Custom injection molding is a mass manufacturing technology applied to produce high-quality plastic parts. It’s a versatile manufacturing process where single-cavity molds are typically applied for low-volume production runs, and a multi-cavity mold is applied when the production demands increase towards medium to high volumes and faster turnaround times.
Multi cavity injection molding involves a multi cavity mold that is built to include numerous identical cavities within a single mold base. It demonstrates a strategic advantage of enhancing production efficiency, ensuring batch-to-batch consistency, and driving cost-effectiveness for medium- to high-volume production runs. In this article, we discuss the technicalities, advantages, and limitations of a multi cavity mold in detail.
Injection molding cavities refer to the number of parts that are formed in a single injection molding process. The number of cavities is directly proportional to the quantity of parts manufactured in each molding cycle. If there are more cavities, then more parts can be manufactured per cycle. In a custom injection molding process, a multi cavity mold increases the production capacity.
A multi cavity mold is a type of mold that has at least two cavities. All the cavities are in even-numbered pairs and are identical. The number of cavities in the multi cavity mold is largely dependent upon the size of the part and tooling.
A multi cavity mold is applied to manufacture multiple identical parts in a single molding process. One production cycle can manufacture anywhere from dozens to even hundreds of finished parts. The production capacity is dependent largely upon the capacity of the injection molding machine.
A multi cavity mold structure consists of various components. Let’s understand these structural components:
The upper and lower template of a multi cavity mold are referred to as clamping plates and are the outermost plates of the mold. They provide structural support to the mold and secure the mold components.
Sliders in a multi cavity mold move laterally to release the molded part from the side features, and they then return to position before the next cycle. They are applied when the part cannot be released through a straight pull and are used to create undercuts or complex geometries.
Mold base in a multi cavity mold provides foundational support to the entire multi cavity mold structure.
Mold cores of a multi cavity mold form the internal features of the part. They are positioned within the mold cavities. Mold cores are mounted on the mold base.
Guiding mechanisms ensure that the alignment is accurate between the upper and lower halves of the mold. Guiding mechanisms are examples such as pins and bushings and they are especially critical in a multi cavity mold, as they prevent any type of misalignment.
Ejector pins push the solidified part out of the cavity once the molding is complete. They are placed in a multi cavity mold for uniform force distribution, and retract after each ejection.
Springs are incorporated with ejector systems or sliders. They apply return force and help to reset moving elements such as ejector plates or sliders to their original position after the ejection.
The cooling system circulates cooling fluids through channels in a multi cavity mold. They generate efficient and balanced cooling which further maintains uniform part dimensions and minimizes cycle time by accelerating solidification of the molten resin into the plastic part.
Part design analysis is an elemental step in designing a multi cavity mold. At this stage, the part design geometry is assessed to determine potential design challenges.
The next consideration factor is the mold material. It should be suitable for high-volume production runs and should be able to resist when subjected to high pressures and temperatures. For e.g., Hardened steel or high-grade aluminum.
In a multi cavity mold, the base of the mold supports the entire structure of the mold. It should be wear and corrosion-resistant.
The next step is to optimize cavity layout in the multi cavity mold for efficient material flow. The cavities should be arranged symmetrically for balance and such that injection molding defects are prevented.
The runner system enables the molten resin flow to the cavities and ensures that the cavities are uniformly filled.
It is essential to implement correct cooling channels and venting systems. They help to maintain an efficient cycle time.
Venting systems enable trapped air to escape during the custom injection molding process, whereas cooling channels enable even distribution of temperature across all cavities.
The role of an ejection system in a multi cavity mold is to ensure that the part removal is smooth. It shouldn’t cause any deformation to the part.
A multi cavity mold is applied to manufacture an array of products for various industries. They are particularly applied, when tight tolerances and cost-efficiency are crucial parameters for high-volume production runs. Let’s understand some of the key applications of a multi cavity mold:
Consumer goods are everyday items that typically need to be manufactured in large quantities consistently. A multi cavity mold is extensively applied to manufacture consumer goods items such as plastic bottles, food containers, bottle caps, toothbrush handles, cosmetic packaging, kitchenware components, etc. The fast cycle times and high repeatability offered by multi-cavity molding help meet market demands.
Medical components require the utmost precision and are often required in large volumes. A multi cavity mold, enables manufacturers to meet such strict regulatory standards in cleanroom environments and is thus applied to manufacture various medical devices and healthcare components such as syringe barrels, test tubes, diagnostic casings, etc.
Automotive manufacturers extensively apply a multi cavity mold for manufacturing small, repetitive parts that require tight dimensional tolerances. Some common examples are clips, fasteners, cable guides, dashboard clips, valve caps, sensor housings, etc.
A multi cavity mold in the electrical and electronics industry enables manufacturers to ensure precision and part uniformity. Thus, a multi cavity mold is applied to manufacture electrical and electronics components such as connectors, switch housings, plugs, etc.
A multi cavity mold demonstrates several advantages. Let’s understand these advantageous aspects further:
A multi cavity mold aims to increase the production efficiency. It is capable of increasing the production capacity of custom injection molded parts to approximately 80%.
If the production volume is large, a multi cavity mold reduces the production costs significantly thus, leading to substantial cost savings for high-volume production runs.
You should note that the initial cost of the mold may be higher due to its complexity, but the overall cost per part is much lower since more molds can be filled simultaneously.
Colorants are added to the resin through various measurements, and while consistency is ensured to a great extent, there is always a possibility that perfect consistency across cycles may be altered. A multi cavity mold enables better consistency of the plastic parts.
A multi cavity mold has various advantages, but it isn’t ideal for every custom injection molding project. Let’s understand these limitations further:
A multi cavity mold is complex in design. This adds to the mold’s manufacturing cost thus, making them unsuitable for low-volume production runs.
A multi cavity mold takes longer to debug especially, if the multiple cavities are not perfectly balanced. It also requires more time to adjust and test to ensure that all the products meet the expected quality standards.
A Multi cavity mold has high technical requirements. A multi cavity mold requires expertise for design and manufacturing and simulation software to predict and solve potential issues.
There are material flow challenges with a multi cavity mold. The material flows in various directions in a multi cavity mold. It is thus necessary to outline the parameters of the material flow.
Multi cavity tooling is an extremely advantageous technique for manufacturing high-quality parts consistently. It’s an intricate technique that requires experience and extensive detailing.