Img-CS Veneer Dryer-Img-CS-Veneer-Dryer

The Density of Plywood is higher than the density of the timber species used to manufacture the products .

The Density of Plywood is higher than the density of the timber species used to manufacture the products .The face/back veneers of plywood weight practically much less than the core veneers. So the density of plywood is mainly depended on the timer species of the core veneers .

Usually 4 kinds of timber species are used to manufacture the cores of plywood ( film faced plywood ) , i.e. birch,Eucalyptus hardwood,other tyeps of  hardwood, pine and poplar. The density of different plywood is listed as follows:


PLYWOOD (FILM FACED PLYWOOD) DENSITY (KG/M3 or KG/CBM)

BIRCH CORE PLYWOOD (FILM FACED PLYWOOD)

ABOUT 680~700

HARDWOOD CORE PLYWOOD (FILM FACED PLYWOOD)

ABOUT 580~620

PINE CORE PLYWOOD (FILM FACED PLYWOOD)

ABOUT 570~610

POPLAR CORE PLYWOOD (FILM FACED PLYWOOD)

ABOUT 500~530

Sometimes, buyers order combi core plywood , such as combined poplar/hardwood, combined birch/poplar and so on . The density of combi plywood is depended on the components of core .

FILM FACE BIRCH BACK JUMBO SIZE PLYWOOD USED FOR CONTAINER OR TRUCK

Film face birch back jumbo size plywood used for container or truck

4’x10′ and 4’x12′ ,

the back is birch ,joint face veneer or whole pieces face ,the face is film used for film faced plywood,whole piece of film .

PUTTY MARKS/PUTTY  SMEAR AND OPEN SPLITS OF THE NATURAL BIRCH PLYWOOD

Putty marks and open splits of the natural birch plywood

If   at each  end well  filled  and  matched  for  colour   ,will be accepted.

Permitted  if  not  conspicuous
Permitted  if  not  severe

GENERAL  GRADING  RULES  –  CHINESE  BIRCH   POPLAR  PLYWOOD  &  RED  FACED
HARDWOOD  THROUGHOUT  PLYWOOD

 

AREAS OF USAGE:
  1. Construction
  2. Ourdoor furniture
  3. Underlayment for engineered flooring
  4. Platform for phenolic Film Faced lamination
  5. Yacht and ship building
  6. Playing sports for children
  7. Furniture manufacturing
  8. Exterior design
  9. Packaging

plywood production process

 

Raw material.

Birch logs serve as raw material for plywood manufacture. The raw material is supplied to the enterprises by railway, by trucks and also by waterway/

Soaking.

The hydrothermal processing of plywood raw material is performed before veneer peeling to increase the plastic properties of timber and to provide qualitative veneer. The hydrothermal processing is carried out by boiling of raw material in boiling pools. There are open pools of cyclic type, and also covered pools of continuous type.

Debarking and Cutting.

Timber products for the peeled veneer manufacture are supplied to the enterprise in blocks. The blocks for peeling after hydrothermal processing are cut for blocks ready for peeling.

Peeling.

Peeling is a process of timber cutting at which a continuous tape of wood – veneer – is removed from the rotating block by the forward moving knife. The continuous tape of wood is cut for the format with the help of scissors and piled. Then veneer is moved to drying.

Drying of veneer.

Drying of veneer is performed by roller dryers. Veneer is moved along the dryer by the system of a pair of rotating rollers. When passing the drying chamber, veneer is dried up to humidity of 6 ±2%. In the cooling chamber veneer is cooled.

Sorting of veneer.

Veneer is sorted by the grades: B, BB, C,D E F C – for the external layers and for internal layers according to the technological instruction.

Repairing of veneer.

Repairing of veneer is a technological process of veneer elevation with the purpose of increase of its grade. The repairing includes removal of defects from veneer sheets with the subsequent closing up of these places by inserts from qualitative veneer, and also gluing of face cracks with glutinous tape, or stapling of cracks with metal clips.

Technological process of plywood manufacture from veneer.

The technological process of plywood manufacture consists of the following operations:

· Preparation of glue;

· Application of glue to veneer;

· Formation of packages;

· Preliminary cold pre-pressing

· Hot pressing.

