In recent years, the market for disposable meal boxes has shifted from foam meal boxes to environmentally friendly meal boxes. The original foam meal boxes were eliminated due to their inability to withstand high temperatures and because their production process is harmful to the environment. They have been replaced by various alternatives such as plastic meal boxes, paper meal boxes, wooden meal boxes, and degradable meal boxes. Among these alternatives, plastic has become the mainstream material for manufacturing disposable meal boxes due to its lower toxicity, higher melting point, strong plasticity, simple production process, and relatively low manufacturing cost. This article will focus on the structural design of disposable meal box molds made from polypropylene (PP), particularly the design points and optimization methods of thin-wall food container moulds.
Before designing thin-wall food container moulds, it is first necessary to understand the main characteristics and usage requirements of disposable meal boxes. Disposable meal boxes generally have the following notable features:
Disposable meal boxes are usually large in shape but relatively thin-walled, generally with a thickness of 0.35~0.5mm, which poses challenges and requirements for mold design.
The usage requirements for disposable meal boxes are very strict: Firstly, they must be reliable in quality, including high strength, attractive appearance, and non-toxic and harmless. Secondly, they must be low in manufacturing cost, including being lightweight, having low material cost, high material utilization rate, and simple production processes. Above all, they must be produced in sufficiently large quantities.
After considering the characteristics of disposable meal boxes, the design of thin-wall food container moluds needs to comprehensively consider multiple factors to ensure the final product quality and production efficiency.
To fully improve material utilization, especially considering the poor fluidity of polypropylene (PP), an efficient injection system needs to be designed. It is recommended to use a hot runner system, whose advantages include saving raw materials, improving molding quality, and increasing production efficiency. Despite the higher manufacturing cost and cooling issues of the hot runner system, it remains the best choice after considering the pros and cons.
A reasonable design of the cooling system can significantly reduce the cooling time of the plastic parts, thereby shortening the entire injection molding cycle. For thin-wall food container moulds, a multi-circuit cooling system is particularly important to ensure that the plastic parts can cool quickly and evenly.
Considering the shape and wall thickness characteristics of disposable meal boxes, using a traditional push-rod ejection system may result in push-rod marks or breakthrough phenomena. Therefore, it is recommended to use a multi-point gas-assisted ejection structure, which can apply ejection force evenly, avoid damage to the plastic parts, and save molding time and improve production efficiency.
In conclusion, the design of thin-wall food container moulds needs to fully consider the characteristics and production needs of disposable meal boxes. By using advanced designs such as hot runner systems, multi-circuit cooling systems, and multi-point gas-assisted ejection systems, production efficiency and product quality can be effectively improved, meeting the market demand for environmentally friendly and efficient products.
Through these optimization measures, the working stability and safety reliability of the mold can be effectively improved, ensuring the best results in actual production and providing a good reference for the design and manufacturing of similar plastic molds.
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