etching with laser

[jimbobk1]

We cut parts from steel sheet, from 1mm to 12mm thick. We would like to etch these parts with a part number, and have had some success. The problem is that some parts etch well and others don't, in the same sheet. Using a ~2kw laser (Bystronics). In some cases, the etched number just fades out over it's length. I'm using text from .125" to 1.0" high and the numbers are typically 8 characters in length, plus a post laser code, 1-3 characters in length. I'm beginning to think the problem is machine related and would like to correspond with other laser users.
Thanks.

"Outside of a dog, a book is a man's best friend. Inside a dog, it's too dark to read." - G. Marx

 

[MacGyverS2000]

YAG using fiber or galvo? CO2?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[jimbobk1]

CO2.
Some parts start out etching nicely for the first couple of characters, then we get burn thru, even in heavier gages (7ga). Some don't etch at all, some do very well.

"Outside of a dog, a book is a man's best friend. Inside a dog, it's too dark to read." - G. Marx

 

[Compositepro]

A surface coating will help make the surface of the part more uniformly absorptive of the laser energy. Apparently Cermark is a popular product for the application. From another thread:

macgyvers2000 (Electrical) 7 Feb 08 8:16

Cutting metal presents a problem for CO2 lasers due to the wavelength... non-organic stuff such as metal tends to reflect light in that range of the spectrum (copper is one of the worst). You can coat the metal with something called Cermark (there are a few others, but that's the most popular), which allows the energy to be absorbed, and it is washed off when you're done. Or you can go to something like a YAG laser with a wavelength of around 1um, readily absorbed by metals (but not nearly as much by organic matter like wood).

You're hitting the metal with such a small spot of intense heat for such a short period of time, it really doesn't have any time to conduct the heat away... you are practically flash cutting the stuff, vaporizing a small divot out of it. Other items, such as wood or plastics, often require blowing forced air at the cutting spot to prevent (or at least mitigate) catching the material on fire. Metals often worked great with oxygen air-assist, whereas wood is just fine with shop air (for thick cuts, nitrogen can be used to prevent charring).

 

[itsmoked]

"CO2.
Some parts start out etching nicely for the first couple of characters, then we get burn thru, even in heavier gages (7ga). Some don't etch at all, some do very well. "

If you have no air you could be laying down a fine soot that alters the energy absorption as you progress.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com