Opening Force vs. Locking Force: What's the Difference?
Understanding the two critical torque metrics and why you need to test both for quality control.
Two Sides of the Same Coin
In packaging quality control, "Torque" is not a single number. It consists of two distinct physical events: Application (Locking) and Removal (Opening). The NLY-20A is designed to measure both with high precision.
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1. Locking Force (Application Torque)
This is the rotational force applied to the closure during the sealing process (usually by a capping machine).
• Goal: To deform the liner/gasket sufficiently to create a hermetic seal against the bottle finish.
• Risk of Low Force: Leaking, bacterial ingress, oxidation (shelf-life failure).
• Risk of High Force: Stripped threads, cracked caps, or a "frozen" cap that cannot be opened.
• Testing Method: Used primarily for setting up and validating capping chucks on the production line.
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2. Opening Force (Removal Torque)
This is the peak force required to unscrew the cap to the point where the seal breaks.
• Goal: To simulate the consumer experience. The cap must be secure but openable by an average person (or specific demographic for CRC).
• The "Relaxation" Phenomenon: Torque drops over time. A cap applied at 20 lb-in might only require 10 lb-in to open 24 hours later due to plastic relaxation.
• Testing Method: This is the most common QC test performed on finished goods after a set "dwell time" (usually 24 hours).
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3. The "Strip Torque" (Over-torque)
The NLY-20A also features a "Strip Ratio" (Broken Shape Ratio) setting. This detects the point where the closure threads fail due to excessive force.
• Why Test It? To ensure your bottle and cap design are robust enough to withstand high-speed capping machines without stripping.
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Summary: Which Mode Do I Use?
The NLY-20A's dual-mode capability ensures you are covered for all three scenarios.
