Injection molding is a method for manufacturing high-volume parts with plastic materials. Due to its reliability and flexibility in design options, plastic injection molding is used in many industries, including: packaging, consumer and electronics, automotive, medical, and many more. Injection molding is typical for manufacturing plastic products using thermoplastic or thermoset polymers but is also used in some metal injection molding applications.
The plastic injection molding process takes place with a machine divided into clamping and injection units.
The process begins by clamping a metal mold with a cavity of your part geometry into place. Next, the injection unit melts plastic pellets and injects it into the mold at a very high pressure (thousands of PSI). Depending on the specifics of the part and the type of plastic, there may be a holding period when the plastic is held under pressure to ensure that is forms correctly. The mold has cooling channels that help uniformly cool the material. During a cooling period, the pressure is released to help with cooling. Finally, the clamping unit is released and mechanisms eject the part from the mold for the cycle to then repeat.
Parts may need further finishing steps, such as removing molding aids like plastic sprues or runners, polishing, or assembly to other components.
The traditional plastic injection molding process can be modified to include processes that help to enhance part quality and part design flexibility. Below are some examples:
Molding with thermoset materials requires heat or chemical means to cure the material. It uses a similar process as thermoplastic injection molding, but may have a hot mold instead of cold and requires a cure time instead of cool time, with the mold closed.
Overmolding is a plastic injection molding process where one material is molded on top of another. This includes molding over part inserts (such as a metal thread). An example of this is if you have a a hard plastic part that has a softer (or rubberlike) component - think of a hair brush or battery-powered drill handle.
After injecting plastic into the mold cavity so it only fills a portion of the cavity, an inert gas is introduced, at high pressure, which results in an air pocket in the center of the part. This reduces part weight while achieving high quality surface finish.
Injection of two different materials using either the same or different injection locations. One use-case for this is it lets a product have a stiffer material as a base, then a softer, more flexible material externally to withstand a wider range of performance applications.
Use of physical blowing agent, chemical blowing agent (CBA), or mold core-back process to trigger foaming of the polymer inside the mold. This is a way to reduce weight of parts while keeping the structural integrity of the part—thus, it is often used in automotive components.
Forming technique typically for producing small components using powders, typically ceramics (CIM) or metals (MIM), and binding agents, typically polymer. The material follows a similar process as traditional injection molding.
Plastic injection molding manufactures high quantities of parts, faster than other manufacturing methods (machining or 3D-printing). High accuracy and automated processes encourage identical part creation, promoting low labor costs. Customization allows flexibility in part design (example, molded-in inserts) and material properties (such as color, clarity, strength, and flexibility).
Image courtesy of Aska Corporation, Japan.
Part designers, mold engineers, and other manufacturing stakeholders can all run into their own challenges, which ultimately affect part quality, and they often need to work together to resolve them if not caught in the early design stages.
The up-front investment in mold tooling cost (thousands to hundreds of thousands of dollars to build) means extra care is needed to prevent tweaking or even having to rebuild molds.
Some examples of molding and process challenges include material variations, weld lines, sink marks, warpage, long cycle times, and incomplete cavity filling.
Molding simulation can help designers and engineers to understand risks early in the design process, allowing the ability to address these before becoming fully invested. Simulation software gives engineers, mold makers, and other molding professionals accurate digital prototyping solutions, and helps bring better products to market faster.
Moldflow simulation can be paired with other simulation tools, including mechanical stress, vibration, motion, computational fluid dynamics (CFD), and Multiphysics, providing a fast, accurate, and innovative approach to solving the most challenging design problems.
Analyze fill patterns and effects of geometry and process setting changes, such as sink marks.
Investigate the causes of warpage, then examine options to minimize or correct part deflection.
Analyze and compare advanced materials for lightweighting efforts, such as with automotive components.
Predict part cooling efficiency. Experiment with conformal cooling or induction heating options before investing in costly molds.
CAM software for high-speed and 5-axis machining—available as Standard, Premium, Ultimate
CAD modeling software to prepare molds, dies, and other complex parts for manufacture—available as Standard, Premium, Ultimate
Explore simulation through use-cases, validation reports, and technical papers from our team of experts.
Interact directly with current Moldflow Insight users and the Moldflow product team.
Read through various articles including injection molding concepts, simulation how-to's, and troubleshooting.
Keep up-to-date with molding simulation through these engineering-focused blog posts.
Interact directly with current Moldflow Adviser users and the Moldflow product team.
Watch and read how Moldflow simulation has directly impacted product design and manufacturing.
Learn how our Product Innovation Platform lets you more effectively design products and manage product lifecycles.
Explore manufacturing software that may help you machine, print, inspect, and fabricate better quality parts, faster.
Absolutely. Manufacturing a prototype, testing it to see where problems lie, iterating the solution, and building a new mold costs time and money. Instead, you can test your 3D design in simulation software and find potential issues before you build a single prototype.
Moldflow simulations can provide an extra step toward molding sustainably by providing insights in your material's environmental impact.
No matter what CAD platform you use, look for injection molding simulation software that connects to it seamlessly so it’s easy to bring your design into its environment. The fewer CAD file conversions needed, the higher likelihood that your simulation will be accurate and free from modeling errors.
Such interoperability should ideally include the ability to update or re-run simulations easily and on the fly as you make changes to your geometry.
If you work with a complicated part or process, or you need to simulate multiple materials or mold iterations all at once, look for software with remote server and/or cloud connectivity, which will give you the capacity to run simulations concurrently.
Most importantly, your injection molding simulation software should answer the questions you are looking to answer about your finished part, like:
Software solutions for plastic injection molding include Fusion 360 Simulation Extension, Moldflow Adviser, and Moldflow Insight. The Fusion 360 Simulation Extension costs $200/month if paid monthly or $1,600/year if paid annually (a 33% savings over paying monthly), and requires an active Fusion 360 subscription.
There are different Moldflow injection molding simulation product versions depending on your needs. Review your options by visiting the Moldflow website, and work with your official Autodesk reseller/partner for pricing. Utilizing a Flex 24-hour subscription lets users purchase daily access to Moldflow Insight, Synergy, and Adviser with Autodesk Tokens, as opposed to a traditional subscription. Moldflow Flex provides a lower-cost option for users who don’t need to use the software every day, and they can access it when needed with Autodesk Tokens, cutting down the cost of a traditional subscription. Moldflow Flex also allows existing named Moldflow users scale their solver (Insight) capacity as needed using Autodesk Tokens. Anyone interested in Moldflow should contact Autodesk or their authorized reseller to speak with a sales associate and find the software version that best suits their needs.
