Aluminum bending after anodize 3

I have items made for me in Eastern Europe. One of my items uses an aluminum faceplate (about 1x2 inches) that is .5mm to .6 mm thick and 1050 alloy. The faceplate must be printed before final manufacturing. The printer wants to anodize the surface first before silk screening. After printing, the faceplate much be bent 90 degrees to form a right angle on one end.

Since anodize does form a ceramic coating will it cause the base metal to fracture or crack during the bending? If it cracks, is this only a local surface cosmetic issue, or is the metal compromised in strength? Printing after bending is not an option and the printer refuses so use any alloy other than 1050. I have been doing the bend operation for many years with no problems, but now the printing process is changing and the anodize step added.

Am I headed toward problems or can I get away with this?

BTW, the products are sold world wide into the model airplane hobby market.

Thanks for some expert advise. I have no clue.

 

[mfgenggear]

no do not bend after anodize,
do all process forming, machining prior to anodize & chem film.
yes asking for problems.

alternative would be to chem film only instead of anodize.
I have silk screened parts mark after chem film.

 

[swall]

The anodize will crack.The base alloy will not.So, corrosion resistance will be impaired in the bend because of the cracked anodize film. It is also possible that the anodize film cracks could initiate fatigue cracks in the base metal.

 

[mfgenggear]

anodize is 1/2 penetration & 1/2 build up.
so cracking the parent material is possible.

depending on what type of anodize, "hard or sulfuric or chromic". the pentration & build up will be more from
hard anodize(.0016-.0024")

may be anodize printing might be an option.

 

[berkshire]

As you bend the material you will get hundreds of micro cracks along the bend line. Whilst the corrosion resistance will be impaired, most model aircraft do not operate in corrosion inducing conditions unless the modeller is cloud flying, has a fuel leak over the part or is operating a float plane.
You may be better off going chem film only if your printer will do that, if not just go ahead and bend the part,any resultant corrosion will be along the bend line only.
B.E.

 

[berkshire]

I forgot to mention that since 1050 is an extremely ductile alloy you should not have any problems with cracks propagating through the bend, unless extreme vibration is present.
B.E.

 

[swall]

Mfgenggear--your description of anodize film build and film characteristics is not fully accurate, in that you are misconstruing a dimensional characteristic with the actual physical nature of the film. If the process produces .001" of anodize film, the dimensional build up is about half of that, or .0005". But, the film itself, .001" thick, is all aluminum oxide and there is a sharp demarcation between the anodize and the substrate. If the part is bent, the anodize will crack, acting just like stress coat, but the cracks will stop at the substrate.

 

[mfgenggear]

Swall

thanks for the constructive advice

my information originally came from Booklet from
Barry Avenue Plating many years ago.

booklet states 50% penetration 50% buildup.
I based this to be true because over the year of inspecting
fabricated aluminim sheet metal & machine parts before & after Anodize.

My apologies if I misconstude the physical nature.
however the statement is true about the penetration & buildup. from the physical change.
It's been a while since I have looked at some micro graphs
of the physical penetration of the Anodize.

But even thou it's not good practice to bend Anodize sheet metal & yes it could crack.

 

Thanks for all the advise. The environment has a lot of vibration from the engines running between 14,000 and 30,000 RPM but the part that is bent has no appreciable load on it. And, in general, the engine only runs for under a minute for each flight. The bent part is not structural.

The finish product is stored indoors and only sees water when the model is lost and if it rains then.

Cost is a major issue, and I do not have the luxury of exotic finishing work or printing after bending. I must print a sheet and then cut out the individual pieces prior to the mentioned bend. In the past I have made a sharp bend and never had a problem, but this was with non anodized parts. The anodize is there for only one reason - to let the ink from silk screen penetrate the surface and adhere. It is not there for environmental reasons.

So, is the consensus that I can do this?

 

[mfgenggear]

anodizing & then bend some samples,
then visualize the parts. ultimately you need to decide.

good luck

 

[swall]

Well, it's obviously bad metallurgical practice to bend anodized aluminum. But, bad practice in itself does not guarantee failure and cracked anodize in the situation you describe apparently does not threaten loss of life or limb, so you may not have a problem.

 

[mfgenggear]

I started in a sheet metal shop, as an apprentice
Inspector,shearing, bending, planishing, welding & so on

then as a apprentice machinist for a gear company
while I was going to college.

then assemble small projects like the shuttle, dc-10
atlas missle tanks

If any my guys ever asked me to bend anodize sheet metal
I would say no!!!
it's not standard manufacturing practice period.
but there is always a variance to the rule and that what make the world go round..
however being this is a model airplane and asthetics is not important ya give it a try.

 

I think I understand the situation. Not as clear cut as I would like and unfortunately, the most attractive path to me is not the best engineering practice. I was hoping for a "go do it" sort of advise.

I can also use 6082 alloy and not anodize at all, but the printing process is more costly and does not yield as good a visual appearance nor as durable. The print shop will not use 6082, or that would be my choice.

Or I can leave all printing off, but then my products look poor.

Thanks guys.

 

[berkshire]

timer guy,
In some sections of the sheet metal industry it is common practice to buy pre-anodised sheet aluminum in the softer grades and fabricate parts by shearing and bending. As previously stated the only detrimental effects will be some loss of corrosion resistance on the bend line.
You may also be able to buy your sheet pre anodised saving you another step 1050 is a pretty soft alloy as long as do not go over a strain hardening of H12.
As far as bending pre anodised material is concerned, you will see some cloudiness at the bend line but that is all.
I would suggest that you do a trial run.
B.E.

 

[mcgyvr]

timerguy,
You say the anodizing is only to allow the ink to adhere and not for corrosion protection at all. So use a different ink..plain and simple and skip the anodizing all together. Sounds like your printer is not that skilled or knowledgable about screen printing. There are plenty of screen inks that will adhere properly to aluminum without anodizing. We use Nazdar screen inks all the time and the 8900 or ADE series (better but its a 2 part mix which can be a slight hassle) will all work without issue if properly applied/dried.

 

Mcgyvr

The hitch to Nazdar 8900 may be the necessary precoat needed. What do you use? Because it is solvent based, is a new screen needed each time or can the screen be cleaned of the 8900 after a run?

 

Berkshire

Now it is looking like 1050 may be too soft. I know I said it was non structural, but the bend part does have a small spring sitting on it, and the spring seems to be taking the bend out. Trying to work with two suppliers 4000 miles away when English is a second language is a real hassle. It looks like we need to find a new silk screen house that is not locked into anodized 1050.

 

[mcgyvr]

Sorry meant Nazdar 59000 or ADE series. Memory is slowly fading.... they make screen cleaning chemicals for all their inks too. We use their SW37 universal screen wash. Just make sure your person who makes the screen uses emulsion for solvent based inks or the screen wash will take it right off. (water will remove the solvent emulsions)

 

Mcgyvr

Do you put this on over bare aluminum? Do you use any coating over it? Is the ink resistant to normal solvents after drying? I like to use an ultrasonic tank with detergent to clean my products after heavy use in the field. I also use Gunk Engine aerosol spray cleaner to remove deposits of oil and sometimes aerosol brake cleaner. Anything ring a bell as being a no no?

 

[berkshire]

Timerguy
Most commercial 1050 is supplied with a hardness of H14 or 1/4 hard, you can buy harder up to H18 depending on what your supplier has. If your spring is deflecting your part you may want to go up a notch on the hardness.
Are you supplying these parts to your printer or are they being made in eastern Europe,and then shipped back to you?
At the risk of prying, is this a cut off timer for a competition model?
B.E.