Measuring Coated Metal Using the SpectraProbe XE
The color of coated metal is closely monitored on coil coating lines. Any on-line instrument used for measurement of this metal must be capable of differentiating between acceptable and unacceptable product and alerting when an "out-of-tolerance" condition is obtained so that outliers can be segregated and necessary corrections made to the process in real time. Ideally, the entire width of the product would be assessed and the system could compensate for changes in product temperature that also cause changes in color.
The HunterLab SpectraProbe XE can accurately detect differences between acceptable coated metal and product that is off-color and can show side-center-side color differences. It can also compensate for temperature changes and log alternate parameters (process variables) along with the color measurements. This instrument has been successfully installed on coil coating lines spanning five continents.
The SpectraProbe XE
The Application
The SpectraProbe XE is mounted for measurement over the coated metal using a rail which allows the sensor to traverse over the entire surface of the product. The sensor is typically installed just before the exit accumulator stack.
| Recommended Color Scale | CIELAB or Hunter L, a, b as a full color descriptor |
| Recommended Single-Number Indices | dE* or dE for indication of total color difference from a standard |
| Recommended Illuminant/Observer | D65/10°. C/2° may also be used. |
Measurement Method
1. Configure a product setup for each type or color of coating with the following parameters:
| ... | Page 1 | |
| Color Scale | L*a*b* or Hunter Lab | |
| Optional Index | dE* or dE | |
| Data Collection Units | Feet | |
| Data Collection Frequency | 25 (depending upon range speed) | |
| Secondary Calibration | Every 30 minutes | |
| Illuminant | D65 or C | |
| Observer | 10 Degrees or 2 degrees | |
| Page 2 | ||
| Product Standard | Numeric for existing products, Adhoc for new products | |
| Offset Correction | Enter values only if hitching the SpectraProbe XE to a benchtop system (such as the LabScan XE) on which the product standards have been measured. | |
| Tolerances (Center to Standard and Cross Shading) | Typically 0.5 for each component of the color scale | |
| Page 3 | ||
| CMC Parameters | Not used | |
| Tolerance Alarm Deadband | 5% | |
| Shade Sorting | Off | |
| Output to Lot File | Check if you would like to save lot data as a text file in addition to saving it in the database and job. | |
| Analog Outputs | Check if you purchased this option and would like to output tristimulus data to a PLC or DCS system. | |
| Optional Parameters | Not used. | |
| Scan Parameter | Not used. | |
| Scan Pattern | As desired. Typically, extended edge detectors are purchased, meaning a scan pattern incorporating edges should be used. | |
| Traversing Type | CS-LC-RL | |
| Page 4 | ||
| Page Titles and Descriptors | As desired | |
| Page 5 | ||
| Shade Space Parameters | Not used. | |
| Switchable Run | Not used. |
2. Begin the run.