The number of cavities in an injection mold and types of parts impact injection molded plastic part quality, mold cost, unit part cost, and productivity. This article covers single-cavity, multi-cavity, and family mold. It will help you in the selection of the best injection mold type for plastic parts.
We suggest you also read this article on Hot runner or cold runner injection molds and Two plate or three plate injection molds.
Single Cavity Mold
Single Cavity Injection Mold consists of one cavity. Therefore one component is produced per injection cycle. Manufacturerers recommend single cavity injection molds for low production volume plastic parts.
Advantages of Single Cavity Injection Mould
Here is the list of advantages of Single cavity mold.
- Low mould manufacturing cost compared to multi-cavity injection mold.
- Single cavity molds are easy to design and manufacture.
- Injection molding machine operators and tool manufacturers have more control over the injection molding process. As a result, injection-molded plastic part quality improves.
- Sometimes two single cavity molds are preferred instead of one two-cavity mold. Because in breakdown conditions, one injection mold can still run.
Disadvantages of Single Cavity Injection Mold
Single cavity mold has the following disadvantages:
- Low productivity.
- High unit part manufacturing cost.
Multi Cavity Mold
Multi cavity mold consists of more than one cavity. Therefore multiple parts are manufactured per injection cycle.
The initial investment cost for multi-cavity injection mold is high. But this higher tool cost can be compensated by lower unit part molding cost.
Advantages of Multi Cavity Injection Mold
Multi cavity injection mold has the following advantages:
- Reduced unit part manufacturing cost.
- Higher productivity.
Disadvantages of Multi Cavity Injection Mold
Multi-cavity injection molds have the following disadvantages:
- Higher mold manufacturing cost compared to single cavity injection mold.
- A higher tonnage machine is required to run a multi-cavity injection mold.
- Longer mold manufacturing lead time.
Family Mold
A Family mold consists of two or more core and cavities for different parts. Therefore multiple separate components are molded in one injection cycle.
In this way, Family mold reduces overall tool manufacturing cost by molding two separate parts using one injection mold.
For example, We can manufacture a product with top and bottom housings in a single injection mold to save tool manufacturing costs. This type of mold is known as family mold.
Advantages of Family Molds
Family mold has the following advantages:
- Lower overall tool manufacturing cost.
- We can manufacture two or more components in one injection cycle. Therefore productivity increases.
- Lower lead time.
Disadvantages of Family Mold
Family molds have the following disadvantages:
- Molten plastic flow balancing in different geometry part cavities is a challenging task. It can result in various injection molding defects.
- Family mold produces different parts in the same material in one injection cycle. Therefore it is recommended to use the family mold for the same material and color parts.
Example of the selection of Single Cavity, Multi Cavity or Family Mold
| S.No. | Requirements | Recommendations |
|---|---|---|
| 1 | We are working on a product where projected yearly volumes are millions of parts. | Manufacturers recommend multi-cavity mold for high production volumes. But make a duplicate mold to reduce dependency and handle tool breakdown. |
| 2 | Expected production volumes are high, but projections are not available. | You can start with a single cavity mold and develop a new multi-cavity or single cavity mold when the production volumes increase. |
| 2 | We require only a few hundred injection molded parts. | We can go for family mold to manufacture multiple parts in one single mold. It will reduce overall tool manufacturing costs and lead time. |
To sum up, A single cavity mold produces a single component per injection cycle. A multi-cavity mold manufactures multiple components per injection cycle.
In a family mold, we can manufacture different components in multiple quantities in one injection cycle. Click this Link! to know various ways to reduce injection mold prices.
We will keep adding more details on a single cavity, multi-cavity, and family molds. Add your comments or questions and suggestions on Various types of injection mold.
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