The design of a plastic bottle’s neck and screw closure is crucial for sealing, convenience, security, durability, and aesthetics. Precise threading alignment maintains a tight seal, preventing leaks and preserving content freshness. Smooth threading improves usability, while secure closures prevent tampering and spills. Durable materials and quality manufacturing ensure longevity, while an attractive design appeals to consumers. Now, let’s explore the fundamental aspects of bottle necks and threads together.
The dimensions “T”, “E”, “I”, “H”, and “S” are commonly used when describing neck and thread systems.
“T” stands for thread and refers to the outside diameter of the thread, determining the mate between bottle and closure.
“E” represents the external diameter of the neck. The difference between “E” and “T” divided by two determines the thread depth.
“I” signifies the inner diameter of the neck, remembered by “I = Internal”. It must be large enough to allow a filling tube to pass through.
“H” denotes the height of the neck finish, measured from the top of the neck to where the diameter “T” intersects with the shoulder.
“S” measures from the top of the finish to the top edge of the first thread, determining closure orientation and thread engagement between bottle and cap.
These parameters specify the dimensions and characteristics of threading, ensuring proper alignment and functionality in the neck and closure system.
You’ve probably seen expressions like 24-410 (24/410) or 33/415 (33-415) used to describe bottle necks and threads. The numbers 24 and 33 stand for the T dimension, while 410 and 415 indicate the thread type, based on how many turns the thread wraps around the neck. Each thread type has a specific H dimension range depending on the diameter, with at least one complete thread turn around the bottle (refer to the diagram below).
The neck types written in this format adhere to norms set by the Glass Packaging Institute (GPI) and the Society of the Plastics Industry (SPI) in the USA. The table below outlines standard dimensions from GPI/SPI 400, 410, and 415 series tables, serving as a guide for better understanding. For comprehensive information, it’s best to consult the Glass Packaging Institute or the Society of the Plastics Industry.
You might be familiar with DIN18 neck, GL18 neck, ROPP28, or PP28 neck and cap systems. These are variations of the thread and neck systems similar to SPI and GPI. Regardless of the system you opt for, ensuring the compatibility between the closure and the bottle is paramount. Thorough and rigorous testing is indispensable in this regard.
Furthermore, it’s advisable to consistently use closures and bottles/jars from the same supplier. This ensures that the closure threads and bottle neck combination have been specifically designed and tested to function together without any leakage risks. With decades of experience in designing and manufacturing closures, bottles, and jars for the cosmetics and food industries, Volksmolds is well-equipped to provide the expertise needed to select and produce high-quality packaging. Don’t hesitate to contact us for assistance or inquiries.
