Production Machining

NOV 2017

Production Machining - Your access to the precision machining industrial buyer.

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40 PRODUCTION MACHINING :: NOVEMBER 2017 PARTS CLEANING for coated, powdered metal or sintered components that are to be spray rinsed. While this component-specific approach allows for two different extraction methods, it still doesn't account for size or shape. So why does this matter? A shop that's responsible for these cleaning processes might think these different approaches are simply different ways of accomplishing the same task, but they are not. e requirement in the industry standards yields an extraction procedure that is verifiable. It can be proven that at least 90 percent of the contamination is being removed. On the contrary, with a one-size-fits-all or component-specific approach, it's difficult to know how much contamination is being removed. e risk is that the components may be dirtier than testing shows. An adequate number of components must be analyzed. According to the industry standards, a certain number of components need to be analyzed to measure a significant number of contaminants that complies with the require- ments for a "blank" value. A blank value is received by conducting the cleanliness inspection without introducing the test components. e same procedure is followed—the same amount of test liquid, duration of testing, filtration, environmental conditions, and so on—in order to determine what effect the inspection environment and equipment have on the inspection results. For gravimetric analysis, the acceptable blank value for both ISO 16232 and VDA 19 is less than 10 percent of the presumed or specified cleanliness level. According to the ISO standard, "using a four-digit balance under uncon- trolled environmental conditions (uncontrolled humidity and temperature), the minimum measurable blank value is 0.3 mg." Under these conditions, the number of compo- nents to be analyzed must be chosen so that at least 3 mg is collected during testing. In other words, the number of components to be analyzed is directly affected by the environmental conditions of the cleanliness inspection and the cleanliness of the compo- nents. In contrast, some customer-specific standards simply prescribe the number of components. One example requires analysis of one to 20 components (preferably five) depending on size, regardless of the type of component. e example given may work well for compo- nents with a large extraction surface area. However, for small components, 20 pieces may not be enough to ensure compliance with blank requirements. Some companies have chosen instead to require analysis of a quantity that's unique to each type of component, such as 200 screws, 10 gerotor sets and 10 covers. Although this might seem like a better approach, consider how widely surface area varies, even for similar components. Can we presume that a small and large screw have similar levels of cleanliness? Consider the ramifications of analyzing too many or too few parts. Too many parts may increase the time, difficulty and cost of analysis. More test liquid may be used, more particles may be collected resulting in the use of more filters, or cascade filtration, and there will be higher potential for inspector fatigue. On the other hand, requiring inspection of too few parts can yield results that aren't representative of actual conditions. It may also make it difficult or impos- sible to achieve blank values or verify the effectiveness of the extraction procedure. Test liquid must be compatible with the component. is includes, but is not limited to, any coating, plating, rubber or seals that make up the component. erefore, the test liquid must be carefully chosen to ensure it is effectively removing particulate contamination without deteriorating any aspect of the component being analyzed. Some customer-specific standards mandate the test liquid that is to be used for all components, such as a cold degreasing agent with a flaming point higher than 55°C. How likely is it that only one test liquid will be compatible | 8 00.24 8.9274 FLEXIBLE & PRECISE n Wash, Rinse and Dry. n Robot-Ready. n Powerful Siemens Controls. n Maintenance- Friendly. THE NEW LEAN JET ® RT-18. NOW THAT'S SMA RT ! PARTS CLEANING

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