Supplier wants manufacturing process notes on drawing

[LKENNEDY]

We have a supplier who regularly comes back with feedback of specific process notes that he thinks should be included in the product drawing.
E.g. there is a recess on one of our parts, and he asked for a note that says "18 x 5 x 5 recess machined post fabrication" as the part was going to be oxy cut first.

I am very new in my role here so am unsure if what he is asking for is reasonable but have always under the impression that the part/product drawing should contain info critical to form and function -Whichever way the manufacturer decides to make it is not really my concern as long as the parts are coming back within tolerance and passing FAI.
Simply, I don't want to include these type of notes - particularly in case we changed supplier and now the drawing is holding them to someone else's process.

With the same supplier we're having an issue where on one part, they drilled holes to 24mm instead of pre drilling and tapping them to M24. The hole callout was very clear that it is a tapped part and now they are asking for notes on the DXF too so this doesn't happen again.

Again, don't want to include this information, as I see it as completely their fault for relying solely on a DXF and not consulting the drawing we also sent. This has put a lot of pressure on the timeline to get the parts re-done. The rest of the assembly is sitting in the workshop waiting to be finished.
Do I just suck it up and put notes on a DXF for them to try and prevent this happening in the future? Or just insist that they have to read the drawing too. Seems insane to me that they wouldn't look at both. Why am I even sending a drawing if it's not being utilised?

Any help is sincerely appreciated.

 

[Stick.]

If the supplier wants process notes on the drawing, they can put them on their shop copies of the drawing, after you've sent the original. You should avoid adding these notes for the reasons you've already stated. I'd also not mark up the DXF. The main issue there is that now you have specified the same thing on two documents, which creates the potential for conflict between them. It also creates a potential for you to miss adding something to the DXF, like adding a tapped hole callout, and then you (or your company's purchasing department) get to have a fun argument with the supplier about whether the drawing or the DXF is the controlling document.

That's all based on my experience, so others may have different opinions or better ways to handle this.

 

[CWB1]

Agreed. I would not add process info to a design print, even for parts made internally. Technology is so prevalent and user-friendly today that even tiny <10-employee tool&die shops will make a quick copy/markup as-needed and store digitally for future use, so there's no need for you to document anything for them.

I also take all supplier recommendations for design tweaks with a grain of salt to avoid limiting purchasing's ability to re-source the part.

 

[Gr8blu]

For the most part, the design drawing (which may be used to source parts from multiple suppliers) covers the design intent - and critical-to-assembly features. Exactly how a part gets made is usually done at the supplier level, on their copies of the "shop" prints - NOT on the "design" drawing (regardless whether the design drawing is a model, a DXF, a paper or vellum original, etc.).

However - there have a been a few (less than 5, total) cases over the last 30 years where a supplier HAS raised a question (i.e. did not demand a change, merely questioned intent) with something that was missed in the original design. On those VERY RARE occasions where the designer agreed that it was indeed missed or that the change would add clarity to the intent, the original design document was updated.

Converting energy to motion for more than half a century

 

[tygerdawg]

This may be a case of helping your customer be better at their own production processes and management systems by saying "no." Agreeing to their request might return as a liability where they will hold you accountable.

I would not add manufacturing process notes to a design engineering drawing, except in the broadest terms. If an existing process has proved successful for a product, it may be considered proprietary. If so, then releasing that information should be covered under separate commercial agreements. If the process data is released and published, who is to say the customer won't take this production work into their own shop to save money?

Here's a war story for context on why or why not (can be argued both ways):
[ul]
[li]Customer asked MyCompany to make a part (a cylindrical element used in a fluid control device...similar to a solenoid valve spool), previously manufactured by OldSupplier[/li]
[li]MyCompany received design drawing and reviewed; challenge accepted; initial prototyping and process exploration performed; quoted; cost & delivery approved[/li]
[li]In the rush to get into production and start making money, the initial prove-out run of parts were inspected and passed, but were not put into functional test on the assemblies[/li]
[li]Much expensive equipment purchased, people hired, floorspace allocated, systems set up, production made ready[/li]
[li]A critical process step was to deburr the corners of machined sealing lands. MyCompany chose an integrated machining step for this[/li]
[li]All product lots met the design drawing but failed Customer's functional tests and performance in assembly[/li]
[li]Deep investigation showed that Customer did not fully understand the fluid dynamics effects of their own product. OldSupplier used a specific type of deburring process step to remove burrs on sealing lands. The debur step rounded the corners and subtly changed the part geometry, but still was within the design drawing specs. But the rounded corners had a significant effect on the performance of the assembly. Who knew?[/li]
[li]The entire affair was a disaster for everyone. OldSupplier wanted to get away from the low-profit high-tolerance labor-intensive process of making the part. MyCompany saw it as high-profit cash cow for years. Customer had no idea how their own product worked.[/li]
[/ul]

If there are any particulars to your manufacturing process, then I'd detail it in process sheet documents. Then let the Commercial People figure out an equitable way to transmit that information to your customer (a commercial fee or licensing agreement). If not particular, give it away under separate document knowing that you may get an End Of Contract notice in the future. Or simply say "No, sorry, we don't do that."


TygerDawg
Blue Technik LLC
Manufacturing Engineering Consulting

http://www.bluetechnik.com

 

[geesaman.d]

There are times when I do add manufacturing details on a drawing that gets made by a vendor, but it needs to be in my best interest.

The vendor could be protecting themselves because if you add those to the drawing, any other vendor has to follow those notes. The philosophy where I work is that we want to define the final part requirements and let the vendor get there the cheapest way possible. And we want to be able to send that part drawing to as many vendors as possible and not limit the eligible vendors or the way they make it.

 

[desertfox]

Hi LKennedy

Its always a grey area regarding process notes but I only put them on if I wanted to ensure something further down the line. I agree in the main with you, in that the drawing and dimensions should dictate the requirements and how a manufacturer gets there is up to them because next week you might change supplier and he makes the part a completely different way. They could mark up there paper drawing copies as suggested by others, however the downside to that is if you modify the component in the meantime and they don't check for updates the chances are you will get an out of date part. The supplier needs to plan how to make the part in my opinion and provide a method statement to his work force to achieve the drawing requirements

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[HR ShoveNstuff]

Hi LKENNEDY,
Your instincts are right, don't do it, unless, like geesaman.d said, its in your companies interest. And duplicating information on the DXF is just asking for conflicting information later on, don't do it.