A Watt, is a Watt, is a Watt. No?

[Patrick Richard]

I don't know much about engraving, rotary or laser, and I hope someone can enlighten me.

I have a project that I was going to do with a flat bed fiber laser. Basically deep engraving into metal. As I learn more, it looks like a CNC engraver might be a better choice, at least for the moment. I've been told a number of time that a galvo YAG would be better than a flat bed fiber laser because it's faster and etches deeper.

What puzzles me is the fiber laser I was looking at (Epilog FiberMark) is 30W but apparently slow and would require multiple passes while a galvo like a Gravograph YAG 200 is apparently 12W (>25kW peak) but goes like stink. I get the speed; it looks like the beam moves like a plotter (vectors) instead of like an inkjet printer. Where I lose traction is that both type of laser are basically using the same wavelength, but the YAG etches deeper with less Watts. The 12W to 25kW is also quite confusing.Can somebody shine a light?

Finally, are galvo YAG lasers much more expensive, or less expensive, than the flat bed fiber lasers? I was told somewhere around $47K for the fiber laser.

Patrick

[Jason Roehl]

Not knowing much about laser engravers, my first question would be: how do the beam sizes compare? A beam size that is half the radius at the same power would be 4 times the energy per unit of area.

[Patrick Richard]

True, that might be a factor. 12W would feel like almost 50W.

[Ernie Balch]

Laser power is not a simple thing. The peak power is what removes material not the average power shown by a meter.

First there is average power, put a thermopile power meter in the beam and you can measure the average power by the temperature. That is fine for a simple CW (continuous wave) laser. If it is a pulsed laser you might only get a 30 nanoSecond pulse at some rep rate but the pulses have a high peak power.

For instance many diode pumped YAG lasers will work over a rep rate range of 5kHz to 30kHZ. You see this huge spikes of laser power that lasts 30 nSec about 5000 times per second so the average power might only be 5 or 10 W but the peak power is thousands of Watts. These high power pulses remove material more quickly.

Modern picosecond and femtosecond lasers typically have micowatts of average power but each pulse is so short that the peak power is immense.

All that being said the simple CO2 lasers we use are CW lasers that are just turned on and off.

Some fiber lasers are CW and some are pulsed.

[George Brown]

From what I read, galvos are much faster, but have a much smaller area where they can engrave due to beam angles.

[Bruce Boone]

The big thing is how the beam is stored up and fired all at once in pulses. This is called a Q switch, and vastly increases power. The pulses can peak out in the kilowatts although the average power is much less. Another huge consideration is wavelength. A CO2 laser has a long wavelength which is optimized for wood but not optimized for cutting metal. The industrial ones cut metal by brute force. They are usually 1500 watts on up, but they are continuous and not pulsed in the same way YAG lasers are. A CO2 metal cutting laser has a special beam outlet nozzle where pressurized air or other gas will assist the cut by pushing the molten metal out of the kerf. A YAG or fiber laser has a beam diameter on the range of 1/10th the diameter of a CO2 laser. The first time I saw a fiber laser demonstration, it knocked my socks off. And that was just 10 watts.

The short wavelength of a YAG or fiber is much more efficient in metal. My YAG literally won't even char wood though! They are made to ablate metal (vaporize it) so it takes a lot of power density to do that. Engravers usually have galvo heads because they are much quicker than carriages. It would still take multiple passes to do the work, but those are all done in the software, so you don't really see that. YAG and fiber watts should be pretty comparable to each other. On a galvo, the lens used makes a large difference in power density. You trade off engraving area for power density. There are industrial units that will do an entire computer keyboard at once in about a second. I use an extremely short focusing 100mm lens to keep the craziest highest power density I can find. The beam kerf is less than .001" as well. Engravers don't seem to get a whole lot more powerful. The problem is that the metal starts to simply turn molten and splash everywhere when you just increase the power. One answer to that is to make the pulses shorter. There are some lasers that have such a short pulse that there is no time to spread heat to the lasing substrate. You can engrave a logo into the head of a match without lighting it on fire with one of those. That's getting into uncharted territory and certainly beyond the scope of normal equipment.