Gluing and laying up

This process includes application of a glutinous layer to veneer by the glue application machine tool by passing of the veneer sheets between the rotating glutinous drums and stacking of veneer sheets in a certain sequence depending on the grade and thickness of plywood.

Plywood Pressing

Plywood is glued by hot technique in hydraulic press with maintenance of a certain temperature mode depending on the mark and thickness of plywood. Before hot pressing the plywood packages pass cold pre-pressing. Stuck together plywood after 24 hour conditioning is sent to edge scrapping and grinding.

Plywood edge trimming

This operation is made with the purpose of giving the certain geometrical sizes to plywood. The operation is made over each sheet by format-edging machine tools located one after another and making paired scrapping of two parallel edges of a sheet.

Sanding of plywood

This operation is carried out for alignment of plywood surface and elimination of difference in thickness, and also for giving the product more attractive commercial appearance. The supreme and average grades of plywood only are exposed to sanding.

Grading of plywood.

At sorting the following is determined: the amount and defects of timber, defects of processing, durability of gluing, sizes, deformation of sheets. The sorters of plywood visually determine the grade of each sheet and reveal the hidden defects: stratifications, bubbles. Bubbles are found by knocking the surfaces of plywood with wooden hammer or with the help of automatic ultrasonic defect scopes. The plywood with stratifications is rejected. At sorting the manual completion of plywood is also carried out with the purpose of elimination of some defects, for example, additional polishing of separate places, puttying of cracks. Some sheets of plywood are directed for additional scrapping with the purpose of elimination of defects which cannot be removed by sorting.

Marking and packing of plywood sheets.

On each sheet of plywood precise marks as a round stamp are put by an indelible paint. The stamps are put in the right corner of the reverse side of plywood. All plywood is packed into the packages providing integrity and safety while delivery. Plywood is subject to protection from above and from below by covers and from the lateral faces – by facings. The marks of packages are made by an indelible typographical paint and are put onto two opposite facings of a package.

Storage.

Plywood is stored in the specially equipped warehouse of finished goods with the environment protection provided.

 

Plywood Production Process.jpg

Plywood Production Process.jpg

Plywood Production ProcessPlywood Production WorkPlywood production

If   at each  end well  filled  and  matched  for  colour   ,will be accepted.

Permitted  if  not  conspicuous
Permitted  if  not  severe

GENERAL  GRADING  RULES  –  CHINESE  BIRCH   POPLAR  PLYWOOD  &  RED  FACED
HARDWOOD  THROUGHOUT  PLYWOOD
GRADE  B/BB
Particulars
Face
Back
Sound  live  knots
Max  diameter  13mm
Not  clustered  Max  4  per  panel
Max  diameter  25mm
Max  5  per  panel
Dead  or  unsound  knots
Not  permitted
Not  permitted
Open  knot  holes
Not  permitted
Not  permitted
Pin  knots
Permitted  if  tight  and  not
clustered
Permitted
Sound  burls
Permitted  if  smooth
Permitted
Dry  pitch  pockets
Not  permitted
Permitted  if  well  filled,
Max  size  100  x  4mm,  Max  2  per
panel
Minor  natural
Discolouratioon
Permitted  if  not  conspicuous
Permitted  if  only  slightly
conspicuous
Stains  /  mineral  streaks
Permitted  if  not  conspicuous
Permitted  if  only  slightly
conspicuous
Decay
Not  permitted
Not  permitted
Cross  split
Hairline,  max  100mm  in  length
Permitted,  Max  1  per  panel
As  per  face
Open  split
Hairline,  max  100mm  in  length
Permitted,  Max  3  per  panel
(unfilled)
As  per  face
Filled  splits
Max  size  150  x  3.0mm,  max  2  at
each  End,  well  filled  and
matched  for  colour
Max  size  300  x  5.0mm,  max  2  at
each  end  well  filled  and  matched
for  colour
Putty  smear
Permitted  if  not  conspicuous
Permitted  if  not  severe
Pinworm  holes  /  tracks
Not  permitted
Occasional  pinworm  holes
permitted  if  Scattered,  well  filled
and  matched  for  colour
Pin  holes
Not  permitted
Permitted  if  not  conspicuous
Vine  marks
Max  size  100  x  4.0mm,  max  2
per  Panel  if  level  and  smoothly
sanded
Permitted  if  occasional  if  level
and  smoothly  sanded
Rough  cut
Permitted  if  smoothly  sanded
Permitted  if  smoothly  sanded
Torn  grain
Permitted  if  very  slight
Permitted  if  slight
Patches
Not  permitted
Permitted  if  not  conspicuous,
max  3  per  Panel.
Shims
Not  permitted
Permitted  if  not  conspicuous  and
do  not  exceed  300  x  5.0mm  long
grain.
Veneer  joints
Max  1  per  panel,  well  made,
parallel  to  edges  and  well
matched  for  colour  and  grain
direction
Max  2  per  panel,  well  made,
parallel  to  edges  and  well
matched  for  colour  and  grain
direction
Tape  or  glue  residue
Not  permitted
Permitted  if  slight  and  smoothly
sanded
Knife  marks
Not  permitted
Max  0.7mm  if  smooth  and  not
Conspicuous
Sanding
Smooth,  free  from  conspicuous
Streaks  or  chatter
Smooth
Bark
Not  permitted
Permitted  if  very  slight
Mechanical  defects  (oil
stains,  chain  marks,
sanding  burns  etc)
Not  permitted
Permitted  if  not  conspicuous
Wet  pitch
Not  permitted
Not  conspicuous
Press  marks
Not  permitted
Not  permitted
Core  voids
Permitted,  max  5mm  wide  filled
with  veneer

