Production Machining

NOV 2017

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

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?????? Cleaning Cleaning Protocols :: 39 one-size-fits-all instead of allowing an effective procedure to be established. e industry standards for technical cleanli- ness are generic by design. Not all components of a system can be inspected in the same manner. When manufacturers fill in the details that industry standards leave unspecified, suppliers may be forced to violate key requirements, leading to erroneous results during inspection. Keeping that in mind, it poses the question: should suppliers use your technical cleanliness inspection procedure? To help answer that, consider three of the 300 require- ments established by ISO 16232 and VDA 19 that are covered in this article. e article will examine whether customer-specific standards comply with them. ey ensure an effective extraction procedure; an adequate number of components; and a compatible test liquid. e effectiveness of the extraction procedure must be verified. Verifying effectiveness ensures that the extraction procedure is removing at least 90 percent of the contamina- tion from the tested components. e process for verifying effectiveness is almost identical in both industry standards. One set of test components is subjected to a process intended to extract particulate contamination. e contamination extracted during this process must then be measured and documented. is process is repeated on the same set of test components for as many as six total iterations. e measure- ment taken at each iteration is then divided by the sum of the measurements up to that step (see Figure 1). Verification is complete when the measurement for a given iteration is less than 10 percent of the sum. en the inspection procedure can be documented as the sum of the extraction processes required to verify effectiveness. As an example, a set of fasteners is subjected to an ultra- sonic extraction process for one minute. e mass of the particulate contamination extracted during this first iteration is found to be 24 mg. e same set of fasteners is subjected to five additional ultrasonic extractions that are one minute each. e mass of particulate contamination for each iteration is found to be 12 mg, 3 mg, 0 mg, 0 mg, and 0 mg, respectively. Using the equation taken from the ISO standard, it can be calculated that effectiveness is verified at the third iteration of the extraction process. is means that this sample size of this fastener must be subjected to the ultrasonic extraction process for a total of three minutes to ensure that at least 90 percent of the particulate contamination has been extracted for inspection. is approach can be compared with a few examples taken from customer specific standards. One such standard requires the test components to be subjected to ultrasonic extraction for 10 minutes. How likely is it that this one-size-fits-all procedure will be effective for all components regardless of size, shape, manufacturing method, and so on? For instance, it is known that ultra- sonic cavitation can erode cast components, thereby generating particulate contamina- tion instead of simply extracting it. Another customer-specific standard takes a slightly different approach by requiring ultrasonic extraction for one minute except S n ≤ ∑S i →1 mg ≤ (24 mg + 12 mg + 3 mg) → 3 mg ≤ 3.9 mg 10 100 10 100 n i=1 :: Since the first editions of VDA 19 and ISO 16232 were published in 2004 and 2007, respectively, most customer- specific standards adhere to or are modeled after them. 1 2 3 4 5 6 Multiple Extractions Using the Same Sample Set Mass (mg) ✓ 100% 80% 60% 40% 20% 0% Individual Extraction Mass/ Total Extracted Mass Fig. 1: Example Extraction Curve

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