated timber, glulam, is being used as beams, straight or curved, and other farming member of buildings, bridges etc.
5:Laminated veneer lumber made with thick knife-cut veneer glued together, is another innovative use.
.
.
.
