Measuring stations inspect glass quality

Two measuring stations supplied by precision sensor specialist Micro-Epsilon are being used by glass manufacturer Schott to inspect the dimensional accuracy and edge quality of flat glass.

At the company's manufacturing plant in Jena, Germany, dimensional accuracy is a critical factor.

Even a small deviation from the required geometry or thickness of the glass can adversely affect the function of the glass at a later date.

Due to its transparency, glass is difficult to measure.

However, technologies are now available to reliably and accurately inspect glass geometry (format, thickness and evenness) and the surface quality.

In this particular application, two different optical methods from Micro-Epsilon are used: confocal chromatic sensors and the light intersection technique.

In the production line at Schott a robot places the glass pane on a transport system, which feeds the pane into the measuring station.

Here, the pane is deposited on a solid block of granite in order to eliminate any vibrations.

Six OptoNCDT 2401 confocal chromatic sensors are located on a traversing beam directly above the pane, which measure the thickness and planarity in six tracks.

The desired distance or thickness data for the confocal principle is obtained from polychromatic white light.

A conventional LED provides the light source.

The sensors have a measuring range of 10mm and only measure the thickness from one side; the granite slab is also used as the reference surface.

A Scancontrol 2800 series laser profile sensor circumnavigates the pane during the traversing process.

The edge is therefore inspected for flaking (small defects, chips or cracks) while simultaneously measuring the edge geometry of the pane.

In this way, the surface profile of the edge of the pane can be accurately reproduced.

Schott is using the two measuring stations in its goods inwards and goods issued areas.

The systems ensure that only 100 per cent intact panes are further processed and despatched.

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