Flip Top Cap Mould, Bump Lotion & Closure Mould
China’s leading reliable plastic cap mould supplier with over 15 years of experience. One stop service — quick delivery, rich experience, top quality. Mould steel P20, H13 and S136.
- 15+ years cap mould experience
- 7 cap mould types
- P20 / H13 / S136 steel
- Design to delivery, one stop
Your one-stop cap mould partner
Topworks is China’s leading reliable plastic cap mould supplier with over 15 years of experience. Our one stop service offers quick delivery, rich experience, and top quality cap moulds.
We have a wide selection of high-quality plastic cap molds that are ideal for product development, prototyping, and production.
We are dedicated to making quality cap moulds with mould steel P20, H13 and S136.
Cap mould range
- Hinged Closures Mould
- Yorker Spout Mould
- Disc-Top Cap Mould
- Flip-Top Cap Mould
- Push-Pull Cap Mould
- Twist Open/Close Cap Mould
- Flapper Closures Mould
Cap & closure mould gallery
How to design screw cap, lid & closure moulds
Undercuts on the inside of a cap — typically inside threads, snap-on ribs, or major undercuts that are part of the product shape — require careful design decisions. The planned method of manufacture (molding, or machining after molding) should be considered. The cap mould could be much simpler if the cap is threaded after molding. It is more important to arrive at the lowest total cost product than at the most elegant method of manufacture.
Inside threads on cap
If the thread must be molded, there are two choices of how to remove the product from the core: by unscrewing or by stripping. The designer should carefully consider production quantities required. Machining after molding can reduce cap mould complexity and cost significantly for lower-volume runs.
Unscrewing method
Threads designed to standard usually consist of more than one pitch. In many screw caps for bottles, jars, and toothpaste tubes, two to six pitches are quite common. More turns mean longer products, more plastic, more molding time, and longer cycles. In many closures, a thread length of one or two pitches is sufficient for good holding power.
The stripper ring holds the cap so it can be unscrewed away from the core. The cap requires ribs or projections on the outside where an external unscrewing device can engage. The design of these aids should be discussed with the mold designer.
Any unscrewing method requires either complicated cap moulds or special machines. Molding cycles are also slower than comparable products that need not be unscrewed.
Stripping ejection (force ejection)
Stripping is the easiest and often the lowest cost solution for ejecting the cap or closure. As the cap mould opens and after the cavity has moved away from the core side, the ejection starts caused by the stripper moving forward. The plastic cap is pushed over the hump in the core, causing the plastic to expand so that the portion inside the groove can slip out.
The ease of stripping depends on many equally important factors: thread angle, projection height, diameter, and the type of plastic and its modulus of elasticity.
Factors affecting stripping ability
Thread angle (α): The greater the angle, the more difficult the stripping action. A sharp angle (α = 90°) makes ejection virtually impossible — the plastic cap would shear off in the groove rather than pull out.
Height “h” vs Diameter “d”: The percentage of stretching f is directly proportional to height h and inversely proportional to diameter d. The greater the cap diameter d, the easier the cap will slip out of its groove. A cap from relatively stiff plastic could be stripped if d is large, but would break during ejection if d is small.
Number of threads (pitches): The easiest way to strip is to specify only one thread (one pitch) so that the stripped thread will not slide into an adjoining groove but continue to slide uninterrupted off the core.
The finish of the groove also influences the ease of stripping, especially with materials requiring high polish for good ejection.
Figure 1 — Stripping influences
Influences affecting the ability to strip a cap. The greater the angle α is, the greater the difficulty in stripping. Screw threads could have a 90° angle if absolutely required, but that would definitely call for unscrewing — stripping would not be possible.
Many screw threads — especially threads for closures — have standardised shapes which originally evolved from threads on glass bottles and jars. Such standards should be followed, and their large tolerances used to obtain maximum benefits for plastic threads.
By considering all factors influencing stripping, the designer will succeed in creating a screw cap with the proper shape of thread cross section and a suitable h/d ratio so that even a relatively stiff plastic can be readily stripped, without the need for an unscrewing cap mold.
Need a cap or closure mould?
Send your cap drawing, material spec, and annual volume. We’ll reply with DFM notes, steel recommendation, and a clear quotation.
- Flip-top, hinged, disc-top, push-pull, twist, yorker, flapper
- P20 / H13 / S136 mould steel
- 15+ years cap mould experience
- Quick delivery, one stop service
Cap & closure mould FAQ
What types of cap moulds do you make?
We manufacture moulds for flip-top caps, hinged closures, disc-top caps, push-pull caps, twist open/close caps, yorker spout caps, and flapper closures — covering bottles, jars, tubes, and cosmetic packaging.
What mould steels do you use for cap moulds?
P20 for general production, H13 for high-wear and abrasive-filler applications, and S136 for corrosion resistance with aggressive resins. Steel choice depends on resin, surface requirement, and target mould life.
Should cap threads be molded or machined after molding?
It depends on volume. For high-volume production, molding the threads is more efficient — the cap mould uses unscrewing or stripping ejection. For lower volumes, machining threads after molding can simplify the mould and reduce cost significantly.
What is the difference between unscrewing and stripping ejection?
Unscrewing rotates the cap off the core — required for deep or sharp-angle threads, but needs a more complex mould and longer cycle. Stripping pushes the cap over the core hump by force — simpler and faster, but only works when thread angle, h/d ratio, and plastic flexibility allow it.
How do I know if my cap design can be stripped?
Key factors: thread angle α (must not be 90°), projection height h relative to cap diameter d (smaller h/d = easier stripping), number of pitches (one pitch is easiest), and the plastic’s modulus of elasticity. We run DFM analysis to confirm strippability before cutting steel.
What is the typical lead time for a cap mould?
30–50 days from design approval depending on cap type, cavity count, and unscrewing mechanism complexity. Trial parts and inspection reports are provided before shipment.
Can you make multi-cavity cap moulds?
Yes. Cap moulds commonly run 4, 8, 16, or higher cavities depending on annual volume and press size. Higher cavitation lowers per-part cost but increases mould investment and lead time.