Going up in power usually means that the laser will be optimized for cutting. I am now looking into a 400 to 500 watt fiber laser that will do cutting. It would have to have a cutting head with assist gas, so would be optimized for cutting and not engraving. I am checking into the possibility of doing both, which means continuous or pulsed operation, so obviously that doesn't come cheap because there are few places able to make a laser with such technology. I'm learning a lot as I explore what might be possible with the different technologies. Part of my main concern is an extremely clean kerf. With the beam width of these lasers being so thin, part of the conical beam tends to get blocked by the surrounding metal as the depth increases. The beam needs to be wobbled in order to be wide enough to allow enough energy to reach the bottom of the cut.

The price you found for the fiber seems about right. The price seems to go up almost exponentially with power. The first ones I looked into was LaserStar and Rofin, which bot have nicely engineered units.

[Patrick Richard]

Ernie,

Thanks a bunch for the primer; it's appreciated. The Gravograph YAG 200 is a pulsed diode laser so I guess that according to your explanation that explains the 12W with > 25kW peak. I can see how the peak power is what does the work, afterall 12W would barely raise the temperature after a long, long period of time.

[Patrick Richard]

George,

I heard the same but my "target" is in the 1.25" x 1.25" or 1" x 1.5" dimension range, so that is not a real limitation for me. The advantage I was seeing in flat bed lasers was that I could load a lot of material in the machine and let it do its magic. That assumption makes sense only if the machine is quick which apparrently it isn't.

If I get much increased speed from a galvo then I can manage to baby sit my production and do them one by one.

[Bruce Boone]

Yup. a watt is energy per unit of time. A joule per second. I have a welding YAG that with a single pulse will blast a hole right through a nickel. They rate those in joules because it depends so much on the pulse.

I have seen tag feeding equipment, where a laser can do a continuous line of them without having to stop to load them. It is important with a YAG or fiber to have it enclosed because the short infrared can be focused by your eyes. This means you would be blinded before you know the beam reflected off something. Such a feeding mechanism has to go through the enclosure without allowing light to escape.

[Patrick Richard]

Bruce,

Thanks again for being generous with your time. You state that the multiple passes are done in the software; is that equivalent to printing 10 times in a row to get 10 passes? Good tip on the focal length, my application could benefit from that; for example the YAG 200 is advertised to have a 2.6" x 2.6" sweet spot with the shortest focal length. That would suit me just fine.

I heard about the splattering problem. Actually the Epilog guy said brass would erupt depending on the parameters, forcing some experimentation on my part. I take it that short pulses would ablate/sublimate the metal while not raising the temperature; pretty good.

At what depth do you feel that you have to start wobbling the beam? From what I saw yesterday, you are going for better precidion that I wood. I'd be happy with a 0.005" space between features.

May I ask what brand YAG you use?

[Patrick Richard]

I know about the hasard to my eyesight; I'd be OK with opening/closing the hood for each tag. To me a nice production run is in the 30 a day range. If I did more that that I'd start having kids so I could spend the money sending them to college...

[Bruce Boone]

Usually, the beam would hatch in one direction, then go 90 degrees from that and hatch again. You would specify how many passes you want. It will do them one after another until you get the depth you want. Aluminum and silver will be easier to engrave than the titanium is. I've done some awesome laser able tags, where the thick coating gets burned off and the letters are a nice golden color. Not much depth, but it was crazy fast and extreme detail. When you get extreme depth, the power needs to be high, so the texture gets coarser. This is fine for some things, but not so good for others. I wobble when I'm trying to get the random black background you saw in the koi ring. You'll need to experiment with number of pulses per second and number of passes to get the results you are looking for. The pattern can be so fine that you see no lines at all. You won't get much depth that way though.

My laser is an 80 watt Sisma. I got it because it was the most powerful one I could find. It was over twice of the cost of the ones you were looking at though. I use it mainly for rotary stuff, but it can do small XY stuff too.

[Rodne Gold]

You want to buy a $50k+ laser for 30 dog tags a day? They THAT profitable?

[Patrick Richard]

Bruce,

Again, thanks for the info

[Patrick Richard]

Rodne,

Well, if I can pay less I will... Initially I'm going with a rotary engraver but if sales increase enough, a laser makes sense. We are not talking $3.95 tags here, nor are we talking about a $13.95 casting that get engraved. I'm suggesting a tag that can be made the specific way the owner of the dog wants.

