Professional training would be good for most of the Plywood QC/QA Parts 3

The white birch plywood ,mostly used for kitchen cabinets and other furniture components and high quality requirements areas such as wiremesh plywood or flooring and other DIEBOARD industry ….

95% of the white birch plywood are exported to North America USA and Canada ,to make cabinet drawersides ,bottoms ,fronts and carcass …It is not like the russia blactic birch ,has 100% birch core veneer insider and outlayer face and bk are also birch .

THe russia birch blactic has a clear wood grain and less mineral streaks ,most of the importers they like the russia birch ,thick face veneer ,premium core construction without major core voids and overlaps .The reason of calling it Baltic Birch plywood is initial supply of birch products produced from trees from the Baltic regions of Europe. Those were countries Finland, Latvia, Estonia and Russia. Later on volumes of supply of Russian birch plywood were dramatically increased. But the product is still called Baltic Birch plywood.

The grading rules of the russia birch plywood is different from Chinese plywood grading rules ,different names letters ,In China,such as B/C ,C/D or D/E E/F ,D+/E and C-/D ….

Baltic Birch plywood is good and better than Poplar core birch plywood because of several reasons:

  1. Birch is very strong material. Plywood made of birch is extremely hard and stable material providing extraordinary technical features.
  2. Appearance of Russian (Baltic) birch is very attractive and suitable for furniture and decoration.
  3. Holding strength of Baltic birch plywood is real good.

Russia grading rules such as see below  Grading like B/BB, BB/BB, BB/CP, CP/CP, CP/C applied to every sheet of Baltic birch plywood on the base of grading of the top and bottom veneer.:

Russian Birch Plywood GOST

All iPc plywood is manufactured in accordance with the Russian Export Grades GOST 1055-71 and exceeds the requirements of the current Standard Export GOST 3916.1-96.

 

Metric Thickness

 

American Equivalent

 

No. Plies

 

Metric Thickness

 

American Equivalent 

 

No. Plies

3mm

1/8”

3

15mm

5/8”

11

4mm

5/32”

3 or 4

18mm

3/4”

13

5mm

3/16”

4 or 5

25mm

1”

17 or 18

6mm

1/4”

5

28mm

1 1/8”

20 or 21

9mm

3/8”

7

31mm

1 1/4”

22 or 23

12mm

1/2”

9

37mm

1 1/2”

26 or 27

Grade “B”: Selected one-piece face generally light and even in color. Occasional small pin knots and some brown streaks may be allowed. Intended for natural finish. No patches allowed. The majority of Grade B veneers are the equivalent of American one-piece select white birch faces.

Grade “BB”: One-piece face generally light and even in color. Occasional sound tight knots are permitted  but open knots and defects in BB have been cut out and replaced with small ovular or round veneer patches before gluing. The veneer selected for the patches is of the same general color as the basic face veneer. Generally there are very few patches per face and many users purchase this grade for cut up for natural finish.

Grade “CP”: One-piece face and very close to Grade BB in quality. Occasional hairline splits are allowed in Grade CP. The ovular or round patches may or may not be matched for color with the base face veneer. There  may be more patches per face than in Grade BB.

Grade “C”: One-piece utility grade veneer available both sanded and unsanded . Open defects and open splits are allowed. Recommended for container, crating, dust panels and usages where construction and strength are important factors and appearance is not important.

Simplified Russian plywood grading rules in accordance with GOST 10.55-71 and GOST 3916.1-96 are presented below:

10.55-71 Grade B Grade BB Grade CP Grade C
3916.1-96 Grade I Grade II Grade III Grade IV
Pin knots Not more than 3 per square meter Allowed Allowed Allowed
Sound intergrown knots Allowed with diameter not more than 15 mm Allowed with diameter not more than 25 Allowed with cracks not wider than 1,5 mm Allowed
Other knots Allowed with maximum diameter 6 mm Allowed with maximum diameter 6 mm Allowed with maximum diameter 6 mm Allowed with maximum diameter 40 mm
Closed splits Maximum length 200 mm Maximum length 200 mm Allowed Allowed
Open splits Not allowed Allowed with maximum size 200*2 mm Allowed with maximum size 300*2 mm Allowed with maximum width 10 mm
Light discoloration Allowed not more than 5% of the surface Allowed Allowed Allowed
Heavy discoloration Not allowed Not allowed Not allowed Allowed
Glue penetration (through faces) Not allowed Allowed not more than 2% of the surface of the panel Allowed not more than 5% of the surface of the panel Allowed
Veneer overlapping Not allowed Allowed with maximum length 100 mm Allowed with maximum length 200 mm Allowed
Repairing by plugs Not allowed Allowed with single plugs Allowed with double plugs Allowed with double plugs
Sanding through faces Not allowed Not allowed Not allowed Allowed

Now,let’s talk about the chinese plywood,make some of the grade custom-made like D+ or C- or E- these grades are created by domestic manufacturers .

