For the carton products, the inspection of the base paper crush strength, the edge pressure strength of the paperboard, and the bond strength, etc., for the accurate evaluation of the quality of raw materials and the effect of the production process, to further control the production process, improve product quality Very important significance. Our factory is a professional packaging and printing factory. Carton production is one of our main products. For this reason, we attach great importance to the production quality of the carton. We have established a laboratory, added testing equipment, and conducted systematic inspections of raw materials and finished products. To ensure the quality of the product. The author will make some conclusions about the experience of debugging, use, and testing of the testing instruments for peer reference.
First, the performance, use, maintenance and adjustment of the electronic compression strength tester
1. Test the performance of the instrument. ZSD-3 type electronic compressive strength tester is the main detection instrument for detecting the physical properties of paper, cardboard and carton. Correct understanding and understanding of the instrument's performance, structure and application knowledge is an effective guarantee for improving the quality of the test. The instrument is composed of base, transmission mechanism, high-precision pressure sensor, electric control box and touch panel. The electronic control system is based on 16-bit single-chip computer 888196 and forms an intelligent detection system. During the test, the sample is placed in the center of the upper and lower platens. After pressing the test button, the upper platen under the action of the transmission mechanism makes the upper platen uniformly drop at a constant speed. When the pressure reaches a certain value, the sample is crushed. The test value is immediately displayed on the LCD screen. At the same time, under the action of the electronic control system, the motor automatically returns and the upper platen returns to the initial position. Two limit switches are installed in the worm gear box of the instrument to control the extreme position of the upper platen to ensure the safe use of the instrument. The measuring range of the instrument is 0 to 3 000 N. If the pressure is significantly greater than 3 000 N, the sensor is easily damaged. Therefore, the limit position of the limit switch is required to be accurately adjusted, and the failure should be promptly replaced if it is damaged.
2. Use and maintenance. The working environment of the instrument is 10~35°C; the relative humidity is less than 80%. It is better to install the air conditioning equipment. The instrument should be placed horizontally on a solid, firm, vibration-free cement or marble platform to ensure accurate test values. During the test, care must be taken to observe the test carefully. If the paper is too soft and the pressure is not enough to generate a sensory effect, automatic parking cannot be achieved. The upper platen will stop pressing underground. At this time, press the parking button immediately to force the parking to prevent Failure of the upper platen to press on the tray or guide block damages the instrument. The instrument's upper and lower platens must not be loosened. Otherwise, the test value will be obviously error. A certain amount of grease (butter) should be kept in the screw and worm gear box to prevent the key parts from being worn and loose and affecting the accuracy of the test data. The flange plate on the instrument not only supports the upper plate, but also acts as a fastening. If the screw is loosened due to tremor and the flange is loose during use, the upper platen will not be completely crushed. Samples, but the LCD screen shows a test result with a significantly lower value, so, usually should pay attention to check the tightening of the flange screws are loose, in order to take appropriate measures to tighten. The degree of parallelism between the upper and lower platens is also directly related to the accuracy of the test. Loosening of the fastening screws on the base and the housing will inevitably affect the parallelism of the upper and lower pressure plates. When the test is performed, a biased contact situation will occur, resulting in inaccurate detection data. If the screws are evenly tightened and there are still uneven conditions, then the gasket method should be adopted to properly raise the low shell so that the relative parallelism between the upper and lower platen is about less than 0.05mm, so as to ensure the detection. accurate.