I've seen products that sell very well, are basically metal "engraved" with a set of punches, and sell for more than my target price. People I've shown the prototypes to have all (no exception) said they want one. When I quoted the asking price, no one (no exception) even flinched. So I ran some numbers, established a break even point, and said what the heck, let's do this.

You have to factor in my very high resistance to risk. I'm a project manager in a consulting firm for pharmaceutical companies so large budgets don't phase me.

[Ross Moshinsky]

I think you'll be surprised how efficient a rotary engraver can be. Assuming 10 characters per line and a single line font, you should be able to crank out a tag every 20-30 seconds. Including programming, loading, unpacking, packing, cleaning, and darkening, I'd say you could crank out 60-100 per hour. I also think you should rethink your cutting depth. There is absolutely no reason to go down 1/32". We've engraved lots of brass and you can go down .006" and leave a mark that won't fade.

I do think you're going to have issues finding customers though. There are thousands of people doing dog tags in the world. I have no idea who you are polling, but assuming they are co-workers, friends, family, and colleagues; it's much easier for them to be positive about your idea than negative.

At the end of the day, you're looking at a $15-20,000 investment to get started, with about half going to a website and marketing.

[George Brown]

Patrick, even though you work with large budgets every day, their budget and your budget are two different things. My work budget is MUCH larger than my personal budget, it is much nicer to spend someone else's money than your own. And at times I have to stop and think, hey, this is coming out of MY money.

Also, I've found people are very willing to say they will buy something until they actually have to shell out the dough! Don't ask how I know. I would take their willingness to buy with a (large) grain of salt.

[Patrick Richard]

George,

I know that. It is easier for me to spend their budget; it is not for them. There are very good at sharing their stress...

I do understand that people say things to make others feel good and that it may (does) skew the calculations. That why I'm starting with a used rotary engraver. I do think that it is not a sustainable approach if the sales go up because of throughput. If I want this to be a business instead of a paying hobby, I have to be able to ramp up and still fit everything within a business day. Step two is get some time off somebody's fiber laser if it can do the job, even slowly or a second rotary engraver. Step three is my own galvo YAG, again if that does the job.

Believe me, no starry eyes here.

[Bruce Boone]

Sounds like a good plan. It's funny, but I take the opposite approach and don't really even try to do the numbers. They are all wild guesses anyway with lots of assumptions. I simply try to get a tool that has excess capability than I know what to do with. This will allow me to do things that I haven't yet even thought of, and allows me to grow into it. I really wasn't sure if a 6 digit laser could really be cost effective in what I do, but I decided to try anyway. As it turned out, it was worth the risk by simply allowing a lot of things that weren't possible before. It paid for itself in a few months. I'll really be going out on a limb for a cutting laser. I really can't foresee that pulling its weight any time soon, but its a tax writeoff, and I'll have capabilities that my competitors would not have. I've always known that I've wanted one. Exactly for what I don't really know yet. When you start thinking in terms of having such a tool, you realize that all kinds of doors that weren't open before can now be opened. For me, that means cut out rings in the style of my Mechanica Crescent Wrench ring, cutout Celtic Knot and puzzle type rings, and crazy combinations of inlays with meteorite and other stuff. It would also allow flat stock, like titanium pendants and similar parts that I don't even consider now. Combining laser cutting, engraving, and welding is something very few shops can do, especially on custom stuff. It's all about the niche. I've always run my business that way and it seems to have worked well for me. Other people's mileage may vary.

[Martin Boekers]

Bruce have you toyed with the idea of a plasma CNC cutter? That may be an interim step.

[Bruce Boone]

I don't think that could get the finish I'm after. I can actually cut through rings with the laser I have, but it's extremely inefficient at it. It whets my appetite for what's next. I had some sample cuts done by the company that makes the laser and it's everything I hoped for. Much cleaner than a CO2 laser or plasma cutter. Again, I'm not scared of the initial cost. I know that sooner or later it will have been worth it. If I wanted to, I could get into camping gear, my old line of bike stuff, rings and pendants, dog tags for pets and people, earrings, meteorite watch faces, etc, etc. It will need to be a very clean cut though.

