Material Callouts on Drawings
Material Callouts on Drawings
(OP)
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)?
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)?
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RE: Material Callouts on Drawings
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
RE: Material Callouts on Drawings
RE: Material Callouts on Drawings
Wanna Tip? FAQ731-376
"Probable impossibilities are to be preferred to improbable possibilities."
RE: Material Callouts on Drawings
RE: Material Callouts on Drawings
Wanna Tip? FAQ731-376
"Probable impossibilities are to be preferred to improbable possibilities."
RE: Material Callouts on Drawings
RE: Material Callouts on Drawings
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
RE: Material Callouts on Drawings
Jesus is THE life,
Leonard
RE: Material Callouts on Drawings
Hot Rolled, Pickled and Oiled.
Wanna Tip? FAQ731-376
"Probable impossibilities are to be preferred to improbable possibilities."
RE: Material Callouts on Drawings
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.
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- Unknown