When inspect the chinese birch plywood ,know the basis natural characteristics and manufacturing defects are very important to make the Grading job and Inspection REPORTS .

First ,should recognize all the characterists and defects.
Second , have a basic criteria range from the buyers ,judge the grade by the criteria range .THat is have a custom-made grading rules for the customers accroding to the clients’s quality standard .
Third ,grade and inspect the plywood according to the special rules .

Chinese birch plywood ,normally poplar core birch face and back .

The Poplar core we will not talk about it here ,many different quality levels of the core platform used for raw /Plain birch plywood,UV prefinished plywood .Different mills have different core construction and grading checklist and criteria range .

Let’s only talk about the birch face veneers types and quality standards .

Chinese birch face veneer have many groups ,imported birch such as baltic  birch logs ,and chinese domestic birch logs from North of China Dongpei areas .

Face veneer thickness :

THe birch face veneer thickness ,I can remember ,before 2006,the thickness of the face veneer is normally thicker than 0.40mm ,if natural brich ,normally more than 0.45mm .So ,it is good to hide the defects of the inside platform ,even without color-matched putty to make sure no telegraphing problems .All the birch logs used for peeling the face veneers are big diameter logs selected .

Recent years ,the birch face veneer thickness reached to 0.22mm to 0.25mm prior to sanding widely used in chinese mills for raw birch plywood .This is the bad result of the competition of the markets .Also the technology improved and developed peeling process and machinery .THen another industry created by the thinner and thinner face veneer industry ,named COLOR-MATCHED PUTTY/GLUE  industry .

So ,when you buy birch plywood from China,make sure your sourcing managers or purchasing agents should understand these years’s quality difference .Understand the end usages of the birch plywood ,some face veneer from Dongbei ,zuogezhuang area ,some birch face veneer from linyi local and pizhou local peeling factories .

Their grading rules are too much different .

Face veneer natural characteristics :

Why I said Natural characteristics but not Natural DEFECTS ?Because these “DEFECTS”are the natural from the threes but not from the manufacturing process .

I believe some people like these characteristics such as pin knots ,burls ,or some people don’t like .Color viriation ,mineral streaks …,bark pockets …dead knots and knot holes …

SOME of the natural defects can be corrected and improved ,sush as the holes can be repaired by color-matched veneer or repair by putty .

Some of the characteristics can not be avoided ,such as the color variation and burls and live knots …,Streaks ..

Knot holes,DEAD KNOTS AND PIN KNOTS  and Mineral streaks ,color viriation are the three major natural characteristics for White Birch face veneer .

Face veneer manufacturing Defects :

THis is more important checking job than the natural characteristics ,I will talk about it when I come back ,will travel outside now .

Just came back from factory .

For the manufacturing defects ,means the defects were made by the human or machinery or production process ,not from the original trees .Such as open splits ,bubbles ,telegraphing ,glue bleeding problems ,SAND SKIP area ,damaged face veneer ,sanding through ,core veneer joint marks ,oil stain ….Color Discoloration …Sanding Quality problems .THESE ARE the normal defects from white birch especially the telegraphing problems because of the thin face veneer .

One thing should be clear ,the white birch dense is bigger than other hardwood ,so sanding the birch plywood,need the surface should be smoothly sanded but not rough sanding .High quality white birch always have a good surface can show the real wood grain and characteristics of the birch .Need a good sanding machine to do white birch plywood .

Open splits and closed splits are the two major manufacturing defects of the white birch ,not easy to use color-matched putty to repair and sand after hot pressing .So ,before the hot pressing,should requested the workers to repair the open and closed splits with face veneer or putty very well .

If the white birch face veneer is so dry ,spray some water to make sure the face is not shrink and the face veneer overlaps will be avoided .If not ,after hot pressing ,the face veneer overlaps will be changed to open splits or closed splits after the workers repair them .

Here ,we will talk about the bleached white birch ,means the original birch is natural birch or red birch ,after chemical bleached,the natural birch will be white color or yellowish color birch ,we call it bleached birch .

So when purchasing the bleached birch ,need to be careful about the color changes ,if put sunshine long time ,the color maybe will change yellowish .If not well bleached,the discoloration is the big problems ,especially when make the UV prefinished ,can see clearly the problems .

Bleached birch has very less knot holes or dead knots ,if lower grade natural birch ,will not be used for bleaching .Just bleach the natural birch without knot holes and dead knots or no black minerals streaks ,to UPGRADE the natural birch to higher grade white birch .

 

 

 

 

 

 

 

 

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