How to calculate the weight of fabric
1. Weight per square meter
Analyze whether the yarn count and density are correct. Cut the two warp yarns and two weft yarns along the four sides of the sample into a rectangle or square. Use a steel ruler to measure its length and width (cm). Then find the area (square centimeters) of the natural cotton sample after cutting, and weigh it on the balance (milligrams)
Weight of sample fabric per square meter per square meter = weight ÷ 1000 ÷ (area ÷ 10000) = weight ÷ area × 10;
1. Use calculation methods and tools together
For example: a sample cloth is 7 cm long, 8 cm wide, and weighs 772 mg. Then the weight per square meter of the finished sample cloth = 772 ÷ (7×8) ×10=138 grams
2. Tool method
Use a circular disk cutting sampling knife, place the fabric sample underneath, rotate it clockwise a few times, and take three circular sample fabrics on the natural cotton cloth (take them 20CM away from the edge or tail) , and weigh it on an electronic balance to measure the specific data.
2. Calculate the weight of color cloth per square meter
The weight per square meter of natural cotton fabric refers to the weight per unit area of the fabric, generally expressed in grams per square meter (g/m2) or ounces per square yard (oz/Y2). The actual weight per square meter is closely related to the cotton mix, yarn count and thickness, finished product width, and finishing process. The weight per square meter is simply calculated:
1. Calculation of weight per square meter of non-elastic fabric:
(warp density/warp yarn count of natural cotton cloth + weft density/weft yarn count of natural cotton cloth)*24.3
For example: Calculate the weight per square meter of 20*16 / 128*60/63〞.
（128/20 + 60/16）*24.3≈246.6(g/m2)
Its weight per square meter is approximately 242-248g/m2.
2. Weight of finished elastic fabric per square meter
Reed width on the machine/finished door width*(density on the machine/number of warp yarns*22.17 + weft density of natural cotton fabric/number of weft yarns*21.4)
For example: Calculate variety C78〞 20*16+70D / 116*48 Weight per square meter
78/58*（116/20*22.17+48/16*21.4）≈259（g/m2）
The actual weight per square meter is about 260-265g/m2.
Note: 78″ is the reed width on the machine, and the finished door width is 58″
3. Simple calculation and weighing
Simple calculation formula: Compare the weight per square meter of natural cotton fabric with the weight per square meter of the weighed finished fabric sample. Under normal circumstances, the difference within ±5 grams is within the normal range. Large differences require careful analysis. Based on our many years of experience, we have summarized a few rules:
Generally, differences within ±5 grams are more normal.
If the difference is large, analysis is required. The principle is as follows: the difference of combed compact yarn is slightly smaller.
(1) Polyester-cotton or polyester-nylon blended chemical fiber fabric yarn and chemical fiber yarn have a conversion constant greater than 583.1 of pure cotton. The same yarn count has a larger number, so the calculation is fixed The weight is smaller than the actual weight;
(2) Strands are made of two or more single yarns that are twisted together. Due to twist shrinkage, the actual yarn count is thicker, and the calculated weight is larger than the actual The weight is small, and when the warp and weft yarns are both strands, the difference is large;
(3) Open-end spinning is a short fiber yarn, which loses more during pre-treatment and scouring during printing and dyeing, and its calculated weight is heavier than the actual weighing;
( 4 ) The weight per square meter is about 5-6.5% larger after washing;
(5) When dyeing dark colors, due to the weight of the dye, the calculated weight is slightly larger than the actual weighing;
(6) The calculated weight of bleached blanks and light-colored blanks is slightly larger than the actual weight;
( 7 ) The weight per square meter after PU coating is 3-7% heavier;
( 8 ) The weight per square meter after grinding is 3.5-6% lighter;
4. Reasons for the reduction in weight per square meter of finished products
① Excessive pre-processing stretching will cause a reduction in weft density.
②The finished door width is stretchedwide.
③Excessive alkali concentration and excessive post-process finishing temperature will cause damage to the spinning fibers.
④ When purchasing raw yarn, the spun yarn is too thin. For example, the actual measurement of 40S is only 41S.
⑤ The original yarn is greatly worn during the weaving process, which will cause excessive hairiness to fall off, resulting in thinning of the yarn and low weight per square meter.
⑥Re-changing or stripping the color during the coloring process will cause a large loss of spinning yarn and cause the yarn to become thinner.
⑦ During the singeing process, the excessive firepower of the singeing will cause the cloth surface to be too dry, and the spinning yarn will be damaged during desizing, causing it to become thinner.
⑧ Damage to the cloth surface during finishing after the catching process and sanding process.
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