what is Unscrewing Plastic Mould

Unscrewing plastic molds are routinely considered as a viable method of closure (Le. screw-on bottle caps, etc.) manufacturing. If you are looking at a closure and have ever wondered what kind of mold was used to manufacture it the serrations on the bottom of closure will reveal if a part has been unscrewed or stripped. Unscrewing plastic mould typically will have a longer cycle time than a stripped closure mold or collapsible core mold, which may cause you to ask why any are made this way.

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.

The main idea behind understanding how an unscrewing mold works is study the actual movements involved in the process of removing a closure from a bottle. When studying the motions used you will be surprised to learn that while you are turning the cap your hand will automatically rise up to the pitch of the threads. A cam action on the stripper bar must do the same thing in order for the part to be removed from the core. Unscrewing molds consist of a rack, motor or hydraulic cylinder and a gear rack.

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

Unscrewing molds are usually necessary when the thread profile and the material chosen cannot flex due to the lack of elasticity in the material. The closure is tightened to provide a seal that would be leak proof. The strip thread mold design is not robust enough to provide a leak proof result. There are Primarily Two Types of Unscrewing Molds: The first type is known as a reciprocating core. This type does not require the stripper action to take part in unscrewing. This type of unscrewing mold requires racks, gears and hydraulic cylinders. It also must have serrations along the parting line of the open end of the closure deep enough to keep it from turning while the core is unscrewing and retracting, yet shallow enough to allow easy ejection. The second type is known as unscrewing stripper mold. In this type of design the core does not reciprocate but simply turns. The outside cam lifter bar of the mold drives the stripper up at the same rate of the thread pitch. This design requires that hydraulic cylinder and the thread cores move simultaneously. If the thread pitch and the cam bar angels are not matched it will cause the threads to strip. Both types of molds require a hydraulic cylinder that has alignment coupler as well as gears, and gear racks.