Have you ever wondered how plastic parts, such as bottles, caps, and phone cases, are precisely manufactured? The answer lies in injection molding, a fast and efficient way of making things. At the core of this process is a tool known as a mold. However, this tool does not work alone; there are several injection mold parts & components.
These parts are the building blocks that shape the things we use daily. Each has a unique function to help the mold work smoothly. So, understanding their differences and basics is crucial before dealing with molds. Are you new to this topic? Worry not! This article will explore different mold components in simple terms. So, let’s get started!
Parts of an Injection Mold
An injection mold may seem like a simple metal block. However, behind its workings, a series of components help it function. So, let’s explore some standard injection molding parts and their specifications.
1- Mold Base
The mold base is the strong foundation of the injection mold. It does not shape the product directly but supports and holds the parts that do. The mold base consists of several thick metal plates. Those plates must withstand high pressure and temperature. Therefore, they are made from durable materials, such as metals and high-carbon steel.
Moreover, the two main sections of the mold base are the core side and the cavity side. The core side is movable, while the cavity side is fixed. These two sections come together when the mold is closed. Besides these sections, there are several other parts inside the mold base. For example, it contains cavity inserts, guide pins, and an ejector system.
2- Cavity and Core Inserts
Cavity and core inserts are the most vital parts that directly shape the products. Actually, the cavity insert is installed on the fixed side of the mold. It is responsible for shaping the outer surface of the product. However, the core insert is present at the fixed side of the mold. This insert shapes the inner surface of the product.
When the mold closes, these two inserts come together, leaving a hollow space between them. This hollow space is exactly the shape of the product. When you inject the molten material, it flows through this space. When cooling, it gets the same shape as a hollow space. Cavity and core inserts are beneficial in many ways. You can easily change them instead of modifying the entire mold when you need to make changes to the product design.
3- Sprue
The sprue is one of the parts that the molten material comes into direct contact with. It is like a funnel that guides the melted material when it enters the mold. It is usually a straight and vertical channel inside the mold base. It is the starting point for the mold, where the molten material flows into the mold.
But how does a sprue work? Injection molding machines push the melted material through the nozzle. The sprue connects the nozzle to the inside of the mold. Its main job is to carry the molten material from the machine into mold systems. Because it handles hot, molten material directly, it is made from steel or other robust metals.
4- Runner System
The runner system is a network of small roads inside the mold. After the molten material flows through the sprue, it enters the runner system. These channels then guide the material into different parts of the molds. In regular molds, the runner system is present near the sprue. However, in insert molds, it is placed carefully due to the already present mold.
The runners generally come in two types: hot and cold runners. Cold runners are simple and less expensive. However, they waste material because they themselves solidify after every cycle. On the other hand, hot runners are complex and costly. However, they keep the material hot, reduce the material waste, and make the injection molding efficient.
5- Gate
The gate is a small but vital part of the injection mold. It is the doorway that allows the molten material to flow directly from the runners into the mold cavity. But how does it work? When melted material passes through the sprue, it reaches the gate. Here, the gate controls the amount and rate at which the molten material enters the cavity.
Therefore, the size of the gate matters a lot. If it is too small, it may not fill the cavity. However, if it is too large, it could leave visible marks and cause material to flow more. There are various types of gates, including edge gates, pin gates, and submarine gates. Each type has a different shape and purpose.
6- Cooling System
The cooling system is another critical part of the injection mold. As the name suggests, it cools the melted material before the part is removed. This system often consists of built-in cooling channels or tubes. Those tubes are usually placed around the core insert where the material is hottest.
These channels carry water or any other fluid through the mold. As the water flows through them, it absorbs the heat from the hot material. As a result, it cools down quickly and solidifies into final products. The material would take a long time to cool down without cooling channels. This can slow down the process and production and affect the overall injection molding cost.
