What is Unscrewing Mold?

One of the most unique types of injection molds is unscrewing molds. Unscrewing molding is a unique injection molding process with mold technology that includes movement and rotation to produce threaded components. Some plastic parts such as caps and closures with detailed threads cannot be removed using standard knock-off methods. After they are molded, parts need to be carefully unscrewed from mold to avoid damaging the threads.

The unscrewing molds are part of everyday use, which may cause you to think that you won’t need to spend much time considering the required design. To demonstrate the wide use of this particular mold type, the following is a shortlist of the types of products that use unscrewing molds in the design:


• Bottle and milk caps

• Condition and shampoo lids

• Prescription medication bottles

• Medical supplies

• Sprinkler and showerheads

• Screws, nuts, and bolts

Here’s How It Works:

• First, the plastic is injected into the tool. After the plastic has cooled, the threaded core starts to unscrew. The unscrewing mechanism works off of a rack and pinion and is powered by a hydraulic cylinder.

• The rack turns three sets of gears which then retracts the threaded core into the ejector box.

• Once the threaded core is fully unscrewed, the mold opens and the ejector system pushes a stripper plate forward to eject the part.

• After the part is fully ejected, the hydraulic cylinder reverses, screwing the threaded core back into the molding position, and the process repeats.

 What is Unscrewing Mold?

What factors need to be considered?

When you need one of these types of plastic molds, there are several things you have to determine to make sure you get the right fit for your product and budget.


The volume of the product will probably determine many different aspects of the final product, including the thread count, the size of the part, and the type of material that will be used during production. While other factors are important, the design of the various unscrewing molds is more complex and costly than many of the other types of molds.

Ease of Removal

The ease by which an unscrewing mold should be removed from the final product is an important factor to consider in the design. Water bottles have only a few threads, sometimes only two or three because they need to be easy to remove. To ensure that the tops do not fall off easily, the threads are spaced out a bit more. An unscrewing mold on a medical device will likely need a lot of threads that are evenly spaced and very difficult to pull off of the device. The material required for these two vastly different uses is affected by how easily the part should be removed from the product.

The Threads

The number of threads is going to vary based on the final product. Water bottles do not require a high thread count because they are relatively light and should be easily removed. If the unscrewing mold is for a plastic part under the hood of a car, it needs to have a higher thread count to be more durable. The number of threads required plays a large role in the final cost of production, so it needs to be tested to ensure it meets the needs of the final product.

Applications and Maintenance

High volume, reliable unscrewing plastic injection molds are some of the more complex plastic injection molds that can be manufactured. Unscrewing plastic injection molds are typically utilized for high volume applications where threaded plastic parts are needed for items such as:

ㆍBottle caps

ㆍShampoo bottles

ㆍPharmaceutical Supplies

ㆍAutomotive parts

ㆍNuts and bolts

ㆍCosmetics packaging

ㆍMedical Supplies

ㆍConsumer goods

ㆍSprinkler heads, lawn & garden parts

ㆍContainer lids

What is Unscrewing Mold?


Most threaded plastic parts on standard plastic injection molds are not easy to remove using standard knock-off techniques. Therefore more complex unscrewing plastic injection molds must be utilized to prevent the threads on threaded plastic parts from being damaged while the parts are coming off of the plastic injection mold.

Because these threaded plastic parts are typically needed in high volume applications for items such as bottle caps or cosmetics packaging, the unscrewing plastic injection mold most operate at a high speed to reduce cycle times thus reducing part costs. The unscrewing plastic injection molds must also be high quality and reliable to operate for a large number of cycles while only needing routine preventative maintenance.


WIT MOLD is a highly skilled mold design and manufacturing company in China, certified ISO2009:2015 international quality standard. Contact us today for your threaded plastic parts!

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