Spectral properties-based system and method for feeding masterbatches into a plastic processing machine

A system for optimizing a match between the color of an in-line part manufactured by a plastic product production machine and the color of a reference part by adjusting the concentration of masterbatch in a mixture of raw material fed to the plastic product production machine, the system comprising:

• a) two illumination light sources;
• b) two measuring heads;
• c) one spectrometer;
• d) a spectrum processing and illumination control unit;
• e) at least one mechanism configured to add masterbatch to the mixture of raw material fed to the plastic product production machine;
• and
• f) at least one controller configured to control the rate at which the mechanism adds masterbatch to the mixture;
• wherein:
• A) the spectrum processing and illumination control unit is configured to:
• i) activate the spectrometer;
• ii) activate the two illumination light sources and the two measuring heads intermittently to enable interlaced measurement of the reference sample spectra and the in-line part spectra;
• iii) measure the spectrum of the in-line part received from the spectrometer;
• iv) measure the spectrum of the reference part received from the spectrometer;
• v) determine the color coordinates of the in-line part and the reference part from the measured spectra;
• vi) determine the color coordinates of a set point, which corresponds to the lowest concentration of masterbatch required to make the color of the in-line part indistinguishable to the human eye from the color of the reference part;
• vii) determine a distance ΔE between the color coordinates of the in-line part and the color coordinates of the set point;
• viii) determine a signal for controlling the feed speed of the mechanism that adds masterbatch to the mixture of raw material fed to the plastic product production machine;
• and
• B) the controller is configured to control the feed speed of the mechanism that adds masterbatch to the mixture of raw material fed to the plastic product production machine by means of the signal;
• wherein, measuring interlaced spectra of the in-line part and the reference part are carried out simultaneously using the same spectrometer, thereby eliminating the requirement for high accuracy spectrometer calibration and allowing the spectrum processing and illumination control unit to determine the signal for controlling the feed speed of the mechanism that adds masterbatch to the mixture of raw material fed to the plastic product production machine in real time on a manufacturing floor while the plastic product production machine is being operated to manufacture in-line parts.