Laser Etching on Stainless Steel Knobs - Quality Issue

[Hiccup]

Hi all,

I source some stainless steel knobs and have encountered a possible quality issue. A substance seems to be coming off. I perform an adhesion and rub test to test the quality of the etching and the last test I did, the substance came off on both tests, resulting in fading.

[FONT=&quot]1. [/FONT][FONT=&quot]Use a white cotton cloth soaked in water and rub printed logo 20 times. Repeat test using cloth soaked in alcohol. Look for damage to printing on logo.[/FONT]​

[FONT=&quot]2. [/FONT][FONT=&quot]Firmly stick 3M tape onto printed logo and then remove tape. Look for damage to printing on logo.[/FONT]​

[FONT=&quot]-Use 70% Isopropyl (rubbing alcohol).

[/FONT]The factory says the quality is fine (same as always) and that what is coming off is just residue that builds up during the process. Is this an accurate statement or is the quality of the etching not up to snuff? Is my quality test reasonable? The knobs have not failed this test before.

 

[Quality Practitioner]

Hi Hiccup,

I have seen this before, the residue is burned in carbon deposits from the process. As long as the information/text that is lasered onto the surface is still clear and legible and to specification text height etc I think this is fine.

Regards
Chris

 

[Jim Wynne]

Hi Hiccup,

I have seen this before, the residue is burned in carbon deposits from the process. As long as the information/text that is lasered onto the surface is still clear and legible and to specification text height etc I think this is fine.

Regards
Chris

Can you comment on Hiccup's test method? It seems that use of alcohol might not be a good thing.

 

[bobdoering]

I have used alcohol in the past to remove the loose burn products. It should have no effect on the laser mark. If the loose product are removed and the actual laser mark is light, then it needs adjusted.

 

[Jim Wynne]

I have used alcohol in the past to remove the loose burn products. It should have no effect on the laser mark. If the loose product are removed and the actual laser mark is light, then it needs adjusted.

I don't know why anyone would want to use an alcohol-rub test on laser etching to begin with. Sounds more like something to use on pad printing or silk screening.

 

[bobdoering]

I don't know why anyone would want to use an alcohol-rub test on laser etching to begin with. Sounds more like something to use on pad printing or silk screening.

It safely removes loose material and dries quick with no residue.

 

[Jim Wynne]

It safely removes loose material and dries quick with no residue.

That's cleaning, not rub testing.

 

[bobdoering]

That's cleaning, not rub testing.

Ends up being the same thing.

 

[Jim Wynne]

Ends up being the same thing.

Well, no. Rub testing with solvents is done on paint or ink (pad printing, e.g.) to test the durability and resistance of the applied material. There's no point in doing that to something that's engraved or etched. If the residue needs to be removed, a cleaning operation is needed, not a test method.

 

[bobdoering]

Well, no. Rub testing with solvents is done on paint or ink (pad printing, e.g.) to test the durability and resistance of the applied material. There's no point in doing that to something that's engraved or etched. If the residue needs to be removed, a cleaning operation is needed, not a test method.

With laser marking, you clean off any loose residue by rubbing it with alcohol, and determine if the remaining marking is legible. It is not a durability test, and the reason why it is a test and not a process is because in most cases the residue is left on the part, and the only issue is if it gets rubbed off will the underlying etch still be readable.