Logistics of a Drawing system... Why not use dates instead of rev #'s? 2

[vonsteimel]

Greetings,
I work for a small mfg company making recreation vehicles. As stated, we are small and have relatively few drafters compared to a company manufacturing products of similar complexity. We fab most of the parts we use in production and the stuff we do purchase, almost always gets modified. There are tons of revisions & changes happening all the time.

To make things more difficult, we do not have a real drawing system nor a rev system. Revisions have no designations and are not tracked anywhere except on the drawing (in the rev block, we write a few words). This means there is no way to tell for sure what the most up-to-date revision is... And this is a Major headache when it comes to servicing and/or supplying parts for older vehicles, not to mention production.

Because the boss doesn't like alpha-numeric systems, I drafted up a brief drawing system using numbers instead of letter designations. Still he asks, why can't we use dates instead of rev numbers? And I had a hard time coming up with a good explanation for him. I suppose we could if we wanted... Has this been done before? Why is no longer the std? Everything I've known has always been letters....

What are the origins and concepts behind the standard letter revision system? And when a company wants to revert to an older revision for a part, do they roll back their system to that old rev or do the just re-issue that old rev with a new rev #?

The logistics of a whole drawing & revision system can be pretty tricky, especially when factoring in the requirements & preferences of an established company...

Where is a good source for figuring out the ins & out needed to setup an adequate drawing & rev system for the future? I've got a document from NASA/Langley on their rev system but its a little above our capabilities. There aren't a lot of dollars available to pour into consultants & software systems so I've got to get this up and running with just plain ole elbow grease... Any help will be appreciated.
Thanks,

VS

 

[cjccmc]

I've never seen Rev's identified by the date, always a letter or number but the date is recorded along with it. It's always a bit of a compromise in deciding on the issues you brought up, I don't think there is one easy way that will eliminate all difficulties. In larger companies there are entire groups like "Configuration Management" and "Change Control Boards" that wrestle with the questions you are facing.

Yes there are documents that describe configuration management systems, but these are likely to be overkill for your operation unless people are willing to operate in a different and more rigorous way. They sound good in theory (like New Year resolutions ;-)) but are easy to let slide with time. If you were to come over to my company for a week and listen to all the engineers bitch about the difficulty of getting a new drawing thru the "release system" you would likely find the simplicity of your own to be a blessing. My guess is that what you're doing now, maybe with a small tweak or two, is probably a reasonable choice for the type of operation involved. Good luck!

 

[MikeHalloran]

The problem with dates is, which date do you use?
In your case, a revision takes a day or so, so it's not an issue.
In a bigger company, getting a single revision through 'the system' can take months, so you'd have to guess at a release date, or use the date you started, which could be embarrassing.

The standard way to get a part made to an older revision is to reach into the file drawer containing the 'RECORD PRINT' for the old revision, MAKE A COPY OF IT, and issue the copy for manufacture. Record prints never leave the file room, not even in THE BOSS's hands. Especially not in the boss's hands. They are the only unequivocal historical record you have of how the part used to look before you last screwed it up, so they are priceless. I suppose these days you could keep record 'prints' on a CD, but the CD should never be lent out to anyone. I'm sure you understand the concept. ... and wish you could instill that much order and discipline.


p.s. Are you building big RVs in Northern Alabama? I _so_ wanted that job. ... despite the obvious disorder.

p.p.s. WRT parts for older vehicles, You probably need to maintain a paper or electronic record of what revision of each and every drawing was used to constuct any particular vehicle, indexed by VIN or something similar. Yeah, I know, order and discipline....




Mike Halloran
Pembroke Pines, FL, USA

 

[ctopher]

What would you do if the dwg had more than one revision during one day?

Chris
SolidWorks 11
ctopher's home
SolidWorks Legion

 

[hokie66]

You folks are talking about drawings of mechanical parts, etc. In another field, structural engineering, it is more or less standard practice to place the revision letter or number adjacent to the item revised, usually in a triangle or some other symbol. In addition, the revised area of the drawing is often clouded. Using the date in that system would be cumbersome.

 

[MikeHalloran]

Ctopher's point is well taken, especially in a 'fast paced' outfit, as I suspect Vonsteimel's is. So you may have to include the date and the time. Or mark the second revision of the day as rev B of that day, etc.




Mike Halloran
Pembroke Pines, FL, USA

 

[pmarc]

vonsteimel,
Look to ASME Y14.35M-1997.

 

[truckandbus]

I guess you could use the date as the rev identifier, but if your company is like most, the date of the drawing change isn't typically the date the engineering release leaves engineering, and it isn't typically the date the change enters production. So I don't see an abvious benefit to that over rev letters.

Since you don't have budget for system enhancements, consider making the rev level part of the part number (i.e. 1515432C could be a brake valve bracket at revision C). This is helpful in parts manuals or build records when you are trying to provide the customer with exactly what they have on their product currently.

If you do include the rev as part of the part number, you have a decent chance of being able to use older versions of the part in production (since technically they are unique part numbers). If your rev is separated from the part number, reverting back to a previous design usually requires going to the next rev level. Bad things happen to inventory control if you don't; bad things happen if you are buying parts from outside vendors if you don't.

You might want to post the question in the configuration management forum as well

 

[MadMango]

I find that using numerical revisions for prototypes work best, with revisions being promoted to alphabetical revision only after a formal production release. This allows you to share drawings external to your company (to ensure vendors can make parts and lower costs), where round-robin type give-and-take iterations with some vendors may be very useful. It also creates a mindset in the shop, as when they see numeric revs they will understand that it is for prototyping. This can lead to them taking special care when making parts, finding the time to manufacture them, and generally increase the babysitting of said parts (though it can also lead to the opposite, where prototypes are manufactured less stringently).

Using dates can be problematic. Today is 01/02/13, but several months and people later it could be seen as February 1st. You'll have to establish a date code and ensure all stick with it. The US Military uses day/month/year in the form of 02JAN13 which proves hard to be ambiguous.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[drawoh]

vonsteimel,

I recommend the following...
[ol]
[li]Use revision letters. Actually, I see no difference between revision letters, revision numbers, or the latest date. Revisions letters are required or at least strongly recommended by industry standards you may be asked to comply with some day.[/li]
[li]Implement design change rules. Do not change form fit and function. If a part must be changed, create a new drawing and part number. You have a shelf in your warehouse tagged for some part, perhaps number 123-456. Anything pulled off that shelf in response to a request for part 123-456, must function as that part. There are many ways this can fail if you do not follow design change rules.[/li]
[li]Do not use the revision letter as part of your part number. This explicitly forbidden by ASME Y14.100, and it is not necessary if you follow the design change rules, noted above.[/li]
[li]Systematically use the latest revision of any drawing.[/li]
[li]When you fabricate parts, log the revision numbers on the work orders and/or purchase requisitions.[/li]
[li]When you build something, log the revision numbers of the assembly drawings. You should be able to reference this to the serial numbers.[/li]
[/ol]

The problem with manufacturing is that you have ten, a hundred, maybe a thousand people all working in parallel. You have to be methodical in your handling of information.

I believe I am answering your question here. Your revision system is part of a complex documentation system, all of which has to work.

--
JHG

 

[TheTick]

I don't see your problem as being whether to use letters, numbers, dates, circus animals or colors. The problem is record keeping.

No one likes to add cumbersome record keeping to a system, but there is far more to this than changing prints. There needs to be a system in place that documents why a part changed, how it affects things, what was done with the old parts, who needs to know (and were they told).

If the powers-that-be don't want to run like a grown-up company, then they will not be able to grow.