Best method for documenting this design

[LONDONDERRY]

Geetings:
Our company has worked with a case manufacture (similar to Pelican Cases) to develop a semi-custom case for our needs. Its a scenerio where the vendor has an off-the-shelf case and we asked them to tweek it. The case has a retractable handles, wheels, latches and protective bumpers, etc. Afterward, the vendor assigned a part number to the case job, and we assigned our internal company part number. The vendor has the documentation on the case which is hand notes, sketchs, some 2d prints, and placed all that in a folder and assgined a job number to it. I had to work with the vendor on this with on site visits

Afterwards, I created a 3d CAD model of the design, and 2d drawings , structured a BOM in Agile PLM of the items I mentioned above and loaded the drawings. I released the design and when supply chain (s/c) went to place the order with the vendor problems arose as such:

1. The case manufacture didn't mentioned the vendors they use for the case design assecs (wheel, latch, ect.)> Because I created a BOM in Agile with these parts called out, s/c was confused if we supply these parts or not and why no vendor is listed
2. The case manufacture was confused when s/c chain sent him a package of drawings I created. He assumed something changed and had to spend 1 week reviewing the notes in the folder to the 2d drawings, and then had to contact me to find out what changed.

So my question is what is the best method to document this? I was told we need to document the case design somehow, as part of an inspection process on our end and if the vendor goes out of business we have something. The problem is I went the tradition route of creating detail, assembly drawings and BOm and this casued a mess with other departments that didn't know the development history I ahd with the case manufacture. In addtion, not stay at their jobs for life, so i want to create a documentation package so when I leave there are no questions on how to build a case.

Some thoughts I had was to remove the Agile BOM and create a source control drawing and place the BOM on that. One other isses is the case design changes based on the contents we need to fit inside of it. So my question is what is the best method for documenting this type of design?

Regards
Frank

 

[KENAT]

Some kind of control drawing, probably Source Control Drawing, would probably be the way to handle that. Although your last line complicates things a little bit.

Maybe a Source Control drawing of the basic case that never changes and then a next level more conventional assy drawing that details the internal foam or what have you?

I'd take a look at ASME Y14.24 to convince yourself what kind of control drawing is truly appropriate.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[swertel]

Source Control Drawing sounds absolutely correct. And, like you said, put your BOM onto the Source Control Drawing. That way you know exactly what the case should consist of, its critical-to-function dimensions, and any other inspection criteria required by your company to verify that the supplier built what you expect.

For any new case requirements, such as changes to design based on contents, well then you have to ask yourself if the case is interchangeable and assign a new part number as required.

--Scott
www.wertel.pro

 

[LONDONDERRY]

Is there such thing as a source control, inseperable assembly drawing, or am I spinning too much?

KENT you point
"Maybe a Source Control drawing of the basic case that never changes and then a next level more conventional assy drawing that details the internal foam or what have you?"

Thats exactly what happens, the case shell design is the same from project to project, but the foam changes based on what we stuff inside.

This brings up a second issue I was going to mentioned. I created detail drawings of the foam insert for a past project, then supply chain (s/c) sent them out, the vendor called me and said, if he made them to the drawing the components inside will move around. Cutting the foam is trial and error and I didn't consider the foam is cut oversize to have a 20% compression rate thats required to hold components inside case steady. The cSo whats the best method for documenting that? I was considering changing the dims to reference only and adding a note saying dimensions are nonimal and doesn't reflect finished product that requires a copression rate for holding

 

[MikeHalloran]

You started going out of business the day you hired a Supply Chain Manager.
... but that's just my opinion.
... based on substantial unhappy experience.
</rant>

The dimensions you put on the drawing are the ones that your inspectors check to assure that you got what you wanted. ... perhaps with a drawing note saying 'assembled dimensions' or some such, so that the vendor knows you're not trying to do his job.
It's not strictly a 'reference' dimension, because you do want it measured, but you also don't want the vendor cutting foam inserts to that dimension, either.

A possible alternative is a note like 'Snug Fit on part XYZ', but then your inspection department will have to keep an XYZ on hand, and maybe a force gage marked 'snug/ not snug'. ;-)




Mike Halloran
Pembroke Pines, FL, USA

 

[LONDONDERRY]

Hey Mike-
thanks for the tip, not sure how it'll panout. I think I'll put some over all dime and a note field saying " All dimensions are undersize and do not account for foam compression rate needed in over all design. sort of like that.
Don't have to tell me about supply chain. bureaucratic group of people that have zero backgroup in understanding engineering documentation and will grind a ECO process to a hault

 

[swertel]

To get a little more technical, you would have to flag each dimension as to note if it is the "restrained" state or the "free" state. That would tell your inspectors how to inspect it.

If in the "restrained" state, then you have to note the requirements to properly restrain it. For foam and other soft goods, I usually say something like, "Restrain until measurement is within the dimension depicted."


--Scott
www.wertel.pro

 

[LONDONDERRY]

Hi Scott-
In all the years of drafting I never heard of these two state, can you explain more, as this might help?

 

[KENAT]

Checkout ASME Y14.5M-1994 section 6.8 regarding Free State Variation & restrained condition.

It's something that is probably underused for many applications.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[swertel]

I'll explain with an example.

Let's say you have a reusable rocket on its side. Because it is made of thin aluminium, the circular rocket body squishes to an egg shape under its own weight. But, you need to measure the ID. And the ID needs to be round to get an accurate measurement. Therefore, you will need to first constrain the rocket into a circular shape and then you can measure the ID.

Free state is the egg shape.
Restrained state is circular.

So how do you restrain it circular without forcing the diameter? That's why you have to specify on the drawing how to restrain something. This technique also applies to other soft goods: o-ring diameters, webbing (stretchy cloth) length, foam thickness, etc.

--Scott
www.wertel.pro

 

[LONDONDERRY]

Thanks for the example Scott, I'll look into this more.
Cheers for now, Frank

 

[Tunalover]

If the only variation between transit cases is the foam cutouts then you can do a tabulated Vendor Item Control Drawing with one view showing the external features and subsequent views showing each cutout. In the caption of the subsequent views you would indicate the VICD dash no. and the vendor part number.

Tunalover