Wire EDM is another one of those crazy tools that if you had one, it would open up all kinds of doors not possible now. If you've never heard of it, it uses a traveling wire and high voltage to spark away metal in an insulating liquid medium such as deionized water. It is painfully slow, but super accurate and can cut through anything that conducts. The sparks are something like 12,000 degrees, so it always jumps to the closest area in the metal and eats it away tiny sparks at a time. I'm having 10" meteorite slabs cleaved in half with it now, that will effectively double the yield of the horrendously expensive material. It could cut through solid carbide, so imagine the tools you could make with such a thing. I don't have room for one now, but who knows for the future. Again, it would be extremely hard to cost justify one, especially a new one, until it starts doing things that you could have never foreseen before. Another one of those answers looking for a question.

[Patrick Richard]

Ross,
I know that the tests I have done with a rotary engraver were sub optimal. We likely went deeper than necessary (0.030”) and slower than necessary. I’m not engraving fonts per se, more user customizable designs, and a lot of metal is being removed on both sides. My guesstimate, based on my tests, was around 45 minutes for one tag. Changing the depth to 0.015” or 0.010” and speeding up the tool should shave a bit of time. I still think we need two passes per side. I really need a picture to show what I have done up to now. The ones I have too much reflection to do justice to the product.

What I have in mind is very different than what is out there; while researching the product I searched far and wide and most tags are thin, diamond drag jobs. My dog goes through those in a month, a month and a half. The prototype has been on his collar for four months now with very little wear. Since it is brass it is slowly developing a patina.

The people I’ve shown the product to are not close to me, so they have less of a stake in pleasing me. They are however dog enthusiasts; some are into dressing up their dogs (I’m not), many will go for $150 collars and leashes, they take multiple obedience classes, and some compete. Definitively up market and low volume. I do not want to compete with the low price, novelty tags.

The $15K-$20K figure is about right if I was starting with brand new equipment. I actually am going to buy a demo unit from the Vision distributor so I expect a sweet deal. I do my own web site programming as I am a software geek and the artsy side is done by a friend.

At this point in time I would not make this my job, just a paying hobby. Time will tell.

[Patrick Richard]

Bruce,

I'm an engineer, so doing the numbers is an addiction... That is not to say that they are not WAGs?

I share your opinions; I guess it is the go big or go home approach. Try something, find something else. Also in my professional life I have never been hurt by going over capacity. If you try to cut it too close I find that needs outgrow the solution.

I find that people appreciate and will pay for special. If your product is a commodity you are fighting Wal-Mart. That is a painful perspective.

[Patrick Richard]

Martin,

I have toyed with the idea of the CNC plasma cutter. If production ramps up, it will become a bottleneck to cut the tags loose from the flat bar, ground the edges, and drill the hole.

When (and if) I go to a galvo YAG, I'll cut the tags and put the hole in with the plasma cutter, and then engrave.

[Patrick Richard]

Bruce,

Stay away from the dog tags...

[Bruce Boone]

Just sayin'. Any market has a high end sub niche that will pay more for something cool and custom. Fishing, RC cars, pets, cycling enthusiasts, hiking and climbing enthusiasts, pen people, model train people, campers, car people, beer drinkers, diving, boat people, etc, etc. Plenty of markets out there. The tough part is coming up with that cool unique thing.

[Patrick Richard]

Bruce,

You are right. I was just joking by the way.

[Dan Hintz]

Bruce and Ernie answered your original question quite well, so this time around I really have nothing to add... but I wanted to post to keep my tag on this thread :)

[Bruce Boone]

And I just love talking lasers! :)

[Patrick Richard]

Just so Bruce doesn't not get the last word in...

I checked the specs for two Gravograph models, the YAG 200 and the Fiber 200. The YAG 200 is 12W average and >25kW peak. The Fiber 200 is 20W average and 12kW peak.

So, the YAG 200 delivers more energy than the Fiber 200 while having a lower nominal power. Thing are not equal after all...

[matthew knott]

Ahh but even this is misleading, the yag will give 25kw (peak) but at that level of peak power the frequency would be low, i would say around 4khz so i would guess that you would be getting around 5 watts of average power. the fibre can produce its peak power at a much higher frequency, again as a guess i would say 30khz, and at this frequency you will be very close to the 20 watt average.

