how to approach these types of drawings

[LONDONDERRY]

I've created a 3d model concept, next detail out the parts (mostly packaging foam), they are sent to case manufacture (similar to Pelican cases). They review the drawings, start to make the case and have to tweak the foam to make the devices inside fit. The drawings more or less give the manufacture a ballpark idea on the shape and size of the foam cutouts. This is a back and forth process with the manufacture a couple of times until the foam is cut and shaped to the right size. Most of the time I have to work with the case manufacture in helping to design the case. There are two issues I'm looking to solve.
1. How do I capture on a drawing perhaps in a note that the drawing dimension are approximate and subject during fabrication
2. SCM treats these drawings like sheet metal and machine shop drawing in that they can go to any place to have them fabricated. They ignore that fact that engineering has to work with the case manufacture.


Regards
Londonderry

 

[drawoh]

LONDONDERRY,

Telling your vendor that your dimensions are approximate, eliminates control over the stuff that arrives on your loading dock. The best thing to do is to apply sloppy dimensions, and work out a design that works with your sloppy dimensions. There always is the possibility that you will have to find a new vendor.

--
JHG

 

[KENAT]

Well,
1. Note something like 'dimensions marked <insert symbol> apply with foam installed in case pn...' or is that not quite what the issue is. Is the issue more that the dimensions you give are nominal?
2. Making final drawing a source control drawing ties down the vendor somewhat - if you really do want to stick with engineering approved vendors and not leave room for purchasing to move at random. Assuming they respect source control drawing of course.

Posting guidelines faq731-376

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

 

[LONDONDERRY]

good suggestions:


I decided on adding two notes on the drawing:

NOTES:
1. FOAM MATERIAL AT VENDOR'S DISCRETION BASED ON DESIGN INTENT.
MINIMUM REQUIREMENT, CLOSED CELL FOAM, COLOR CHARCOAL GRAY.

2. ALL DIMENSIONAL CALLOUTS ARE APPROXIMATE AND SUBJECT TO
CHANGE DURING FABRICATION/ ASSEMBLY BY MANUFACTURE

 

[cowski]

It sounds like you are in the prototyping stage to determine the final dimensions. Does your vendor have experience making foam packaging for other items? If so, work with their engineer/designer to finalize the details then revise your drawing accordingly. If they do not have such experience, there may be a lot of back and forth during this stage. Order prototype, check fit, revise drawing, repeat...

 

[MikeHalloran]

SCMs do not respect vendor relationships. You will have to develop a complete and accurate set of drawings of the exact finished product you need. The SCM will then send the drawings to anybody, anywhere, for quote, and will go with the lowest bidder.

If you require a back-and-forth sequence to arrive at the proper dimensions, and are accustomed to doing it all with a single vendor, consider issuing a contract to that vendor's engineering department to conduct the back-and-forth and to mark up a set of prints, all as a nonrecurring engineering charge, or a subcontracted project, or whatever means you have for spending a lump of money without SCM interference.

Be sure that the finished drawings include exhaustive inspection requirements so you can reject something that BillyBob carved out with a chainsaw.

Or just shoot the SCM staff.


Mike Halloran
Pembroke Pines, FL, USA

 

[LONDONDERRY]

cowski=- Yes I'm in prototype stage, but I work with the vendor in designing the case, They have the packaging experience more so than I do, so I rely on them. They are a small mom and pop shop so no engineering, They make the outer case shell from vacuum form and we bring devices and they package them in with foam and such. We sort of give them a concept to work by and a few drawings but they design the case and we approve it. It half design and half artwork.

Mike as usual you have a soft spot with SCM. These clowns think these are shop drawing and can go anywhere to bid on them.. The vendor I deal with is a case manufacture and like I said above I have to visit the vendor many times and work with them on creating case design, but SCM doesn't see it that way and they are totally ruining relationships with all the vendors I have to deal with..

Here is the name of the vendor:
ATS Cases Inc.
Northboro, MA

 

[ctopher]

Why not add notes "Pound to fit, paint to match"?
Do the drawing correct up front minimizes the back-and-forth design approach.

Make a drawing with the final dimensions you need, send them the drawing.
You can do the same with the foam. I have done this a lot in the past.

