The typical turnaround for injection molding varies between 6-10 weeks. 4-6 weeks to manufacture the mold, plus 2-4 more weeks for production and shipping. If design changes are required (something quite common) the turnaround time increases accordingly.
In comparison, parts made in a desktop 3D printer can be ready for delivery overnight, while industrial 3D printing systems have a typical lead time of 3-5 days. CNC machined parts are typically delivered within 10 days or as fast as 5 days.
If you look around you right now, you’ll see at least a few products that were manufactured with injection molding. You’re probably looking at one right now actually: the casing of the device you are using to read this guide.
To recognize them, look out for these 3 things: a parting line, witness marks on the hidden side, and a relatively uniform wall thickness throughout the part.
We’ve collected some examples of products commonly manufacturing with injection molding to help get a better understanding of what can be achieved with this manufacturing process.
Lego bricks are one of the most recognizable examples of injection molded parts. They’re manufactured using molds, like the one in the picture, which produced 120 million lego bricks (that’s 15 million cycles) before it was taken out of commission.
The material used for Lego bricks is ABS because of its high impact resistance and excellent moldability. Every single brick has been designed to perfection, achieving tolerances down to 10 micrometers (or a tenth of a human hair).
This is partly achieved by using the best design practices, which we’ll examine in the next section (uniform wall thickness, draft angles, ribs, embossed text etc.).
Many plastic packaging products are injection molded. In fact, the packaging is the largest market for injection molding.
For example, bottle caps are injection molded from Polypropylene. Polypropylene (PP) has excellent chemical resistance and is suitable to come in contact with food products.
On bottle caps, you can also see all the common unavoidable injection molding imperfections (parting line, ejector marks etc.) and common design features (ribs, stripping undercuts etc.).
Model airplanes are another common example of injection molded parts. The material used here is mostly Polystyrene (PS), for its low cost and ease of molding.
What’s interesting with model airplane kits is that they come with the runner system still attached. So, you can see the path the melted plastic followed to fill the empty mold.
Almost every plastic component in the interior of a car was injection molded. The 3 most common injection molding materials used in the automotive industry are Polypropylene (PP) for non-critical parts, PVC for its good weather resistance and ABS for its high impact strength.
More than half of the plastic parts of a car are made from one of these materials, including the bumpers, the interior body parts, and the dashboards.
The enclosures of almost every mass-produced consumer electronic device were injection molded. ABS and polystyrene (PS) are preferred here for their excellent impact resistance and good electrical insulation.
Many sterilizable and biocompatible materials are available for injection molding.
Medical grade silicone is one of the more popular materials in the medical industry. Silicone is a thermoset though, so special machinery and process control are required, increasing the cost.
For applications with less strict requirements other materials, like ABS, polypropylene (PP) and Polyethylene (PE), are more common.
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