Drawing Material Specs - Initial vs Final Condition 1

[idgara73612]

I do a lot of sheet metal design, and so inevitably, I have a lot of cases where I cannot meet both the strength req's AND bend radius limits with a certain material. For example, I have an .063 AL 6061-T6 part with a .06 bend radius. That BR is too small for -T6, but can be hit with 6061-O. In this case, I generally define both the initial and final condition (temper) of the material. We have gotten into some discussions lately regarding which of these should be placed in the drawing title block.

My view is that I want to define the FINAL condition in the material spec field. Others say that field should contain the INITIAL condition.

My reasoning for FINAL is that I don't care how you want to achieve it, but at the end of the day I need a part in-hand that meets the dimensions and material spec. In this case, I put the FINAL condition in the mat'l spec field (i.e. 6061-T6 per AMS 4027), and will include a drawing note saying something similar to "Make from 6061-O. After forming, heat treat to final condition shown." I consider this note to be more of a courtesy to the shop guys, but not req'd. If they think they can hit the bend radius with -T6 right off the bat, then go right ahead. If they feel they need to form it in -O then heat treat, go right ahead. Again, as long as it's -T6 when it's finished, I don't care how it gets there.

The shop guys are saying that the INITIAL condition should be the one in the title block, and the notes should identify what the final condition is. They say this more for procurement purposes, so they know to order -O, as opposed to ordering -T6.

Strictly in terms of the drawing, this is about where the discussion ends - but in terms of modeling, it is also beneficial to define the FINAL condition, so that any analyses are done using the correct mat'l properties. And our drawings pull the material directly from the model... so, another point for FINAL condition.

I'm interested in your opinions on this, and if there is any spec anywhere which touches on this. I haven't been able to find one.

 

[KENAT]

You want to specify the final condition per ASME Y14.5M-1994 1.4.

Putting the non mandatory process information is acceptable so long as it's clear it's non mandatory. e.g. "MAY BE MADE FROM MATERIAL IN THE 6061-O CONDITION AND HEAT TREATED AFTER FORMING TO FINAL CONDITION SHOWN" or similaR.

For the part they should have some kind of routing or equivalent which is where they could record the required material condition to order.

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[BiPolarMoment]

I waffle on this. On the one hand the design drawing is supposed to document what the part needs to be (e.g. not specifying manufacturing methods unless it is important to the design). On the other hand sometimes not spelling something out (that may seem 'obvious') can burn you on the back end. This may also depend on whether this is an internal vs. external mfg. and/or if you/they have a capability of creating an electronic BOM that could dictate the material 'make-from' that need not be on the drawing. I typically walk some middle ground as far as what manufacturing information makes its way to the drawing, usually because ambiguity in our existing documentation doesn't explicitly tell the mfg. NOT to do something and they choose to interpret it differently. e.g. our notes don't [always] dictate an order of operations by default so do you laser mark then passivate, or passivate then laser mark? And the answer may be 'both'.

 

[3DDave]

The -O condition can go on the flat pattern drawing, along with the rough size of the sheet, plus the procured sheet size and any nesting pattern. Which should be a manufacturing generated document. Which manufacturing can turn over to procurement along with the other tool and die orders related to the manufacture of the part. When the part is formed and heat-treated, it and the engineering drawing can go to QC to see if if meets the requirements.

 

[idgara73612]

3DDave,
You make an interesting point, that I hadn't thought of... Separating the flat pattern and the engineering drawing. We just combine those two - the flat pattern is just another view on the drawing.

 

[BiPolarMoment]

I alluded to this but did not explain--for internally manufactured parts (and now for a couple external) we create a drawing for the intermediate form e.g. a casting or forging that is later machined to net shape. I don't think this typically includes differences in material properties but certainly has different dimensions.

 

[dgallup]

I think we are all in agreement that the drawing of the finished part absolutely has to have the final heat treatment specified. Additional info really depends on how your company does things. We (engineering) used to just throw designs over the wall to manufacturing and let them figure it out. Now that every project has an APQP team with members from all departments we have found it much more efficient to create one drawing that has all the manufacturing steps on separate sheets. We always had operation sequence drawings it's just that in the past they were drawn by different departments by different people in possibly different CAD systems. So now we have both the raw material spec and the finished part spec on different sheets.

