How Deep? Engraving Metal with a Laser

[Matt Geraci]

In general - How deep can one expect to engrave various metal parts with a fiber laser? Is a 20w good or 50w the way to go for detail and depth? 20w good and just engrave multiple runs on the same piece? Looking to engrave images into metal parts on guns and have detail and depth - I want "ridges" or a "tactile experience" when someone runs their fingers over my work.

Background: New here, but have been running a small business engraving with a sandblaster for 15 years now. Love the process, creative outlet doing one-of-a-kind stuff, still have my day job but have landed a few larger contracts the past few years that make this engraving stuff have potential to be the retirement/replacement gig. Decent customer base. Working out of my office and garage. I recently lost a contract to engrave some metal parts (for rifles). I get great detail and depth with my sandblaster setup - pride in detail AND depth that I can achieve in glass, rocks, and metals. But my costs were higher on this job as prep work and clean up to mass engrave these odd shaped parts are killers (1-man-shop). And keeping them clean and sand free requires meticulous prep and taping (Pain in the...) I lost this contract to a guy with a laser whose designs were rough etchings. He had to have a lower power CO2, just taking the top coating off the metal, poor quality (my opinion) but his price way lower than mine. SO... If I'm going to take the next step a laser may be the way to go, likely fiber. Doing my research, reading tons (great info here! Thank's y'all!), and trying to find a good company/laser setup. I think engraving metals is where i want to focus, so a fiber laser is what I'm looking at. 20W vs 50W, gantry-vs-galvo... Any answers to the first question would be appreciated, any input on expanding into lasers from sandblasting or other thoughts appreciated as well.

If I can't engrave deep with a laser I think I'll stick to my sandblasting, but I think there may be potential to expand?
Best wishes-
Matt

[Dave Sheldrake]

Hiya Matt,

Fiber gantry machines are in general higher powered cutters rather than engravers, for engraving a Galvo is the way to go (think 10 to 30 x faster than a gantry)

Depth...no real limit, what limits you is time, depth is a product of power/time/speed so say 10 passes with a galvo @ 20 watts can be matched by 5 passes at 40 watts (not quite the exact maths but close enough)

Going back to that time/speed calculation.....a 1 watt laser will eventually cut through 10 feet of hardened steel....eventually (think years or decades) a 145 gigawatt laser will fuse Hydrogen into Helium...everything else power wise is somewhere in between :)

Matty Knott is the go to chap around here for Fiber Galvos...while I have them they aren't really something I use very much but there are a lot of clever chaps here who have them and will be better equipped to answer :)

cheers

Dave

[Tim Bateson]

Here is a good chart - I'm sure different metals will vary - This looks like cast or aluminum.

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[Dan Hintz]

Here is a good chart - I'm sure different metals will vary - This looks like cast or aluminum.

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Unfortunately, that "chart" says nothing about how long it took to do each of those engravings. You could make the 20W look like the 40W with double the passes... but how long did the 20W take to do what it did in the first place? Also, without knowing the font size, you can't really say how deep the engraving on each example is... could be 5 mils, could be 50.

[Tim Bateson]

Unfortunately, that "chart" says nothing about how long it took to do each of those engravings. You could make the 20W look like the 40W with double the passes... but how long did the 20W take to do what it did in the first place? Also, without knowing the font size, you can't really say how deep the engraving on each example is... could be 5 mils, could be 50.

True this may not be a scientific example. However, I am assuming the same pass/mutiple passes were performed in each test. The chart to the right demonstrates the correlation between Wattage/Time/Depth. Until I see a more scientific/controlled test, this example works for me.

[greg lindsey]

I have a 30w Fusion Fibre and if you're wanting to raster to a specific depth you will be waiting some time, When I first got mine I thought it would engrave deep quickly, not so much. I found that vectoring would get you deep rather quickly, but of course it will be hairline widths. I can post some pics and a table later today. It's my belief that more wattage wont really get you any deeper in most cases, it will just make the run times faster (rastering) BTW, almost all of my runs are on 316 SS .037 to .060

[Gary Hair]

The two biggest factors in getting deep marking are 1 - Galvo or gantry and 2 - power
A gantry fiber is pretty much useless for deep engraving, you negate the potential of a fiber by forcing it to run like a typical co2 machine. As for power, the more the better - up to a point. I was told that the higher the power, the larger diameter the beam. So at some point you actually have more power density in a lower power machine than a higher power machine. I don't know what that point is, but I think it exists. I have a 30 watt galvo and can get the requisite .003 for firearm engraving pretty quickly. A typical name, city, state, etc., will take 5 minutes or less. I haven't tried anything much deeper than that, I don't have a need for it so I'm not going to experiment to find out what it takes. Having had my laser for over a year, I can tell you that I will go with a 50 watt next time, the time savings may be worth it in the long run. Unless you are cutting or going really deep, 30 or 50 watts should work out fine.

[Matt Geraci]

Thanks everyone for the great input. There's a lot to consider - various metal types, power versus beam diameter, lasing time. If I do delve into lasers the overarching theme I've heard from almost everyone is to go big when it comes to power. Out of curiosity, would a 50w CO2 do anything to metal?

Greg - would love to see some pictures of your work
Gary - what kind/brand of fiber galvo machine are you running? Love to see pics of your setup.

A 30-50w fiber galvo sounds where I'd need to be...? That being said looking at that chart posted, it looked like there was some scorching on the 40w and 50w examples. What kind of "collateral damage"/scorching occurs that one might have to polish out or clean up after a job on metals? All the sale brochures show these clean and pristine parts... but life isn't that easy... is it...???

