Color quality control system

The spectrophotometer, in comparison, describes color by measuring reflectance at several wavelengths and provides more accurate and reproductive measurement including the effect of different illuminants. There have been continual advances in computerized color quality control systems that use the spectrophotometer and more powerful and versatile software. 

Quality control systems usually used for judging the quality of oils and fats or oil blends used in margarine production could evaluate color, color stabihty, flavor, flavor stabihty, free fatty acid, peroxide value, active oxygen method (AOM) stabihty, iodine value, shp melting point, fatty acid composition, refractive index, crystallization rate, and sohd fat/temperature relationship (solid fat index) (5, 91, 112, 113). 

One of the reasons for the tremendous success of plastic products in the consumer market is that products made from plastic materials are aesthetically more appealing in terms of color and feel than products made from other materials. The majority of quality control systems fail to recognize the importance of visual standards or guidelines. Quite often, too much emphasis is placed on measurement and testing of the product and not enough on the visual standards. 

While quality was formerly achieved by inspection of final products, it is accomplished now by prevention through controlling critical steps in the production processes along the agri-food chain. Hazard analysis critical control points (HACCP) represent a typical example of such a preventive approach. Although this concept was developed primarily to assure food safety, the basic principle is also applicable to assuring non-safety quality attributes such as color, flavor, and nutritional value. " This section translates the HACCP principles into a critical quality control point (CQP) concept that can be part of a system to assure food quality. 

This observation has become an important contributor to the development of rapid, automatic scanning of outer tissues of grains (primarily bran tissues) which contribute both strong color and taste characteristics to grain products such as wheat flour. The ability to measure both the concentration and distribution of such components is paramount to quality control in bakeries, and to definition of raw materials. An example of the systems necessary for routine analysis is included in a following section. 

In quality control of colored objects, production requires more consistency than absolute accuracy. After all, there will generally be a product standard having the correct color to which we may reference the color of parts from the current production run. Since the production part and the product standard will be free from the small errors in accuracy, because any small inaccuracies will be the same in measurements of the batch and the standard and thus will subtract out in the different components. What is needed is an instrument with higher day-to-day objectivity than our visual system, and for such an increase in consistency, one must be willing to give up some of the absolute accuracy. This requires an analog simulation of visual colorimetry. 

In 1983 the FDA issued what became known as the Blue Book (because of the color of its cover). This publication gave guidance to inspectors on what was reasonable to accept as validation evidence for computer systems. The Blue Book formally introduced the expectation of a documented life-cycle approach to validation. The aim was to build quality into software from the earliest stages of the life cycle (quality assurance) rather than vainly trying to test quahty in at the end (quality control). 

The simplest color sensing systems are responsible for monitoring only one color across a scene. These are typically used in quality control applications such as monitoring of paints, to ensure consistency between batches made at different times. More sophisticated color sensors look at the color distribution across a two-dimensional image. These systems are capable of complex analysis and can be used for checking multi-colored labels or for identifying multi-colored objects by their color patterns. 

Control and Instrumentation The purpose of the control and instrumentation system is to provide a system that enables the process to produce the product at the desired moisture target and that meets other quality control targets discussed earlier (density, particle size, color, solubility, etc.). This segment discusses key considerations for dryer control and instrumentation. Additional more detailed information can be found in Sec. 8, Process Control. ... 

The American Academy of Ophthalmology (AAO) recommended to the agency that a uniform color coding system be established for the caps and labels of all topical ocular medications. An applicant should either follow this system or provide an adequate justification for any deviations from the system. Although ophthalmic drug products can be considered topical products, they have been grouped with injectables because they are required to be sterile [21 CFR 200.50(a)(2)], and the descriptive, suitability, and quality control information is typically the same as that for an injectable drug product. 

The creation of a control system requires that the firm create or establish quality specifications. The lack of a clear quality specification means that the workers do not precisely know what a quality job looks like. Once the specifications exist, it is important that they be shared with all employees. For example, if the paint store employees do not understand that they are expected to play with the tints until they match a customer s paint chip exactly, they might give the customer paint which is mixed so that it is only close to the exact color the customer wanted. The quality specification is necessary for the employees to understand when they have done the job correctly. 

For the visual assessment of a color, a reference sample is needed. Systems of physical color samples are available for reference purposes, such as the Munsell system, DIN color chart. Natural Color System and the more customized RAL and Pantone color charts. The ISO grey scale is defined for the visual assessment of color differences and used for the specification of color tolerances for quality control purposes. 

Color labs are outfitted with laboratory size equipment that simulates the larger machines used for production internally and by their customers. Typical processing equipment found in the lab are small extruders, two-roll mills, ban-burry mills, and media mills. Small rotational, injection and blow molding machines are used to duplicate the customers process. Instruments and computers are required for testing physical properties and color. Most labs have a computer-controlled color measuring system and a light booth to evaluate color. The spectrophotometer with computer is initially used to assist in colorant formulation and later as a quality control (QC) tool to provide certification of the quahty of match to standard. The light booth provides a standardized set of conditions to visually observe color and appearance. 

In looking back over 26 years of commercial experience It Is appropriate to comment on product quality. Significant improvements have been made compared with the commercial Delrin of 1960 in terms of melt stability, molecular weight distribution and control, the level and uniformity of physical properties and the color and colorability of natural color product. These product improvements were achieved by persistent chemical and engineering effort on the chemistry of the process, modernization of equipment, compounding technology and automated measurement and control systems. 

Automation by fast, stable and accurate control loops for consistency, flow, pressure and level is elementary for providing the necessary constancy in the approach flow system. Variations in pressure for example will mainly directly influence the MD profile whilst stock consistency deviations will affect both CD and MD basis weight profiles. In addition the retention on the paper machine and the chemical conditions of the water systems must be kept constant. Here a retention control loop is standard in many appHcations keeping the white water consistency constant by adapting the quantity of retention agent added. Controls for filler, color, air content, cationic demand or zeta potential are also available today. Combining the different controls to a total control concept will lead from purely functional controls to control systems which also address quality and production issues. 

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