06 Dec 2018
Members of a startup company discuss details over coffee.

Startups Need These 6 Things from Injection Molding Services

We all start somewhere. Even a business like Rex Plastics, rapidly closing in on its fiftieth anniversary, had humble beginnings. But starting a new product is about more than having a good idea. You also need to figure out how to turn that idea into a manufacturable product, manage upfront costs, and eventually produce enough […]

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15 Aug 2026
Stacks of colorful legos that mimic a rising bar chart.

How Tolerance Stack Up Affects Multi-Part Plastic Assemblies

When a plastic component is designed and manufactured, each individual dimension has an acceptable range of variation. In a multi-part assembly, however, those small variations can combine and affect how the finished product fits and functions. This is known as tolerance stack up. Tolerance stack up is especially important for injection molded plastic assemblies because […]

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20 Jul 2016

Gates and Parting Lines: Fundamentals of Plastic Design Part 5

Gates and parting lines are two of the most important design considerations in injection molding. Although they are often overlooked during the early stages of product development, both have a direct impact on part quality, cosmetic appearance, manufacturability, and tooling costs. Every injection molded part requires a gate to allow molten plastic to enter the […]

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17 Jul 2026
A welding machine in a medical mask production run.

Designing Plastic Parts for Ultrasonic Welding

Ultrasonic welding is one of the most common methods for joining injection-molded plastic parts. It provides a fast, clean, and reliable way to create permanent assemblies without the use of adhesives, solvents, or mechanical fasteners. From medical devices to industrial equipment, ultrasonic welding creates strong, repeatable joints while supporting high-volume production. However, successful welding depends […]

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22 Feb 2016
A warped ruler twisting into the air.

Fundamentals of Plastic Part Design Part 3 – Sink and Warp

Part manufacturers should always give careful consideration to the materials used in plastic part design, as this decision will have significant consequences for sink and warp in plastic injection-molded parts. Let’s take a look at what makes a part sink or warp, and some helpful advice for avoiding these in the injection molding and design […]

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10 Feb 2025
Gray POM plastic car gears nestled among white plastic nurdles.

POM Plastic (Polyoxymethylene): Properties, Grades & Applications

Polyoxymethylene (POM), commonly known as acetal plastic or acetal resin, is an engineering thermoplastic widely recognized for its superior mechanical properties, dimensional stability, and resistance to moisture and chemicals. In this blog, we’ll explore the defining characteristics of POM, its advantages in injection molding, how it compares to acetal resin, and the diverse applications that […]

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27 Mar 2016
An up close image of a plastic water bottle cap. You an see the ribs in the plastic design.

Plastic Rib and Boss Design: Sizing and Sink Prevention

Plastic Rib Design Ribs are a great way to add strength and stiffness to a plastic part without significantly increasing material usage or overall part weight. When designed correctly, ribs help prevent flexing, warping, and deformation in large flat surfaces, allowing designers to maintain thinner nominal wall sections. This approach not only improves part performance […]

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14 May 2026
A robotic arm aids in the process of creating food service plastic containers.

Ejector Pins, Sleeves, & Lifters: Why Parts Stick in Molds

In injection molding, part ejection is one of the most important stages of the manufacturing process. Once molten plastic cools inside the mold, the finished part must separate cleanly from the tooling before the next cycle can begin. If ejection is not properly considered during product design, parts may stick, warp, crack, or suffer cosmetic […]

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30 Apr 2026
A plastic structure with a lightweight design: blue plastic criss-crosses and supports the piece in its most important places.

Lightweighting Strategies for Plastic Part Design

Lightweighting has become an increasingly important strategy in plastic part design, particularly for companies looking to improve efficiency and reduce material consumption without compromising performance. In injection molding, lightweighting involves optimizing part geometry, material selection, and structural design to reduce overall weight while maintaining the strength required for the application. While lightweighting is often associated […]

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27 Feb 2026
Green o-rings on a white background.

A Guide to Gaskets, O-Rings, & Snap Seals

Sealing performance is often one of the most critical but overlooked aspects of plastic part design. Preventing water intrusion, blocking dust, and maintaining internal pressure are cornerstones of properly designed gaskets and sealing features. They truly determine the long-term success of a product. In injection molded assemblies, sealing is not just about adding a gasket. […]

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