Buffered Packaging Design Theory and Existing Problems

In order to protect the goods from being damaged in the process of circulation, they are not damaged due to impact and vibration. The packaging used is called cushion and vibration-proof packaging, also called buffer packaging. With the development of economy, the products are trans-provincial and cross-border transportation has increased. The buffer packaging of products has received more and more attention. The rational design of the packaging structure will minimize the loss of goods during transportation, handling, and storage. This is the significance of buffer packaging.

1 Development of buffer packaging design theory

During the Second World War, Mindlin LU and his research team led by Bell Laboratories of America applied various kinds of military supplies, especially high-precision electronic equipment, to apply vibration analysis theories in the mechanical field to the past. A unique 'buffer-packing theory' has been formed in the packaging field of 'trial exploration' or analysis and design based on experience. In 1968, Newton "2" proposed the theory of boundary conditions for the damage of packaging products, established a brittleness assessment theorem and its testing methods, and was incorporated into the American Materials Testing Standard (ASTM). Mindlin and Newton's pioneering work laid the foundation for the analysis and design of modern cushioning packaging.

In the 1980s, based on the theory of brittle-valued boundary conditions, U.S. MTS Systems Co., Ltd. and the School of Packaging at Michigan State University jointly developed a 5-step design method for buffer packaging, and later developed a more complete buffer packaging design. The six-step method (1) determines the circulation environmental conditions; (2) the product crispness estimation; (3) the product redesign; (4) the calculation of the cushion material; (5) the design of the packaging system; (6) the experimental packaging system prototype, The ASTM standard “3,” which should be implemented at each step, is given so that the buffer packaging design theory has made rapid progress.

Over the past decade, scholars from various countries, including Chinese packaging and scientific and technical workers, have paid great attention to and actively invested in, which greatly promoted the exchange and development of buffer packaging design theory, such as computer-aided design techniques for buffer packaging, and various types of linear and nonlinear buffer packaging. System impact and vibration response analysis, buffer packaging system analysis and design model, buffer packaging probabilistic design method and other fields have achieved a series of important results.

In short, more than 40 years since the publication of Mindlin's paper, great progress has been made in the research of buffer packaging design theory. The research on the mechanical properties of cushioning materials, evaluation of product brittleness, dynamic model, and design methods is increasingly practical and accurate. The design practice of buffer packaging is also increasingly reasonable. The main results are reflected in the following aspects L4]:

1) Established the theory of product cushioning and vibration isolation;

2) Determine the maximum acceleration value that a large number of products can withstand without physical damage or functional failure, that is, product fragility;

3) The major industrial countries have successively conducted investigations and tests of the circulation environment and achieved great results, laying a solid foundation for the packaging and transport testing of products;

4) developed a lot of advanced packaging testing equipment, and the computer is used in packaging test data processing and buffer anti-vibration packaging design;

5) Many countries (including China) have formulated a variety of packaging standards for cushioning and anti-vibration.

2 problems with buffer packaging design theory

Although the research on buffer packaging technology has made great progress, there are still a lot of problems in buffer packaging design theory and methods that need further study and exploration, mainly in the following aspects:

1) Newton's method for characterizing the vulnerability of a damaged boundary is based on the theoretical basis of a single-degree-of-freedom linear packaging system, but actual products, especially sophisticated electronic devices, have multiple Fragile components, and different impact frequencies, waveforms have different impact amplification ratios for the product, and the different responses of the products form different incentives and impact amplification ratios for the fragile components of the product. Therefore, the fragility evaluation method, which is an important basis for buffer packaging design, has yet to be developed. However, no more authoritative and more reasonable experimental theories and methods have yet been developed [4].

2) In the packaging project, the problem is dealt with by a single degree of freedom, in addition to its practicality and simplicity. It is also very important to study the basic laws of packaging dynamics. In theory, any product can be regarded as having infinite degrees of freedom. Even considering only a limited number of fragile components, many items must be packaged in 2 or more degrees of freedom in order to provide a reasonable package design. . There are two basic situations: one is that the package content itself is a multi-degree-of-freedom system, such as certain instruments and equipment, and their mass, elastic components, and damping elements are the same in size and distribution as the buffer packaging system, if forcibly simplified Single-degree-of-freedom systems can cause large errors; the other is that there are subpackages in large packages, such as container transportation. However, the current domestic and foreign standards have not included the multi-degree-of-freedom packaging problem [4].

