Does "Interchangeability" include manufacturability? 1

[ptruitt]

I would appreciate your opinion. I would also like to know if you work for a small or large company. And I would also like to know if your company is highly regulated (such as medical or aviation) or not. (I am wondering if size or business focus affects the definition a company might have regarding interchangeability.)

 

[KENAT]

What's the complete question?

I currently work at a mid size US company that is not in a highly regulated industry. I have worked in aerospace/defense which was highly regulated.

By "Interchangeablitly" do you mean when refering to whether a change to a part is a rev change or requires a new number?

I suggest looking in ASME Y14.100-2004 or similar standard.

In my experience interchangeability probably wouldn't affect manufacturability, but I'm not totally sure what you mean by that.

Method of manufacture shouldn't normally be an issue unless it affects end function. For instance in many cases a cast or forged version of the same basic part may be entirely interchangeable. However, in some situations a cast part may not have performance equivalent to a forged part so would not be interchangeable, for instance if the 'brittleness' of the cast version caused lower performance than the cast one.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

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

What is Engineering anyway: faq1088-1484

 

[ptruitt]

Thank you! I know it is an odd question, but I don't want to prejudice answers by saying too much. Should the size of a company or a company's regulatory requirements affect the definition a company might have regarding interchangeability?

 

[KENAT]

WHAT DO YOU MEAN BY INTERCHANGEABILITY or at least what context? At least say if you are refering to the context of revision changes V part number changes.

WHAT DO YOU MEAN BY MANUFACTURABILITY do you mean ease of manufacture? I can't see how this is directly linked to interchangeability from a revision point of view. Obviously changes are sometimes made to improve manufacturability, and changes are often reviewed to see if they negatively impact manufacturability. However, when deciding if the change needs a rev or a new part number manufacturability itself doesn't seem to be a consideration.

I will say this, my current employer plays fast and loose with the definition of interchangeability when it suits them to save work, at least in the short term. In Aerospace/Defence while sometimes suggested, this rarely if ever happened.

At least once a product is 'released', i.e. some are in service at the customer etc. then I think the ASME Y14.100 definition should be followed regardless of company size or sector. There may be exceptions but I can't think of compelling ones. I was thinking maybe stand alone items that don't get refurbished or repaired etc. may not require it but even then for legal reasons it may still make sense to follow Y14.100.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

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

What is Engineering anyway: faq1088-1484

 

[ewh]

Not in my opinion; interchangeability is what is is, regardless of the company makeup.
I agree with KENAT. Manufacturability should not be considered when determining interchangeability, unless it affects the function of the part. That said, it is almost always better to strive for economy.
To expand on KENAT's example, manufacturing has a shelf half full of machined widgets and half full of cast widgets, all mixed up. Both types meet their expected functional requirements, and each can be used in place of the other without adversely effecting the final product. Even though the machined widgets cost 4X more to produce than the cast widgets, they are interchangeable.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[ptruitt]

Thank you! Basically, I am having the same issue as Kenat and I would like to add some voices to my own. I will share these helpful posts with my co-workers and, hopefully, make some headway. If anyone else has additional input, I would really appreciate it.

 

[Radagast]

We built part "X" (Interchangeable/Replaceable) for company "y" using process "Z" per contract so "Yes" Manufacturability can come into question.

Mike

 

[ptruitt]

How about that! That is certainly a clear example. It is not the situation that my employer is in, but I appreciate its addition to the topic.

 

[PeterStock]

If process "Z" is specifily stated on the drawing, the yes manufacturability can come into question, but only as requiring a change to the drawing. If the parts can be stored in one bin and it not matter which one is pick out, then then they can be the same part number. If not, then they must be different part numbers. If there is a significant chance that the new process method would cause or prevent a failure in use, then even though the parts are interchangable from a physical standpoint, then they are in fact not interchangable, a new part number should be used.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[ptruitt]

Author Frank Watts recommends basing interchangeability on a product design requirements document. In the case that Radagast sited, his customer's explicit production process would be listed as a requirement in that document. Radagast would base interchangeability on the implications of that. If the customer changed the process, then Radagast would need to make a non-interchangeable change. I can see that a contract might take the place of the document Watts recommends, but having the document might be an additional step that would allow additional changes that Radagast would want to class as non-interchangeable that the customer might not have an interest in. I like having the document in place as Watts recommends. With discipline, it maintains a consistent rational that can be referenced to add clarity to the history and evolution of product design well beyond Change Order documents and drawing revision notes. It can also be copied, modified, and used as the design control basis for new products.

 

[Radagast]

let me elaborate, there were features that were I&R. i.e.. Hole patterns. These here controlled using their tooling by contract.

 

[KENAT]

This is why I asked for clarification on what the OP meant by "manufacturability". Places I've worked this means ease of manufacture (or lack there of). This wouldnt' directly be related to whether the part was interchangeable.

Method of manufacture which several (including I with my forging V casting example) have elluded to, sometimes does effect interchangeability, though not always, or perhaps even most of the time.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

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

What is Engineering anyway: faq1088-1484

 

[Radagast]

You comments are exactly why I needed to clarify Kenat.