Removing engravings

Help Support GroupDIY:

beatnik

Well-known member
Joined
Oct 18, 2009
Messages
953
Location
Dorset, UK
I have a few front panels that were poorly engraved. I would like to remove the engravings and get the panels re anodized. I was hoping to get everything under one roof, but so far the anodizing companies that I have found don't offer sanding.

What machine could be used for removing the engravings ? and what sort of surface preparation would be required for a smooth anodized finish ?

If you are familiar with this process and can share some tips that would be very helpful.
 

abbey road d enfer

Well-known member
Moderator
Joined
Jan 22, 2008
Messages
13,725
Location
Marcelland
What machine could be used for removing the engravings ?
A rotary brush is commonly used for that, but it will take much time to go deep enough. It may result in overheating, and deformation, if not done carefully.
and what sort of surface preparation would be required for a smooth anodized finish ?
It's almost impossible to revert from brushed to smooth. You can sand with increasing grade for a semi-smooth finish, though.
 

JohnRoberts

Well-known member
Staff member
Moderator
Joined
Nov 30, 2006
Messages
21,850
Location
Hickory, MS
If by engraving you are talking about patterns literally cut into the metal with the metal removed it is difficult to put that metal back. You can reduce the area surrounding the engraving down to the depth of the engraved text or legend. Alternately you might be able add aluminum back with heli arc welding, but I have never seen that done successfully. Another old machine shop trick is "knurling" where you impress a crissed-crossed pattern that squeezes metal up between the parts pushed down. I have seen this used on metal lathes to build up a round piece's diameter, unlikely to be useful in the flat.

This makes my response typical for the internet, full of information, but totally useless. :cool:

JR
 

beatnik

Well-known member
Joined
Oct 18, 2009
Messages
953
Location
Dorset, UK
I have done some research and it seems a linisher / belt sander would be the right tool to use.
A local community workshop has one but the belt is for woodworking and it's not suitable for aluminium.
If anybody knows a company in the UK that would offer this kind of service on a small batch of about 10x parts I would be glad to hear about it.
 

abbey road d enfer

Well-known member
Moderator
Joined
Jan 22, 2008
Messages
13,725
Location
Marcelland
Aluminium clogs common sandpaper. You need expensive silicon carbide sand paper.
Anyway it will not result in a smooth finish.
What kind of finish do you want? Paint or anodization? Sanding would be adequate for paint (powder) but not for anodization. Brush would be good for both.
 
Last edited:

beatnik

Well-known member
Joined
Oct 18, 2009
Messages
953
Location
Dorset, UK
I would like to re anodize with a smooth finish.

The engravings are milled rather than laser etched. I feel that the drill brush think might be good for removing the anodization, but to get deep enough to delete the engravings it will take ages and it risks creating an uneven surface.

I thought that using the belt sander to lower the panel 0.2mm and then subsequent fine grit sanding and polishing done with the rotary tool should bring back a smooth finish.
 

abbey road d enfer

Well-known member
Moderator
Joined
Jan 22, 2008
Messages
13,725
Location
Marcelland
I would like to re anodize with a smooth finish.

The engravings are milled rather than laser etched. I feel that the drill brush think might be good for removing the anodization, but to get deep enough to delete the engravings it will take ages and it risks creating an uneven surface.
I never suggested using a drill brush. Rather something similar to that

I thought that using the belt sander to lower the panel 0.2mm and then subsequent fine grit sanding and polishing done with the rotary tool should bring back a smooth finish.
You would spend a lot of time and money trying to get a flat finish, but you could finish with a sandblaster.
 

beatnik

Well-known member
Joined
Oct 18, 2009
Messages
953
Location
Dorset, UK
Right that machine should leave less marking than the linisher, it probably needs more time tough.

I will try finding a shop with that kind of machine. I think the anodizing company offers sand blasting as well, I will ask
 

lens42

Member
Joined
May 15, 2015
Messages
5
Get a machine shop or a hobby machinist to fly cut the surface down 0.01” or whatever is needed to get under the engraving. You should get a near mirror finish if done properly.
 

Disco Volante

Active member
Joined
Jun 20, 2021
Messages
32
Location
Sweden
Anodization creates a very hard surface coat of aluminium oxides. It is porous until boiled, therefore can be stained. It would not get near any of my cutting tools.
In my shop I sometimes have to redo an anodization, in which case I use a sandblaster to get rid of the anodized surface. There is some risk of deformation with sandblasting though, which can sometimes be alleviated by blasting both sides. After blasting, a belt sander or a mill "fly cut" would remove the engraving.
I believe there are chemical ways of removing anodization, but I have not tried any...
 

gyraf

Well-known member
Staff member
Moderator
Joined
Jun 4, 2004
Messages
10,480
Location
Aarhus, Denmark
from researchgate.net:

Crystalline Al2O3 at room temperature is hardly soluble in any solvent, even concentrated acid or alkali, for kinetic reasons. Only amorphous Al(OH)3 may be soluble. Al2O3 only reacts with as strong solvent as melted NaOH.

..so no chemical route really
 

Marik

Well-known member
Joined
Jun 3, 2004
Messages
1,649
Location
Salt Lake City
As already was mentioned, before fly cutting you will need to chemically remove anodizing. For such a small batch you will probably need to pay a minimum set up fee to anodizing facility and machine shop. Usually $60-$75. For both anodizing and fly cutting that would come to some $120-$150. I think that would be cheaper and take less effort just to remake the panels… from my experience it is much easier to make a new part than fix an old one.

On the other hand, if the facility, which screwed up your panels takes pride in their work, they should offer you reimbursing for damaged parts.
 
Top