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Injection Molding Threads
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Injection Molding Threads
Injection Molding of your plastic components with internal and external threads.

Injection Molding Threads


It's commonly to see threads on everywhere, a cap of soda bottle,  a nut that attaches to the drain pipe underside of the kitchen sink, a cool-looking screws used to assemble a child's toy, etc. These are some examples of the injection molding threaded parts we encounter everyday. Injection molding threads is used widely in our life, how to make your injection molding parts in specific threads? These needs to have full considerations not only with part design but also from the manufacturing perspective.


Injection Molding Threads



Injection Molding Threads Types



1. Injection mold external threads

Injection Molding Threads

Making half of threads each on cavity and core side on the mold tool. In this way, the thread can be formed completely after cooling, it solves undercut problem for tooling, and raises the production efficiency. The only concern is the tiny parting lines on thread. These lines are fine for thread's attachment, but not kindly for precised transmission especially for gear components. Depending on the part's size and geometries, TEAM Rapid always makes the parting lines on injection mold external threads as small as we can!

2. Injection mold internal threads

Injection mold internal threads, or thread which not allows to have parting lines on, for these moldings, the thread needed to made on mold tool completely without division. We need a third component named thread core/thread cavity, it has the completed geometries of threads. The tooling structure for these moldings is more complicated than injection mold external threads, the production cycle time can be varied depending on the thread released methods.


Injection Molding Threads Released Methods


Mold structure for external thread is not complicated, the simple open-and-close mold is good to release undercuts. But for injection mold internal threads and those external threads that can't have parting lines, undercuts need to be released before opening the mold. Typically, we have the following three injection molding threads released methods:


Force Release Manual Insert Fully Automatic

                           Force Release                                                          Manual Insert                                                         Fully Automatic


1. Force Release

- Thread size, pitch and depth should be small enough to force out. 

- Injection material should be flexible enough to avoid crack issue.

- Wall thickness is consistent, it can't be too thick and without sharp corners. 

- Draft and radii on thread are necessary.


2. Manual Insert

Thread core/cavity is placed into the mold, and ejected out together with the molded part, then released threads by hand. The method of manual insert is suitable for low volume production. In order to raise the production efficiency, we usually makes 2 or even more thread core/cavity for interchanging.


3. Fully Automatic

Fully automatic unscrew molding, it is a unique injection molding process includes movement and rotation to produce injection molding threaded parts. First of all, we need to build automatic unscrew molds. Unscrewing action of these injection molds are accomplished with hydraulic or electric motor, making the thread core/cavity precisely have threads ground on them.  The cycle time for automatic unscrew molding can be much shorter than manually unscrewing, but the cost of automatic unscrew mold is expensive. Depending on your production amount, such as large volume production, the automatic unscrew molding cuts down the unit part price, even if by several cents per part, the total cost can be cut down much!


PP, ABS, POM and PA are the materials used commonly in thread molding, to keep production rolling along smoothly, you can contact with our team at sales@teamrapidtooling.com to get more supports of injection molding thread parts.


FAQ about Injection Molding Threads


Heli-Coils1. What are the different types of threads in injection molded parts?

American Standard 60?? sharp thread, tapered pipe thread, and buttress threads are the most frequently specified thread profiles used for plastic molded parts. Among these 3 types, the American Standard or machine screw is the most common. For some special threads, we can consider about post machining threads.


2. Can helicoils be used in plastic molded parts?

Heli-Coils are placed onto the plastic molded parts to enhance the strengthen and holding power of the screws. They are usually made in hard plastic, steel or aluminum, and install onto the parts after molding.


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