The importance of raw paper procurement and inspection in a carton factory
In the entire process of carton production, the procurement and inspection of raw paper are crucial steps. Carton factories carefully formulate raw paper procurement plans according to the actual production needs. As the basic material for carton production, the quality and quantity of raw paper are directly related to the smooth progress of subsequent production and the quality of finished products.
The purchased base paper must undergo strict inspection, which mainly serves two purposes. On the one hand, it is necessary to prevent unqualified base paper from entering the factory. If unqualified base paper flows into the production process, it may lead to various quality problems in the produced cartons, such as insufficient strength and easy breakage, resulting in huge economic losses. Through inspection, the losses caused by base paper problems can be minimized. On the other hand, the performance of the base paper can be thoroughly understood through inspection. Base papers with different performances behave differently in the production process and are suitable for different scenarios. By correctly selecting base paper based on the inspection results, production costs can be minimized while ensuring the quality of the finished products.
Detailed description of the base paper inspection process
1. Verification of delivery note and quantity
After the arrival of the base paper, first, it is necessary to verify whether the delivery note is consistent with the procurement plan and whether the quantity of the arrived goods matches the delivery note. Information such as the variety of the base paper, the marked grammage, specifications, and the number of pieces can be confirmed on the spot. Regarding the weight, it needs to be weighed by a weighing scale, and the weight deviation should be strictly controlled within ±3‰ (three per thousand). If the actual weight is insufficient, it should be deducted according to the regulations. This step is the basis of the base paper inspection, ensuring the accuracy of the procurement information and the authenticity of the quantity of the arrived goods.
2. Appearance inspection of the toilet paper roll
The appearance inspection of toilet rolls mainly includes aspects such as the clarity of markings, the condition of packaging damage, and whether the base paper is damaged or damp. If damage or dampness is found in the toilet rolls, corresponding measures need to be taken.
If the damage or moisture occurs on the side of the toilet paper roll, the method for calculating the weight to be deducted is as follows: First, count from the outside to the layer that is not damaged or affected by moisture, and assume it is the Nth layer; then measure the distance D from the 16th layer to the core; then, combined with the specification L (unit: meter) of the toilet paper roll and the basis weight G (unit: gram per square meter) of the base paper, calculate the weight to be deducted through the formula W = 10⁻³G × L × (2 × 3.14 × D) × N (unit: kilogram).
If the damage or moisture occurs on the end face of the roll paper, it is generally not allowed to exceed 2 cm. Once this standard is exceeded, it will be handled as a return. This is because the damage or moisture on the end face may have a relatively large impact on the overall performance of the base paper, which in turn affects the production quality of the cartons.
3. Inspection of other appearance details of the toilet paper roll
In addition to the above appearance inspection items, some other appearance details of the rolled paper also need to be inspected. For example, check whether there are obvious marks on the end face at the joint of the rolled paper, which helps to identify the joint position during the production process and avoid affecting production efficiency and product quality due to joint problems; examine whether the end face of the rolled paper is flush with the core, whether there is a collapsed core in the rolled paper core, and whether the diameters of the two end faces of the rolled paper are the same. These factors will affect the operational stability of the rolled paper on the production equipment; check the tightness of the rewound paper and whether the tightness of the two end faces is the same, whether the strapping of the rolled paper meets the standards, and whether there is a color difference among a batch of rolled paper. These appearance details also reflect the quality status of the base paper to a certain extent.
4. Inspection of moisture content of toilet paper rolls
The moisture content of rolled paper is one of the important factors affecting the performance of base paper and the production quality of cartons. An insertion-type moisture meter is used to test the moisture content of the rolled paper, and the testing process shall be carried out strictly in accordance with relevant standards. Sampling shall be conducted according to GB13024 - 2003 and GB13023 - 1997. Three reference points shall be evenly selected on each of the two end faces of the rolled paper, and the insertion depth shall be no less than 0.6 cm. The average value of the test results at these six points shall be taken as the moisture content of the rolled paper.
In the base paper supply contract, the delivery moisture content is usually specified, such as (8.0±2.0)%. If the measured moisture content of the rolled paper is within the delivery moisture content range, it is judged to be qualified; if it exceeds the range, it shall be handled as agreed by both parties. Generally speaking, if the moisture content M₁ of the rolled paper exceeds the upper limit Ma of the delivery moisture content and the weight of the rolled paper is W, the weight to be deducted is W×(M₁ - Ma)/Ma; if the moisture content M₁ of the rolled paper is lower than the lower limit Mb of the delivery moisture content, the rolled paper shall be put on the production line for trial use. If it does not affect normal production and the quality of finished products, it shall be treated as qualified; otherwise, it shall be returned.
