Chapter II Structural Design and Evaluation of Packaging Containers
Section 1 Overview
The structural design of the packaging container is based on scientific principles, and is based on different packaging materials and different packaging container molding methods from the inside and outside of the packaging container. Must follow the scientific design, reliability, aesthetics and economic design principles, we must consider all kinds of contradictions, trade-offs and achieve the best.
Section 2 Packaging Container Structure Design Procedure
The structural design of packaging containers is an important part of the entire packaging design system. Interconnect with other packaging design, mutual restraint and mutual contrast. Its design general process is shown in the figure.
From the overall structure of the design process, it can be roughly divided into the following four stages:
1. Design condition analysis stage
Explicit design requirements, investigate and study the necessary data, analyze the categories, physical state, physical and chemical and biological characteristics of the packaged products, clarify the packaging environmental conditions, circulation conditions, market conditions, etc.; understand the packaging materials, container types and existing The production conditions.
2. Design phase
At this stage, the design parameters, such as the measured value and allowable deviation of the packaged product, should be determined; the design scheme of the container should be designed; and the optimal design plan should be determined through comparative analysis and evaluation of various packaging container structural design schemes.
3. Detailed structural design stage
The structural design plan is transformed into concrete and detailed structural expressions, that is, the strength, stiffness and stability of the structure are analyzed and calculated, materials are selected, technical requirements are determined, and a complete set of drawings, preparation specifications and related technical documents are drawn.
4. Improve the design phase
According to the problems exposed in the trials, use, identification and market feedback of samples, the structure of the packaging containers should be properly treated to ensure quality.
Section III Design Contents of Packaging Container Structure
First, the specific design content
(1) Packaging Container Appearance Design
That is, the three-dimensional appearance of the packaging container is designed. The design must not only meet the aesthetic principles in the design but also take into account the effects of the packaging container forming process.
(2) Internal structure design of packaging containers
That is, the internal structure of the packaging container is designed, which includes the design of the container wall thickness, the design of the partial structure, and the calculation of the structural design. The container structural design calculation includes the design calculation of the structural dimensions, the design calculation of the packaging container capacity, and the strength and stiffness design calculations.
Second, the size of the design and optimization
Most of the packaging containers belong to a geometric body. From the economical point of view, it is always desired that the material consumption of the manufacturing container is minimized under the condition of satisfying the packaged product, and the amount of material consumed by the container and the wall thickness and external surface area of ​​the container are the same. D. The smaller the general wall thickness is, the smaller the consumables of the packaging container are. Therefore, in the design of the wall thickness dimension, under the condition of satisfying the strength and rigidity, try to select the smaller value. When the wall thickness is determined, the packaging container can be optimized. Optimize the design to get the optimal size of the packaging container.
The basic idea of ​​this kind of packaging container optimization design is outlined as follows:
Step 1 Create a Mathematical Model
a. Determine the design variables
The dimensions to be determined in the structural design of the packaging container, such as the wall thickness and the dimensions of the container, are used as design variables. Often denotes n design variables.
b. Construct an objective function
The objective function can be constructed for the purpose of the packaging container which can generally use material consumption or minimize the cost of the packaging container. That is, the equation of the objective function is constructed on the basis of the internal volumetric equation of the packaging container and the total area equation of the manufacturing container packaging material, including all variables (design variables) that determine the shape of the container.
For a single objective function with n design variables can be written as:
F(X)=F(x1,x2,x3...xn) ...........................(4.1).
c. Determine the constraints
That is, the conditions for limiting the value of the design variables are determined, and there are container internal volume limit requirements and strength conditions for the packaging containers.
Constraints are often expressed in the following forms:
g(x) ≥ 0 i=1, 2............m............(4.2)
Working as above, the mathematical model of the packaging container can be expressed as:
Find Design Variables... X=[x1,x2,...xn]
Minimize the objective function... MinF(X) ... (4.3)
Satisfaction constraint... g(x) ≥ 0 i=1.2.3.....m
Step 2 Optimization Design Calculation
a. Select optimization calculation method
Since the development of the optimization design method, many optimization calculation methods have been given. There are also many optimization calculation programs used in the engineering. For the optimization of the mathematical model of the packaging container, an appropriate optimization calculation method is selected.
b. Calculation Select the appropriate optimization calculation method, become the mathematical model for solving the packaging container, and calculate the optimal size of the packaging container.