Now if we make the part from a casting or forging then that gets it's own part number and drawing since we buy those parts. We also typically machine a family of different parts from a common casting or forging.

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[djhurayt]

How about this option.
1) Material spec for the finished part that QC will be checking in your material spec field, in this case 6061-T6

2) Then place a one line BOM that shows the flat pattern blank size, and in either the part number field or a material field within the BOM use the material for the blank that the finished part is made from, in this case 6061-O

Ex:
PART NUMBER-------DESCRIPTION
6061-O----------------24 x 36 x .063 ALUM BLANK

or
MAT'L-----------------DESCRIPTION
6061-O----------------24 x 36 x .063 ALUM BLANK

This would be similiar to haveing a cast blank (part A) that multiple part (part B, C, D, ...) are made from. The drawings for PART B, C, or D etc. would have a BOM in it calling for a qty of 1 of a part number "part A" in order to make a part B, C, ...

 

[drawoh]

idgara73612,

Why bend aluminium 6061 at all? The material sheet metal shops like to work with is 5052-H32. It takes your bend radius without the heat treatment. It is not quite as strong as 6061-T6, but if there are no cracks in the bends...

You paying a premium to use an exotic material. You are not doubling or tripling the strength. You are selecting a process that has workmanship issues, making small safety factors a bad idea.

--
JHG

 

[drawoh]

You want to specify the final condition per ASME Y14.5M-1994 1.4.

This conforms to the letter of the standard. The problem is that aluminium 6061-T6 is an unusual material for sheet metal fabrication. The probable explanation for it is that the designer does not know what he is doing. There is so much of this in drafting. The shop that substitutes 5052-H32 or 6061-0 will under-quote the guy who takes this drawing seriously and who plans on 6061-0 and heat treatment. A note that suggests ordering 6061-0 and heat treating, shows that the OP wants 6061-T6, and that they know that the material is not bendable in its strong state.

Plan on doing a hardness test when the parts come in.

--
JHG

 

[KENAT]

Why'd you take that sentence of mine out of context Drawoh?

While I didn't say it as it wasn't really part of the OP's question, for something like that putting the note about allowing forming in O condition obviously makes sense and my 2nd paragraph touched on this.

There are environments where having the manufacturing info on the same drawing can be very appealing, but those environments can change over time and then it can cause issues.

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[drawoh]

KENAT,

I am sorry. I interpreted that as part of your reply. It is a reasonable response I would agree with most of the time. This is a tricky context, sort of equivalent to asking a welding shop to work to [±].005"[ ]tolerances. You need to confirm to the vendor that you are competent, and that you really mean it, and that you understand that they must jump through some expensive hoops to meet your requirement.

--
JHG

 

[Meshca]

Wanted to expand on BiPolarMoment and 3DDave's ideas.

There's a possibility of creating 2 part numbers, 1 acting as 'raw stock' for the final part:

1. "Part 1A" is burned and bent with the 6061-O plate as the raw stock and

2. "Part 1B" is a derived "Part 1A" but with "1A" as the raw stock.


Assuming you have part numbers for the material procurement, "1A" could be a custom material with a designation of '"Part# 1A" heat treated to 6061-T6'

"Part 1B" > calls for custom material "1A" > which calls for "Part 1A" to be heat treated > calling "Part 1A" procures 6061-O.


A company I worked for did something similar to this. They would have a part number for a flat pattern of a part to be made offsite. They made this into a custom material to be used when the bent part is called out.

 

[drawoh]

Meshca,

This allows you to subcontract fabrication and heat treatment separately, and stock the intermediate parts. I would want some very obvious indication that the part has (not) been heat treated. Perhaps the part can be anodize black after heat treatment. Perhaps you can buy production a hardness tester. If strength matters, you do not want untreated parts slipping through to assembly.

This whole problem goes away if you change the material to 5052-H32.

--
JHG