Laser Diode Engraving

[John Champlain]

For you hobbyists here, this is my latest engraving using my software. At 3 hours, I know it can't compete with commercial speeds, but I'm happy with it.
On Baltic Birch ply at .006" pixel resolution.

Regards
John Champlain

273717

[Dan Hintz]

How big is it?

[John Champlain]

Hi Dan,
It's 6" x 8" I really don't have the patience to tackle much larger, although my machine will do about 16" x 22".

http://youtu.be/LlDgTUm8Fi0

John

[Jeff Woodcock]

Very nice work John!

I sure do like your new option combining the analog modulation and variable feedrate processes within the same g-code file in your latest release. It definitely gives more control of the outcome which really makes the LD photo engravings stand out. :)

Jeff

[Dave Sheldrake]

Really nice piece of work, diodes are coming on in leaps and bounds, sooner or later somebody will devise a method of manufacture that allows using them directly at higher speeds.

cheers

Dave

[Joe Hillmann]

What is the reason for running the laserhead at an angle rather than across or up and down? Also what is the reason for setting up the laser vertically rather than horizontally?

[John Champlain]

Thanks Guys.

Dave,
Jeff actually has started using them at higher speeds already. He has a dual diode setup that is very ingenious, and which uses two diodes to combine into one beam.


Joe,
Engraved images seem to have a better contrast when run at a 45° angle. We are still testing why, but it appears mostly related to a decrease in ipm + the raster lines are slightly spaced closer together when on an angle for a given pixel resolution.

My machine is mounted at about a 18° degree to the vertical as a desk space saving feature only. My work area is very limited for the laser. Its actually on a back screened-in porch at my home (wife kicked me out of the garage :().
Regards All,
John

[Jeff Woodcock]

Dave,
Jeff actually has started using them at higher speeds already. He has a dual diode setup that is very ingenious, and which uses two diodes to combine into one beam.



This one was done @ 225 IPM with a .005" pixel resolution only using half power on Birch Ply. My limitations at this time are the mechanics of my servo CNC router. It's a linear rail, ball screw machine and there is allot of weight to move back and forth. My two 445nm laser diodes are in a V configuration that focus to the same intersecting point.

Jeff

[Dave Sheldrake]

How are you combining Jeff? PBS cube?

cheers

Dave

[Jeff Woodcock]

Dave,

There is no cube to combine the beams. Both diodes are mounted at a slight angle in a V configuration so the two beams intersect each other at the same focal point. Here is a picture of one of the heat sink half's. You can see I also have a third laser diode in the center that allows me to align up on the material.

Jeff

[Dave Sheldrake]

Ahhh,

If no cube then how do you overcome the phase stacking issue?

cheers

Dave

[John Champlain]

Dave,
Being a hobbyist, I am not conversant with laser theory or practice, but Jeff's method does not "combine" the laser beams in the normal sense of making one beam out of two or more. His laser beams remain separate until right at their focal points at the material surface. Would this explain why he does not have any apparent phase interference issues?

Thanks,
John

[Jeff Woodcock]

Dave,
Being a hobbyist, I am not conversant with laser theory or practice, but Jeff's method does not "combine" the laser beams in the normal sense of making one beam out of two or more. His laser beams remain separate until right at their focal points at the material surface. Would this explain why he does not have any apparent phase interference issues?

Thanks,
John

Thanks John.

Dave, what John said. :)

[Dave Sheldrake]

Hiya John,

Unless the beams are combined (from a physics standpoint) there will be little to no benefits of using two diodes.(In reality there are quite a few drawbacks that will increase losses rather than reduce them by having two focussed at the same point)

cheers

Dave

[Dave Sheldrake]

You could either go to two different wavelengths(say 405 and 650) and combine using a Dichro plate or stay with the same wavelength and use a PBS cube in reverse (although you would need a 90 degree shift on polarisation) (PBS cubes only allow combining once though whereas a Dichro would allow combining multiple beams of different wavelengths in a stack)
The problem with an angular attempt at combining beams is the phase spaces will overlap and cause interference and noise leading to much bigger spot sizes and lower power density.(The cancellation effect will also be much more pronounced)

The cancellation effect is used in industrial lasers to prevent damage to the optics from reflected beams so can in some cases pretty much wave any of the gains having two beams may provide.

cheers

Dave

ps: If did use the Dichro method remember you can only use wavelengths that are different in the full beam, ie: you cannot combine a 650 - 532 and then try adding another 532 at a second plate.