Core  gaps
Permitted,  max  200  x  5.0mm,
smooth  and  not  severe

There are the following grades of birch plywood depending on quality of face veneer: B, S, BB, CP, C.
The common combination of face and back veneer marks the grade like: B/BB, S/BB, BB/BB, BB/CP, CP/CP, BB/C, CP/C, C/C.

according to TU 5512-001-44769167-02

Defect

Grade

B

S

BB

CP

C

1. Knots:

a) pin knots

Allowed

b) inter-grown, sound lightа and dark knots

Not taken into consideration in size (mm)

Sound knots with splits not more than 1,5 mm

Allowed

Light knots up to 10 mm

Light and dark knots up to 10 mm

Light knots up to 25 mm, no more than 8 knotsа per m2of the sheet

Light and dark knots up to 25 mm, no more than 3 knots per m2of theа sheet

Light and dark knots up to 25 mm, no more than 20 knots per m2 of the sheet; 5 knots of the amount up to 40 mm

With radial checks no more than 1.0 mm wide

c) partly inter-grown

Among inter-grown knots up 5 mm , no more than 3 knots per m2 of the sheet

Allowed among inter-grown knots up 10 mm , no more than 3 knots per m2 of the sheet

Allowed among inter-grown knots up 15 mm , no more than 10 knots per m2 of the sheet

Allowed

Allowed

d) black, loose knots and knotholes

Among inter-grown knots up to 5 mm, no more than 3 knots per m2 of the sheet on condition of putty closing and sanding

Not allowed

Not allowed

Not allowed

Allowed up to 40 mm, no more than 10 per m2 of the sheet

2. Splits:

a) closed splits

Allowed edge splits

Allowed

up to 100 mm long, no more than 1 split per 1 m of panel width

up to 200 mm long, no more than 2 splits per 1 m of panel width

up to 200 mm long, no more than 2 splits per 1 m of panel width

b) open splits

Not allowed

Allowed edge splits

up to 2 mm wide, 200 mm long, no more than 1 split per 1 m of panel width In case of putty repair

up to 2 mm wide, 250 mm long, no more than 1 split per 1 m of panel width

up to 2 mm wide, 600 mm long, no more than 3 splits per 1 m of panel width

up to 10 mm wide, 600 mm long, no more than 3 split per 1 m of panel width

3. Defects of wood structure:

a) cross grain, wavy fiber, curlyа grain

Allowed

b) inter-grown bark pocket (light)

Not allowed

Allowed

c) inter-grown inbark (dark)