Here are some examples of my sandblasting work into metal. Leaving stencils on after blasting allow some nice color fills.
Thanks everyone-
Matt

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PS --Dave -
...a 145 gigawatt laser will fuse Hydrogen into Helium...Dave- That's what I want! Right there! 145 GW!! :)

[Matt Geraci]

Tim- I see you've got an Epilog M2 Fusion 50/30 on order. Would love to hear your thoughts on your research and decision to go with that machine and feedback when you get it set up. That sounds like a great unit and something that's on my radar, as space is always at a premium. But I'm a little skeptical of "dual-use" products though. Waiting on a video from Epilog.

[Rich Harman]

I was told that the higher the power, the larger diameter the beam. So at some point you actually have more power density in a lower power machine than a higher power machine.

My understanding is that the larger the beam diameter, the smaller the spot size for any given focal length - so greater power density just from enlarging the beam (like when using a beam expander). Larger beam + higher power would double dip on that benefit.

[Dave Sheldrake]

My understanding is that the larger the beam diameter, the smaller the spot size for any given focal length

Yup, the spot on my 200 watt is smaller than the 180 watt as the input beam is bigger.

That's a lot of the problem with bigger tubes and engraving...the higher power density due to the bigger input beam ;)

[Gary Hair]

Out of curiosity, would a 50w CO2 do anything to metal?

Not without something like Cermark.


Gary - what kind/brand of fiber galvo machine are you running? Love to see pics of your setup.

It's a G Weike machine, just like the LF20 they show on their website but with 30 watts.


What kind of "collateral damage"/scorching occurs that one might have to polish out or clean up after a job on metals? All the sale brochures show these clean and pristine parts... but life isn't that easy... is it...???

It really depends on your settings. You can use lots of power, low frequency, low speed, and alternating hatch angles, and hog out metal fast, then adjust the hatch, frequency and speed to clean up the results. You won't have perfection, but close enough for 99% of the work you'll encounter.

[Gary Hair]

My understanding is that the larger the beam diameter, the smaller the spot size for any given focal length - so greater power density just from enlarging the beam (like when using a beam expander). Larger beam + higher power would double dip on that benefit.

I don't believe that applies to fiber, just co2.

[Rich Harman]

I don't believe that applies to fiber, just co2.

I think it applies to all forms of electromagnetic radiation.

[Dave Sheldrake]

I think it applies to all forms of electromagnetic radiation.

Yup it does indeed :) both ends of the visible spectrum below UV and above IR even to the X Ray range when building explosive lenses for thermonuclear weapon implosion systems.

[matthew knott]

I was just using a 50 watt fiber today for deep engraving, its pretty tasty, In simple terms most pulsed fiber lasers (the ones you guys will be looking at for engraving anyway) are around 1mJoule, doesnt matter if its a 20,30, or 50 watt. What this means is the maximum pulse on all the lasers is the same, the way power comes into effect is as follows
20w laser gives 1mJ @ 20khz
30w laser gives 1mJ @ 30khz
50w laser gives 1mJ @ 50khz

So what does this mean, well running a 20 watt at 2.5 times slower will give exactly the same results as a 50 watt, on our 20 watts we normally use a speed of 200mm/second for deep engraving, we can now run at 500mm/second and get the same result.
(this all assumes the M2 values of the lasers are the same, and they tend to get worse as the power goes up)
I would like to get a higher mJoule laser as for deep engraving this makes a big difference but cost is an issue.

Just as important is getting the correct focus lens, the shorter the lens the higher the power density, but also you get a smaller working area so its a trade off, i would recommend a 163mm lens as its a good all-rounder and will do a 120x120mm square.
Prices are coming down all the time and galvo machines are great value when compared to only a few years ago, but beware spending lots of money wont necessarily get you a better machine (just a more expensive one)

[matthew knott]

I was just using a 50 watt fiber today for deep engraving, its pretty tasty, In simple terms most pulsed fiber lasers (the ones you guys will be looking at for engraving anyway) are around 1mJoule, doesnt matter if its a 20,30, or 50 watt. What this means is the maximum pulse on all the lasers is the same, the way power comes into effect is as follows
20w laser gives 1mJ @ 20khz
30w laser gives 1mJ @ 30khz
50w laser gives 1mJ @ 50khz

So what does this mean, well running a 20 watt at 2.5 times slower will give exactly the same results as a 50 watt, on our 20 watts we normally use a speed of 200mm/second for deep engraving, we can now run at 500mm/second and get the same result.
(this all assumes the M2 values of the lasers are the same, and they tend to get worse as the power goes up)
I would like to get a higher mJoule laser as for deep engraving this makes a big difference but cost is an issue.

Just as important is getting the correct focus lens, the shorter the lens the higher the power density, but also you get a smaller working area so its a trade off, i would recommend a 163mm lens as its a good all-rounder and will do a 120x120mm square.
Prices are coming down all the time and galvo machines are great value when compared to only a few years ago, but beware spending lots of money wont necessarily get you a better machine (just a more expensive one)

[Paul Phillips]

when building explosive lenses for thermonuclear weapon implosion systems.

Aha! I knew it! That's exactly what I suspected you do as (one) part of your top secret government side work Dave! ;)

[Matt Geraci]

So the hammers have the same power they just hit at a faster rate?