Material Callouts on Drawings 4

[MadMango]

I'm just wondering how people define material used on drawings?

Usually for our common parts, we only place HRPO in the material section of the title block. This has been sufficient for our uses in the past. Upon further investigation, I found out that we sometimes get in AISI 1008 or AISI 1005 (both are HRPO), depending on the mill we order from. The materials are similar, but not technically the same.

I'm wondering do the majority of people simply callout HRPO, or do you specify an AISI number or UNS number? Or, do you create engineering specification sheets, and reference that spec on your drawings (along with binding Purchasing's hands)?

Wanna Tip? faq731-376
"Probable impossibilities are to be preferred to improbable possibilities."

 

[swertel]

Depending on the product needs, customer wants, and contractual agreements, yes to all the above.

We have a standing "Unless Otherwise Specified" that the equivalent material can be substituted without the design group's permission. When the product requires a specific material because of the reasons stated above, we call out that spec on the drawing face (Parts list) and flag it as no substitutions allowed. That still allows purchasing to get the material from any supplier, as long as the material meets spec. Sometimes we need to get very specific and we call out the supplier. That is a whole other story.

--Scott

 

[TVP]

I think that my company (an automotive suspension supplier) is pretty typical of most technically-proficient Tier 1 suppliers in that HRPO is not an acceptable material call-out. We use industry standards (SAE, ASTM, etc.), customer standards (Ford, GM, etc.) and our own internally-developed standards for proper material specification. Merely specifying the chemical composition without anything for mechanical properties, surface condition, etc. is rarely sufficient for the products that we develop.

 

[MadMango]

TVP, which standard is the most commonly used (SAE, ASTM, ISO) in transportation applications? I guess if you distill my original question, that's what I'm trying to get at.

Wanna Tip? faq731-376
"Probable impossibilities are to be preferred to improbable possibilities."

 

[TVP]

It depends. If you are referring to hot-rolled carbon steel then ASTM A 1011 is the newest standard, which covers various grades (structural quality, drawing quality, deep drawing quality, etc.). It also covers HSLA steels. SAE J2340 is the latest standard for high strength steels, which covers HSLA, DP (dual phase), low carbon martensitic, etc. SAE J2329 covers low-carbon sheet steels, both hot-rolled and cold-rolled. FYI, these are all product standards, not individual material or chemical composition standards. ASTM A 1008 is similar to ASTM A 1011, but covers cold-rolled materials.

 

[MadMango]

Thank you, this will get me going down the proper path now. Now I just have to bicker with Purchasing, as every time Engineering tries to create Engineering Specifications, they think we are binding their hands and stopping them from doing their work.

Wanna Tip? faq731-376
"Probable impossibilities are to be preferred to improbable possibilities."

 

[ornerynorsk]

Purchasing always likes to be the hero! They'll buy any crappy material that's available if you don't put the blinders on them with the right specs and callouts. The more critical the application, the more precise the specs need to be. It also doesn't hurt to require the material certs from your vendors, regardless if it's raw material or finished product. Anyone who complains too loudly is generally padding their own margin with a lesser material. This is a very, very common "shell-game" in industry.

 

[griffengm]

Our company uses ASTM, SAE and AISI standards. We then create part numbers for the various size materials. Material specs were set this way so that we were not trying to buy something too far out of reason and adding costs. Design knows they must stay within these guidelines when developing a product and purchasing has industry standard specs for vendors. If the vendor can't meet the spec, we probably don't want him as a regular supplier anyway.
This issue goes deeper into some organizations than others. Last week I encountered a firm who, in cost cutting efforts, was using drop to make some brackets used in semi-trailers. The drop was from steel requiring special weld wire and usually parts made from it were flagged to alert weldors to change the set up of their machines. The flag was not being added to the brackets so they were being welded with the wrong wire. The practice stopped when this was pointed out but it illustrates why good specs and follow thru are important.

Griffy

 

[metman]

What does HRPO stand for/

Jesus is THE life,
Leonard

 

[MadMango]

[blue]Metman,[/blue]
Hot Rolled, Pickled and Oiled.

Wanna Tip? faq731-376
"Probable impossibilities are to be preferred to improbable possibilities."

 

[McLeod]

As has been noted, the width of the spec window depends on the criticality of the application - as wide as possible, and as specific as necessary. In the medical field, we frequently call out type, grade, and treatment (usually hardening and passivation) of material, as well as applicable standards, for anything that comes into contact with the patient, and most other custom parts as well.

It's a question of verification and validation time and cost as much as anything else. If our V&V test samples are made with 17-4 PH condition H900, then the production units had damn well better be made of the exact same stuff. If purchasing or the vendor wants to change the material, they have to get R&D's signature on the print change. Sometimes a simple engineering review suffices to support such a change, but in other cases further testing is required, which may negate the proposed cost savings. I'm sure just about everyone here can think of cases in which bad things resulted from seemingly simple spec changes.

We do sometimes make allowances for less-critical or standard parts. A stock retaining ring or set screw might be called out only as "stainless steel".

Purchasing and Manufacturing do tend to push single-mindedly towards wider specs because it suits their departmental goals: "cost bad, margin good!" This occasionally conflicts with the greater financial interest of the whole organization, because the costs associated with recalls, failure investigations, lawsuits, and regulatory scrutiny can far exceed the savings of a material substitution. Quality Engineers can be your best friends in that type of debate.

"Marketing - where the rubber meets the sky."
- Unknown