Injection Molding

Injection molding allows for large volumes of uniform, complex parts. However, you must pay attention to vent and gate placements, weld lines, corner transitions, wall thickness, rib and boss design, and more to ease ejection and achieve precise parts.

With injection molding, you can easily achieve repeatable part tolerances of ± 0.500 mm (0.020’’). In some cases, you can even produce parts with tolerances of ± 0.125 mm (0.005’’), giving you parts that are accurate enough for most applications and comparable to 3D-printed or CNC machined parts.

Today, there are over 25,000 engineered materials that are compatible with injection molding, including thermoplastics, thermosets, resins, and silicones. With all of these options, you’ll be able to find one that offers the right balance of physical, mechanical, and chemical properties. Commonly used materials include acrylonitrile butadiene styrene (ABS), polyethylene (PE), polystyrene (PS), and polypropylene (PP). You can also use a mixture of materials to produce a part with the strength, impact resistance, or stiffness you need. For example, you might add glass fibers to your thermoplastic to create a strength-enhancing composite.

You also have a variety of options when it comes to colors. Consider using masterbatches, pre-colored resins, liquid colorants, or salt and pepper blends to achieve your desired color.

While it can take several minutes — or even hours — to 3D print or CNC machine a single part, most injection molding cycles only last 10 to 60 seconds. Even if you have a complex geometry that takes around 120 seconds to mold, you can include several smaller parts in one larger mold. This helps maximize efficiency and gets the most out of each mold, allowing you to create hundreds of identical parts an hour at a low cost.

One of the main benefits of plastic injection molding is its high repeatability. Once you’ve created your mold, you can produce thousands of parts before needing to maintain your tooling. An aluminum mold will generally last between 5,000 and 10,000 cycles, and a full-scale steel production mold can last for over 100,000 cycles. Plus, since injection molding uses the same mold for each part, you’ll have identical products.

Though injection molding generates less post-production material waste than many other manufacturing processes, it still creates excess scraps. However, you can easily regrind, melt, and reuse any sprues, runners, or other leftover plastic parts to save on material and reduce material waste.