# Etching Steel Using a 2.5 watt Diode Laser



## RJSakowski (Jan 23, 2019)

I recently purchased five pairs of 1-2-3 blocks. My intention was to use them for setups when machining.  They arrived last week and on first inspection, actually looked reasonably good.  I want to do more thorough metrology but thought that I should serialize them first.

A carbide scribe could do the job but the ridges that would result would have to be  removed.  My thinking turned to electrochemical etching. The process that I used was coating the work with a resist and scribing through the resist to expose the metal. A 14 volt power supply was connected positive to the work and negative to a Q Tip bud dipped in a saturated salt solution. The wet Q Tip is then gently rubbed over the work for about 30 seconds. 

I tried some test pieces and the etching was deep enough to be easily legible. The problem was that the surface exposed by the scribe was anything but art.  A better way of cutting the pattern in the resist was required.

The obvious choice was the Tormach CNC.  I could generate precision artwork and use the CNC to cut it into the resist.  A short time ago, I had gotten my 2.5w laser operational on the Tormach.  At the time, I had thought about using it for making printed circuit boards.  The laser isn't powerful enough to directly cut the copper  but if I coated the board with a resist, maybe I could expose the copper to chemically etch the pattern.  The idea was put on a back burner until yesterday when I thought using for the serial numbers.

I set the laser up and coated a piece of steel with some red nail polish.  I ran the laser at 3 ipm and 8 ipm (two of my jog shuttle's feed rates) and etched the resultant burns.  The laser had indeed exposed the steel and there were two clear etched lines.

Tormach's Path Pilot has a conversational program for engraving text.  It will create G code for any True Type font.  True Type fonts are all outlines rather than a single line but there are a few fonts around where the outline is reduced to a single line, which is what I wanted for my serial numbers.  The font that I chose was CamBam_Stick_2.ttf and I chose a .150" height.

The program is intended to be used with an engraving tool and had to be modified for use with the laser, namely adding code to turn the laser on at the start of a cut and off at the end of a cut.  I have set my CNC up to use the G code coolant control to turn the laser on and off by redirecting the coolant power to a relay which switches the power to the laser.

After running the code on a piece of scrap to determine that the program worked and the resulting etching was satisfactory, I put the nail polish resist on all twelve blocks.  I chose to mark the upper right corner of a 1-2 surface.  This will give me a consistent reference when I start measuring required the use of high powered lasers.  the blocks.  I the created the twelve G code programs and modified them for use with the laser.  I numbered the five pairs consecutively from 11 through 20  and my old blocks as 01 and 02.

Running the program took 1 minute for each block, including part change out.  I ran the etching for 30 seconds, wiping the salt solution off when completed followed by a rinsing wipe and acetone wipe to remove the nail polish.

The serial numbers turned out very well, looking like a professional marking. The entire process was simple and straightforward.  With the growing popularity of CNC routers and lasers, the available artwork is growing exponentially.  The combination of the laser resist etching and the electrolytic metal etching opens the possibility of high definition artwork on metal that had previously required the use of high powered lasers.




A 1-2-3 Block In CNC just finished.



10 blocks with resist etched, waiting for electrolytic etching





12 finished blocks





detailed view of etched blocks

The G code used to cut the "15" block is below.  Note that PathPilot set the structure up with variables ro permit making changes easier.  It makes reading the code more difficult though.

EDITED TO INCLUDE SAFETY PRECAUTIONS

EYE PROTECTION, PPE
 Whenever working with lasers, considerations for personal safety are paramount.  A 2.5 watt laser is capable of burning flesh so keep hands away from the focused beam.  Serious eye damage will occur if directly viewing the beam. Eye protection should always be worn while the beam is activated.  I have found that red safety glasses provide the best beam attenuation.  They are available on eBay for a modest cost.

USE PROPER VENTILATION
The electrolytic  etching process generates a small amount of chlorine gas.  This gas can cause serious lung damage if a sufficient quantity is inhaled. Think WWI trench warfare.  The amount of gas generated increases with an increased etched area.  Do the etching process outdoors or in a non-living space.  A welding hood will provide suitable ventilation.  Chlorine gas can also attack  exposed metal so if any significant amount of etching is being done, it shouldn't be done next your machines.


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## ttabbal (Jan 24, 2019)

Nice! I have a small laser on the CNC router for that sort of thing. Burning mask materials for etching or sandblasting. You do have to make sure it's laser/burning safe. The smoke from some materials can be toxic, but they do make known safe masks. 

It also does some interesting engraving projects on wood, leather and plastic.


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## JimDawson (Jan 24, 2019)

That is awesome!


