EoW September 2012

Technical article

Any number of recipes can be stored. Until now the recipe database is very simple and should include search functions in future software. Connection to the line PLC should be possible via simple digital 24V signals (signal status and device enable) where fault messages are implemented to the coil protocol like spark or diameter faults or with a more complex network communication via TCP/IP to have access to the recipe database or to support host computer link. Figure 9 shows the main screen that includes the most important information for the line operator. Additional windows can display more details, like separated L*/a*/b*-channel measurement, various signal history or trend information. For later evaluation, a subsample of raw data is stored on the IPC hard disk. To be independent of all production lighting conditions, the scan field is covered and illumination is done by an internal LED light source (see Figure 10, white arrow). According the higher luminance variation compared to a* and b*, a modification of equation (1) should be tested: While equation (1) represents a circular error distribution, the modification is an elliptical distribution with enhanced tolerance in the L* channel (for f > 1). Technical aspects are almost solved; the main focus is now the improvement of device interface and handling. This needs feedback from the wire and cable production companies. Another point of discussion should be the combination of stripe and main colour. For example main colour red with a brown stripe is difficult to separate – for an automatic device as well as for a line operator. So this is not a problem in colour measurement itself but a possible improvement of quality control by a simple redefinition of colour pairs with high ∆ E. n eq (2)

simultaneously to the decreasing stripe width. After around 5 seconds, the raw signal moves only within the main colour tolerances. The co-extruder was switched on again at around 50 seconds on x-scale and stripe signal ramped up in 5 seconds to normal condition. The last setup in Table 2 is to test the stripe to main ratio. As the sensor only detects the average colour in the scan field, it isn’t possible to measure the stripe width directly. In case of a constant longitudinal product rotation, the time interval of main t m and stripe t s colour found in their tolerance interval can be integrated for certain time T and the resulting time ratio

should be almost same as the geometrical ratio. First trials under optimum conditions gave almost satisfying results with T>10s, but scan field size, jitter and rotation irregularities are still a challenge for an evaluation with high evidence.

Actual device specifications and forthcoming development

The user interface of the device should be quite easy to control for the line operator without losing setup flexibility or detail information, comparable with inline wire centricity measurement. Based on an IPC, control of the sensor is completely transparent for the user. A non-contact measurement reduces the risk of sensor damage. Very often the wire isn’t completely dry while passing the device. This caused contamination of the sensor surface but could be solved by installation of a permanent compressed air blowing over the sensor. To protect the optics during production start/stop and bare wire running, the sensor is moved into a safe position until normal production. Temperature compensation is done automatically. As already mentioned, colours are detected as relative measurement, so the system needs a teach-in for each geometry/colour combination. This is done once after the wire runs in good production and the detected reference can be stored for further production of this wire type.

Siebe Engineering GmbH Industriegebiet Fernthal 53577 Neustadt/Wied Germany Email : vkde@siebe.de Website : www.siebe.de

References

Edward H Adelson, MIT, 1995

[1]

https://www.ral-farben.de/492.html?&L=1

[2]

[3] Joint ISO/CIE Standard: CIE Colorimetry – Part 1-5, ISO 11664-1··5/CIE S014-1··5/E:2006-2007 [4] Masataka Okabe, Kei Ito (2008-02-15). Color blind barrier free. http://jfly.iam.u-tokyo.ac.jp/color/

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September 2012