Not allowed

Allowed

d) false heartwood

Not allowed

Allowed no more than 25% of the sheet surface

Allowed no more than 75% of the sheet surface

Allowed

e) flecks

-fiber veins and their traces

Not allowed

Allowed up to 175 mm long, 4 mm wide

Allowed up to 250 mm long, 10 mm wide, no limits in number

Allowed

-veins grouping

Not allowed

Allowed not more than 60×40

Allowed

4. Chemical coloring

Not allowed

Allowed

5. Fungal affection

a) fungous stain (blue stain fungi, colored spots)

Allowed insignificantly contrasted to the color, up to 15% of the sheet surface

Allowed

Allowed up to 50 % of the sheet surface

Allowed

b) brown streak

Not allowed

Allowed

Allowed up to 50 % of the sheet surface, general area of redtop together with false heart shouldn`t be more than 50 % of the sheet surface

Allowed

6. Knots and holes repair

Allowed as per item 1 d) of present table

Veneer patching with selection of color and direction of wood grain up to 1 peace per m2 of the sheet

Knots and knotholes of sizes more than indicated inа items 1b) and 1c)а should be repaid by veneer patches

Allowed

Veneer patching with selection of color andа direction of wood grain. Total number of patches with allowed sound inter-grown knots shouldn`t be more as per item 1 b). One double patching is allowed on the sheet

Allowed double patches. Allowed repair of holes from fallen patches with putty and following sanding

7. Splits repair

Not allowed

Allowed as per item 2b) of present table

Allowed putty repair and sanding of splits with width up to 10 mm and length up to 250 mm

Allowed putty repair and sanding of splits with width up to 10 mm and length up to 600 mm

Allowed putty repair and sanding of splits with width up to 25 mm and length up to 1000 mm

8. Glue penetration

Allowed 1 per m2,а in shape of streak with length up to 175 mm and width up to 1 mm

Allowed in shape of spot no more than 15×15 mm, up to 3 spotsа on the sheet

Allowed 1 per m2,а in shape of streak with length up to 250 mm and width up to 1 mm or in shape of spot no more than 75×75 mm

Allowed

9. Imprints and hollows

Not allowed

Allowed 1 spot on the sheet up to 5 mm in size in case of putty repair and sanding.

Allowed 1 per m2, up to 6 mm in size on condition of putty repair and sanding.

Allowed on condition of putty repair and sanding.

Allowed

10. Mechanical defects: -scratches

Not allowed

Allowed

11. Sanding through

Not allowed

Allowed no more than 5 % of panel surface

Allowed no more than 10 % of panel surface

12. Spots of production nature

Not allowed

Allowed

13. Presence of glue tape

Allowed in non-sanded plywood

14. Edge defects after cutting (splitting, scriber saw traces) and sanding

Allowed within 2 mm from panel side

Allowed withinа 5 mm from panel side

Allowed withinа 5 mm from panel side

Allowed withinа 5 mm from panel side

Allowed within 5 mm from panel side

15. Roughness parameterа per GOST 7016-82, mkm

-for sanded plywood

100

-for non-sanded plywood

200

16. Warp

Doesn`t apply to thickness under 5 mm, For plywood over 5 mm thick allowed up to 15 mm per 1m panelТs diagonal length

Film-faced plywood  

Film-faced plywood is subdivided into grades based on the surface quality. The common combination of face and back surface marks the grade like 1/1,1/2, 2/2.

according to TU 5512-002-44769167-98

Defect

Grade

1

2

Film lifting-off and breaking

No

Film crumbling on the edges

No

Allowed up to 5 mm from the edge on condition of waterproof painting

Overlaps of a film

No

Allowed

Burnt film

No

Without film damages

Spots from outfall knots and splits in inner lays

Allowed no more than 2 spots per 1 m2 in dot elements structure

Allowed

Whitish stainsand strips on the film

No

Allowed

Hollows

No

Allowed up to 0,3 mm

Scratch

No

Allowed without coating damages

Splitting at the edge

No

Up to 15 mm on condition of waterproof painting

Drips on the surface

Allowed up to 3 mm at edges

Allowed up to 3 mm at edges

Splitting at the edge

No

Allowed

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