Quality inspection of flat glass

Two new measuring stations from Micro-Epsilon are being used to inspect the dimensional accuracy and edge quality of flat glass at Schott based in Jena. Dimensional accuracy is a critical factor in industrial glass, which is used for demanding technical tasks. An example of this is glass used in the production of photovoltaic modules. 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. Glass is renowned as being difficult to measure because of its transparency and so only the latest technologies are able to reliably and accurately inspect the material for its geometry (format, thickness and evenness) and surface quality.

Two different optical methods from Micro-Epsilon can be used for this application: confocal chromatic sensors and the light intersection method. In the production line, a robot places the pane on a transport system, which feeds the pane into the measuring station. Here, the pane is deposited on a solid block of stone in order to avoid 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 information 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 stone slab is also used as a reference surface.

A scanCONTROL 2800 series laser canner circumnavigates the pane during the traversing process. Therefore, the edge is inspected for flaking while simultaneously measuring the edge geometry of the pane. A laser line is projected onto the pane and the diffuse reflected light is received by a CMOS matrix. In this way, the surface profile of the edge of the pane can be accurately reproduced. The two new measuring systems are used in goods inwards and issue. They ensure that only 100% intact panes are further processed and despatched.