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Need help developing title block verbiage for undimensioned drawings

Need help developing title block verbiage for undimensioned drawings

Need help developing title block verbiage for undimensioned drawings

(OP)
Hello all, and thank you in advance for the help I know I'll receive here. You've collectively been so helpful in the past, and I thank you for that! :)
I work for a company who's core manufacturing process is laser cutting & bending sheet metal parts. For the sake of this question, we can disregard the sheet metal bending aspect. Most of our parts start out as a flat pattern of a bent part. These flat patterns can be complex in shape, and also contain complex shapes cut out of them. Fully dimensioning them is neither practical nor necessary, as we deal with the DXF files for use in laser or water-jet processing. I know I can add a SURFACE PROFILE note or title-block tolerance that can control the outer profile of the part, but can this same profile tolerance control the interior profile shapes (slots, holes, complex contours, etc.)as well as the location of these various cutouts within the part? Would a "CAD IS MASTER" note along with the general surface profile tolerance note be sufficient to convey the intent of both the profiles and location of the profiles?

RE: Need help developing title block verbiage for undimensioned drawings

Do NOT use "Unless OTHERWISE SPECIFIED" unless you know what you are doingbigsmile

See the last couple of debates about this issue.............

RE: Need help developing title block verbiage for undimensioned drawings

What is the goal? That is to say, what are the drawings to be used for?

RE: Need help developing title block verbiage for undimensioned drawings

(OP)
Trying to develop the note mostly to give our expectations to outside vendors who supply us with the laser or water-jet processed flat parts. There's never been an issue, but it's still a good idea to have dimensional controls in place, so we're not buying bad parts. Right now, the only useful info on the drawings specify the material to be used. Part processing has always been via. DXF files.

RE: Need help developing title block verbiage for undimensioned drawings

blades741,

Are you a jobbing shop that fabricates parts to the customer's drawings?

The really important thing standards like ASME Y14.5 do is define everything I put on my drawings. You offer to fabricate my parts as per my drawings. The drawing is an unambiguous specification of what I want. My purchase order calls up my drawing.

If you are creating drawings in-house for your fabrication department, there are no contractual issues. You and your fabricators should be working as a team.

The note "CAD IS MASTER" has no meaning to me. On our drawings, after "UNLESS OTHERWISE SPECIFIED", the note states that "ALL UNDIMENSIONED FEATURES ARE TO BE FABRICATED TO THE SIZE OF THE 3D CAD MODEL.", accompanied by some notes on default profile tolerances.

I was under the impression that punching and laser/waterjet cutting were accurate processes, and that the big tolerance issues involved bending and welding. Are you solving a real problem?

--
JHG

RE: Need help developing title block verbiage for undimensioned drawings

(OP)
We are a manufacturer, and the note I am looking to formulate is for our outside suppliers who do primarily water-jet cutting. We do our own laser cutting in-house, so the note is more for the benefit of outside suppliers. Yes, the typical tolerance expectation for laser or water-jet is quite close (+/- .002, typically, on our 30 year-old laser). I'm wanting to put a 'Profile of Surface' tolerance of .010 for our UOS callout. To reiterate, my real concern is if (or how) I can control the overall part tolerance.

Let me ask drawoh, your note that states "ALL UNDIMENSIONED FEATURES ARE TO BE FABRICATED TO THE SIZE OF THE 3D CAD MODEL"... does this fall under the jurisdiction of a 'general' profile tolerance on your drawings? Something needs to govern the undimensioned sizes of features & feature locations.

RE: Need help developing title block verbiage for undimensioned drawings

Something like

Quote:

CAD model defines BASIC dimensions. All cut edges subject to a profile tolerance of xx.

Of course you need to establish appropriate datum features too.

RE: Need help developing title block verbiage for undimensioned drawings

blades, profile tolerance will control internal features. Whether it controls them to the required functional tolerances is another matter.

Our default notes for hybrid MBD are:

NOTES: UNLESS OTHERWISE SPECIFIED
....
X. DIGITAL PRODUCT DEFINITION PREPARED IN ACCORDANCE WITH ASME Y 14.41-2003.
Y. THIS DRAWING SHALL BE USED WITH MODEL (INSERT PART NUMBER) (REVISION PER THIS DRAWING) FOR COMPLETE PRODUCT DEFINITION. MODEL GEOMETRY IS BASIC.

