Sensor systems
20 November 2023
11 October 2023
1 September 2023
24 August 2023
26 July 2022
Specialist article on Kunststoffe International 05/2022
(Category: Measuring Technology - Compounding & Recycling)
Inline color calibration with respect to plastic recyclate The Windows® Software SPECTRO3 MSM DOCAL Scope facilitates inline calibration of the color sensor system in different ways, which are explained below in further detail.
Calibration with RAL plastic color cards The nonprofit organization RAL gGmbH, Bonn offers a collection of 300 different colored plastic cards calibrated according to the d/8° method. The corresponding L*a*b*-values are noted on every sleeve that is enclosed with the plastic color card. In addition, for the RAL plastic color cards, which can be obtained from Sensor Instruments GmbH, the respective L*a*b*-value, which is obtained from the 45°/0° measurement, is noted on both the RAL plastic color card as well as on the sleeve and in addition, assigned a 5-digit number. Sensor Instruments assigns and enters successive 5-digit numbers for new RAL plastic color cards to be calibrated, along with the L*a*b* color value that is calibrated on the RAL plastic color card, to a calibration file. Thus, during the calibration process, the sensor system only has to be presented the RAL plastic color cards to be calibrated and the matching 5-digit number input in the software. With this calibration mode, reference is made solely to the RAL plastic color cards, as a result of which a location-independent comparison of the measurement results is made possible, for example, for companies with several locations, since in such a case, manual color measuring instruments, the so-called manual colorimeters, can be dispensed with. Calibration using injection molded color platelets and recyclates But very often, it is exactly this relation to the manual or laboratory colorimeters already present in the facility that is desired, since it then becomes possible to better compare the measurement values between production and laboratory. This referencing to colorimeters that are already available in the facility through the SPECTRO3 MSM DOCAL Scope software is described in some more detail below. To do this, apart from the inline color measurement systems, Sensor Instruments also supplies laboratory equipment that work according to exactly the same process and whose sensor systems are identical. The systems that are available are both those that measure through an inspection glass as well as those which directly view the recyclate itself, of which measurements are to be taken. Inline colorimetry using the SPECTRO-3-0°/45°-MSM-INLINE-ANA and the matching laboratory equipment SPECTRO-3-0°/45°-MSM-CMU In both cases, calibration can be done directly with reference to the recyclate, while the L*a*b* reference values are determined using injection molded platelets, made from the same batch of the recyclate that is available to the devices to be calibrated. The L*a*b* reference values are determined using the injection molded platelets by means of the manual or laboratory colorimeters available in the respective facility. Inline colorimetry using a SPECTRO-3-FIO-MSM-ANA-DL in conjunction with a frontend KL-D-0°/45°-85-1200-D-S-A3.0-VIS and the matching SPECTRO-3-0°/45°-MST laboratory device Here too, the injection molded platelets provide the L*a*b* reference values. The optical frontend is pointed directly at the recyclate at a distance of 85 mm. The recyclate that is available during the calibration is also used for making the injection molded platelets. Thus, the injection molded platelets and the recyclate originate from the same batch. When calibrating using a SPECTRO-3-0°/45°-MST laboratory device, it is recommended that when recording the measurement value during the calibration process, the recyclate holding bowl should be moved in the x and y directions with the distance to the front end of the sensor being constant, so that the random position of the pellets can be compensated. Inline, this is done by transporting the pellets on a jolting conveyor. Here, the recyclate flow assumes a speed of typically 50mm/s to 100mm/s. During a calibration process with a duration of 30s, for example, the recyclate stream moves through 1.5m to 3m, i.e. an average is calculated across this measurement path during the calibration process. The measurement result is then correspondingly accurate and independent of the random position of the granulate grains. Even with vibrations that set the pellets in resonance and then cause them to "bounce", this can achieve significant compensation during the measurement process with a duration of a few seconds. What is decisive here is the large light spot size of approximately 20 mm diameter, as a result of which, even at standstill, optical averaging takes place across a large number of pellets. |
SPECTRO-3-0°/45°-MSM-INLINE-ANA + SPECTRO-3-0°/45°-MSM-CMU (Inline color measurement system) Calibration with RAL plastic color cards or using injection molded color platelets and recyclates SPECTRO-3-FIO°-MSM-ANA-DL + KL-D-0°/45°-85-100-D-S-A3.0-VIS SPECTRO-3-0°/45°-MST (Inline color measurement system) |
11 October 2023
Test report on Inline color measurement of recyclates The increasing use of recyclates in the plastics industry means that efficient product control is assuming ever-greater importance. Whilst laboratory-based random quality control was sufficient in the past, the industry is increasingly considering the deployment of 100% control, especially in terms of the color gradient. Sensor Instruments has launched a number of inline systems to perform this function. Providing production staff with information about recyclate production at a very early stage, this covers not only the trend in the color of the recyclates, but the color of the recyclates in combination with their temperature, whilst monitoring the product flow level. The product flow level is important for exact determination of the recyclate color, whilst also providing timely information about a possible blockage of the sieve immediately after the vibrating feeder. The data is also made available for quality assurance via a digital-serial interface (Ethernet).
