Engraving on circular Aluminium Alloy shaft with color and finish 1

[GauravD28]

Need help with a method to engrave some information which includes some color on a circular aluminium shaft of about .6" dia. The shaft also has a aluminium oxide coating. Currently we are gluing a decal with the information on the shaft but there are times when the glue wears off. I looked into laser engraving but not sure if we can apply color afterwards as it may wear off. Please suggest some ideas.

Gaurav
Mechanical Engineer - Design

 

[MikeHalloran]

The heat from the laser typically burns any pre-existing finish, which often provides enough contrast.
BUT... a shaft, in an aerospace context, is probably stressed, and probably subject to fatigue failure from stress concentration, which a laser pixel certainly is, so you need to get some other departments involved before you go substituting any kind of engraving for a decal. Hell, you could get in trouble for the extra weight of a coat of lacquer or a layer of clear adhesive tape over the decal.


Mike Halloran
Pembroke Pines, FL, USA

 

[GauravD28]

True. Is there a way we can do the finish after the laser engraving and applying the color. Also I was looking at UV printing techniques. Is it a viable option?

 

[MikeHalloran]

When you have something engraved in a traditional way, with a spinning cutter that looks vaguely like a tiny end mill or countersink, there remains a clearly defined cavity of consistent depth, that is fairly easy to fill with paint. Laser engraving leaves a tiny crater, or rather some neat arrays of very tiny craters. The craters don't have the sort of surface recommended for good paint adhesion, and I don't know of anyone who claims ability to do so.

UV can be used to hasten the cure of some kinds of paints and inks. I'm not familiar with it.
You could screen the image of the decal on, in ordinary ink, or in epoxy ink, with a clear over coat.

I'm guessing the aluminum oxide coating to which you refer is an anodized finish, which comprises electrochemically converting the actual surface of a very clean aluminum part to aluminum oxide. The oxide ends up microcracked, so there will be corrosion in the cracks unless a coat of sealer is applied. The sealer is often dyed some attractive color, both for cosmetic reasons, and to provide proof that the anodizing has been done and the sealant has been applied. There are some outfits that can reproduce graphics, like labels, in the sealer coat.

You cannot anodize over dirt, or sealant, or paint, or labels, or fingerprints.


Mike Halloran
Pembroke Pines, FL, USA

 

[GauravD28]

Thank you Mike. Shall look into screen printing options.

 

[WKTaylor]

Solid shaft or hollow shaft?
IF hollow what is the wall thickness?
How long is the shaft?
Shaft alloy/temper?
Is there an area already deliberately designated for markings?
What anodic coating [spec] are You applying?
Is shaft highly loaded in torque and/or bending and/or tension/compression?
Environmental exposure...?
Does it HAVE TO be permanently marked, IE: NOT just because of typical Part markings... but for serialization or other special data?
Is the shaft ground/turned to a very fine finish [16-uin RA... or better]?
Is the shaft peened?

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can b

 

[MikeHalloran]

About durability: A few years ago, I went to a big box pet store, and bought a black anodized aluminum dog tag, for my dog. For $12 or so, you get the blank tag and a barcoded paper. You put the tag in a self-standing, automated, laser engraving machine, scan the barcode to tell the machine its services have been paid for, and then you compose what you want to tag to say. Up to four lines of text, a limited selection of icons, both sides. You watch the laser burn the coating, and in a couple of minutes, out comes your personalized tag. It's been a couple of years, the tag is still attached to a very active dog, and all of the text is still easily visible.




Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

There are industrial ink jet printers that can apply epoxy based ink. This ink is very durable when fully cured, and the process will not damage the surface coating.

 

[WKTaylor]

OK...

Adding to tbuelna's comment regarding Part Marking [PM] with epoxy ink [ink-jet print, rubber-stamp, etc]...

In aerospace we often add a clear polyurethane [MIL-PRF-85285, MIL-PRF-81352 Ty III, etc] over-coat onto epoxy-ink [typical A-A-56032] PMs which form a fairly decent, and long-term, chemical and abrasion barrier.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can b

 

[GauravD28]

Thank you all. Looking into inkjet printing option with overcoat.