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Inadequately Dimensioned Drawings from Customers.

Inadequately Dimensioned Drawings from Customers.

(OP)
From experience (I actually had my first dismal one today), how do you handle poorly dimensioned drawings -- drawings that do not have the dimensions necessary to manufacture, design tooling, or redraw without fair struggle? The customer did not have any other drawings to share. I went ahead and discussed it with a few of the related parties that I work with about what is required for the part. Angles, flange lengths and center points locations were missing, just to name a few. Thankfully a more skilled and experienced coworker was able to draw a close mock-up for it (I plan to interrogate his thought process and drawing thoroughly). It was a strap handle that is to be welded on to a frame so we had some freedoms with the particulars.

RE: Inadequately Dimensioned Drawings from Customers.

The first step we go through is to bring this up with the customer and ask for any additional design files (drawings, CAD, exported generic files, etc) that they may have so that we can at least get the needed dimensions off them. Some customers will not have anything to work with as it sounds like is the case for your customer. In that case you can ask for a sample part you can measure or print off the drawings they have provided to scale and manually measure the needed dimensions off of that. Hopefully they at least have enough views to show all the part features even if they weren't dimensioned. For the added effort to recreate drawings the customer should expect some NRE charges.

RE: Inadequately Dimensioned Drawings from Customers.

The last resort is measuring a print to scale dimensions from. I can sometimes import a PDF, if supplied, into CAD software and 'trace' over it to get pretty close. Usually I'll have enough dimensioned data to align and scale the print to meet the lines I've drawn from dimensioned data. That will get the undimensioned features on the imported PDF (sometimes a scanned file) located NEAR-TO-TRUE size, location, and orientation.

Knowing that typically people will not go out of their way to place things in oddball locations, I might round things to the nearest 1/32" or center things that look like they should be centered, etc. So long as it suits the assumed/known function of the part at hand. Many times assumptions can safely be made if you know what the thing IS.

When you cannot come to an agreement with the customer, there's been two successful approaches IME. One is, time allowing, sending them a sample piece as a 'first article' to approve along with a drawing we create, and all subsequent parts will be made to that 'shop drawing' and supplied sample part. Another is supplying our 'best effort' on the minimum # of parts the customer needs to 'get by' for now, and then making any revisions to our 'shop drawing' based upon feedback from our initial parts. This is based on the assumption that the customer will be paying for all of those 'best effort' tryout pieces, or understanding that it may come with some modifications as necessary in-use.

A lot is based on the relationship and communication with the guy holding the check book.

RE: Inadequately Dimensioned Drawings from Customers.

Beware of the booby trap when scaling drawings. For several years we had a customer who supplied AutoCAD drawings to us for parts he needed, where his draftsmen would just go in and change dimensions without updating the part. I know this is bad practice and you cannot do this with a parametric modelling program, but you can and people did this with the older 2D programs.
B.E.

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

RE: Inadequately Dimensioned Drawings from Customers.

If the customer can't give you dimensional requirements, then perhaps they can give you functional requirements. Perhaps the part just needs to mate with some other components that do have decent drawings available.

When other approaches fail, I've had good luck converting vector drawings provided in PDF format to DXF using Inkscape, and then importing to CAD software. This has usually resulted in errors of less than a micron for the features I've been able to check.

Quote (berkshire)

Beware of the booby trap when scaling drawings. For several years we had a customer who supplied AutoCAD drawings to us for parts he needed, where his draftsmen would just go in and change dimensions without updating the part. I know this is bad practice and you cannot do this with a parametric modelling program, but you can and people did this with the older 2D programs.

You can do this quite easily in SOLIDWORKS, and I would bet the same is true of many other parametric modeling programs.

pylfrm

RE: Inadequately Dimensioned Drawings from Customers.

It is also easily doable in UG/NX.

RE: Inadequately Dimensioned Drawings from Customers.

I would not quote such a poorly defined project. If the customer does not know what they want and can not communicate it to you, how will anybody know how to accept or reject the parts you make? If it really is in your financial interest to pursue this project, I would somehow (using some of the ideas presented above) create a drawing you are comfortable with and get the customer to sign off on it.

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

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: Inadequately Dimensioned Drawings from Customers.

(OP)
The part is a strap fastener guide (pretty much shaped like a handle) made from 5/16 aluminium bar stock that has 2 brake forms on each side and smashed ends for welding to a frame. Due to the simplicity of the part we are able to get by with 'doing the best we can with what we have'. My objective with this post is to see what tactics my peers have utilized from their experience to overcome this unfortunate obstacle we face in the real world. Ah, and as always: Production is #1.

RE: Inadequately Dimensioned Drawings from Customers.

Sending things out to be made, of various sizes and process, I've worked with various levels of detail, there were things I cared about, which I dimensioned, and things I didn't which I didn't FTD (fabricator to determine) was the expression at one place. So if they haven't completely designed it, I'd treat it like a cartoon, and they dimension what they care about, design of the balance is up to you. I've sent and received approval drawings for review.

And yes, it is as trivial to edit a dimension on a drawing and make it non-associative to the geometry as it is with a pencil or 2D program. Some drafting templates make these edited dimensions stick out from the rest.

RE: Inadequately Dimensioned Drawings from Customers.

And you need to have a conversation with your person who quoted the job. The customer may get a bad part and additional burden, not covered in the quote, is placed on you.

Ted

RE: Inadequately Dimensioned Drawings from Customers.

I would definitely go with best guesses and an approved first article. I would not give the customer a drawing to sign. You made the effort you should keep the booty. Without that drawing your customer will have a much harder time shopping the job around why hand it over?

Keith Cress
kcress - http://www.flaminsystems.com

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