Crucial control for (ultra) light weighting

In the industry magazine Glass Worldwide issue November/December 2011 you’ll find an article with this title. The article contains the latest about the Gob Assist. Below you’ll find a summary of this article.

Glass container manufacturers throughout the world face some important challenges:

  • Living up to customers’ expectations, which are continuously moving towards lower costs and higher quality
  • Remaining competitive, among one another but most importantly among manufacturers of other packaging materials like cans, cartons and PET
  • Contributing to the environmental needs of lowering energy usage and (carbon) emissions

In this context, the industry is slowly working towards using less glass for a bottle, while making the bottle stronger. Nowadays, although some successes have been realized overall, weight reduction is a slow process and one that generates many negative impacts. In most cases, while weight has been reduced, production speed and/or pack rate decreased, making the (ultra) lightweight bottle more expensive. Moving forward in this direction will not help the glass container industry to face its challenges. On the contrary, in the long run moving forward in this direction and using the same process capabilities will kill the industry; Japan is a good example. 

The challenge, therefore, is to reduce the weight of the product, while improving strength levels and not losing out on production speeds and/or pack rate. In this respect, among others (e.g. glass homogeneity), even and controlled glass wall distribution is of the utmost importance. Controlled glass wall distribution implies measurement and steering.

With the XPAR Vision InfraRed Dual camera system (IR-D), every product is measured just after the forming machine. Besides visualizing critical defects (inspection), the IR-D measures glass distribution (horizontally and vertically) in terms of variations in intensity and asymmetry of every product made. Tolerance settings are created for every product type, according to customer requirements. These tolerance settings (warning, alarm and reject) are the basis for measurement and thus steering.

Glass wall distribution has vertical and horizontal dimensions. Both horizontal (circumferential) and vertical glass wall distribution are highly influenced by gob loading into the blank mould. Controlled glass wall distribution requires controlled gob loading into the blank mould. In turn, this requires measurement (and steering) of the gob loading process.

The Gob Assist monitors the speed, length, position, shape, orientation, time of arrival and trajectory of gobs falling into the blank moulds.
Via customer trials, it has been concluded that speed and position are highly critical parameters for controlled horizontal glass wall distribution and that a change in speed results in a change of position (and as a result as an SOP, which causes a change in gob speed, which should always be followed by a gob position correction).

Via experiments with Gob Assist in relation to the InfraRed Dual camera system, the relationship between loading and glass distribution has been analyzed. Through these experiments, XPAR Vision has proved that a change in loading position of more than +/- 2mm has a significant negative effect on (horizontal) glass distribution.

In the knowledge that a change in loading position of more than +/- 2mm has a significant negative effect on glass distribution and that the current practice involves loading results of up to +/- 10mm, it should be concluded that a lot can be gained. Moreover, nowadays and with Gob Assist, a tool is available that allows for measurement and steering of loading position within a range of +/- 0.25mm.
Using IR-D and Gob Assist allows glass container manufacturers to make step-wise changes towards (ultra) lightweighting, without losing out on other critical variables, such as speed and pack rate.