3. Do a good job of adjusting the instrument to ensure that the test value is accurate. Tuning is an important and meticulous task. After testing a project, before testing another project, the instrument should be zeroed and adjusted because the trays and guides for detecting the ring pressure strength, side pressure strength and peel strength are Blocks and stripping racks are not the same weight, their own weight on the pressure generated by the lower platen must have a size difference, so it must be zero, remove the pressure of the test attachment on the pressure plate to ensure the accuracy of the test. When zeroing, test attachments (such as stripping racks, trays, etc.) should be placed on the lower platen, and the dial switch on the back of the instrument should be set to the red dot side. Then, adjust the zero adjustment knob on the right side of the instrument. It is appropriate to adjust the 1F value on the LCD screen to between 0 and 0.2. After adjustment, switch the dial switch back to the side without red dot, and then press the reset button to perform formal inspection. In addition, when the instrument fails to repair, if it is suspected that the indication is not accurate, the weight of the standard weight can be used for verification. The method is: remove the inspection attachment on the lower platen, and let the upper platen rise to the spacing when the weight can be put into the lower platen. After the zero adjustment is completed, press the test button to press the upper platen for a short period, and then place the weight on the lower platen. The error value between the value displayed on the LCD screen and the weight should be ≤±1%. The relative error of indicating value repeatability should be ≤1%, which is in accordance with the instrument technical parameters.
Second, conscientiously put a good inspection process technology, and constantly analyze and summarize testing experience, improve the accuracy of inspection
Turn off good sampling techniques. Sampling is a meticulous and serious task that does not allow for sloppy work. Otherwise, the accuracy of the test will not be discussed. Sampling should be taken from different locations. For example, the roll paper should be taken from two sides and different parts in the middle. Three corrugated cartons should be selected as test samples, each of which was cut from seven different samples, a total of 21 samples, of which 12 were used for the detection of adhesive strength and 9 were used for the detection of edge pressure. The basic requirement for sampling is that the pattern taken must be flat, with no creases, no wrinkles, no dents, no bends, no deformation, and no damage; the corrugated board should be free from stumbling, non-flat buckling, No damage, no blistering, no degumming and no deformation, which is the basis for determining the accuracy of the test. Sampling should be divided into three links, namely, hair samples, large samples, and small samples (standard samples). The hair sample is mainly selected from the preliminarily selected paper (board) and cut out with a knife or scissors. The paper edge does not require a very neat appearance. The sample size is based on the size of the standard sample size, and the hair sample is cut into a rectangular shape of an appropriate area as appropriate, and the trimming edge is aligned with the silk or corrugated file of the paper so that the standard sample can be cut accurately. After the sample is cut, it can be easily and accurately cut into standard samples. The standard of the ring pressure strength, its long side must be in parallel with the transverse filaments of the paper, so as to detect the transverse crushing strength of the paper. For the standard of edge pressure strength and bond strength, their tongue and groove should be perpendicular to the long edge of the paperboard. Defects such as test patterns, size deviations, and burrs will affect the inspection results. Therefore, the sampler's rules must be accurate and the knife edge must be sharp. In order to improve the accuracy of the test, the paper wool sample should be hung in a constant temperature and humidity laboratory, after 24h treatment, and the sample of the corrugated paperboard should be subjected to a constant temperature of 48 hours. Constant humidity treatment can make the characteristics of the sample relatively stable. However, the acceptance of corrugated paper materials is often difficult to achieve. Based on this situation, we have conducted experimental analysis and summarization, using the test result multiplied by a certain coefficient, and thus obtained a relatively accurate test conclusion. The specific approach is to divide the same sample into two parts and arrange them separately for inspection under two conditions. One is to conduct self-inspection under natural conditions by the laboratory of the factory, and the other is to send the sample to the laboratory of the professional organization in the standard. Under the condition, the paper sample is pretreated and then tested. Then, the two test results are compared and the coefficient of difference between the two is obtained. After many such comparison experiments, a more accurate coefficient is finally obtained. Take the ring pressure index as an example. After dozens of comparison experiments, the coefficient is always between 1.22, 1.23, and 1.24. We set the coefficient to 1.23 so that the result after each self-check is multiplied by 1.23. The numerical value, in order to test the judgment result, can obtain relatively accurate test conclusions and play a better control role for the raw materials.