7- Ejection System
Once the material cools and takes its final shape, it must be removed. That’s where the ejection system comes in. This system efficiency pushes the molded part out of the mold. Actually, ejection systems contain ejector pins. These are small metal rods placed behind the cavity. When the mold opens, the pin moves forward and gently pushes the part out.
Modern molds, such as 2-shot molds, can have ejector plates, sleeves, or stripper rings instead of pins. These make the ejection more efficient. However, remember that timing is crucial in the ejection process. If the part is ejected too fast, it can become damaged or deformed. That’s why this system must be carefully controlled and well-designed.
8- Guide Pins and Bushings
Guide pins and bushings are essential mold parts that ensure accuracy. HOW? This part helps the two halves(cavity and core side) come together perfectly in line when the mold closes. The guide pins are metal rods. They are present on one half of the mold, usually the core side. However, the bushings are hollow metal sleeves.
They are placed on the other half of the mold, usually the cavity side. When the mold closes, the pins slide into the bushing. This creates a seal, keeping everything aligned inside the mold. This part also prevents the mold halves from shifting, which can lead to flash. Flash refers to extra plastic that leaks out and can cause material waste.
9- Venting System
The venting system in molds is designed to release air and gas. This air gets trapped in the injection mold when molten material is pushed with pressure. If this gas has nowhere to go, it can cause problems, such as the formation of bubbles. These bubbles can create gaps in the final product and weaken it. That is where the vents come into play.
These are tiny and narrow grooves or gaps placed in certain areas of molds. Typically, they are located at the end of the cavity’s corners. When air enters inside with molten material, it quickly passes through these pores. However, these grapes are too narrow for thick molten material. They only allow air to escape, keeping everything clean and smooth.
10- Slides and Lifters
Not all the parts in injection molding are simple shapes. Some have intricate features, such as holes and undercuts. So, those parts are challenging to remove from the mold. So, the slides and lifters are specifically designed to handle complex-shaped parts. Slides are moving parts that move horizontally when the mold opens or closes.
Slides help create side features, such as holes and cutouts. These features are otherwise challenging to form by the regular up-and-down movement of the mold. So when those features are made, the mold opens. As a result, the slides pull back gently and release the part. Lifters also do the same job, but they move diagonally. They also help remove complex geometry parts that cannot be removed straight.
Maintenance Tips For Injection Molds
Injection molds are valuable tools for shaping a wide range of products. Their parts work continuously and often get deranged. So proper care is crucial to keeping them working efficiently. But how can you take care of them? Here are some maintenance tips!
- Regular Cleaning: Over time, molds collect leftover debris from the materials. This buildup can cause defects to the mold parts and surface. Therefore, you should regularly clean them using a soft cloth and a suitable cleaning agent.
- Lubricate Moving Parts: Ejector pins, slides, and lifters move during every cycle. They can get stuck, grind, or wear out if not lubricated. Always apply lubricants, such as grease, for smooth movements.
- Check Wear and Damage: Molds are not meant to last forever. Due to continuous use, they can get deranged. Inspect the mold frequently for signs of wear, scratches, or cracks. If you find such a sign, immediately repair or replace the part.
- Control Mold Temperature: Molds are designed to work in a specific temperature range. If they become too hot or cold, it can cause the wrapping to become loose and develop cracks. Therefore, monitor the temperature and ensure the cooling channels function properly.
- Store Molds Properly: When not in use, store molds in a safe and secure location. It is recommended to apply rust-preventive spray or oil. They will prevent the mold from jamming. Additionally, cover the mold thoroughly to avoid dust and moisture from entering.
Conclusion
Injection molding is one of the popular manufacturing processes. However, behind its popularity, injection molds have a key role along with their parts and components. In this article, I discuss the different parts of molds. All those parts work together and shape the products.
However, each part has a special job. Even if the smallest part fails, the molding process will be affected. That’s why understanding the basics of these parts is crucial to avoid any mishap. Additionally, remember that the mold components also require proper maintenance. Without proper care, they become damaged and worn out more quickly, resulting in financial loss.