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SPECTRO-3-FIO-MSM-ANA-DL (Inline color measurement system) |
1 September 2023
24 August 2023
Following color Sometimes it makes sense to follow. For example, your conscience or good advice from friends. But following people or brands on Instagram or LinkedIn? That is not obligatory. And what about the mainstream? "All is well! Just not always, just not everywhere and not for everyone" (to “follow” Novalis). At Sensor Instruments, although we prefer to choose our own path, we do see the need to follow certain things; for instance the colors.
Especially in terms of the color of recyclates, our esteemed market companions have been quite busy lately. Today, almost every company in the plastics recycling sector uses a portable device to measure the color of recyclates. These do their job, with the expected ease of use, at an affordable price and with precision. But are they really precise? |
Inline color measurement systems |
26 July 2022
Specialist article on Kunststoffe International 05/2022
(Category: Measuring Technology - Compounding & Recycling)
The Color Loop Ensuring Color Consistency of Recycled Materials The mass of recyclable plastic waste has been growing steadily for years. This is mainly the result of technical advances made in both processing and sorting. At the same time, the recycling targets set by the EU are piling more and more pressure on companies to increase the amount of recycled plastics in their products. This in turn is raising the requirements imposed on the recycled materials themselves. Aside from the nature of the polymer and the previous application, the color of the recycled material is important.
► Specialist article on en.kunststoffe.de |
Laboratory measurement systems SPECTRO-LAB-SYSTEMS SPECTRO-3-0°/45°-MSM-LAB-ANA-P |
20 June 2022
Color measurement of recyclates In terms of process technology, it is relatively easy to keep the color value of a package constant when virgin plastic granules are used, since the process of color homogeneity is quite well mastered by masterbatch producers. Technically sophisticated dosing systems mix masterbatch and base granules in the empirically determined optimum ratio. The minimal color deviations from packaging to packaging are thus no longer visible to the naked eye. The term dE (distance between two color values in the L*a*b* color space) used in professional circles is below 1.
With the help of color sorting during the separation of the recycling stream, an attempt is now made to keep the color of the plastic recyclate constant. To ensure that the tolerance limits for the color value are not exceeded, however, constant product monitoring is required with regard to the color. The SPECTRO-3-0°/45°-MSM-LAB-ANA-P laboratory instrument from Sensor Instruments GmbH, described below, is designed to help monitor and document the color progression of the recyclates. The idea is to take samples from the recyclate stream at regular intervals and then feed them to the laboratory color measurement system. In addition to the color value L*a*b*, the device also displays its deviation dL*da*db* from a reference color value. Furthermore, each sample is documented and can subsequently be provided with a label indicating the respective date, time and L*a*b* and dL*da*db* value. ► Press release (Word/pdf) |
Laboratory measurement systems SPECTRO-LAB-SYSTEMS SPECTRO-3-0°/45°-MSM-LAB-ANA-P |