When it comes to plastic production, both plastic product design and mold design play crucial roles. The latter, in particular, is intricately linked to plastic processing. In fact, the efficacy and quality of the mold design and manufacturing can make or break the outcome of the entire production process. In designing plastic molds, there are various structural components to consider, all of which are aimed at achieving optimal results.
The determination of the parting surface is crucial in mold design as it serves as the contact area between the concave and convex molds. Numerous factors come into play when deciding its location and form, including the product's shape and appearance, the thickness of the walls, the molding method used, any subsequent post processing techniques, the type and structure of the mold, the chosen mold release method, and even the structure of the molding machine itself. Considering all these aspects ensures that the mold functions effectively and produces high-quality products.
Designing the structural components of complex molds, such as sliders, lifters (both inclined and straight), etc., is an incredibly critical process. The success of the mold depends on the designer's ability to create a durable, efficient, and cost-effective design that balances the mold's lifespan, processing cycle, and product quality. As such, the designer must possess a comprehensive understanding of mold design and continuously strive to simplify and optimize the mold's core structure. Achieving these goals requires a high level of skill and experience, making mold design a challenging yet rewarding field.
Mold structure design
When it comes to plastic parts, there are certain challenges that need to be addressed. These parts typically have small dimensions and require a high level of accuracy. Additionally, they need to be user-friendly with no cracks or bending issues. And finally, mass production is a key consideration. To tackle these issues, the mold design is crucial. For example, an eight-cavity mold has been used successfully in the past. By carefully designing the mold, it's possible to overcome these challenges and ensure that plastic parts are produced with the required level of quality and consistency.
When designing a mold with multiple cavities, it is crucial to achieve a balanced gating system to ensure equal feeding to all the cavities. As the number of cavities increases, the length of the runner channel needs to be extended. However, this elongation can result in a loss of injection pressure and heat before the molten material reaches the cavities. Therefore, it is essential to carefully design the runner system to avoid defects in the final molded product.
Improper design of the runner system can lead to various molding defects, such as inadequate filling in some cavities or overfilling in others. Additionally, poor fusion or weak internal structure can occur if the injection pressure is increased excessively, potentially resulting in flash formation. To address these issues, a non-balanced arrangement is utilized in the flow divider design described in the paper.
By precisely determining the size of the gate and flow divider, the injection process can be adjusted to achieve consistent shrinkage in each cavity. This ensures that the produced plastic parts meet the required accuracy level for interchangeability. The gate is strategically positioned at the rough end of the plastic part, known as the Y end. This location promotes smooth flow and feeding while also preventing undesirable welding marks. Furthermore, the molecular orientation of the plastic material is carefully controlled to meet the bending requirements without risking fracture.
Overall, the aim is to achieve a balanced gating system and optimize the runner design to ensure uniform filling of all the cavities while minimizing the occurrence of defects.
The design concept for the cooling system revolves around creating a device that doesn't require any additional structure on the mold itself. It aims to fulfill the cooling requirements and mold structure while maximizing the number of cooling circuits and the size of cooling channel openings. To achieve this, cooling water holes are added to the upper and lower cavity plates as well as the movable and fixed templates. During installation, the water holes on the upper cavity plate align with those on the fixed template and are sealed using sealing rings. Similarly, the water holes on the lower cavity plate align with those on the movable template and are also sealed using sealing rings. These water holes are strategically placed between the upper and lower cavity plates and the movable and fixed templates.