What is the basic structure of a mould?

（Cavity）：The cavity is the hollow space within the mould that gives the final shape to the product. In injection moulding for a plastic toy, the cavity is precisely machined to replicate the outer shape of the toy. Its surface finish and dimensional accuracy are of utmost importance as they directly transfer to the product. Any imperfections in the cavity, like rough spots or incorrect dimensions, will result in a defective product. High - precision cavities are often made from hardened steel or other durable materials to withstand the pressure and wear during the moulding process.

（Core）：Cores are used to create internal features or hollow spaces in the moulded product. For example, when manufacturing a plastic pipe, a cylindrical core is placed inside the mould cavity. The molten plastic flows around the core, and after solidification, the core is removed, leaving a hollow interior. Cores can be made from materials such as metal or, in some cases like sand casting, sand. In injection moulding of complex parts with multiple internal cavities, multiple cores may be used, and they need to be accurately positioned within the mould cavity.

（Sprue）：The sprue is the main channel through which the molten material, whether it's plastic in injection moulding or metal in casting, enters the mould. In injection moulding machines, the sprue connects the nozzle of the injection unit to the rest of the gating system. It has a tapered shape to facilitate the smooth flow of the material and to minimize pressure losses. In metal casting, the sprue is where the molten metal is initially poured into the mould.

（Runners）：Runners are the channels that distribute the molten material from the sprue to the individual cavities in multi - cavity moulds or to different parts of a complex single - cavity mould. They are designed to ensure an even flow of the material to all parts of the mould. The size, shape, and layout of runners are carefully calculated based on factors such as the volume of the mould cavity, the viscosity of the molten material, and the injection or pouring pressure. For example, in a mould for producing multiple small plastic parts, a well - designed runner system can ensure that each part receives an equal amount of plastic, resulting in consistent product quality.

（Gates）：Gates are the small openings through which the molten material finally enters the mould cavity. There are various types of gates, each with its own advantages and applications. Edge gates are simple and commonly used for parts with flat surfaces. Pin gates are suitable for small, intricate parts as they allow for precise control of the material flow. The size and location of the gate significantly affect the quality of the moulded part. If the gate is too small, the material may not fill the cavity completely, leading to incomplete parts. On the other hand, if the gate is too large, it can cause issues like flash (extra material around the part) and uneven filling.

## 导向机构（Guiding Mechanisms）

（Guide Pillars）：Guide pillars are long, cylindrical rods that are typically installed on the moving half of the mould. They fit into corresponding guide bushings (also known as guide sleeves) on the stationary half of the mould. Their primary function is to ensure that the two halves of the mould open and close accurately, maintaining proper alignment. This is crucial for preventing misalignment between the cavity and core, which could lead to defective products. In large - scale injection moulds, multiple guide pillars are often used to provide stable and accurate alignment.

（Guide Bushings）：Guide bushings are precision - machined sleeves that house the guide pillars. They are usually made of materials with low friction, such as bronze or self - lubricating polymers, to facilitate smooth movement of the guide pillars. The tight fit between the guide pillar and the guide bushing ensures minimal clearance, which is essential for maintaining the alignment accuracy of the mould halves.

（Ejector Pins）：Ejector pins are small, cylindrical rods that are used to push the moulded part out of the mould cavity after the material has solidified. They are strategically placed around the cavity, usually in areas where the part is likely to stick to the mould. When the mould opens, the ejector pins are pushed forward by an ejector plate, which is connected to the machine's ejection mechanism. For example, in a plastic injection mould for a small electronic component, multiple ejector pins may be used to gently push the delicate part out of the cavity without causing any damage.

（Ejector Plates）：Ejector plates are flat plates that connect to all the ejector pins. When the machine's ejection mechanism activates, it applies force to the ejector plate, which in turn moves all the ejector pins simultaneously. This coordinated movement ensures that the moulded part is evenly pushed out of the mould. In some cases, there may be multiple ejector plates in a mould to provide more precise control over the ejection process, especially for complex - shaped parts.

（Slides）：Slides are used when the moulded part has features such as undercuts (recessed areas that prevent simple ejection) on the sides. In a plastic injection mould for a part with a side hole, a slide can be designed to move horizontally to create the side hole during the moulding process and then retract to allow the part to be ejected. Slides are typically driven by mechanisms such as inclined pins (also known as angle pins) or hydraulic cylinders.