At the end of note Y if applicable I'll add a default surface profile tolerance.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Need help developing title block verbiage for undimensioned drawings

blades741,

If you are sub-contracting waterjet cutting, then you need proper drawings.

Yes, we have a titleblock that assumes that the fabricator will work to our as-modelled dimensions. The note also states that the undimensioned features are basic, and yes, you need to specify datusm. The "UNLESS OTHERWISE SPECIFIED" part is important too. If we have critical features, we explicitly apply tolerances, which over-ride the titleblock.

--
JHG

RE: Need help developing title block verbiage for undimensioned drawings

This is a contractual obligation and should be spelled out in the contract as to which model file will be sent. It's never made sense to me to have a 'see cad model' note because with a drawing in hand there is no cad model. It needs to be spelled out somewhere and building the drawing and the model file as attachments to a contract via PDF keeps them all together. The contract tells where to look for the right data, not the drawing.

RE: Need help developing title block verbiage for undimensioned drawings

Because the drawing does not embed the data. It also doesn't have the terms for forwarding any updates where the drawing would not change but the CAD data does change, for example layers or accuracy.

Basically a drawing does not set the terms for data transfer, unless someone puts a four or five paragraphs that would be in the contract on the face of the drawing.

Payment terms, inspection documentation requirements, and delivery schedules are also not on drawings. The contract specifies what data and in what form the data will be transmitted and should include checks to make certain that the intended data is the data that is sent and used.

It's lazy on the part of the contracts department to push off items that should be under contractual control to an ad hoc process. And it is lazy on the part of the contracts department to feign stupidity and an inability to understand data transfer. "Send them a CAD file so they can make the part" is not a responsible attitude.

RE: Need help developing title block verbiage for undimensioned drawings

"It also doesn't have the terms for forwarding any updates where the drawing would not change but the CAD data does change, for example layers or accuracy. "

If the document control rule is that the revision of the model match the revision of the drawing - as my note implies - then the rev of the drawing ticks up if the model changes.

I'm sorry, but I'm just not getting your point on this one Dave.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Need help developing title block verbiage for undimensioned drawings

3DDave,

Sending the model is a purchasing procedure. The drawing, in its own, obviously, is not sufficient to do fabrication.

--
JHG

RE: Need help developing title block verbiage for undimensioned drawings

I don't think the model, in the form of 2D DXF is sufficient for fabrication either as it does not communicate anything about tolerance, material, etc.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Need help developing title block verbiage for undimensioned drawings

dgallup,

In our case, the assumption is that the fabricator has a PDF of our drawing and the 3D model in the form of a step file. It actually is a process I dislike intensely. I am perfectly capable of producing complete drawings to the ASME Y14.5 standard complete with GD&T, quickly. We know that at least one of our shops takes the models and the drawings, and they complete the drawings. Another assumption is that our shops have CMMs. One of our shops doesn't, and as far as I can tell, they just don't do inspection, and neither does our in-house inspector.

We do not have a clear understanding of how MBD saves money and/or improves quality.

--
JHG

RE: Need help developing title block verbiage for undimensioned drawings

Kenat,

As in all things local circumstances make a great difference. For those with captive manufacturing, either in house or just never going to a different outside supplier, and especially for 'typical' manufacture, such as making molds for plastic parts, then almost nothing needs to be put in writing.

For the more turbulent procurement where who knows what will get the package, then it doesn't mean much to see that note on a drawing. One supplier will want one of the dozen versions of STEP, or some tweaked IGES file, or just a pile of DXFs or won't be satisfied without some other format. To say there is CAD data elsewhere is possibly true and entirely uninformative. It's 2016. Of course there is CAD data elsewhere. But the contract is going to cover who gets to decide what the format is, how it is delivered, and how disputes over the suitability of the CAD data will be handled.

Until they read the contract a note that there's some other source of data is not enough to decide on whether or not to even accept the contract. After reading the contract the note will be redundant.

It still tickles me that people put "CAD Generated" in the margins of drawings. It's like putting a "Horseless" sticker on their car so people aren't confused.

RE: Need help developing title block verbiage for undimensioned drawings

The note on the drawing can serve as a flag to doc control/purchasing that a copy of the model needs to go out with the drawing. It's a flag to the vendor to ask for the model (and specifically what model) if they don't receive it with the drawing.