3) In the packaging design process, the anti-vibration packaging is neglected because it focuses too much on cushioning. In the fourth step of the six-step buffered packaging design, 'Computation of liner materials', it was proposed that the impact and vibration coordination should be considered. However, only the buffer design part has criteria for reference, and the vibration-proof packaging part does not. Any standard can be used. The investigation and analysis of many actual product damage cases show that with the development of commodity transportation equipment and loading and unloading technologies, the impact is often not the main cause of product damage, and the damage is often caused by vibration. However, there is insufficient research on anti-vibration packaging technology, or buffering and anti-vibration are not well designed. The main problem is that "5": First, after the buffer design, only the calibration of the packaging system will occur resonance, or just use the vibration isolation principle for passive vibration isolation design; Second, the use of impact brittleness as a surpass The design was damaged, but in fact many components are damaged under repeated load conditions. In view of the above, the shockproof packaging design still needs further in-depth research.

4) The aforementioned five-step or six-step method of buffer packaging design is a category of “value setting method.” When the buffer packaging satisfies the design conditions, the fixed value design method considers that the packaging product is absolutely safe, otherwise it is considered absolute. In fact, the design parameters such as circulating environmental conditions, cushioning material properties, cushioning cushion geometry, and product crispness all have features that vary randomly, contain a lot of subjective and objective uncertainties, and are difficult to accurately characterize product cushioning packaging. The degree of suitability, and thus the protective capabilities of cushioned packaging products should use a probability to describe "6", I believe that the establishment of buffer packaging probabilistic design method is very appropriate and necessary.

3 The development direction of buffer packaging design theory

3.1 Computer Aided Cushion Packaging Design and Analysis

At present, in the buffer packaging design process of the product, the buffer material selection and the size calculation must not only look for many diagrams and tables, but also require a lot of time to calculate, analyze, compare, and ultimately select a reasonable buffer packaging scheme. This traditional manual design method restricts the development of cushioned packaging design to a certain extent due to the deficiencies of its complicated process, difficult choice of programs, and a large degree of reliance on the designer's own experience. Computer simulation and information technology quickly penetrated into the field of packaging design, making computer-aided buffer packaging design and analysis possible. The introduction of computers into the design and development of products enables people to liberate them from previously complex manual designs, significantly shortening the product development cycle, and the calculation results are accurate and reliable. Therefore, major industrial countries have invested a lot of manpower and material resources to develop various intelligent packaging systems "7." Computer aided design technology will surely have a broader application prospect in the field of buffer packaging.

3.2 Cushion packaging design based on system analysis

From the system point of view, buffer packaging is a systematic project. The buffer packaging system should be developed in the order of system analysis-system design-system implementation-system operation and evaluation. However, in the development process of the previous buffer packaging system, because the developers pay more attention to the design of the packaging system itself, the importance of other stages, especially the system analysis stage, is ignored, resulting in unreasonable packaging design. The waste of resources is a great "8." In order to minimize the waste of resources in the development process of the buffer packaging system and strive to develop an optimal packaging system, the buffer packaging system must be developed according to the laws of system engineering so that it has the best protection and economy. Social adaptability and ecological characteristics are both the overall goal of the buffer packaging system and the development direction of the buffer packaging design theory.

3.3 Introducing Reliability Theory to Study Design Problems of Cushion Packaging

As mentioned above, the design of cushioned packaging is affected by many factors with random variation characteristics such as circulation environmental conditions, cushioning material properties, cushion cushion geometry, and product fragility, and it is difficult to accurately characterize the suitability of the product cushion packaging. Because the reliability theory and method can reflect objectively and accurately the influence of the external incentives and structural performance characteristics on the design structure, it is very appropriate and necessary to introduce the reliability concept to study the buffer packaging design affected by a large number of uncertainties. . That is, consider the failure probability or reliability index of the packaging product to characterize the ability of the buffer packaging to protect the product and the appropriate degree of buffer packaging, and use the probabilistic method to design the buffer packaging. The research and application of reliability theory and method in buffer packaging design will surely make buffer packaging products have better economy and applicability.

(Wen/Zhou Mingyan Zhang Junling

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