（Inclined Pins/Angle Pins）：Inclined pins are often used to drive the movement of slides. They are angled pins that are fixed to one half of the mould (usually the stationary half) and engage with a slot in the slide. When the mould opens, the relative movement between the two halves of the mould causes the inclined pin to push the slide sideways, allowing it to perform its function, such as creating or removing a side feature in the moulded part.

（Cooling Channels）：In processes like injection moulding and casting, cooling channels are an essential part of the mould structure. They are designed to circulate a coolant, usually water or a special cooling fluid, through the mould. This helps to control the temperature of the mould and, in turn, the rate at which the molten material solidifies. In injection moulding of plastic parts, proper cooling is crucial for ensuring dimensional stability and minimizing shrinkage. The layout and design of cooling channels are carefully optimized based on the shape and size of the mould cavity and the material being processed.

（Heating Elements）：In some moulding processes, especially for materials that require specific temperature conditions for proper curing or flow, heating elements may be incorporated into the mould. For example, in the moulding of certain thermosetting plastics, heating elements are used to raise the temperature of the mould to initiate the chemical curing process. These heating elements can be in the form of electric resistance heaters or heating cartridges that are embedded within the mould structure.

（Mould Base）：The mould base is the structural framework that holds all the other components of the mould together. It provides support and stability during the moulding process. In injection moulds, the mould base typically consists of two main parts: the stationary platen and the moving platen. The cavity and core are mounted onto these platens. Mould bases are made from high - strength materials, such as steel, to withstand the high pressures and forces exerted during the moulding process.

（Support Plates）：Support plates are used to reinforce the mould structure and distribute the forces evenly. They are often placed behind the cavity and core inserts to prevent them from deforming under the pressure of the molten material. In large - scale moulds, multiple support plates may be used to provide additional strength and rigidity.

BBjump, as a sourcing agent, understands the significance of each part of the mould structure. When clients approach us for mould - related products, we first conduct a detailed analysis of their specific manufacturing requirements. If a client is involved in high - volume injection moulding of small, intricate plastic parts, we focus on ensuring that the gating system is optimized for precise material flow, and the ejection system is designed to handle the delicate parts without causing damage. We work closely with our network of reliable mould manufacturers to select the right materials for the mould components, considering factors such as durability, heat resistance, and cost - effectiveness. For clients in the casting industry, we pay attention to the design of the mould cavity and core to ensure accurate replication of complex shapes. By leveraging our industry knowledge and relationships, we help clients source moulds that not only meet their technical specifications but also offer long - term reliability and cost - efficiency.

The choice of mould material significantly impacts the structure design. For example, if a soft or brittle material is used for the mould cavity, it may require additional support structures, such as more robust backing plates or ribs, to prevent deformation during the moulding process. On the other hand, a high - strength, heat - resistant material like tool steel may allow for a more streamlined design as it can withstand higher pressures and temperatures without the need for excessive reinforcement. Additionally, the material's thermal conductivity can influence the design of the temperature regulation system. Materials with high thermal conductivity may require a different layout of cooling channels compared to those with low thermal conductivity to achieve efficient cooling.

In most cases, the basic structure of a mould needs to be adjusted when switching between different types of materials. Different materials have varying properties such as viscosity, melting point, and shrinkage rates. For instance, a mould designed for injecting low - viscosity plastic may not be suitable for high - viscosity rubber. The gating system, temperature regulation system, and even the ejection system may need to be modified. The gating system may require larger gates and runners for more viscous materials to ensure proper flow. The temperature regulation system may need to operate at different temperature ranges depending on the material's processing requirements. And the ejection system may need to be adjusted to account for differences in the material's adhesion to the mould.

Common signs of a faulty mould structure include inconsistent product quality, such as parts with varying dimensions, surface defects like flash or sink marks, and incomplete filling of the mould cavity. If the mould's alignment is off due to a problem with the guiding mechanisms, it can result in misaligned parts or parts with uneven walls. Issues with the ejection system may cause parts to stick in the mould, leading to damage during removal. Problems with the temperature regulation system can cause uneven cooling or heating, resulting in warped parts or parts with internal stresses. Additionally, excessive wear or deformation of the mould components, such as the cavity or core, can also indicate a structural problem.