Again I say the drawing is part of the contract.

I haven't seen anywhere near the amount of confusion you allude to on 'generic' CAD format. Rarely have I had use of step questioned on piece parts. (collaboration with vendors on larger assemblies is another matter).

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Need help developing title block verbiage for undimensioned drawings

(OP)
Most of our 3 or 4 outside machine shop vendors request either STEP or DXF files of the parts they produce for us, even though the part is fully defined on the drawing. They are reminded when we supply the CAD files that they are still responsible for delivering parts TO PRINT. We even have some vendors that actually re-draw the entire part from our print, on their sheet/title block format. I haven't quite figured out the economics of that just yet...

RE: Need help developing title block verbiage for undimensioned drawings

As a contract drafter who sends files to laser and water-jet cutters , I send a dimensioned print of the flat pattern with tolerances and revisions also with a revision number in the title box, together with an un-dimensioned " Cutting Pattern" together with a one inch " test square" included in the step or DFX file also with a revision number. This way the cutter can check their finished part to the dimensioned drawing after the fact and make any tool offsets if needed.
B.E.

You are judged not by what you know, but by what you can do.

RE: Need help developing title block verbiage for undimensioned drawings

Kenat,

"I haven't seen anywhere near the amount of confusion"

In contrast, I have.

I have also seen companies that supplied deficient parts because the supplier got an updated drawing with a contract, but since the contract said nothing and the drawing didn't supply any indication of the exact CAD data, they just went with the model they had gotten for a previous revision.

Execution of a contract should not depend on one guy on the shop floor knowing the phone number of another guy in the drafting department to get data.

I think it is better to fix the system so it works right instead of being complacent and hoping it doesn't go wrong. If procurement doesn't care to talk with engineering about how a product will be procured, adding a non-specific note to the drawing isn't the patch that is required, because, as noted above, procurement often doesn't read drawings.

If the drawing is incomplete it needs to specify exactly what is required to complete it - use "Filename.Extension, Revision, xxxxx Bytes, Dated YYYYMMDD.HHMM to complete", and not a general purpose note.

RE: Need help developing title block verbiage for undimensioned drawings

Quote (3DDave)

"Filename.Extension, Revision, xxxxx Bytes, Dated YYYYMMDD.HHMM to complete"

Such information is often unreliable or invisible (if embedded in proprietary CAD format) by the time it gets to the end user.

A possible alternative is to include the supplementary data as an attachment within a PDF drawing. That PDF file could then be included as an attachment within a PDF contract. For extra assurance, digitally sign everything.

pylfrm

RE: Need help developing title block verbiage for undimensioned drawings

Already said that "It needs to be spelled out somewhere and building the drawing and the model file as attachments to a contract via PDF keeps them all together."

What I called out was the text that would be applied to a note in the field of the released drawing, not invisible at all.

RE: Need help developing title block verbiage for undimensioned drawings

3DDave,

Sorry, I missed that.

I didn't mean that the note itself might be unreliable or invisible though. I meant information in the file you're trying to identify with the note. Sometimes the vendor doesn't have the right software to read the metadata, and is left with just a filename.

pylfrm

RE: Need help developing title block verbiage for undimensioned drawings

Typical file transfer will keep the last modified date and the file size. So will using the Zip format, so these are available to the operating system. Rev may not be, but with name, date, and size, the file should be adequately identified to prevent getting the wrong one.

RE: Need help developing title block verbiage for undimensioned drawings

3DDave,

Our POs specify the revision number of the fabrication drawing.

A better process is to follow design change rules that do not allow changes to parts. Any change to form, fit or function results in a new part number. Revisions correct spelling mistakes and bad drafting.

--
JHG

RE: Need help developing title block verbiage for undimensioned drawings

What happens is someone sends several suppliers a part file for them to look at, ahead of the contract, as a preliminary. They get comments, other things happen, changes are made and the drawing is finally released. No one tells drafting that contract has been let and nothing tells supplier that changes were made. Hilarity ensues.

RE: Need help developing title block verbiage for undimensioned drawings

One thing that caused confusion in the ordering chain is the PDF.
If a model is modified using a cad program the drawing updates, the drafter may have to update the revision letter manually.
Unless the PDF is overwritten it just sits there like a landmine , waiting for purchasing to send out the wrong one.
B.E.

You are judged not by what you know, but by what you can do.

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