Visual Inspection of Bent Sheet Metal?
Visual Inspection of Bent Sheet Metal?
(OP)
Hi All,
We are dealing a vendor that is insisting on using VERY tight bend radii on aluminum sheet metal pieces and we basically have no choice but to visually inspect their parts and be done with it. It is far from an ideal situation, but I've been asked to find a standard that addresses visual inspection of Aluminum alloy bent sheet metal.
I see standards from NASA and AIAA discussing active Nondestructive evaluations, but nothing about purely passive visual inspection. Is that because this is frowned upon without the use of active ND testing?
I'm sure there are specs I'm just missing or maybe you all have some helpful trade knowledge about changing surface roughness, elongated grains, discoloration?... Thanks!
We are dealing a vendor that is insisting on using VERY tight bend radii on aluminum sheet metal pieces and we basically have no choice but to visually inspect their parts and be done with it. It is far from an ideal situation, but I've been asked to find a standard that addresses visual inspection of Aluminum alloy bent sheet metal.
I see standards from NASA and AIAA discussing active Nondestructive evaluations, but nothing about purely passive visual inspection. Is that because this is frowned upon without the use of active ND testing?
I'm sure there are specs I'm just missing or maybe you all have some helpful trade knowledge about changing surface roughness, elongated grains, discoloration?... Thanks!





RE: Visual Inspection of Bent Sheet Metal?
It can be a very slippery slope once you capitulate your apparent or perceived authority as The Customer.
If your vendor is insisting, perhaps it is they that should inspect and cull out the bad ones per your requirements, although "per your requirements" has, at this point, lost its flavor.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Visual Inspection of Bent Sheet Metal?
The closest thing I've found (but have not purchased) is ASM Handbook 17. Anyone have experience with this?
RE: Visual Inspection of Bent Sheet Metal?
If you are concerned about the bend radius, add a minimum radius to your drawing or your contract, to which you can inspect without ambiguity.
Mike Halloran
Pembroke Pines, FL, USA
RE: Visual Inspection of Bent Sheet Metal?
Do you have some typical failure samples from which to build an inspection protocol? What equipment do you have at your disposal? What kind of production volume are you dealing with? Would a cheaper/better solution be to just buy the correct tooling for them?
Just a couple of thoughts. Good luck.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Visual Inspection of Bent Sheet Metal?
Right now, it's unfortunately been decided that 'we will let them implement their own manufacturing techniques and visually inspect them. they will eat the cost of failed inspections".
Thus, my problem... I don't see any visual inspection standards for this ANYWHERE. ugh....
RE: Visual Inspection of Bent Sheet Metal?
What drawing (or otherwise contractually stated) requirement is it that you want to visually inspect?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Visual Inspection of Bent Sheet Metal?
I have walked into a nightmare. Trust me, I know how ridiculous this all is.
RE: Visual Inspection of Bent Sheet Metal?
One type of anodize, I want to say chromic, will accentuate certain types of defects but I forget the details and it doesn't sound like an option for you as you are welding after forming.
However about requiring the visual inspection be conducted under a certain magnification or similar, while still quite subjective I've seen this kind of thing done before e.g.
INTERNAL SURFACE OF ALL BEND RADII SHALL BE VISUALLY INSPECTED UNDER 2X MAGNIFICATION IN WELL LIT AREA. ANY VISIBLE CRACKS SHALL BE CAUSE FOR REJECTION.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Visual Inspection of Bent Sheet Metal?
You can't. You have to assume they're all cracked.
Does your end product function OK with completely cracked bends?
If not, you shouldn't ship squat until you find a new vendor, fix your documentation, and fire the MBAs.
Mike Halloran
Pembroke Pines, FL, USA
RE: Visual Inspection of Bent Sheet Metal?
And yes I agree that we have to assume they are all cracked because there is no control in place (vendor or company) that determined when the cracks were formed. Some were before welding, some may have been after shipment, some could've been in the field. Who knows!
RE: Visual Inspection of Bent Sheet Metal?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Visual Inspection of Bent Sheet Metal?
RE: Visual Inspection of Bent Sheet Metal?
Other than possible heat treatments like annealing or changing the grain direction on the part isn’t the real problem the design requires a radius that is not achievable on a regular basis in this material?
RE: Visual Inspection of Bent Sheet Metal?
From vendor: "we orientated the grain in such a way that it allowed us to fit as many pieces into one sheet".... haha
RE: Visual Inspection of Bent Sheet Metal?
1. Under 10x magnification, no more than 25% of any bend length shall be cracked.
2. From a distance of 18" no cracks shall be visible prior to paint.
3. No cracks permissible thru material.
"Art without engineering is dreaming; Engineering without art is calculating."
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RE: Visual Inspection of Bent Sheet Metal?
I realise it is a very grey area we are talking about here as minor cracks may not be acceptable and it could be argued that is a given but as there will always be some kind of cracking or at least thinning on any bend in sheet metal, it is a grey area.
If you changed the tolerance on a hole that then required a different process it would not be unreasonable to expect to pay more for the part. I don’t see this as much different.
Why not talk to the vendor and ask what would the cost implications be to solve this problem, it could be you only get 99 parts from a sheet not 100 with a very small cost increase to change the grain direction for example. There could be a very cheap and simple solution out there if both parties look for it.
If both parties just dig their heels in and think right I will show them who is boss, you will probably arrive at the situation where they think right they will now reject 50% of the parts so we will double the cost.
RE: Visual Inspection of Bent Sheet Metal?
KENAT - no, they didn't mention this type of quality control, hence the reason the company is in such a mess. I only hope it's a lesson learned for them.
ajack1 - no, you're not missing something. we have had phone conferences, which has driven the company to this temporary "solution". sometimes reasonable solutions DON'T get arrived at, at which time one of the two companies normally makes some type of corrective action in regard to the other company.
RE: Visual Inspection of Bent Sheet Metal?
Could be a recipe for lots more entry's in the accident log and higher use of band aids from the company first aid kit depending what you mean and how big the cracks are.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Visual Inspection of Bent Sheet Metal?
- specify a minimum inside radius
- specify a grain direction
- use a softer temper of material
- or combinations of the above,
... and that's it.
Sorting for cracks by visual inspection or by touch is not a common or accepted technique, which is why you can't find a standard for doing it.
Judging by the little you have revealed here, I can only infer that whatever drawing exists is utter crap. You might wish to start fixing that, just in case your company manages to survive this particular clusterf*ck.
Mike Halloran
Pembroke Pines, FL, USA
RE: Visual Inspection of Bent Sheet Metal?
I'm inheriting a bad situation and I'm trying to do what I can in order to mediate it.