11.07.22 | 5 min read

Custom Injection Molding: Building the Right Relationship

Efficiently taking a product from design through production requires a custom injection molder that fits your needs.

A world without plastics seems unimaginable, as plastics have become a ubiquitous and essential part of our everyday lives. Custom injection molding gives manufacturers a competitive advantage in a crowded marketplace, allowing for versatility in design and functionality.

It should be no surprise that the global injection molded plastics market was valued at $284.7 billion in 2021 and is expected to grow as demand increases. The growth of injection molding has been driven by modern innovations that maximize quality in complex design production. But not all injection molders are the same, and for the best outcome, creating a partnership that fits your needs is vital. 

What is Custom Injection Molding?

Custom injection molding allows engineers to design a plastic product or component according to their needs and specification. Unlike cheap, high-run commodity products, custom injection molded products often require a high level of precision and have a much higher bar for quality. Custom products may also include overmolding or insert molding to combine the plastic with other materials such as metal.

In addition to providing part design flexibility, custom injection molding incorporates design-for-manufacturing (DFM) principles to ensure parts can be molded efficiently on the plastic injection molder’s presses. Some aspects of the design may increase the mold’s costs unnecessarily. For example, undercuts can make it impossible to eject the part from a straight-pull mold and require a side pull or cam action. Likewise, insufficient draft angles can make removing the part from the mold difficult. DFM allows engineers to redesign parts to improve manufacturability and reduce costs without negatively impacting the part’s fit or function.

DFM can also be used to make a part or parts more cost-effective. For example, it may be more cost-effective to combine two parts, eliminating fasteners and extra assembly steps. A more cost-effective material may be recommended, or insert or overmolding may be incorporated to replace assembly steps after molding.   

Choosing a Custom Injection Molder

Many injection molders would love your business, but it is critical that you align yourself with a partner that can meet your needs and takes the initiative to save you time and money. Some injection molders are build-to-print molders that do not provide a truly custom solution. They may not be able to mold your part to your specifications, leaving you starting from scratch with a new molder. Here are a few things to look for in a custom injection molder. 


An experienced plastic injection molder will have encountered many unusual or unique issues and will likely have a solution for yours. Look for an injection molder that has experience tackling challenging projects. Choose a partner that has a strong and proven track record. Ask about projects where similar tolerances were met or specific design features that were successful.

Ask to contact some of their customers and see examples of their work before signing a contract. The company may not reveal details, but you should be able to obtain enough general information to feel confident in the injection molder’s experience.

Production Capabilities

Production capabilities will play a significant role in choosing a custom injection molder. Injection molding machines can mold parts of a specific size range. Machines’ sizes are expressed as tonnage; the higher the tonnage, the larger and more complex the part they can make. Ensure they have the correct machines to produce your part. Not all injection molders have overmolding and insert molding capabilities, so if this is something you need, verify it can be done. 

The number of machines will also give you an indication of capacity. Just because they can manufacture your part doesn’t mean they can do it efficiently and meet your timelines. 

Look at capabilities and services beyond molding. If you need metal components, can they make them, or will they need to be sourced? Will they optimize your part and molds for the greatest cost savings? Do they offer prototyping services? Do they have other value-added services such as assembly, kitting, warehousing, and shipping? Even though you are looking for an injection molder, having them do other services can reduce your total overall costs. 

Strategic Fit

Not every plastic injection molder will be a good fit, which is okay. It is crucial that you find a partner that aligns with your needs. If you are looking for a collaborative partnership, you won’t be happy with an injection molder that doesn’t offer suggestions or promptly return your calls. Do you need a long-term or short-term partner? What is the injection molder’s reputation in the industry? Do you have shared values? Finding a partner that matches your expectations will lead to success. 

Trust Your Custom Injection Molding to LMC Industries 

Aligning with your priorities to create the part and experience you expect makes us successful. We strive to deliver the highest quality injection molded parts, whether they are stand-alone parts or combined with metal stamping through insert molding or overmolding. With over 60 molding machines, we have the capacity to deliver. We can make your tight-tolerance parts run more efficiently through prototyping, DFM, and automation, meeting your turn-around times and making your parts more cost-effective. 

Our experience with the stringent quality requirements of the automotive industry is carried throughout our facility. We use advanced product quality planning and other tools to consistently meet your quality objectives.

Ready to re-engineer your results? Take the first step toward smooth production runs and quality results. Contact us to request a quote.

Article | Plastics

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