With the continuous changes in the world economy, the corrugated carton industry is gradually rising during this period. As a low-profit industry, corrugated carton will be cautious every step of the way. The quality control of corrugated boxes is a systematic project, which involves all aspects of the production process.
Source and development of standards
Each customer will have its own independent inspection standards. At the beginning of receiving customer orders, we must carefully analyze customer standards, and there are often a lot of text narratives in customer standards. Since there are many statements that have nothing to do with the relevant process, the operators are often confused. If we distribute these standards directly to the workshop or various departments, these standards will often be shelved and rendered ineffective.
The work we have to do at the beginning of receiving customer orders is to transform some standards into internal standards of our own enterprise, and these standards need to be simple and clear, easy to understand and operate. After decomposing the customer standards one by one, they are distributed to procurement, technology, production, quality inspection, etc. according to the order of production. Each department then sets its own work flow and operation plan in a certain order.
Base paper is the main raw material of carton, and is often the first step in carton quality control.
The quality of base paper involves carton compressive strength, burst strength, edge compression strength, moisture-proof effect, folding strength, printing effect, die-cutting operation, etc., so the quality of base paper procurement is the source of the entire quality control. The customer’s standard often provides the physical indicators of the carton, paper name and weight requirements, and we need to calculate the relevant physical indicators of the paper according to these requirements to serve as the standards for procurement and acceptance.
The relationship between corrugated base paper and carton physical indicators
Corrugated boxes are composed of corrugated base paper at various levels. The resistance formula is to calculate the compressive strength of the carton based on the physical properties of the cardboard base paper to see if it can meet the requirements: it can also be selected according to the compressive strength requirements of the predetermined corrugated box Corrugated cardboard base paper.
P=Px·KP–The empty box compressive strength of corrugated cardboard box (unit N) Px–The transverse comprehensive ring compressive strength of corrugated cardboard base paper (unit N/cm).
Among them, the calculation formula of the comprehensive ring compressive strength of the three-layer corrugated cardboard base paper is:
Px=(R1+R2+RmC)/15.2 The formula for calculating the comprehensive ring compressive strength of five-layer corrugated cardboard base paper is:
Px=(R1+R2+R3+RmlCl+Rm2C2)/15.2Rn–the test force value of the transverse ring compressive strength of the face paper (N/0.152m) Rmn–the test force value of the transverse ring compressive strength of the corrugated paper (N/ 0.152m) C—corrugated shrinkage rate, that is, the ratio of the length of corrugated core paper to facial paper.
(CA=1.532, CC=1.477, CB=1.361)
K——The effective value of comprehensive ring compression in the compressive strength of empty cartons, the calculation formula is KA=30.3+0.2752-0.000522K=c=27.9+0 2652- 0 000522K=B: 24.6+0 2352 One 0 000522K five AA=41.7+0.355Z-0.000522K j BB=33.2+0.3052-0.000522K five cc=38.1+0.3452 one 0.00522K j AB=38.2+0 335Z-0.000522K j Ac=40 2+0.355Z -0.000522K j Rr=35.7+0.325Z-0.000522 three A–three-layer A corrugated box, the range of the perimeter of the three-layer box:
70cm～200cm Five AC——Five-layer AC corrugated box, the value range of the perimeter of the five-layer box:
The 70cm～300cm compressive strength formula can only estimate the ring compressive strength of paper. In fact, there are many factors that affect the compressive strength of corrugated boxes, which should include the ring compressive strength, tensile strength, burst strength, compactness, and Water resistance and water absorption of paper, etc.
Tensile strength, the tensile strength of corrugated base paper depends on the fiber structure of the base paper and the adhesion between the fibers. The tensile strength not only affects the tensile strength of the base paper in the machine during use, but also affects The compressive quality of the carton after it is formed. Under normal circumstances, if the ring compressive strength of the paper is very good, but the fracture length and tensile strength are not good, the carton will often cause a large amount of deformation during the compressive test, and the final deformation will be like Accordion shape, this is because the fiber texture, structure or the connection force between the fibers is poor, and when the carton is subjected to the compression test, the fiber at the edge of the pressure line is first stressed, and this loose and weak fiber can’t work well. The force received by the carton is transmitted to the whole carton, but the passive part is under pressure. As the edge collapses locally, the stressed part gradually moves toward the middle of the box, forming a test phenomenon that deforms like an accordion. However, if the tensile strength is good, this kind of situation will not occur. The carton will withstand a lot of pressure under the condition of small deformation. If it is increased, the carton will collapse from the center of the box surface due to the overall inability to withstand the pressure.
