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topic 45834

How to print onto open-pore Anodized Aluminum



A discussion started in 2007 & continuing through 2017

(2007)

Q. Hello, This is Chaithanya from Bangalore, India.

We are printing on open pore anodised unsealed aluminium for applications such as name plates. Soon after printing we seal the pores in nickel acetate solution.

The open pore anodised unsealed plates are being purchased from a sub-contractor and now with increasing demands and also complaints on quality, we have decided to set up a plant of our own. We feel that having the plant in house would help us with better quality , various options in finish and delivery time with respect to our application.

I would like to know from you the type of anodizing required for our printing application and books you recommend us to read and understand. Also since I can travel , would like to know if there are any training programs conducted on this subject.

Thanks

Chaithanya Aanand
Printer - Bangalore, India


(2007)

A. You are making a lot of assumptions in thinking that you can do it better than the vendor. That presupposes that your vendor is not much good. Try another vendor first while you do the homework for setting it up in house. Far too many people think that the process is a "just dip it" which is far from the truth. For books, take a look at the gotta have it books in the library at this site.
Do not forget that you need a laboratory for maintaining control of the tanks.

James Watts
- Navarre, Florida



(2007)

Q. I've seen anodized aluminum with a pattern that looks like a print of dollar bills scattered all over the floor. Any ideas on the process?

Tyler Anderson
hobbyist - North Branch, Minnesota, United States


Surface Treatment & Finishing of Aluminium and Its Alloys
Wernick, Pinner & Sheasby



probert book
Aluminum How-To

by Robert Probert
$89 New
The Chromating - Anodizing - Hardcoating Handbook

(2007)

A. Hi, Tyler. The general idea involved in coloring or printing onto aluminum is that anodizing the aluminum builds sort of a honeycomb pattern on the aluminum surface, with billions of tiny "drill holes" extending into the anodized layer that can absorb dyes; after exposing this honeycomb to dyes or inks which are absorbed into the drill holes, the aluminum is put into boiling hot water or other agents which swells the aluminum oxide and "seals" it, closing off the tops of the holes.

Thus, aluminum is often colored by dipping into a vat of dye after anodizing and before sealing. Or lettering is put on aluminum by silk screening it with inks after anodizing and before sealing.
----

When it comes to more complicated patterns, "splash anodizing" is common. Exactly how it is done by different companies is usually still trade secret info, but may involve masking before dyeing, and/or overpainting. However, this process probably applies mostly to one-of-a-kind patterns, like fades, rather than intricate repeatable patterns.

When we look at a repeatable intricate pattern, like dollar bills, you have to start thinking to yourself that the manufacturer probably started by printing that pattern onto paper and then transferring it to the parts. Two ways of doing such a transfer are "sublimation printing" and "water transfer printing".

In sublimation printing onto anodized aluminum (although I can't pretend to have seen it done or to know the trade secrets involved in doing it well), the pattern is printed onto paper with inks that turn to gasses when heated. The paper is pressed against the aluminum, heated to cause the dyes to sublimate, absorbed into the anodized pores, then sealed.

In water transfer printing, the pattern floats off from the paper onto the surface of a tank of water, sort of like a stretchable decal. the part is dipped into the water and pulled up through it, and the "decal" wraps around it. Again, although I've seen this done on metals in general as sort of a paint, whether it works as an absorbable dye into the anodized film is not something I actually know. Good luck.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



August 13, 2012

Q. I represent a medical company that manufactures not only implants and tools, but the casing in which they are shipped, stored, and re-cleaned in. Typically, we manufacture the cases from 5051 aluminum, and the bulk of our printing occurs on this material.

However, we have recently begun considering bringing both the silk screen and deep image anodizing in-house, due to disappointment with our various suppliers.

I have done extensive research on both processes, finding myself time and again directed to this plethora of knowledge along my journey.

However, I have some more questions, and a thirst for advice, on a few topics.

1: Dye Sublimation to Aluminum - Any recommendations in regards to preparation and process would be greatly appreciated. As of right now, we do not have the fullest understanding of all options before us. Our current working theory is anodize, die sub, seal. However, the actual substrate process is hazy at best.

2: UV Inks and Curing for our Silk Screen Process - The Lead Supervisor does not take well to the idea of a conveyor fed oven or curing station, citing the space requirements. So far, UV Ink seems the most economic and space-efficient method, but I'd like to hear more options. Suggestions for saving space and cost are a very large hinge point for this particular project. Has anyone had any luck with LED Cure Lamps so far? Or should the process be formed around Mercury Arc Lamps still?

