Background:
Linescanners are often installed on machines where there are accessories or constructed parts installed or manufactured by the OEM.
From time to time questions arise from the end-user that the expected temperature profile does not fit to the expectations or modelling of the customer. This can be in terms of overall nominal values (sometimes relating to recipe or setpoint temperatures) and/or temperature distribution across the manufactured product.
A prime example is in float glass manufacturing where the linescanner (installed most often to control cooling) is protected from heat by a cooled housing, mechanical shutter and/or protective window film. In addition to the device protection accessories supplied with the linescanner, the sight path to the "glass ribbon" also incorporates a large "fan tail" construction. This is so that the heat is kept inside the machine (in this case the Cooling Lehr).
Glass float lines will often have Ircon ScanIR2 replaced with either ScanIR3 or MP150
During commissioning this alignment would have been set, verified and confirmed with the customer as being optimum or acceptable.
A typical thermal profile of such a glass ribbon looks like this:
When the profile starts to deviate from this ideal, questions arise as to the reliability of calibration of the linescanner. However, in our consolidated experience, the root cause is alignment or obstruction:
1. Misalignment to the shutter
2. Shutter only partially open - pneumatic or mechanical failure
3. Linescanner front window or protective window contamination
4. Issues with customer control system
The guidance is applicable to any linescanner application where alignment and machine obstruction may be an issue such as extrusion coating lines for EC or glass tempering lines with GS packages.
Please download the attached .pdf file of the slides in this graphic