It is worth noting that the moisture content test of the roll paper should not only be carried out during the incoming inspection, but also be followed up on - site during the use in the workshop, that is, quality tracking. Once problems such as abnormal moisture content are found, contact the supplier in time to solve them, so as to ensure the smooth progress of production and the stability of product quality.
5. Inspection of base paper performance
Since general carton factories do not have the detection conditions of a constant temperature room and considering the timeliness of inspection, the performance inspection of base paper should be carried out under normal conditions. As long as there are no obvious defects on the surface of the rolled paper, samples should be taken from the second layer, and the technical indicators of the base paper, such as basis weight, ring crush strength, bursting strength, breaking length, water absorption, etc., should be inspected according to the methods specified in relevant national standards.
Quantitative inspection: Mainly check whether the base paper has the situation of exceeding the specified grammage or having insufficient grammage. The accuracy of the grammage will directly affect the cost and quality of the carton.
Ring crush strength and bursting strength tests: These two tests are the most critical. The test results are analyzed using regression analysis (see the article "Influence of moisture content on the strength of corrugated cardboard" for details), and then combined with the standards agreed upon by both parties to determine whether the base paper is qualified. The ring crush strength and bursting strength determine the compression resistance and damage resistance of the carton.
Tear length test: It is mainly used to understand the tensile strength of the base paper, which is the main basis for judging whether the base paper is suitable for corrugated production line.
Water absorption test: Water absorption plays an important role in aspects such as the bonding performance, printability of the base paper, and the degree of influence by atmospheric moisture.
In addition, for indicators such as the tightness, smoothness, folding endurance, flat crush strength, and oil permeability of the base paper, it can be decided whether to conduct inspections according to specific production requirements.
6. Test result recording and supplier management
The inspection results of each batch of base paper should be carefully recorded, analyzed and compared. Through the analysis of the inspection results, excellent suppliers can be selected. These suppliers should have characteristics such as stable quality, reasonable price and timely supply, and they should be retained in the supplier list. At the same time, unqualified suppliers should be removed from the supplier list to ensure the quality of the base paper and the stability of supply. The inspection results of the base paper will also serve as an important reference for the configuration of base paper for corrugated board production, which helps to optimize the production process and improve product quality.
Quantitative testing method when there is no quantitative sampler
In the actual inspection process, if there is no quantitative sampler, the ring crush strength specimens can also be used to test the grammage of the base paper. Since the size of the ring crush strength specimen is lengthwise × crosswise = 15.2 cm × 1.27 cm, and its area is 19.304 cm², the total area of 5 ring crush strength specimens is 96.52 cm². The specific operation method is as follows: Weigh the total mass M of N ring crush strength specimens, convert it into the mass of 5 ring crush strength specimens, first multiply it by 100 and then divide by 0.9652, and the grammage W of the base paper can be obtained.
For example, if the total mass M of 10 ring - crush strength test specimens is measured to be 2.89 grams, then the basis weight W of the base paper is W = 100M/(2×0.9652) = 149.7 g/m², that is, 150 g/m². Another example, if the total mass M of 8 ring - crush strength test specimens is measured to be 3.84 grams, then the basis weight W of the base paper is W = 100M×5/(8×0.9652) = 248.7 g/m², that is, 249 g/m². This test method is particularly suitable for the basis weight and strength testing of small specimens, providing more flexibility and feasibility for inspection work.
Supplementary inspection techniques for the basis weight of base paper
The grammage (also known as basis weight, g/m²) of paper and cardboard is one of the most basic technical indicators. Generally, enterprises will be equipped with a grammage sampler. By taking 10 circular paper samples with an area of 100 cm², weighing them in sequence, and then calculating through a formula, the grammage value can be obtained. However, some enterprises directly use a paper cutter to take square paper samples of 10×10 cm² for weighing. This method will produce relatively large errors. It not only fails to ensure the authority of the test results, but may also cause unnecessary conflicts between paper - making enterprises and carton enterprises.
If there is no dedicated quantitative sampler, the ring crush test sampler can be used for quantitative testing. The specific operation is as follows: Equip an electronic balance with a maximum weighing capacity of 110g and an accuracy of 0.01g. Cut 8 samples at equal intervals along the longitudinal direction from a paper sample. The area of each sample is 15.2×1.25 cm², and the area of the 8 samples is 15.2×10 cm². Weigh the 8 samples together. Divide the weighing value by 1.52 and then multiply by 100 to obtain the quantitative value of the base paper. This method provides a feasible solution for enterprises in the case of lacking a quantitative sampler.