Tightness, paper tightness tests the pressure effect of the base paper in the production process. The tightness will affect the fastness between the fibers and then the ring compressive strength and tensile strength of the base paper, and the final impact will be in the direction of II. To the compressive strength of the carton, and because the tightness of the paper is not enough, it will also affect the moisture absorption of the carton, causing the carton to excessively absorb moisture during use or storage and reduce the compressive strength of the carton itself.
Bursting strength refers to the uniformly increased maximum pressure that the paper or cardboard can withstand per unit area under the experimental conditions, perpendicular to the surface of the pattern. Bursting strength reflects the carton’s ability to withstand the handling, loading and unloading, impact and tearing forces during the circulation process. More and more cartons are used. Customers have made clear regulations on the breaking strength of the cardboard when placing orders. We need to use the customer’s standard to accurately calculate the breaking strength of the base paper. Generally speaking. The burst strength of corrugated cardboard is equal to the sum of the burst strength of the lining paper, the face paper and the sandwich paper multiplied by a coefficient of 0.92, and it has nothing to do with the burst strength of the corrugated core paper. Based on this relationship, we can infer the breaking strength of the paper according to the customer’s standards, so as to formulate the grade and origin of the paper, and formulate the corresponding acceptance standards.
The quality of paper is not judged solely from a certain physical index. The physical properties of paper should be a comprehensive index. Sometimes, in order to prevent carton companies from cutting corners, customers who use carton boxes require the compression and burst resistance of the carton, and at the same time put forward high requirements for the matching of base paper. In order to meet the requirements of customers, carton companies have only Increase paper weight and reduce paper grade to ensure cost. The customer’s request has already rejected the low-weight and high-strength corrugated paper. In fact, considering the overall performance, the low-weight and high-strength corrugated paper is much more stable than the low-grade and high-weight corrugated paper. Because the stability of the base paper reduces the individual differences in the physical properties of the carton and increases the safety of the carton, it is difficult for low-grade and high-weight paper to achieve this effect. In the compression design, due to the instability of low-grade base paper, it is difficult to accurately estimate the compression resistance. After the completion of the carton, the physical properties of the individual vary greatly, and the inferior products doped in the carton are used or transported. In the process, it will become the first point of damage, which will affect the use of the entire batch of cartons. When encountering this situation, we need to communicate with customers to find a combination of carton price and paper cost.
The relationship between the size provided by the customer and the production size. As the outer packaging of the product, the carton should be tailored according to the size of the contents, and the customer’s standard; the carton often provides us with the inner size or contents of the carton, which requires At the beginning of production, we converted to a production size that we can directly operate in all processes.
Corrugated box, as a kind of packaging container, has a certain volume and wall thickness, and correspondingly has a certain external volume. The size, arrangement and quantity of the contents determine the inner size of the carton (that is, the volume of the carton). The influence of the inner size, wall thickness and production process determines the production size of the carton (that is, the size of the knife edge pressure line in the carton production process). The production size, wall thickness and the influence of the production process determine the outer size of the carton (that is, the outer volume of the carton after it is folded and formed). Theoretically speaking, the inner size plus the wall thickness equals the production size, and the production size plus one wall thickness equals the outer size. In fact, the size of the carton, especially the outer size, is a comprehensive analysis of data. The quality of the cardboard and the production process, especially the overlapping tongue part of the carton, will have a certain impact on the outer volume of the carton. The outer volume of the tongue must be Add two wall thicknesses on the basis of the production size. The conversion of the three sizes in the carton production process requires a certain experience basis. If necessary, make a sample box for further confirmation. [next]
The inner size (X.) can be represented by Li×BixHi.
Use L for outer diameter (X). XB. xH. Express.
The production size (X) is represented by LxBxH.
However, the two long sides and two wide sides in the production size plan will be different. Following certain principles, we can make certain modifications according to customer requirements.
The formula for calculating the inner size of the corrugated box is Xi=Xmax·Nx±d(Nx+1)+K+T where Xi–the inner size of the carton (mm) Xmax–the maximum outer size of the contents.
Nx–the number of arrangement of the contents in a certain direction of the carton.
d–The margin between the contents and the gap between the contents and the carton, that is, the tolerance coefficient.
K–Carton inner size correction coefficient is a special correction for the special carton design process. It can take a positive value or a negative value. Generally, a carton does not need to take a value.
T-the total thickness of the lining or buffer.
For example: a mosquito-repellent carton, the inner box specification is l30x130X25mm, the arrangement is 3×2X10, that is, the carton has 3 inner boxes on the long side, 2 inner boxes on the wide side, 10 layers high, and one five-layer board on top and bottom. Liner, try to calculate the inner size of this mosquito-repellent incense carton.
