Injection molding is one of the most widely used methods for manufacturing plastic products. Plastic parts are produced by an injection molding company that specialize in using this process. Their products comply with market demands, making them ideal for household items and medical devices.
Let’s briefly understand how injection molding works.
Plastic injection molding involves inserting molten plastic material into a mold cavity under high pressure in molding. This initial step is called die casting.
The material is then cooled and solidified into a perfect mold shape.
Then, a mold tool called ejector pins are used to push or eject the molded part out of the mold cavity.
The process occurs in an injection molding machine. Injection molding results in single-cavity and multi-cavity molds. Choosing the mold type can significantly influence your production efficiency, manufacturing costs, and product quality.
This guide will introduce you to single-cavity and multi-cavity molds in great detail, along with their advantages, differences, and practical applications.
What is Single-Cavity Mold?
As the name suggests, a single-cavity mold has only one cavity, resulting in a single product per single cavity injection molding process. You use a single cavity mold for prototypes, low-volume production, or complex parts requiring precise detailing.
This mold type focuses on achieving meticulous detail and high quality for the desired part instead of maximizing output. You build a single-cavity mould with simplicity in mind.
The structure includes a single cavity where you inject a molten plastic material, cool it, and solidify it to form the final product. This mold design is more straightforward because you focus on producing a single part.
Single cavity molds are preferred in experimental stages or as custom products with intricate designs. They are a good fit for medical devices, aerospace, and automation industries, where precision and reliability are paramount.
Advantages of Single-Cavity Molds
A single cavity mold offers an array of advantages. Some of them include:
Precision and Quality Control
Monitoring and maintaining high standards is more manageable since only one part is made at a time, offering greater control over molding conditions.
For example, parts like surgical tools need exact dimensions to function correctly. Single cavity injection molding ensures this level of precision.
Lower initial investment
Single cavity molds have lower tooling costs than multi-cavity molds. So, they are a lower-cost alternative for businesses testing new designs or dealing with uncertain market demands.
For instance, a company designing five product variations can use a single cavity mold to perfect each design before high volume production.
Design Adjustments
If you need to change the design, it’s faster with a single cavity mold because only one cavity needs to be adjusted. This is especially helpful in prototyping, where products often undergo multiple revisions.
For example, if a new medical device requires a structural change, this mold allows the change without affecting the entire setup.
Minimal Downtime
When a defect occurs, it only impacts one part, not an entire mold. This reduces delays and keeps production on schedule.
For instance, if you’re making custom aerospace parts and encounter a defect, the single cavity ensures you don’t waste time fixing multiple cavities.
Great for Niche Markets
While not suitable for mass production, single-cavity molds are perfect for small-batch, high-quality identical parts.
For example, a company making specialized car components can use a single mold to meet specific demands without increasing the production volume.
What is Multi-Cavity Mold？
A multi-cavity injection molding produces multiple parts in one injection cycle. Multi-cavity molds have more than one cavity and produces multiple parts simultaneously.
As a result, a multi-cavity mold is extremely helpful for large-scale production industries like consumer goods, packaging, and automotive parts.
Multi-cavity injection molding must make sure that a steady flow of molten plastic is provided to each cavity. It results in you having greator control over molding conditions, which produces multiple cavities.
This sort of mold suitable for the plastic parts of products that have stable and high demand for volume, such as bottle caps or small electronic enclosures.
Advantages of Multi-Cavity Molds
There are many advantages in using a multi cavity mold. These incude:
Higher Production Efficiency
A multi cavity injection molding process cuts down the time for large scale production since it forms multiple parts at a go.
For example, instead of creating one bottle cap per production cycle, a mold with eight cavities means that more eight caps can be manufactured at once.
Lower Cost Per Part
While the tooling costs for a multi-cavity mold is relatively high than a single-cavity one, the cost of an individual part reduces as the number of parts produced increases.
This makes it suitable for mass production since its a cost-effective product.
Faster orders
Since multi-cavity molds produce many parts in one go, they are useful when you have a large order. Faster orders are even more beneficial for industries like consumer goods, where quick reaction times are essential for plastic products.
