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Thermoplastic Injection Molding (TIM)

Why choose ASH for my Thermoplastic Injection Molding Needs?

  • State-of-the-art Equipment:
  • Focus on Timeliness
  • Strict Quality Checks
  • Customer Focused Sales Staff

Thermoplastic injection molding is a manufacturing process that creates fully functional parts by injecting plastic resin into a pre-made mold. Thermoplastic injection molding has several sub categories, such as rapid injection molding, which is best utilized in fine tuning prototypes prior to a product being given the go-ahead for production. Another sub category, production injection molding, is best utilized for full product runs.


Developers utilize the thermoplastic injection molding process for many applications, as it can produce anything form car door panels to cell phone cases with good accuracy and surface finish. What's more is that it's the industry standard for producing plastic parts, so developers can be certain they're putting out a quality product if they go this route in the development process.


Here's a closer look at thermoplastic injection molding:


How it Works

We already noted that thermoplastic injection molding consists of injecting a thermoplastic resin into an already crafted mold to create parts in the shape of the mold. But here's a closer look at how the process works:

  • A mold is made based off a CAD file. That's the laborious part of the process as it takes time to create the mold. Such molds are typically made from aluminum or steel.
  • After the mold is created, the thermoplastic resin is injected into it and then left to cure and form the part. The material is first fed into a heated barrel before being launched into the mold to cold and cure.
  • Following curing, the part is removed from the mold and the process starts over until the part run is completed.


Every production process has its pros and cons. Before we cover some of the limitations, here are some of the advantages of thermoplastic injection molding:

  • Accuracy: Thermoplastic injection molded parts are able to be produced with pin-point accuracy, which is a major advantage over other prototyping processes like 3D printing. (More on this later when design considerations are discussed.)
  • Surface Finish: Thermoplastic injection molding can be executed with a variety of general and engineering-grade resins. The process is also able to create parts with pristine surface finishes, which makes the production process viable to create not only prototypes, but small and large production runs. Rough or pebble textured surface finishes can also be created with the production process.
  • Speed: Parts that are thermoplastic injection molded are typically turned around within days. If it's used for prototyping, this allows developers to make design changes quickly, thereby enabling it to go to market sooner. And if the process is being used for manufacturing, runs can be completed within days, so they're able to be on store shelves sooner. The longest part of the injection molding process is the time that needs to be spent creating the mold. However, molds can also be created to fine-tune prototypes and then used again for a manufacturing run.
  • Predictor of manufacturability: We already discussed how thermoplastic injection molding can be utilized for prototyping purposes. And here's why - parts can not only be completed and turned around quickly with days, but the two benefits of the technology mentioned above, accuracy and surface finish quality, make the process a great predictor of manufacturability. Often times, developers will order several early prototyping runs on other technology, then use thermoplastic injection molding to validate product design prior to green-lighting the product for manufacturing. Since parts can be crafted in several different resins, developers will also experiment with surface finishes and materials to see what they want to manufacture in.


As we previously noted, every production process has its share of pros and cons. Here's a look at some of the cons of thermoplastic injection molding:

  • Cost: The biggest downfall of the process is arguably cost. That's because the tooling and time needed to create the mold is expensive, meaning that developers will be paying for these up-front tooling costs.
  • Speed: We also mentioned "speed" as an advantage of thermoplastic injection molding, however, whether speed is a pro or con varies based on what thermoplastic injection molding is being used for. For instance, if it's being utilized for early prototypes, speed is a con. Why? Because compared to other prototyping technologies like 3D printing, it's a much slower and more expensive process. 3D printing, conversely, takes hours to create one-off parts, where thermoplastic injection molding can do so in days because there's tooling involved.
  • Flaws: Like all production technologies, thermoplastic injection molding can produce bum parts. These may be caused by a variety of factors, including defects in the tooling, poor product design, too hot of thermoplastic resin material, injection speeds that are either too fast or too slow, a lack of venting in the tooling, debris on the tool surface and a lack of proper cooling around the tool.

Design Considerations

We've already covered how thermoplastic injection molding can produce parts with very good accuracy, which thereby makes the process an ideal one for both prototyping and manufacturing runs. However, in order to produce the best possible parts, product design has to meet minimum and maximum requirements regarding thickness. Specifically, the thermoplastic injection molding process is able to create parts within 0.2 mm tolerance. Furthermore, the process can produce more advanced parts with tolerances as precise as 5 micrometers regarding diameter and linear features. Surface finish accuracy is typically anywhere from 0.5 to 1 micrometer in accuracy.



Thermoplastic injection molding can be accomplished with just about any engineering-grade plastic resin. But that's not even including more general resins. Engineering grade resins are typically utilized to create final prototypes before manufacturing, while general resins are used to craft early prototypes or parts of a product that are of lesser importance. When we talk about general resins, we're referring to the likes of ABS, nylon, PET, polypropylene, polyethylene and TPE. Engineering-grade resins consist of lexan, noryl, valox and ultem. As we previously mentioned, the plethora of pastic resins that can be processed via thermoplastic injection molding allows product developers to experiment with different materials and surface finishes for their products.


To recap, thermoplastic injection molding can be implemented for prototyping, short-run and long-run manufacturing due to its speed, quality of finished parts and the variety of general and engineering-grade resins that parts can be produced. But like all production processes, mistakes can happen, potentially delaying your product order. That's why it's important to go with a trustworthy, experienced company for your part production needs.


For more information on how the thermoplastic injection molding process can work for you and your part run, contact us today.

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