Torque testing

Torque testing measures the rotational force required to turn or twist an object. In packaging, it is most often applied to closures such as caps, lids and twist-top mechanisms to ensure they open and close within defined performance limits. This is particularly important for threaded closures, push-and-twist child-resistant caps and other twist-to-engage systems.

Torque is the product of rotational force and distance from the rotation axis. In packaging, it directly relates to how much effort is needed to engage or disengage a closure. Too little torque can lead to leaks or compromised product integrity, while too much can make a package difficult to open or risk damage during automated capping.

Static torque measurement evaluates a closure’s resistance at a single point, for example, the initial twist required to open a cap. Dynamic measurements record how torque changes throughout the rotation. Both approaches give packaging engineers and quality controllers valuable data to maintain consistency, functionality and safety.

Torque testing underpins closure performance, ensuring that products remain sealed and safe throughout distribution, storage and use. It verifies that the force required to open a closure is neither too high, which could cause consumer frustration or accessibility issues, nor too low, which could result in accidental opening or contamination.

In sectors such as beverages, pharmaceuticals, household products and cosmetics, precise closure torque helps maintain:

• Product safety - preventing leaks, spoilage or accidental ingestion.
• Regulatory compliance - meeting national and international standards for closure integrity and child-resistant designs.
• Brand consistency - providing a uniform user experience across production batches.
• Ergonomic performance - ensuring closures are user-friendly while maintaining a reliable seal.

Child-resistant packaging is a key example where torque testing is critical. Push-and-twist mechanisms must balance safety for children with accessibility for adults, meeting legislative requirements without compromising usability.

Torque testing can be carried out using manual or automated methods, depending on production volume, precision requirements and budget.

Manual torque testing uses handheld devices where the operator applies rotational force and reads the measurement from a dial or digital display. It is best suited for lower-volume production checks or field testing.

Automated torque testing uses motorised systems to apply consistent rotational force, eliminating operator variability and enabling repeatable, high-precision measurements.

Common torque measurement types include:

• Peak torque - the maximum force required to open or close a closure.
• Breakaway torque - the initial torque needed to start movement after seating or tightening.
• Slip torque - the torque at which a closure rotates freely without further engagement.
• Release torque - the force required to fully disengage a closure.

Automated systems can produce a torque-to-turn curve, plotting how resistance changes throughout rotation. This can identify manufacturing inconsistencies or design issues. In the beverage sector, for example, lightweight PET caps may be tested to ensure breakaway torque remains within a typical range of 0.8 to 1.2 Nm for consistent performance.

Mecmesin has decades of expertise in closure torque measurement, offering solutions designed for accuracy, repeatability and easy integration into quality control processes. Systems range from compact benchtop testers for laboratory use to fully motorised systems for high-throughput environments.

• HelixaPro - high-precision control for low-torque applications, such as cosmetic jars or small medical closures.
• VortexPro - robust motorised torque testing for a wide torque range, suitable for production and laboratory use.
• Tornado - a portable, easy-to-use manual tester for rapid checks on production lines.

VectorPro software enables real-time data capture, programmable test routines and detailed torque curve analysis. Pass or fail criteria can be applied automatically, and results exported in formats suitable for compliance and auditing.

Mecmesin also provides consultation, calibration services, custom fixture design and operator training, ensuring that torque measurement remains accurate and compliant for specific product designs.

Mecmesin torque systems are engineered to comply with industry standards, including ASTM D7860-14 for child-resistant packaging. This standard specifies the measurement of closure torque under defined conditions, including the application of downward force for push-and-twist caps. Mecmesin’s pneumatic and custom-fixture solutions can accurately simulate real-world opening conditions.

Other standards may be relevant depending on sector, geography and closure type, covering safety and performance requirements. Adhering to these standards supports regulatory approval, reduces liability risk and demonstrates due diligence.

Torque testing is used across a broad range of packaging designs, including:

• Plastic bottle closures for beverages, cleaning products and personal care items.
• Cosmetic jars where slip torque and bridge torque tests confirm tamper evidence and ease of opening.
• Pharmaceutical containers requiring strict adherence to torque specifications for safety and compliance.
• Speciality closures such as multi-way or sustainable designs, where materials and geometry affect torque performance.

Custom fixtures, such as nesting bottle holders or mandrels, are often required to secure and align samples consistently during testing.

Torque testing can be influenced by several factors:

• Operator variability during manual testing.
• Misalignment if samples are not securely held.
• Torque loss over time due to material relaxation or environmental exposure.
• Inaccurate results from uncalibrated equipment.

Solutions include using automated testers to remove operator influence, custom fixtures for secure alignment, regular calibration schedules and pneumatic or motorised downward force systems for repeatable testing of child-resistant designs.

Automation is becoming increasingly common, improving accuracy and enabling in-line testing during production. Data systems are now linking torque results directly to compliance management tools, allowing immediate action if results fall outside specification.

Sustainability is also driving change. As materials become lighter and closures are redesigned to reduce environmental impact, torque testing ensures that these innovations still meet safety and usability requirements. For example, the move to lightweight caps in the bottled water industry has made torque measurement essential to maintain a reliable seal without increasing opening difficulty.

Torque testing is a critical part of packaging quality control, ensuring safety, compliance and brand integrity. Mecmesin’s applications engineers can advise on test methods, equipment selection, fixture design and standard compliance to suit the needs of your packaging. From consultation to global after-sales support, expertise is available to help you optimise closure performance testing.