How to Determine the Right Cavitation for My Mold


When beginning the process of making a mold for your manufacturing project, you may be wondering if high cavitation injection molding is a better option than a low- or single-cavity mold as if there’s a one-size-fits-all answer—but of course there isn’t. The right mold cavitation for your project depends on the particulars of what you’re manufacturing and the needs of your business: how much volume you need, what lead time you can accept, the tolerance you’re looking for.

Balancing all of these factors should help guide your decision about the mold cavitation that’s right for you. So even if there’s not a cut and dry way of figuring out if you should use high cavitation injection molding, we can help you think through all the influencing factors.

Here’s what you should keep in mind.

1. Higher Cavitation Entails Higher Upfront Costs

The higher your mold’s cavitation, the more the initial tool building process will cost you. You’ll have to pay for the design and the fabrication of your mold; unsurprisingly, the bigger the tool you need the more it will cost you to make. If you’re committed to a high-volume production, you don’t need to worry about recouping this initial expense, but for a smaller run, high cavitation injection molding is probably not worth the cost.

High cavitation molds aren’t just more expensive to make: because of their greater complexity, they also take longer to get up and running and initial test runs can be more complex for your injection molding partner. That means that if you’re looking for a short lead time, you may want to start with a lower-cavitation mold. This is particularly true if you’re making a product whose design you expect to tweak and refine, since high cavitation molds will leave you less adaptable to design changes. Later, once you’ve begun production and arrived at a design you don’t expect to change, you can then look into switching to a higher-cavitation mold if your volume needs demand the switch.

2. Don’t Forget to Factor Down-Time into Your Projections

Even the best-run manufacturing system isn’t going to be operating at 100% capacity 365 days a year. You don’t know exactly when, but you know there are going to be unexpected personnel shortages, vacations, sick days, bad weather, power outages, and other surprise disruptions to your molding partner’s operations.

And that’s without factoring in the production delays that come from your mold itself. Every so often—sometimes even every day—your mold must be disassembled and cleaned to maintain clear vents and high production quality. Further, injector pins and springs break, water lines and cooling systems need maintenance, and the system needs to be periodically lubricated. When parts are scarce, these repairs could take weeks. 

Ultimately, that means you shouldn’t expect to get the hypothetical “full potential” of your mold each year, no matter the cavitation. A much more reasonable estimate is somewhere between 60% and 70%. If all of your production is resting on a single high cavitation mold, you are far more vulnerable to costly disruptions to your business.


3. High Cavitation Can Lead to Lower Tolerances

To determine the right mold cavitation for you, you need to know the tolerance you can accept. It’s a fairly straightforward tradeoff: the higher the cavitation, the lower of a tolerance can be held. In part, this is because the manufacture of products with unusual geometries demands exceptionally challenging milling, and this challenge only intensifies with higher cavitation molds.

But the tradeoff also reflects the limits of high cavitation injection molding itself: this production technique necessarily introduces variance across the cavities of the mold. It is simply impossible, for example, to make eight cavities without discrepancies among them. As a result, a single batch from a high cavitation mold can simultaneously contain units that are at the maximum of a critical dimension and other units at the minimum. This variance can tank your CPK values and, depending on your business’s needs, lead to a product that you can’t use.

To discover more about high cavitation injection molding and to talk through the right strategy for your goals, talk to one of SigmaPro’s engineers today.