For those who require multiple molds or products produced using the well-tested plastic injection molding method, there are a few different options available to you. Two of the most popular, similar in some ways but also distinctly different in others, are known as multi-cavity molds and family molds.

At EnviroTech Custom Injection Molders, we’re proud to offer numerous injection molding services, from standard plastic injection molding to bulk molding, machining, mold testing and plenty of others. We’ll assist you with selection of the ideal mold format for any project you’re in need of help with, from resin choice through several other areas. Here are some general qualities to keep in mind when choosing between multi-cavity molds and family molds, plus a final word on making your decision.

Basics and Mold Types

The simplest difference between multi-cavity molds and family molds is also the one that defines their separation in most circles: The actual type of cavity involved in the mold. Both these types involve multiple cavities, but it’s the actual qualities of these cavities that makes the difference.

With a multi-cavity mold, the various cavities involved will all produce the same part – just at higher volume due to the ability to produce multiple such parts in each production cycle. A family mold, on the other hand, refers to multiple cavities that are cut into different parts – a single cycle will actually create more than one separate type of part, as long as it’s made using the same material. There are several other differences, which we’ll get into below, but simple mold type is often the primary driver of your choice between these two, as it defines the variety of parts available to you.

Lead Time

As manufacturers well know, lead time in our industry refers to the time between the beginning of the process to the final product. Naturally, this is a vital factor for any major process, including injection molding – techniques that require shorter lead times are ideal, especially if they can produce high-quality parts despite this limited need.

And within this realm, multi-cavity molds are the much better option compared to family molds. Multi-cavity molds have short lead times, allowing for each production cycle to produce several parts and increase your overall yield. Production capacity is far higher within a given part type. Family molds, on the other hand, come with a much longer lead time, so they’re generally used by clients who don’t require particularly high production capacity.

Quantity Considerations

From a general standpoint, multi-cavity and family molds can produce the same quantity of products in each cycle – both are capable of producing multiple. While there are often distinct scenarios where one or the other will have a significantly higher output capability, in a broad sense, they are not noticeably different in this area. Naturally, however, your choice will be between a high level of production for identical parts versus that same level of production for varied parts.

Costs and Color

Another area where the two are generally pretty similar, with some differences in specific cases but no distinct gaps from a broad standpoint, is overall tooling costs. Both area definite upgrades from single-cavity molds in terms of cost efficiency – you get a greater quantity of products for the same cost with both multi-cavity and family molds, and this is often one of the key factors in choosing them. Family molds are sometimes offered at a slightly lower price due to slightly higher defect risks (more on this in our next section), but even these differences are generally minor.

However, when it comes to costs per part, multi-cavity molding is much more cost-efficient. This is because molding plates are made from stainless steel, which requires fabrication for multiple parts – and fabricating different parts is much more costly and time-consuming than fabricating the same part multiple times. If you’re considering both options for a similar range of bulk part production needs, you will almost always land on multi-cavity molds as the ideal option.

When it comes to color, there are virtually no limitations for either of these types. Every part within a multi-cavity or family mold can be produced at exactly the same color within that production process, ensuring conformity across an entire line of products if needed.

Part Symmetry

One quick note on an area where multi-cavity molds tend to hold some advantages: Final part symmetry. Family molds often aren’t balanced when they’re filling out due to the simple fact that different parts within the mold have different shapes – unfortunately, within some jobs, this does raise the risk of certain molding defects or related issues.

With multi-cavity molds, you don’t deal with these risks. Because every part within the mold is identical, the mold itself will be balanced as it fills out, minimizing any risk of part defects or shape concerns. For particularly high-volume manufacturers who might have both options open to them, the multi-cavity mold tends to be the preferred option for this reason – you could produce roughly the same quantity of parts using the family mold, but the risk of defects makes this less prudent.

Making Your Choice

As we noted earlier, the primary driver in which of these options you choose is your part needs. Those who require only one part type, but in great quantity, will generally prefer the multi-cavity mold; those who need several different parts in the same mold will go with the family option. The two start to bleed closer together when we’re talking about major bulk part needs, but the majority of bulk manufacturers tend to navigate toward multi-cavity molds due to cost efficiency and the lower risk of mold defects.

For more on these two molding types, or to learn about any of our custom injection molding services, speak to the staff at EnviroTech Custom Injection Molders today.