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[tbuelna]

It is always best to make your engineering documents as specific as practical, but also not specific in any way that will limit you to using a particular vendor. It is common with a new product design to go thru several revisions prior to delivery of the first conforming article. And it is important that design changes made during the development period are fully documented. This would include a technical coordination memo documenting the revision and that both parties have agreed to the terms of the change, and transmittal of any revised documents/drawings that the purchase contract is based on. This will ensure that all parties involved understand and agree to any changes.

Sometimes vendors are willing to eat the cost of implementing these development changes as part of the price of doing business. But if the cost and schedule impact of these changes gets out of hand the vendor will often ask for the PO to be changed to include the added non-recurring costs. Typically, a vendor will make their own set of manufacturing drawings to make your product based on the source control drawing you supply. And any changes you ask for after they release their drawings will require them to revise their internal documentation, which involves some cost for them.

Of all people, your SCM or purchasing dept. should be the ones demanding tight configuration control of source control drawings. Since a drawing that may eventually be used for competitive bidding by several vendors should be very specific and not allow for various interpretations that might affect the bids. It's always a good idea to be as accommodating as possible when it comes to development design changes on a new product requested by your supplier. But once they deliver the first conforming article, you need to start holding them accountable.

 

[LONDONDERRY]

Lots of good information thanks.

In regards to you suggestions ctopher, in the beginning I've done the approach of creating a final design, detailing out the parts (mostly foam) send them to the vendor. What happens next is I get a phone call and the conversation goes as such:

IF we cut these foam part according to your drawing, then the devices inside will not be held in place during transport. The parts have to be oversize to allow compression on the parts you want hold in place.

 

[ctopher]

OK. So, they tell you how much oversize they need to be, then make the drawings to those dim's from then on.

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[dgallup]

Why don't you supply them with the envelope of what you want to pack and ask them to figure out the foam requirements and supply the drawings? I always try to get the supplier to apply their expertise, saves time and effort.

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[LONDONDERRY]

Hi dgallup-
That's the approach I've been sort of taking, I send over the 3d model and some drawings with rough dimensions and the case manufacture looks them over cut the foam, tweaks it and then I pay a visit to approve the on off design, then go back and reverse engineer the changes (which I hate to do). But based on my original question is what type of notation to place on a drawing to mention that all dimensions are approximate and subject to change during first article .. maybe I'll just say that I guess.

Thank you all for the tips.. I think I understand how to approach this

 

[KENAT]

Londonderry, the way we handle that here is drawings not formally released have numeric revision levels, big stamp about prelinary draft etc. and rev control is entirely left up to the engineer, and orders get placed through a semi manual process.

Once a part is formally released and under full ECO release we go to alphabetical revs, demand for production is automatically driven by our ERP system etc.

So, on something like this I keep sending back and forth numeric revs with verbal or maybe email disclaimer about dimensions are approximate and subject to change during first article until I'm happy then go to ECO.

Based on what you say I'm not sure I'd even send preliminary drawings just the part outline info then dimension up what they come up with or similar.

I may be missing something - and am not saying our rev control thing is necessarily the best thing in the world.

Posting guidelines faq731-376

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

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

 

[3DDave]

It seems more like you want a spec control drawing. One that tells the case maker what the performance of the case will be. It probably means drop testing with accelerometers, but may just preclude observable damage to either the case, it's foam, and the specified contents. You would end up issuing approval for conformant cases and they would submit drawings/other document controls to show that their production doesn't change with time or they will have to retest. You might include on your drawing a particular order of storage/approximate locations if there are user instructions you want to control for your customer.

 

[dgallup]

My approach is to not supply any drawings, just the part envelope. Let them come up with the design and supply the drawings to you.

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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.

 

[tbuelna]

What you need to do is issue a revision to the SCD for this product that covers the changes requested by your vendor. Not a big deal, and it is commonly done with development hardware.

You should never release engineering documents like SCDs that provide vague requirements. The requirements on an SCD or procurement spec should always be as specific as possible. And if your vendor wants to make any changes, you should issue a revision to the SCD and confirm it by sending it to your vendor along with a technical coordination memo. Spending a couple hours documenting each change will prevent conflicts between you and your vendor later on.