Last week, we discussed the special marks on closures and bottles that are intended to support a faster and non-destructive seal integrity test method: application angle measurement using vision systems. We mentioned that we believe that the visual application angle inspection will be a wonderful way to test the seal integrity on 100% of the packages, but for an error proof operation the vision systems must be calibrated/validated frequently by using leak and torque testers. One method for automatically calibrating the visual seal integrity tester is by using application angle and torque measurement.
As bottles pass through the vision system, the angle measurement is conducted. Using the angle result, an automatic sampling system triggers the off-line torque testing of bottles/caps with average and extreme low/high application angles. After the automatic application angle measurement, the angle and torque values are correlated, determining the angle to the torque conversion “multiplier”. This variable is then fed back to the visual inspection system, allowing the automatic angle to torque conversion and presenting the calibrated torque value directly on the vision inspection HMI screen. Certainly, additional quality assurance tests can be conducted at the same time, such as: release, tamper evident bridge break, strip torque testing and weight measurement. After destructive testing (TEB break/strip torque/measurement/application angle), samples can go to the reject lane, while products tested by means of non-destructive methods can be returned to the production line.
So, what’s the secret of Mesa’s application angle measurement technique?
Using a highly sensitive strain gage-based torque transducer and our proprietary “floating” closure gripper and adjustable pressure bottle gripper, our servo-driven automated torque tester can accurately detect both small and large changes in the torque value. In the example application below, we used a CSD closure from a production line and charted the torque/angle data points during an 1800 degrees rotation cycle.
A closer look at the angle range from 900 degrees to 1800 degrees reveals that the threads jump consistently 360 degrees apart. The jumps are indicated by the torque minimums measured at 1048, 1409 and 1769 degrees. The repeatability of the thread start measurement therefore is 360 +1/-0 degrees.
The first thread jump minimum can be adjusted by an offset value (if necessary) and used as the application angle.
Certainly, the above detailed technique or similar principles can be used to automatically measure and detect virtually any torque transients. Using our adjustable pressure closure and bottle gripper, we can automatically and securely grip smooth surface caps, and pump dispenser closures or child resistant closures as well. Because the gripping pressures are adjustable and calibrated, all torque testing variables are controlled/monitored and validation ready. After a few “training” cycles, the above described technique can be fine-tuned to filter out even the CR engagement transients from the thread jump minimums.
For decades, Mesa Laboratories has customized similar measurement techniques in the automatic detection of characteristic torque transients for the quality control of medical devices, pharmaceutical and beverage closures. Should you have a similar, unique measurement application in mind, do not hesitate to contact us with your product testing and evaluation projects.
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