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## RJSakowski (Jan 24, 2019)

I should have included two safety warnings in the OP.  

EYE PROTECTION, PPE
 Whenever working with lasers, considerations for personal safety are paramount.  A 2.5 watt laser is capable of burning flesh so keep hands away from the focused beam.  Serious eye damage will occur if directly viewing the beam. Eye protection should always be worn while the beam is activated.  I have found that red safety glasses provide the best beam attenuation.  They are available on eBay for a modest cost.

USE PROPER VENTILATION
The electrolytic  etching process generates a small amount of chlorine gas.  This gas can cause serious lung damage if a sufficient quantity is inhaled. Think WWI trench warfare.  The amount of gas generated increases with an increased etched area.  Do the etching process outdoors or in a non-living space.  A welding hood will provide suitable ventilation.  Chlorine gas can also attack  exposed metal so if any significant amount of etching is being done, it shouldn't be done next your machines.


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## mattthemuppet2 (Jan 24, 2019)

that is really impressive, well done! The etching looks professional and the possibilities are endless


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## Karl_T (Jan 24, 2019)

Impressive!

Could you recommend which laser to buy to replicate your work?


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## Boswell (Jan 24, 2019)

This is a fantastic capability. Thanks for the detailed information.   Just a note on lasers. The proper safety glasses depend on the type (Frequency/color) of the laser. Red glasses might be perfect for you laser but not appropriate for a different laser. I remember seeing somewhere online a listing of the proper glasses for the different laser types.


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## RJSakowski (Jan 24, 2019)

Boswell said:


> This is a fantastic capability. Thanks for the detailed information.   Just a note on lasers. The proper safety glasses depend on the type (Frequency/color) of the laser. Red glasses might be perfect for you laser but not appropriate for a different laser. I remember seeing somewhere online a listing of the proper glasses for the different laser types.


 This is good advice.  Here is a link to a chart for laser safety glasses.   https://www.lasermet.com/eyewear_detail.php?range=7  Optical densities for different wavelength rangess are given.

An optical density of 4 will reduce the intensity of a 2.5w laser beam by a factor of 10,000 or the equivalent of a .25mw laser.

Regardless, glasses or not, one should never look directly at any laser beam.


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## Boswell (Jan 24, 2019)

RJ is right, Never expect the glasses to save your sight. They are the last line of defense when something goes wrong like a reflection that redirects the beam to your eye etc.


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## RJSakowski (Jan 24, 2019)

Karl_T said:


> Impressive!
> 
> Could you recommend which laser to buy to replicate your work?


I purchased the laser from Bang good.  The laser that I bought is no longer available  but here are  a number if similar products.  My laser is a 2.5w 445nm blue laser with adjustable focus. I adjusted the beam for the shortest focal length.  This gives a smaller beam diameter and a higher intensity.
https://www.banggood.com/search/blue-laser-50000mw.html  At the time the 2.5 w laser was the highest power that they offered.  Were I to do it again, I would opt for a higher output.


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## Karl_T (Jan 25, 2019)

OK, got one on the way. Shall I muck up your thread with my build?


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## brino (Jan 15, 2020)

Now how the heck did I miss this thread?
I'm almost a year late to this party!
-brino


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## middle.road (Jan 15, 2020)

brino said:


> Now how the heck did I miss this thread?
> I'm almost a year late to this party!
> -brino


/me coming in right behind you...


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## Chewy (Jan 15, 2020)

Me Too!!  But this a very good answer to another thread I posted.


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## Boswell (Jan 15, 2020)

Don't forget to purchase the proper laser safety  glasses for the wavelength of the laser you purchase.  Eyes are hard to replace.


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## mcdanlj (Jan 15, 2020)

Adam Haile of Maniacal Labs posted a nice portable engraver design that is shielded and completely open source:









						New Open Source Laser Engraver Design
					

No question, just showing off      Been working for most of the year on a new laser engraver that I designed in collaboration with a friend who’s a woodworker. Unlike most of the diode engravers it’s designed to be small, lightweight, and portable so that it can be brought to the work piece...




					forum.makerforums.info


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## rwm (Jan 16, 2020)

Looks like they now have a 7watt laser available. At what energy would you be able to engrave the steel directly?
Robert
Edit:
To be scientifically correct- at what power would you be able to engrave directly?
R


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## RJSakowski (Jan 16, 2020)

rwm said:


> Looks like they now have a 7watt laser available. At what energy would you be able to engrave the steel directly?
> Robert
> Edit:
> To be scientifically correct- at what power would you be able to engrave directly?
> R


A great question.  My guess is that 7 watts isn't nearly enough.   I focused my laser to the smallest possible point to maximize the power density.  On 1 oz. copper pc board, it has no effect.  Of course, a lot depends on the wavelength of the laser as well.  From tidbits that I have seen, it is looking like around 50 - 100 watts, usually a fiber laser, to do the job.  I have also seen unconfirmed statements of 20 -30 watt lasers being used though.