Think of it like this both lasers are boxers
The fibre puches you pretty hard 30 times every minute!
The yag punches you twice as hard as the fibre but only 4 times a minute!

Add up all the energy of the punches over the minute and thats the average power.

Laser manufactuers always spec the power as high as they can get it, hence the tell you the maximum peak power (measured at one frequexny that suits) and the average power (measured at a totally different frequency again to give the highest reading).

My point is trying to but a laser of the spec sheet (unless you know exactly how to read it) is tricky. Real world samples everytime to be sure.
How much are the lasers costing you are looking at?

[Ross Moshinsky]

Don't buy from Gravograph.

If you do, don't say I didn't warn you.

[Patrick Richard]

Care to expand? You do have a lot of their stuff.

[Patrick Richard]

If I may ask, I want to engrave deep, lets say 0.020" into a slab of 6061 aluminum or c360 brass. What do you recommend? I'm looking for a system capable of doing this without having to wait forever. Some people say a galvo YAG would achieve my goal while a fiber laser would be slow.

[Dan Hintz]

If I may ask, I want to engrave deep, lets say 0.020" into a slab of 6061 aluminum or c360 brass. What do you recommend? I'm looking for a system capable of doing this without having to wait forever. Some people say a galvo YAG would achieve my goal while a fiber laser would be slow.
Let's separate a few things first...

Galvo (short for galvonometer) is a method of directing the laser's beam by bouncing it off of a moving dual-axis mirror. The advantage is the moving portion is very light and therefore quite fast... the disadvantage is the working area is usually pretty small (8-12" square, depending upon focal length) since the mirror itself doesn't move position, only aim. The other option is a flying head where the focal lens moves right above the area to be engraved... with the opposite advantages and disadvantages as the galvo.

So, neither of the two options will have an effect on the power of the laser. YAG versus Fiber is a whole other story.

[Patrick Richard]

Dan,

I kind of new that but it is still a nice resume. My target is quite small; typically smaller than 2" by 2". So as I see this, assuming both type of laser (YAG or fiber) have the power to do the job, either a flying optics laser that can be loaded up with lots of target and take its own sweet time or a galvo that does one piece at a time. Whichever is faster at doing a job is better.

In your opinion
- Can a fiber laser do what I want? Add any qualifiers you see fit.
- Can a YAG do want I want? Add any qualifiers you see fit.
- Is a flying optics laser faster at doing 72 parts (12" by 24" bed loaded with 2" by 2" parts) than a galvo?

[Scott Shepherd]

Patrick, any reason you're stuck on the laser? If you're talking about engraving around a diameter, you could do some incredible stuff with a CNC milling machine with a 4th axis. You could use some micro bits and do some awesome stuff. It would be deadly accurate and very high precision. They make rotary engravers look like junk.

I'm sure Bruce will comment as he's been through a lot of different things and I'm sure he's gone down that route, but I've used many of them for larger things that had extreme tolerances and their ability to do insane things is there.

[Ernie Balch]

Assuming you have equal laser power densities the speed of rastering or vectoring will be the same.... but the galvo easily will win because it can instantly jump from writing area to writing area thus saving huge amounts of time. Of course software for engraving will be optimized to take advantage of the great speed.

Thinking about max speed of engraving in a galvo system you should pair it with a higher power laser source, thus writing very fast and indexing fast between parts.

A conventional flying optic engraving system is much more massive and cannot move nearly as fast so you would not benefit as much from a higher power laser source.

ernie

[Patrick Richard]

Ernie,

Thanks,

I'm due to receive test results from Epilog on one of their FiberMark systems tomorrow. It'll guide my decision one way or another. If it can do the job then it'll be a question of throughput. I'll try to get a galvo manufacturer to run a similar test to make a final decision.

Anyway I decide to go the rotary engraver way at least at the beginning and possibly to graduate to laser sometime in the future.

[Ross Moshinsky]

Care to expand? You do have a lot of their stuff.

Customer service and technical support. Their software is also buggy and poorly written. Also their pricing model is VERY high.

No real complaints about the machine. The company that supports them on the other hand is horrific.

[Patrick Richard]

Ross,

Thanks for your input, appreciated