Pharma glass defects - 27. Offset Finish

Hello everyone – welcome to Part 27 of an ongoing series devoted to defects in pharmaceutical glass vials.  Today’s post concerns the “Offset Finish”, a defect in which the flange is not concentric with the body of the vial.  Take note – we’re talking about the entire finish being shifted off the central axis of the vial as illustrated in Figure 1.  This is in contrast to the “Pulled ID” defect where just the interior of the flange is offset and/or has an elliptical geometry (there will be a separate post on this defect in the future).

An Offset Finish defect can be created during the conversion process as the result of a misalignment between the glass tube and tooling used to create the neck/flange regions of a vial.  It can have various consequences for the fill-finish process, including poor machinability (e.g., for processes such as washing that grip the vial by the neck), increased likelihood of needle strikes during washing/filling, and reduced compatibility with stoppering and capping operations.  Given this potential impact on manufacturing, an Offset Finish can be classified as a Major B defect if it exceeds the defined offset or runout specification as determined by a calibrated measuring device OR by using a defined limit sample (see Footnote 1).  It is otherwise considered an Acceptable Imperfection.

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Footnotes

1.       I would need to go back through all of my posts to double check, but it feels like I may not have used the term “runout” before.  In case you don’t already know, runout (also called “circular runout” to be more specific) is a measurement of a circular profile when rotated about a central datum axis.  An appropriate gauge can be used to measure the distance between a surface of interest (e.g., the outer surface of a flange) and a rotational axis.  The difference between the minimum and maximum recorded distances is equal to the runout.  A perfectly circular flange that is exactly centered on the central axis of the vial should therefore have a runout of zero.  The usefulness of runout is not restricted to the finish of a vial – it could also be used to characterize the circularity of the body and heel regions.

About the Author

Matthew Hall is Technical Affairs Director for Corning Pharmaceutical Technologies , a manufacturer of primary glass packaging for parenteral drug products.  Based in upstate New York, Dr. Hall serves as a technical expert supporting business operations, sales, and marketing and educating customers on pharmaceutical glass packaging.  He is a member of the Parenteral Drug Association and the International Society of Pharmaceutical Engineering.