The limiting factor is the rate of heat dispersal from the impact point.  It is possible to calculate that for any metal based on the thermal conductivity of that metal. Conductive heat transfer is proportional to temperature and in order to engrave, the laser has to be dumping energy into the impact point faster than heat is leaving. The resultant temperature increase will have to excceed the auto-oxidation temperature of the steel at a minimum which is around 1500ºC in air.


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## ttabbal (Jan 16, 2020)

I recently got a 60W CO2 and can't do much to metal directly. What I've read is that the fiber lasers can do it at about 30W, but CO2 needs in the 100W range. Either way, you're into it a good 3k for Chinese units. 

The diodes and CO2 work great for burning the dye off anodized parts, paint and powder coats.


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## rwm (Jan 17, 2020)

That 7 watt laser on Ali is claiming that it can etch stainless. I wonder how/why?
Robert


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## ttabbal (Jan 18, 2020)

Typical over-spec nonsense. I doubt it's even 7W output. Maybe input. Even my 60W CO2 is peak, 50W "real", running it at 60W will blow the tube quickly. It's just how they do it over there. You have to just know that if you are going to buy direct. 

You can mark on metal with various compounds, a diode could do that. Stuff like Cermark. It's stupid expensive though. Some people have had luck with dry moly lube, and a few other things. Those are more like powder coating than marking the metal directly. Some of them may have an etching reaction with the metal when combined with the heat from the laser. 

I have seen some recent claims that a 40W CO2 with an upgraded lens was able to mark stainless directly. I haven't seen it confirmed though. For all I know they burned an oxide layer or something.


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## coherent (Jan 18, 2020)

ttabbal said:


> I have seen some recent claims that a 40W CO2 with an upgraded lens was able to mark stainless directly. I haven't seen it confirmed though. For all I know they burned an oxide layer or something.



Cermark is a spray product that enables marking on most metals including stainless. Only problem is it's expensive. I have a 40 watt laser and an alternative to Cermark is using a spray dry moly lube. I had mixed but acceptable results with the dry moly on stainless. A little trial and error with amount and proper drying etc..  Never tried the Cermark due to the price and no real need.


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## homebrewed (Jan 22, 2020)

At work we had a Q-switched YAG laser system that was used to remove epoxy molding compound from integrated circuits.  Peak power was at least in the tens if not hundreds of kilowatt range, and it was barely able to directly write on stainless steel.  Not an apples-apples comparison to a CW laser (and different wavelength, 1064 vs 455nm) but it gives you an idea of what's needed to direct-write on steel.  One of the problems is that a large percentage of the incident beam is reflected.  Epoxy absorbs much more of the energy so it's readily ablated with the laser.  It also produces some really nasty byproducts so the system came with a charcoal filter + HEPA arrangement to protect personnel from the fumes.

You wanted to stop the process before getting down to the integrated circuits in the molded packages.  The laser beam would toast them in an instant.  We finished up the decapsulation process by putting a drop or two of fuming nitric acid in the cavity.  Surprisingly enough, the IC itself would be OK after being abused that way.  Most of the time anyway....


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## Janderso (Jan 22, 2020)

Incredible,
The world is passing me by.
I remember we used acid etched plates on the pad press for baseball printing back in the 80's.
Somehow the negative print only allowed the acid to etch the intended design?? The ink would fall in the etched print, the silicone pad would pick it up and over and down it went on the balls.
I don't remember how they did it. It was an outfit in Danvers MA. that set up the machines then they went to Haiti where I set them up for production.
Lasers on Hobby Machinists, very impressive sir.


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## rwm (Jan 22, 2020)

You know, I have one simple request. And that is to have sharks with frickin’ laser beams attached to their heads!  
Dr. E.


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## addertooth (Sep 13, 2020)

I work with solid state (and tunable dye) lasers too. I have a 40W 808 nm (infrared) behemoth and several less powerful lasers.  I will throw in something most people are not aware of.  The shorter the wavelength (the closer to UV and the further from Infrared), the more damage a laser does.  My lowly 7w 445 nm laser WILL cut through the spring from a ball point pen, IF G2 optics (narrow, very close, tight and low loss) is used.  But then, a small spring does not have a good way to dissipate heat.  I suspect a printed circuit board would shrug it off like a non-event.


