The Case for Re-sizing Your Injection Unit

Re-sizing is an activity we discuss several times a week with our clients. Anyone who has downsized an injection unit that’s pressure-limited on a troublesome job or has upsized to increase shot capacity for a new, larger job you’re quoting knows the value of this service. The fact is, having a properly sized injection unit translates directly into cash – often well into the hundreds of thousands of dollars. But for every client we talk with about this service, there are likely five who have no idea we have this capability. In addition, there are several misunderstandings regarding re-sizing that we hope to clarify for you. One recent project resulted in a hard savings of $50,000 in the first year alone! Down-sizing or right-sizing are definitely worth investigating!

Factory vs Custom Re-Sizing

The first thing to understand about re-sizing is the spectrum of engineering work required. This is largely determined by the screw diameter change required for a project. Nowadays, most injection molding machines come with an “injection unit” nomenclature. That means when you purchase your machine, you will have one of a few (usually three) screw diameters to choose from – often they are referred to as the “A”, “B”, or “C” screw. This makes it relatively easy to change shot sizes since all the back-end components stay the same and only a screw, barrel, and end cap are required to make a change. Pretty much any reputable seller of screws and barrels can provide an “A” screw package to downsize your “C” screw unit. Essentially, all the engineering has already been done by the OEM. That doesn’t mean, however, that they can perform the necessary engineering work to optimally size the injection unit. What if you need to go smaller than an “A” or larger than a “C” screw to achieve the results you’re looking for?  That is the difference between a factory and a custom re-sizing. For the money required to re-size, it’s worth it doing right – the first time!

Molders Services is a fully capable and proven engineering firm and can redesign your existing injection unit with a far larger or smaller screw diameter than is commercially available. Whatever is best for your application.

The Devil Is in the Details

When looking at a potential re-sizing, there are several factors we consider before making a recommendation. The entire process starts with valuable input from you:

  • What are your project goals?
    • Are you pursuing this option because you’re pressure limited on a job?
    • Are you experiencing quality defects as a result of residence time that needs to be eliminated?
    • Do you need to decrease recovery (cycle) time?
    • Are you looking to simply increase or decrease machine shot capacity to grow your business opportunities?
    • Are the potential savings enough to warrant the change?

Whether the project is being driven by a specific job or machine capability, we begin by performing shot calculations on all the jobs the machine runs. At MSI, we assure, for example, that a barrel can be built within your design envelope that will contain the new injection pressure on the downsizing. This allows us to arrive at a recommendation for the project that not only serves your requirements, but is also practical. Depending on all circumstances, we may even determine that a re-sizing is not the best solution. Purchasing a new barrel, screw, tip, and end cap can be very expensive. Sometimes, the savings simply isn’t enough to justify the project. At MSI, we’re not afraid to tell you that. But many times we can custom design a screw to meet your goals without actually having to change the diameter. Every machine and job is different, as is every optimal solution. Regardless of our formal recommendation, you can be assured you will receive a proposal from us that contains not just all the costs associated with component changes, but a full accounting of any additional machine modifications we recommend, as well as the results you may expect upon project completion.

Concerns and Misconceptions – Get the Facts

We routinely have clients express concerns over making a machine into a non-standard design. While a re-sizing does indeed change the screw OD, this in and of itself doesn’t make a machine non-standard. In truth, any screw we produce is a custom design, so it’s a misnomer to say any design is “standard.”  At MSI, we go to great lengths to assure a re-sized machine is just as serviceable as any other machine, short of the new screw, barrel, and end cap. We always make sure, for example, to build the new injection unit to one of the nominal screw diameters offered by the OEM to facilitate the use of off the shelf tip assemblies. In other words, we would never build a 35mm Toshiba when their closest nominal is 36mm.

Equally important is that we nearly always stay within the barrel design envelope, so clients may even re-use their existing heater bands. This allows the newly re-sized injection unit to be a plug-and-play swap for any old components. Going back to the old injection unit is as easy as changing a barrel and screw. Nearly 100% of the time there are no permanent modifications that need to be made to a machine. Generally speaking, you won’t be able to tell the difference in a machine from its external appearance after it is resized. MSI customers can rest assured they will have all the facts from us prior to proceeding with any re-sizing project.


Contact MSI today to discuss whether re-sizing is right for any of your applications!