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Revision control and use of "PRELIMINARY" stamp/watermark 1

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Andrew314

Andrew314

Mechanical
Feb 28, 2022
1
Good afternoon, gents. We are currently updating our very old procedures for engineering documentation, and I am surprised at the amount of disagreement we are having. Long story short, we stick to using Numerical revisions for preliminary versions and Alpha revisions once released. Of course the released documents are always under CM control. The disagreement is in the area of the use of "preliminary" watermarking on drawings. For instance, a revision needs to be made, but other exercises need to happen before the full implementation of the ECN (quoting, review, etc). For this instance, let's say the drawing that will be revised is at Revision B. In this instance, the drawing is modified with desired changes and revision is updated to C, and clearly marked "PRELIMINARY". At that point, the preliminary drawing may be sent out for quoting, dfm analysis, or anything else. We have two groups of people that have the following two opinions:
1) If ANY changes are made to the Rev C drawing marked "PRELIMINARY", the drawing revision MUST increment (in this case, to D).
2) If changes are made to the Rev C drawing marked "PRELIMINARY", the drawing revision can stay at C. When the drawing is finalized and the ECN/ECO has been reviewed and released, it will be released at Rev C.
For option 2, if changes are made, either the file name would have a unique identifier to differentiate between the preliminary versions, or the original preliminary watermark will have a unique identifier in it, such as "Preliminary_01"

In your experiences, which method would you personally use?

 
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Once files have gone out the the immediate engineering group (exact limits may vary a bit) I would say option 1 is superior.

Certainly once drawings start going out of the organization I'd be vary careful making a change and not having an explicit revision change. My employer has got pretty strict on drawings not going out of the organization without the revision being formally process through ECO - though we can usually manage this in a few hours. This is in part due to getting burned by suppliers mixing up revs...

Now that isn't to say extracts of a drawing couldn't go back and forth with supplier if needed to verify specific details or similar but strict document control has its benefits so long as ECO's (or whatever you call your release process) can be done in a timely manner.

(BTW when working somewhere that ECO's could take a lot longer to process I may have voted for option 2 but it does have risks/issues.)

Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​
 
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I am with Kenat on this, option 1 is the preferred method as it controls the changes. I have worked at places where they sent out a drawing for quotation and then made a change and kept it at the same revision. When they ordered the production parts, the vendor say that they had the same revision print, made the parts and then demanded to be paid for the scrapped parts as they did not meet the design of the 'latest' drawing of that revision. We did send them an updated print with the order.
I suppose IF you have enough procedures in place that specifically say drawings marked with PRELIMINARY are NOT to be used for producing parts, option 2 may work. I would never use this method with an outside vendor.


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli
 
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Philosophically, it's annoying that a revision is essentially "wasted," since it never went into production; nevertheless, unless there is strong discipline and safeguards, I agree that the revision should be rolled to avoid confusion in manufacturing.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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Your whole process sounds convoluted. Use a standard release process, no watermarks or secondary suffix nonsense. Your print is either within your control or it isn't. If the print is within your control then its not released, if it isnt then it needs to be released. Your release process should include ALL necessary reviews for that revision including manufacturing prior to each release.
 
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We used to use alphanumeric letters up to the 'Released for Construction'... never 'Issued for Construction', for some obscure legal reason... RFC were given revision number 0, and then all revisions were numeric 1 through to whatever. We also had a CAD 'block' with "Preliminary, not to be used for Construction" that was often applied.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik
 
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I'm sorry but it is insane you would release a rev C drawing to a vendor with a preliminary stamp, and then make changes and send rev C again. You are begging for problems, not only wasted money but possible safety issues if something is built wrong. All to save what, typing a letter D?
 
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There's a plausible argument to be made that significance of the drawing should be directly encoded in the drawing revision, like, say, C0-review, to make it clear that the drawing is not released. This would make it more obvious that no production or revision should be based on that drawing, without having to dig through the title block or notes or watermark or whatever to figure that out.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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Two drawings with different information are never issued as the same revision. As canwest notes... you're just looking for problems.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik
 
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