Solution: In view of the stability of the inner box of the mosquito coil, the tolerance coefficient is 1, the high tolerance coefficient is 0, the correction value is 0, and the thickness of the five layers of cardboard is 7mm. The inner size of this carton is calculated as:
Li=Lmax·n+d(n+1)=130X3+1 X(3+1)=394B=Bmax·n+d(n+1)=130X2+1 X(2+1)=263Hi=Hmax· n+d(n+1)+T=25X10+7X2=264 That is, the inner size of this carton is:
LixXBixHi=394X263X264 needs special reminder that when calculating such as mosquito-repellent incense carton, we must consider the influence of the mosquito-repellent incense on the volume and shape of the inner box. Which inner diameter. This information must be communicated correctly to ensure that the design is accurate.
Remarks: This calculation result is theoretical calculation data. If there is not much practical experience, sample boxes must be made for trial installation before formal production of batch cartons to determine the qualified size and avoid batch loss.
With the inner dimensions of the carton, the basic dimensions of the carton can be determined. Theoretically speaking, the length and width are each added with a cardboard thickness, and the height is added with two cardboard thicknesses to convert it into the manufacturing size of the carton. After the production size is determined, we have to further determine the expansion drawing of the straight line production size. The expansion drawing needs to set the size of the sticky mouth, the size of the sticky mouth overlap, the molding situation, the corresponding situation of the flap, etc., if these conditions cannot be the same Once it is set, it will encounter many difficulties in the subsequent process or the market.
There is a key problem in making the size through the outer diameter size conversion: because each manufacturer has different measurement methods for the outer diameter, such as the measurement method of the long side outer diameter size, some include the lap tongue, and some do not include the overlap. In connection with the tongue, even some individual carton manufacturers or manufacturers confuse the outer diameter size with the production size, which often leads to errors in information transmission, and ultimately to loss of batches. Therefore, in the process of receiving orders, the business must clearly understand the specific requirements of the customer, and correctly convey the customer’s information to the production and technical departments.
There are some cartons that need to ensure the outer diameter when they are used, such as containers or standard bases. At this time, customers often give us the outer diameter of the carton, that is, the outer volume of the carton. At this time, we must be able to correctly The diameter size is converted into the production size by calculating the length and width, one wall thickness, and the height two wall thicknesses. Because of the space, we won’t go into details here.
Some methods in the production quality control process, no matter how well we do the preparation work, we will also encounter many problems of this kind or that in the production process. We need to eliminate the problems that have occurred one by one, and use this experience as Prevention, so as not to repeat it again next time. Let’s explore some small methods in the production process.
High standards, strict requirements. When describing the establishment of standards, we mentioned the standards for breaking down customers. In fact, there is another reason why the customer’s standard cannot be directly used as the production standard during the production process. Since the customer’s standard is already the bottom line of acceptance when the cartons are delivered, once some situations occur, they will face unqualified treatment. Therefore, we must establish our own safety production standards in production. Take the pressure resistance standard as an example. The customer’s standard is 2200N, so the standard in our production process should be 2640N. According to the sequence of processes, the standard of the previous process is even higher. Because we have set a strict safety factor when setting the paper standard, the physical indicators of the paper should be effectively converted during the production process.
Elimination method Since carton production is a systematic project, we often encounter many problems in the production process. When encountering some problems, we need to know the causes of these problems, and then investigate them one by one until the cause of the problem is eliminated. Take the unqualified compressive strength as an example. When testing the compressive strength of a carton in a round die-cutting process, it is found that the compressive strength is unqualified. First, check the compressive test records of the previous process for any problems, and eliminate them first.
If there is no problem in the test records of the previous process, check the problem of the process again, check whether there is obvious indentation of the paper feeding roller on the surface of the cardboard, and then carry out the compression test after raising the paper feeding roller to a certain height:
Check the front and back of the cardboard to see if there are any excess creases or indentations. If there are, remove them and test.
Contrast method We often encounter some difficult problems in the quality control process, and sometimes workers do not understand well in production. We might as well use the contrast method to see if there is such a situation in the upper process or other units. We May wish to change your thinking, change the operation for comparative testing.
Nothing is immutable in the innovation law. When we encounter problems, we might as well make some changes in our thinking. In the quality control process, if we stick to the rules, some problems will always exist for a long time. The problem will always have its roots. We may wish to make changes to find the roots, but this change must follow certain principles and change blindly. It would be counterproductive.