To balloon Parts List items Size or not to balloon Parts Lists items Size?

Roberts2600

Starting to get Involved
There's been a recent query regarding whether the sizes listed in the parts list should be ballooned in accordance with AS9102C standards. In the AS9102 training class I attended over a year ago, we were instructed to balloon design characteristics on the drawing. However, the examples provided during the training did not include a parts list on the drawing. Instead, they solely featured plan views and detailed (section) views with various dimensional tolerances.



Now, the question has arisen as to whether we should balloon the sizes listed in the parts list, which primarily consist of tolerances related to width and/or thickness. In the scenario I'll illustrate below, I would balloon items 1 through 3 but omit items 4 and 5.



For instance, Item -102 Vinyl would typically be considered a material, which would be documented on Form 2 and since not balloon it would not appear on Form 3. Meanwhile, Item -101 Strap would be classified as an engineered component and thus would be documented on Form 1 with a First Article Inspection Report (FAIR) in copy. Both items -101 and -102 would have the material Certificates of Conformance (CoC) included in the data packet of the FAI, providing confirmation of their material, thickness, and/or widths but would not be actually measured and listed on Form 3.

So, the question is whether to balloon Parts List items Size or not to balloon Parts Lists items Size?

To balloon Parts List items Size or not to balloon Parts Lists items Size?


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John Predmore

Trusted Information Resource
Focusing on vinyl as your example, I imagine there are two possibilities. You buy bulk material, or you buy pieces cut by someone else to a specified size. Either of these cases would be listed on Form 2. Either you buy as COTS item or you get a certificate of conformance from the supplier for a customized material order.

If you do any subsequent processing in your factory - cut to size, drill a hole, apply a dye or perform some surface treatment - the dimensions and characteristics of that additional processing must be specified in some documentation. That documentation would be referenced, and those characteristics would be inspected, on the FAI on Form 3. Any characteristics of supplemental processing might be 'bubbled' if it makes sense to do so.
 

Roberts2600

Starting to get Involved
@John Predmore We purchase vinyl in bulk rolls, which are subsequently cut to shape. I reason that since the design drawing explicitly specifies a total thickness in its plan view and considering that our material is procured to a precise 0.02" thickness and certified by the Certificate of Conformance (CoC), there shouldn't be a necessity to remeasure the vinyl before its utilization. Furthermore, when the total thickness is measured the vinyl is accounted for in the assembled widget.

However, from what you're implying, it appears that I might be required to measure the vinyl and then reference it to what, Form 2? I believe I've connected the dots effectively without the need for re-measuring the vinyl before assembly. Please help me to further understand. Thanks!
 

John Predmore

Trusted Information Resource
I consider First Article Inspection a risk reduction activity, and an inexpensive guard against human error sometimes encountered in process design and setup. Obviously, a sample size of one is admittedly low statistical assurance that your production parts will consistently confirm over many lots of material, different environmental conditions, different operators, the conditions of tool wear and other variables. But that is not the purpose of FAI. In my opinion, the purpose of FAI is a low-cost demonstration that no dimension/characteristic was overlooked or recorded incorrectly anywhere in the process.

If the vinyl pieces are cut from bulk stock of vinyl, then somewhere length and width dimension(s) and tolerance(s) are specified. I don't know if stretching and spring-back of vinyl is a concern with your tool/process, but a simple inspection of one cut sample can largely put this hypothetical concern to rest. I am not knowledgeable to list all hypothetical concerns, but stretch/spring-back is one that occurs to me.

To continue the discussion on vinyl - you know your materials/process better than I. If there is literally nothing that is done or could be done that could change the thickness of material, then I could be convinced to agree no reason to re-measure thickness compared to initial order. Actually, it is not me you have to convince, but rather your customer and/'or the manager who approves FAI reports. If there is any conceivable possibility that material thickness could potentially change due to humidity/flexure/processing, then re-measuring thickness is a pretty inexpensive inspection. If your customer/manager knows as little about your material/process as I do, it might be simpler and expedient (and ultimately lower risk) to just re-measure thickness of one piece after processing, and then documentation is thorough and no one will question your decision to omit any dimensions.
 

Roberts2600

Starting to get Involved
@John Predmore Thank you for your advice, I do appreciate it. In our specific scenario, which wasn't depicted in the diagram above, we typically employ multiple layers of vinyl (interlayer) between items -101 (inboard) and -103 (strap). These layers undergo autoclaving, which may alter the overall thickness of the vinyl. Ordinarily, our drawings specify a dimensional thickness requirement that must be adhered to. Hence, instead of directly measuring the vinyl, my focus is on meeting the dimensional thickness outlined in the balloon 3 design characteristic.

It seems that there isn't a clear-cut right or wrong answer to this question; rather, it's about mitigating risks and seizing opportunities to enhance our processes. Ultimately, the acceptability of the First Article Inspection (FAI) depends on the customer's evaluation and whether they are willing to accept it with an accompanying explanation if they believe the vinyl should have been captured pre-autoclave. Once again, I truly value your insights on this matter. Thank you for your input!
 
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