Showing posts with label Color Measurement. Show all posts
Showing posts with label Color Measurement. Show all posts

High-Speed Color Measurement for Modern Manufacturing

Advances in High-Speed Color Measurement for Modern Manufacturing

Understanding how high-speed spectrometers measure color on manufacturing assembly lines provides a glimpse into the complex world of precision quality control and modern manufacturing techniques.

A spectrometer measures the amount of light absorbed or transmitted across different wavelengths. Color measurement involves analyzing the spectrum of light reflected off an object to determine its color.

In a typical setup on a manufacturing assembly line, a light source illuminates the product or material whose color we want to measure. This light source must remain consistent in its intensity and spectrum because any variation can influence the accuracy of the color measurement.

When the light hits the object, the object absorbs specific wavelengths of light and reflects others. The reflected light then enters the spectrometer. Inside the spectrometer, the light is dispersed, often with the help of a diffraction grating or a prism. This dispersion breaks the incoming light into its constituent colors or wavelengths, similar to a rainbow when sunlight passes through raindrops.

An array of detectors inside the spectrometer captures this dispersed light. Each detector is sensitive to a specific wavelength or a narrow range of wavelengths. By measuring the intensity of light each detector receives, the spectrometer builds a spectrum – a graphical representation of light intensity versus wavelength.

This spectrum effectively captures the color profile of the object, and a computation derives color values, typically regarding color spaces or systems like the CIELAB or RGB. These values provide a quantitative measure of the object's color compared to a standard or reference value.

In a manufacturing assembly line, the speed of this process is paramount. High-speed spectrometers capture and process data in real-time, allowing them to analyze the colors of objects as they race along the line. Suppose the color of a particular product deviates from the set standard. In that case, the system can instantly flag it for inspection or removal, ensuring that products maintain a consistent color quality throughout the production run.

The integration of high-speed spectrometers into manufacturing lines, coupled with sophisticated software, ensures that color consistency and quality meet the strict standards demanded by today's consumers and regulatory bodies. This method not only optimizes the quality of the final product but also minimizes wastage and enhances efficiency in production processes.

Micro-Epsilon stands as one of the top sensor manufacturers globally. For over 50 years, they have consistently provided reliable and high-performance solutions, especially in situations demanding high precision measurement or inspection. Their product line includes sensors for distance and displacement measurement, IR temperature measurement, and color detection, along with systems for dimensional measurement and defect detection.

The Micro-Epsilon colorCONTROL ACS7000, color measurement system, recognizes reference colors through direct comparison and distinctly identifies individual colors based on their coordinates in the color space. Equipped with a high-speed spectrometer, the colorCONTROL ACS7000 excels in applications that require online examination of colors and shades with utmost precision.

AP Corp.
(508) 351-6200

In-Line Color Measurement for Recycled Plastic

Recycled Plastic with Color
Photo 1 - Recycled Plastic with Color

Color measurement is a well-accepted technology to check the quality of the color values in the production process. Usually these measurements are performed "off-line".

The delay between sampling and obtaining the results from the laboratory can be time consuming. A significant disadvantage is that only a single measurement is generated in this time period and the quality of the color during, before and after the sampling point is unknown.

With the in-line color measurements taking place directly in the melt, not only is complete documentation possible, but when color variations occur, immediate intervention can take place.

Reflection probe
Photo 2 - Reflection probe in strand pelletizer.
When recycling plastic to convert to new uniform  colored pellets many challenges can take place. Recycled plastic is much more inconsistent than virgin material. Understand-ing this inconsistency will help on your color dosing to provide a more homogeneous final product. With the proper color measurement system you can know the color values of your extrudate in real time. This allows for closing the loop on your color by changing your dosing rates to meet your specifications.


Photo 4 - Stainless Steel NEMA4 box with touch-screen.
Technology from Equitech, a manufacturer of in-line process instrumentation, deploys a probe directly in the molten polymer. Their Reflection Polymer Melt Probe (RPMP, Photo 2) is installed on the exit (adapter) of the extruder by using ½”-20 UNF thread (typically Dynisco®). The RPMP is screwed into position in the adapter between the extruder and the die. The RPMP consists of the threaded body and optical fibers. The sapphire lens on the tip of the probe is the observation window and is very well suited to the harsh conditions in the extruder (temperature, pressure, and friction through flowing material). The self-cleaning function of the sapphire is ensured by the shear force of the material flow. Ideal installation is directly into the melt stream in the adapter.

Off-line measurements are used more effectively by downloading them to the Equitech Inline Color Spectrophotometer. This can be done manually or through OPC communications. By having the laboratory target values displayed on the Equitech system the operator can view trends of L*, a*, b* and Delta E.

This method provides complete documentation of a particular extrusion run. It also matches the known laboratory measurements giving confidence that an extrusion run has maintained specifications throughout its entirety. When color variations occur, notification can take place via digital alarms. Intervention can take place via OPC or analog signals i.e. L* feedback for closed loop color control.

EquiColor Software
Photo 3 - Trend charts of EquiColor Software

Illumination of the polymer through the sapphire window is achieved by 6 circumferentially-positioned glass fibers which convey the light of a xenon flash lamp. The reflection from the illuminated surface is detected by one center-positioned optical fiber. This reflected light is then interpreted by the spectrophotometer. Color values such as L*, a*, b* C*, h are calculated from this spectral curve, and displayed as trend charts, (see Photo 3).

For a continuous process monitoring, 10 to 60 seconds is recommended as the measurement interval. Intervals as fast as 1 to 2 seconds are possible. The calibration of the spectrophotometer is designed specifically for the demands of the production process. Calibration can be done without interruption of the process.

  • Real-time information about process stability & quality
  • Impact of speed changes on the quality of the extrusion
  • Controlled color changes: start phase, end of run  
  • Avoid off-specification batches & waste production
  • Detection of dosage elevations
  • Optimized recipe formulation & process design
  • Available feedback loop for L* closed loop control via feeder
  • Comprehensive quality audit trail customer documentation
For more information, contact AP Corp. by calling (508) 351-6200 or visiting

Reprinted with permission from Equitech International Corporation.