Third, the ring pressure strength, side pressure strength and adhesive strength of the test requirements and detection of numerical conversion method
1. Ring pressure strength testing requirements and conversion formulas. The standard sample specification should be: length (longitudinal) 152.0 ± 0.2mm, width 12.7 ± 0.1mm, take 10 pieces to be tested, 5 of which are tested outwards outwards, and the other 5 pieces are tested outwards by loading them into a circular tray. After that, the results of these 10 tests were used to calculate an average value for conversion. In order to improve the accuracy of the test, care should be taken to carefully test the quantitative indicators because the quantitative detection of the numerical values ​​has a direct influence on the results of the conversion of the cir- culation index. Therefore, the quantitative test sample should have a certain representative, it is best to take 10 samples from different parts of the paper tube for testing, find the average value, so that the test is relatively accurate. If 10 samples are taken from a longitudinal part of the paper cylinder, the detection value is often not representative, because the lateral thickness error of the paper tube is relatively larger than the longitudinal error. In addition, the accuracy of the test sample thickness is also related to the conversion results of the ring crush strength. Because of the different thicknesses of the specimens, the diameter of the core used for detecting the ring pressure is also different. Therefore, the thickness test should also be used to test several points in different parts, find the average value, as the final test results. The thickness index is accurately detected, and the gap between the sample placed in the tray is appropriate, which can ensure the accuracy of the ring pressure strength detection. This requires that the diameter of the tray must be selected strictly in accordance with the thickness of the sample. The following is a comparison table of the ZSB-3F1 ring pressure tray and the thickness of the sample, and the conversion formula of the ring pressure strength and the ring pressure index:
(2) Conversion formula of ring pressure strength and ring pressure index
1 Ring pressure strength: R=F/152. In the formula: R represents the ring pressure strength, unit KN/m; F is the force value that reads when the sample crushes, unit N; 152 is the length of the sample, unit mm.
2 Ring pressure index: Rd=1 000R/W. In the formula, Rd represents the ring pressure index in units of N·m/g, R represents the ring pressure strength expressed in KN/m, and W is the quantification of the sample in g/m2.
2. Side pressure strength testing requirements and conversion formulas. Side pressure strength refers to the pressure per unit length, that is, the ability to withstand the pressure in the direction parallel to the corrugation. In accordance with the relevant standard rules, specimens with side pressure strength are cut from three specimens, and each specimen is cut from three specimens with no mechanical indentation, printing marks and damage. The corrugation direction of the specimen should be a short edge. Specifications are 25mm x 100mm, error ± 0.5mm. It is required that the knife edge of the sampler should be kept absolutely sharp, and the position of the blade on the knife holder should be installed properly. The angle between the cutting edge and the sipe should be adjusted to 45°. In addition, the knife edge must not touch the bottom of the sipe to prevent the blade from bending and deforming, so as not to damage the corrugated edges of the sample taken out, which may affect the detection accuracy.
The conversion formula for edge pressure intensity is: R=F/L×103. In the formula: R is the compressive strength of the edge of the corrugated cardboard sample, expressed in N/m; F is the force value read when the sample is crushed; L is the length of the long side of the sample, and the unit is mm.
3. Bond strength testing requirements and conversion formulas. The adhesive strength test is mainly used to test the fastness of corrugated board tapes. The inspection of A-type corrugated paperboards requires that the pin of the stripping frame should be Φ3mm, while the corrugated holes of B and C type corrugated paperboards should be thin, and the stripping frame should be inserted. Needle should use 2mm more appropriate. Each pin on the stripping frame should be exactly aligned with the center of the corrugated notch. After equalizing the spacing, tighten each of the screws. Adhesive strength of the test sample, required to take 12 pieces, that is, from the three sample boxes were taken four pieces of corrugated direction is the short side (ie 25mm), the material is intact, no degumming, no foaming sample block. Sample size is 25mm×80mm, error ±1.0mm, which can better ensure the accuracy of the test.
The conversion formula for bond strength is: P=F/L. In the formula, P is the adhesive strength of the corrugated paperboard sample, expressed in N/m; F is the force value read when the sample is separated, and the unit is N; L is the size of the long edge of the sample and the unit is m.
To sum up, only the use of test equipment performance and methods can be mastered. At the same time, scientific and reasonable methods can be used to test samples to obtain more accurate test data. This will provide a good basis for ensuring product quality.
(Author/ Kang Qilai)
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