When Injection Molding Isn’t the Right Manufacturing Method for You


Here at SigmaPro, we’re big fans of injection molding. It’s what we do best, after all. But that doesn’t mean that the advantages of this method are what best suits your needs. 3D printing is a great alternative to injection molding for parts with certain geometric requirements, tolerances, and production runs. And sometimes, despite its high cost per unit, machining parts will be your best bet.

As part of our commitment to customer service, we want to help you find the manufacturing method that’s right for you—even when it’s not a service we offer. Since it’s challenging to sort through the diverse manufacturing methods on the market, we’ve put together this list of factors to help you weigh the advantages and alternatives to injection molding.

Injection Molding Is Best for High-Volume Manufacturing

Getting plastic injection production off the ground involves a lot of upfront costs and high-skill work. First, we have to design and iterate the optimization of the part for manufacturing (a process called “DFM” or “design for manufacturability”), which takes time. Once that’s done, we must create the actual mold (also called a tool) we’ll use to manufacture the final product.  These tools are often designed to last for years if well cared for, as lengthy production is usually expected for injection molding projects. And for as long as production continues, the injection molder must also cover all the costs involved each time the mold is pulled or reset for maintenance or other various reasons.

Whether the initial costs of creating the steel mold and other costs incurred in starting an injection molding project are worthwhile depends on your anticipated production volume. That’s why we suggest that when you’re picking a manufacturing method, you determine as precisely as you can your initial anticipated annual volume—and therefore how long it will take to recoup these initial costs. The right timeline will vary from business to business, but we suggest that, if it’s going to take longer than five years to make back your initial investment, an alternative to injection molding may be preferable.

Injection Molding Is Designed to Produce Parts with Certain Attributes

Every manufacturing method has its strengths and weaknesses. So, to choose the method that’s right for you, you have to know which attributes of your finished product are most important to you. This knowledge empowers you to get only what’s essential to you and your goals—and therefore get the most bang for your buck.

With injection molding, the parts can be molded with certain textures and colors and other difficult to produce features, which can save you the possible painstaking time involved with adding these features through other methods. Injection molding, specifically micro molding, also allows for highly complex geometries—without sacrificing tolerance, regardless of how many units you produce in a given run. If these advantages of injection molding aren’t what you need, this method may not be the right one for you.

Non-Standard Injection Excels in the Manufacture of High-Performance Parts

Modern injection molding isn’t just a single manufacturing method: it includes a great diversity of different technologies that expand on the capacities of traditional injection molding. If you need exceptionally tight tolerances, for instance, consider looking for a supplier who specializes in micro-molding. Vertical machines offer fast cycle times and a more flexible insert molding process, which empowers you to mold over an existing object. Two shot molding—another non-standard injection molding method—allows you to work with two separate molded materials on the same part. 

You should consult with a trusted supply partner to help you determine which, if any, of these injection technologies is a good fit for your part. To do so—and to narrow down suppliers—it is essential to know as precisely as possible the final specifications of your part and the ways you need it to perform. The right supplier will be able to help you sort out the best manufacturing method for your project.

Bottom Line

When deciding how to manufacture your small plastic parts, you need to consider cost, geometry, part feature requirements, tolerances, and volume. Sometimes, an alternative to injection molding may be more cost effective when you can accept a low tolerance or anticipate a small production volume. To know when the advantages of injection molding are right for you, you must have a good grasp on your requirements and restraints and partner with a supplier like SigmaPro, who can support you in gathering the data necessary for making this decision.