Thanks for your input, and forgive my lack of formal understanding.

Zane Unverzagt
Medical Manufacturing Employee - Fort Wayne, Indiana, USA


August 13, 2012

A. Hi Zane.

Although I have a good understanding of anodizing, I think you know a lot more about these imaging processes than I do. Maybe thinking out loud to bring myself up to speed will help bring others up to speed, especially if you correct me where my thinking is wrong.

Dry ice goes directly from solid to carbon dioxide, and that is a well known example of sublimation -- the process of a material going directly from solid phase to gas without the intermediate step of liquid phase. Sublimation printing, as I understand it, starts with printing an image onto paper with an inkjet printer, but using special sublimation inks in the cartridges rather than conventional inks. When the paper with the image is sandwiched with another item and heated, the ink sublimates, which transfers the image to the T-shirt, coffee cup, or whatever. I have not seen sublimation printing on aluminum, but I suppose that after anodizing and before sealing, the aluminum is sandwiched with an image printed onto paper, and heated so the image sublimates into the anodized aluminum pores, which are then sealed.

This seems to me like it would be an ideal process for high resolution graphics or multi-color printing, but it wouldn't seem to be as simple, quick, and inexpensive as silk screening or other older technologies for simple black lettering.

Something to recognize about anodizing is that it is an EPA categorically regulated metal finishing process -- CFR 433 (Code of Federal Regulations). That doesn't mean you can't do it in house, but metal finishing was the first operation that most large manufacturers like automobile and appliance manufacturers outsourced, and not without reason. It is frankly a pain to operate these wet process lines with their acids & alkalies, exhaust & fume scrubbing, wastewater treatment, and hazardous waste accumulation headaches if you can outsource it to anodizing jobshops. But I understand that you may not be able to. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



Anodizing digital images onto complex 3D aluminum parts

December 22, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I've seen parts on the internet that are anodized and then have a digital image somehow printed into them. I don't understand how this could be done on some more complex three dimensional parts.

Anybody know how this is done?

Nick Barsalou
Hobbyist - Rexburg, Idaho, USA


February 2015

A. Hi Nick. We appended your inquiry to a related thread. Depending on how complex the three dimensional shape is, I'd bet that the pattern is transferred to the aluminum either by sublimation printing or water transfer. Look at "water transfer printing" on youtube and see if it looks promising for what you are envisioning. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


August 3, 2015

A. Why not directly print onto the anodized aluminum using a normal inkjet printer that has a CD / DVD printing tray, assuming the parts are small enough? Just tape the part to the tray and print as normal. Any high-quality, waterproof, fade-resistant ink should work.

Note that the anodizing must be unsealed, so the pores are still open and can absorb ink. After printing (and the ink dries fully), submerge the part in boiling water to seal the pores.

Michael Noble
- Adelaide, SA, Australia



Problem with sublimation coating on aluminum

August 6, 2016

Q. Hello
My name is Mayank soni. I am from India. We are doing sublimation print on aluminium sheets. We have a problem which is, after transferring the image onto aluminium sublimation sheet, then after 2 or 3 months that Image is split automatically. We don't know how this is happening; all we are doing sublimation ink and in transferring print. Please advise me for this problem if someone knows.

Thanks, regards,

Mayank soni
- India [ Mumbai]


August 2016

? Hi Mayank. Sorry but I am not understanding what you mean by "image is split automatically". Can you try some additional words? Are you working with anodized but unsealed aluminum, or have you coated the aluminum with a polyester coating, or what? Thanks.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



July 3, 2017

Q. Can someone get me a direction for printing on aluminum. Printing on Aluminum should be open-pore anodized and then the oxide layer is closed in a sealing salt bath. Aluminum anodizing should print in all colors and biocompatible. This anodizing print should be scratch-proof, solvent resistant, thermally stable and weather resistant.

SATISH BOKADE
Adler Mediequip. - Pune, Maharashtra, India


July 2017

A. Hi Satish. The whole process can't be described in a short response, but you may wish to start with our Intro to Anodizing Aluminum, and then move on to the two previously mentioned anodizing books. After you have an understanding of the overall process, it will be easier to visualize what people are talking about regarding dyeing while the pores are open, then sealing in the dye. You can have as many colors as you want, but each will need a vat of that color dye and one or more rinse stations, or a silk screen printing station. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



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