Types of seams include neck-ring seams, a protruding seam of glass that runs vertically from the body of the container up to the finish.Baffle marks, meanwhile, can include a rough or damaged baffle seam on the bottom of a container. Pressure checks are cracks through a container’s wall that can appear at a seam. Blank and mould seams typically extend from a container’s shoulder to its base. They can appear on a container’s body, edge or side. The severity and quality impact of seams depend on the manufacturing process.
Mould, blank, neck and heel seams are generally created when the hangers and inserts used in individual section (IS) machines fail to close precisely. Over time, hangers, especially blank hangers, can warp, which further prevents the inserts from closing completely. One major glass container manufacturer using triple gobs wanted to remove those seams and any potential defects resulting from them. The hanger inserts were held in place with four pins, which required extensive machine downtime and effort to replace.
The solution was a modified hanger insert design that utilizes a single pin, allowing the inserts to “float.” As a result, the hangers were able to close completely with equal pressure, even if a hanger warped, thus removing seams. The single-pin design allowed the inserts to be replaced much more quickly, within minutes, lessening downtime.
The hanger inserts the container glass operation had been using typically would last six months or less, whereas the newly designed hanger inserts lasted two or more years.
To extend insert service life, periodic cleaning is recommended. Eventually, the oil used to keep mould equipment lubricated can harden, leading to crust buildup on inserts, affecting the smoothness of its movement. Pyrotek, which acquired the patented single-pin hanger insert modification technology earlier this year, is researching other applications for container glass manufacturers.
Top, IS machine hangers with inserts. Left to right, glass containers with visible seams.