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## vtcnc (Jul 28, 2021)

We have a 3kW fiber laser at work, Trumpf Tr if laser 2030. It can directly engrave stainless. But RJs quality of etch here is better quality marking in my opinion than direct engraving which is more like cross hatching on the laser.


Sent from my iPhone using Tapatalk


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## whitmore (Jan 9, 2022)

What no one has mentioned yet, is dry film  photoresist; you can get a double-sided sheet of gooey photoresist
in a clear wrap; pull off one (protective) side sheet, press the goo film against your clean surface, and apply
a warm roller, iron (maybe with a PTFE protective sheet so the iron doesn't stick), and/or bake the
photoresist on.

Then print your pattern onto a transparency negative (some of the coated laser-printer clear sheets work well)
apply the pattern over the spot to be etched, and shine UV lights (LEDs or fluorescent) on it.
The exposed (transparent) parts harden.  

Strip off the film from the top, and apply developer (it'll dissolve the protected bit, representing your
line art).   Then, a cotton swab and some ferric chloride will etch your letters in.   Remove the resist
by some brisk scrubbing.

Assuming you've got a laserprinter (inkjet ought to work, too) and not an X/Y laser, the extra work doesn't
seem too bad.   Near-UV LED modules in 3 to 10W sizes, and modest precautions (UV lenses like for
welding should protect your eyes) suffice for exposing the film.   Developer can be washing soda/water.
There's materials in the usual (Amazon, eBay, AliExpress) places, 'dry photosensitive' or 'dry photoresist'
will find it.

p.s. if you want crisp images, the  laser-print ink will be DOWN on the surface, so you want to print the
image mirror-reversed


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## RJSakowski (Jan 9, 2022)

whitmore said:


> What no one has mentioned yet, is dry film  photoresist; you can get a double-sided sheet of gooey photoresist
> in a clear wrap; pull off one (protective) side sheet, press the goo film against your clean surface, and apply
> a warm roller, iron (maybe with a PTFE protective sheet so the iron doesn't stick), and/or bake the
> photoresist on.
> ...





vtcnc said:


> We have a 3kW fiber laser at work, Trumpf Tr if laser 2030. It can directly engrave stainless. But RJs quality of etch here is better quality marking in my opinion than direct engraving which is more like cross hatching on the laser.
> 
> 
> Sent from my iPhone using Tapatalk


Photoresist is a good alternative for etching metal.  I used it in my business for 22 years to make printed circuit boards.  I started with Eastman Kodak KPR and KPR liquid resist, progressing to Kepro laminated circuit board using dry film resist.

Originally, my artwork was laid out  on transparent film which was used to make a negative photomask for exposing the photoresist.  With the advent of computers and printers, I could print photomasks directly on transparencies.  Another process that worked was to print on regular paper and bond the print side to the photoresist and gently wash the the paper away to leave the artwork in place.  For a time, there were special kits available from DigiKey which used a similar process.

For exposure, I made a light box using four fluorescent tubes with a timer.  For controlling exposure, I used a gray scale which had a range of different densities painted on a transparency.  I would expose to a particular level which would provide a proper resist mask. Lacking a light box, exposure to sunlight is a good way to get a uniform exposure.  The work is oriented so that it directly faces the sun which prevents undercutting astound the edges of the art. Some test pieces should be tried first to determine the correct length of exposure.  Obviously, you are limited to cloudless days.


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## addertooth (Jan 9, 2022)

I always found light sources which were most nearly a "point source" provided edges with the best definition.  This was important when doing small font on panel legends and 1mm traces on circuit boards.  I did it back in the day when you would apply your artwork to a clear mylar sheet, to do small production runs.  Later, I would use Programs by Orcad to do the artwork, print out a black and white copy, create a large negative, and overlay the negative on the board with Kodak KPR4 photoresist.  The per-use cost with the Kodak product was much cheaper than the applied resist film.  

I also used a photo-reactive silk screen coating.  For large production I would use that, with a resist which was silk-screened onto the surface for direct etch.  As I recall, the resist washed off with Xylene.   I really liked doing black anodized aluminum panels, which were etched with Sodium Hydroxide.  This gave really nice silvery-white marks/letters against the black anodized finish.  

In the really early days of making panels, I used a Gorton Pantomill to do marks and legends on panels.. but the fineness of details was driven by how fine of a rotary engraving tip you were using.


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## RJSakowski (Jan 9, 2022)

Xylene was the recommended developer for KPR and KPR3.  I was glad when the DFR laminated pc board came out as the developer was sodium carbonate and the stripper was sodium hydroxide.  No more obnoxious fumes.


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