Plywood Quality Inspection Process
plywood quality process
1. The grading of plywood products should be inspected according to four aspects: appearance quality, size, physical and mechanical properties and formaldehyde emission. Among them, physical and mechanical properties and formaldehyde emission should be sampled and sent to the laboratory for inspection.
2. The inspected products must be randomly sampled from the whole batch of finished products, and the sampling quantity is determined according to the national standard.
3. Appearance quality inspection is generally judged by visual inspection of allowable defects on plywood. The grade depends on the allowable material defects, processing defects, and requirements for splicing, etc.
4. Size inspection of plywood
4.1 According to the different nominal thicknesses of plywood, the deviation between the average thickness and the nominal thickness of the plywood, and the maximum difference in the measurement of the thickness of each board shall comply with the regulations. The average thickness of the board should be accurate to 0.1mm.
4.2 For plywood that meets the specified size, the length and width tolerances are +5mm, and negative deviations are not allowed.
4.3 The difference between the two diagonal lengths of plywood shall not exceed 3mm.
4.4 The warpage of plywood with a nominal thickness of more than 6mm shall not exceed 1%.
5. Measurement method
5.1 Sampling As the batch testing of finished products, it should be sampled according to the provisions of GB9846.6.
5.2 Moisture content during measurement The measurement should be made on plywood whose moisture content meets the requirements of GB9846.Carried on.
5.3 Instruments
5.3.1 Thickness measurement Vernier caliper, the reading accuracy of division is 0.05mm.
5.3.2 Length, width and diagonal measurements A suitable steel tape measure with a reading accuracy of 1 mm.
5.3.3 Measurement of warpage A metal ruler or cord of appropriate length, and a suitable measuring instrument with a reading accuracy of 0.5 mm.
5.4 Procedure
5.4.1 Thickness Measure at the middle of each of the four sides of the board, at a distance of not less than 10mm from the edge of the board, with an accuracy of 0.1mm. When measuring, the measuring instrument should be in contact with the board slowly and without excessive pressure. Take the arithmetic mean of the above-mentioned 4 times to measure the average thickness of the sheet.
5.4.2 Length and width Measured parallel to and 100mm from the edge of the board to be measured, accurate to 1mm. Measure the length and width of each board twice. Take the average of the above two measurements in the same grain direction as the length and width of the board, respectively.
5.4.3 Diagonal Measure along the two diagonal directions of the board, accurate to 1mm. The difference between the two diagonal directions is the contrast of the diagonal length of the board.
5.4.4 Warp degree Place the plywood on the water platform with a concave westward facing upward and without any external force, place a metal ruler or a taut cord on the board surface along the two diagonal directions respectively, and measure the board with a measuring instrument The maximum deviation between the surface and the ruler or string (that is, the maximum chord height of the diagonal), accurate to 1mm. Use the following formula to calculate the warpage, accurate to 0.1%. Warpage = maximum diagonal chord height (mm) / diagonal length (mm) × 100 (%) Note: The diagonal length is the measured value of 5.4.3.
5.5 Representation of results All measurement results and calculation results shall be recorded. Representation method: thickness, accurate to 0.1mm; length, accurate to 1mm; width, accurate to 1mm; diagonal length difference, accurate to 1mm; warpage, accurate to 0.1%.
5.6 Test report The test report shall include the following: a. The species and type of plywood, and all the details required to identify this plywood: b. Sampling method: c. Moisture content of the rubber platen during measurement: d. measurement results.
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