Team Rapid Manufacturing Co., Ltd

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

Thread Plastic Injection Molding 

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 thread plastic molded parts we encounter everyday. Thread molding is used widely in our life, how to make your plastic parts in specific threads? These needs to have full considerations not only with part design but also from the manufacturing perspective.

Molded Threads

Types of Thread Molding

Types of Thread Molding1. Molding with external 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 there are tiny parting lines on thread, these lines are fine for thread's attachment, but not very good for precised transmission especially for gear components. Depending on the part's size and geometries, TEAM Rapid always makes the parting line as small as we can!

2. Molding with internal threads.

Molding with 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 seperating. We need a third component named thread core/thread cavity, which has the completed geometries of threads. The tooling structure for these moldings is more complicated than the first one, the production cycle time can be long or short depending on the thread released methods.

Thread Released Methods

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

Force Release1 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.

Manual Insert2 Manual Insert:

The thread core/cavity is placed into the mold, and ejected out together with the molded part, then released by hand. The method of manual insert is suitable for low volume production,typically, 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 thread molded 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 to get more supports.

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