Consistent quality
A well-designed multi-cavity mold requires that all the cavities receive the same amount of molten plastic, so that you can have identical parts. For example, if you’re producing food trays, you need to have the same size and quality that meets industry standards.
Optimized Use of Resources
Multi-cavity molds ensure that each function of each multi-cavity injection molding process is optimized at the maximum capacity of the machine.
This cuts down on time and energy wasted, and makes it possible for manufacturers to produce even more of the good without investing in new machinery.
Multi-cavity vs Multi Molds: The Key Differences
Multi molds, also known as family molds, are mold sets that produce parts with different shapes and functions in one injection molding process. They are different from multi-cavity molds which create multiple identical parts in one process.
They are called family molds because they create a “family” of parts that are used together in a product. For example, a multi mold might produce a plastic lid and its corresponding container in the same cycle.
Cycle Time
Multi-cavity moulds offer faster cycle times because several identical parts are produced simultaneously. However, multi molds have a slightly longer production process.
This is because each cavity may require some adjustments for the different components that are produced, which increases the entire mold’s injection cycle time. However, this reduces the need for additional cycles, since multi molds create many parts in a single cycle.
Mold Cost
Multi-cavity molds initially require a substantial cost due to the precision required to create multiple parts. However, this high cost is covered by the reduced cost per part in high-volume production.
Multi molds also have a high initial cost, but they also produce multiple unique components in one cycle. This significantly saves a lot of money in overall manufacturing costs.
Design complexity and flexibility
Multi-cavity molds are simpler to design, as each cavity is identical. As a result, it reduces errors in design.
Multi molds, however, are inherently more complex because each cavity is unique. While you are provided with more flexibility in producing unique parts in one cycle, it does require careful planning during the mold design phase.
Production Efficiency
When it comes to production efficiency, multi-cavity molds take the lead because they manufacture large quantities of the same part quite instantly.
Multi molds are less efficient in their cycle time. However, they are more valued when multiple components are needed in one run. As a result, they streamline the production process and reduce the need for additional setups, which saves both time and resources.
Choosing Between Single Cavity and Multi Cavity Molds
Choosing the right mold depends on several factors, including your production goals, budget, and product complexity. Below is a table summarizing the key considerations to help you decide:
| Criteria | Single-Cavity Mold | Multi-Cavity Mold |
| Production Volume | Low to medium volume | High volume |
| Tooling Costs | Lower initial costs | Higher initial costs |
| Cost Per Part | Higher for small runs | Lower with large production runs |
| Design Adjustments | Easier to implement | Complex, affecting multiple cavities |
| Cycle Time | Longer, one part per cycle | Shorter, multiple parts per cycle |
| Complex Part Handling | Ideal for intricate and detailed designs | Best for simple, repetitive designs |
| Scalability | Limited for large-scale operations | Highly scalable for high-demand production |
For example, if you’re a small business testing a new product, a single-cavity mold offers greator flexibility and a lower initial cost. However, if you’re manufacturing bottle caps or food containers, a multi-cavity mold ensures frequent parts production and lesser costs per part.
Make a decision with your exact requirements in mind because your choice of mold will directly impact your production efficiency and profitability.
Which Plastics Are Ideal For Injection Molding Process
Choosing the right plastic depends on what qualities you need in your final product. These qualities could be durability, flexibility, or resistance to heat and chemicals. Below are some of the most commonly used plastics for injection molding:
Acrylonitrile Butadiene Styrene (ABS): Known for its toughness and impact resistance, ABS is ideal for automotive parts, consumer electronics, and toys.
Polypropylene (PP): Lightweight and chemical-resistant, PP is widely used for packaging, medical components, and automotive interiors.
Polyethylene (PE): Highly durable and versatile, PE is suitable for bottles, containers, and piping systems.
Polycarbonate (PC): With excellent strength and optical clarity, PC is used for safety glasses, medical devices, and electronic components.
Nylon (Polyamide): Known for its heat resistance and strength, nylon is ideal for gears, bearings, and mechanical components.
Polyethylene Terephthalate (PET): Commonly used in food packaging and bottles due to its transparency and recyclability.
Each material must meet specific molding conditions to determine the final product’s quality and performance. For instance, PET requires that you dry it before molding to avoid defects.