So what is quality control and how should a company go about developing a QC program? A good place to start is with a definition of quality. D. Edward Demmings defined it as the "absence of variance." That seems reasonable, but there must be a standard in place and processes designed to achieve it. If a recognizable standard exists and processes have been developed to meet those standards, the only missing element is reliability. Reliability does come from control of variables. Another definition is "the expectations of your most demanding customers." If a company continually meets or exceeds customer expectations, they are doing pretty well. Add these two thoughts together and you have "systematic control of process variables to deliver goods that make customers happy."
- Consider what this means to quality control within your operation.
- Are the standards well defined, understood by everyone and applied consistently?
- Are process variables regularly measured and reliably controlled?
- Is the quality standard as cost effective as it could be?
First, consider the development of specific standards and the application of a quality policy. Frequently, quality standards are not defined or not consistently applied. Or the standards may be written but poorly understood. A defect is rejected one day and accepted the next. First shift rejects a condition and second shift accepts the same condition. Be specific and consistent.
If a plan for a control variable exists, it can only be applied by regularly measuring it and confirming that the standard is being met. You have specific gun settings, but the book they are written in has a coating of dust on it and no one knows what the settings should be anymore. "Just cover it" is the standard. The film build range has grown from 2 to 3 mils and now routinely exceeds 4 mils. Without routine measurement, no standard can be confirmed and maintained.
In some cases, a quality standard has been developed that exceeds the operational controls of the system or the capabilities of the system. For example, the system was designed with a three-stage washer and the company expects superior corrosion resistance. Or costs are based on certain assumptions about film build and no controls exist to keep film builds within the range needed to meet the cost assumption.
Control of variables is challenging but very important for accuracy and consistency. Fast and precise color match is an example of quality control that may be very important to some operations. For example, suppose that you use wood, metal and fabric in the same assembly and the colors need to be the same. The controls that are in place and the reliability of your suppliers are critical to the success of your business. Methods of color examination and measurement must be precise and used as a routine part of your business.
Because one of the primary purposes for applying a coating is to provide aesthetic appeal it seems like a good idea to understand some of the factors that help us achieve accurate color match. Two articles in this months issue deal with the color issue and its impact on the coating business. Just one of the important variables that must be controlled to maintain excellence in quality.