Blockboard QC Inspection Checklist : Part 2 Blockboard–Measurement of Shape Size (GB 5855-1986)

Blockboard QC Inspection Checklist : Part 2 Blockboard–Measurement of Shape Size (GB 5855-1986)

This standard is applicable to china blockboard. It specifies the method of determining the shape size, sawing error, warpage and waviness of blockboard. The definition of this kind of blockboard can be found in GB 5849-86 Definition and Classification of Blockboard.

2 Measuring Instruments and Equipment

2.1 steel tape, 3000 mm, accuracy 1 mm.

2.2 vernier caliper with accuracy of 0.02 mm.

2.3 ruler, length 1000 mm, straightness less than 0.1%.

2.4 ruler, length 300 mm, straightness less than 0.1%.

2.5 ruler with 500 mm length and less than 0.1% straightness.

2.6 gauge, 0.05-10 mm.

3 Sampling

Sampling is carried out according to the relevant provisions of GB 5850-86 “Technical Requirements and Acceptance Rules for Blockboard”.

4 methods

4.1 The determination of length and width of blockboard. Measure with steel tape at the center line of length and width, accurate to 1 mm.

4.2 To determine the thickness of blockboard, four points are measured with vernier calipers, whose positions are 20 mm from the center line of length and width to the edge of the board. The reading of each point is accurate to 0.1 mm, and the arithmetic average is accurate to 0.1 mm.

4.3 The determination of diagonal sawing error of blockboard.

4.3.1 Method: The Blockboard was flattened and the length of its two diagonals was measured with a steel tape ruler with an accuracy of 1 mm.

4.3.2 According to formula (1):

……………………………………………………… (1)

In the formula, the sawing error of_-diagonal line,%;

Lmax – Long diagonal length, mm;

Lmin – Shorter diagonal length, mm;

L – The diagonal nominal length of the measured blockboard, mm.

Note: The calculation is accurate to 0.01%.

4.4 Determination of Edge Straightness of Blockboard

4.4.1 Method: When measuring, the flat side of a straight ruler with length of 500 mm is close to the measuring side, and the maximum gap width between the plate side and the ruler side is measured with a plug ruler, which is accurate to 0.05 mm.

4.4.2 Formula (2) for calculating the edge straightness of blockboard is accurate to 0.01%.

……………………………………………………… (2)

In the formula: Un – non-straightness of the edge of the joinery board,%;

Delta – maximum gap width, mm;

L – Length of ruler, mm.

4.5 Determination of Warpage Degree of Blockboard

4.5.1 Method: Put the joinery board on the platform (convex face down); put the length of 1000mm ruler along two diagonals at any place on the board surface, its straight edge is close to the board surface, and measure its maximum chord height with a plug ruler.

4.5.2 is calculated by formula (3) and the accuracy is 0.01%.

……………………………………………………… (3)

Formula: W – warpage of blockboard,%;

H – diagonal chord height, mm;

L-diagonal nominal length, mm.

Determination of Ripple Degree of 4.6 Blockboard

The straight edge of the straight ruler with length of 300 mm is close to the panel of the blockboard, and the maximum distance between the straight ruler edge and the corrugation of the board surface is measured with a plug ruler.

When measuring, the ruler of the straight edge should be greater than 20 mm from the edge of the plate, and three places with large waviness should be selected for arbitrary measurement. Take the maximum value, accurate to 0.05 mm.

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