[John Champlain]

Thanks Dave,
We understand what you are saying and have been told that by others. We are not sure why Jeff's setup appears to work about twice as good as mine. We both use the same laser diodes, but Jeff is able to run at roughly twice the speed as I can with my single diode, Jeff being limited some by mechanical issues. Perhaps his two beams may be ever so slightly focused on different spots so there is no, or minimal, interaction. We really don't have test equipment to find out if this is the case or not.

We did find this article with a statement that we thought could have some bearing on it, but not sure.
http://www.sciencedaily.com/releases/2013/09/130925132323.htm

"The discovery, Lukin said, runs contrary to decades of accepted wisdom about the nature of light. Photons have long been described as massless particles which don't interact with each other -- shine two laser beams at each other, he said, and they simply pass through one another."

Of course, most (all?) of light/laser theory is so far over my head that I know better than to get into any deep discussion, else my ignorance will shine (pun intended :)). I'm just happy we are able to achieve some success in what we set out to do with laser diodes and hobby equipment/setups.

Best Regards, and Thanks,
John

[Dave Sheldrake]

Hiya John,

I'm familiar with Lukins paper and it is indeed very exciting but he is dealing with Photon binding in a medium (something that has long been suggested but never observed) based around the Particle-Wave duality theory (that likely has a rather shiny Nobel waiting for the person that can best demonstrate it outside of mathematical calculation).
The corner stone of Quantum Mechanics is that very duality. ("Light" (EMR) has the properties of both waves and particles with one end of the spectrum behaving more like waves and the other end behaving more like particles but neither loosing the other property all together)

The separate spot model would work and the likely easiest method to see the effect would be close examination of the material unless using a digital wavefront camera.

The reason I queried it was the lack of benefits benefits between using two non-combined lasers verses one single higher power diode in a different wavelength? 445's are getting much cheaper and 808's are very good prices with high power C-mounts really dropping in price now. The Axiz modules are good but a little bit of shaking when moving and those spots will be all over the place.

I do find the idea of direct diode marking interesting (and full credit for trying it out) but until there are significant advances in cooling and duty cycles as well as available power the benefits of twin diodes don't seem to be apparent.

best wishes

Dave

[Ed Newbold]

OK guys, you've got my attention. I've been using a ULS M-300 for about 10 years now, and haven't heard about laser diods. Can someone point me to some meaningful information so I can catch up and learn about constructing/using a laser diode system?

Thanks a million.

Ed in Columbus, OH

[John Champlain]

Ed,
I have some info available on my web site: I removed link so as to not violate forum policy - contact me direct - John

After you look at it please contact me off list.
Thanks,
John

[John Champlain]

Thanks Dave,
Much of laser theory is somewhat way over my head (which is obvious), so I do make some (?) mistakes as I muddle along. :)

As to duty cycle, I've not had any problems running 1 and 2 watt diodes at full amperage for two to 4 hours straight now for some modes of mirror engraving. Maybe I've just been lucky. I have destroyed three diodes in the past due to my mistakes in wiring them up, which gets expensive real quickly. Hopefully I have learned to avoid repeating those mistakes.

My Best,
John

[Dave Sheldrake]

Ed,

Think of a Lasing Diode as an LED that shoots out a laser beam of one colour rather than scattered light that is a combination of lots of colours.

John,

You will get clobbered by the mods for linking to a commercial site you have an invested interest in.

cheers

Dave

[Dave Sheldrake]

've not had any problems running 1 and 2 watt diodes at full amperage for two to 4 hours straight now for some modes of mirror engraving

That's great going for diodes John, I remember when Tweakie did his, then again Tweaks is a frighteningly clever chap.

cheers

Dave

[John Champlain]

Thanks Dave. Link removed.

Tweakie has been a big help to us. I regret not being able to pop in on him (due to distance) for a visit.
John

[Jeff Woodcock]

That's great going for diodes John, I remember when Tweakie did his, then again Tweaks is a frighteningly clever chap.

cheers

Dave

Dave,

Tweakie has never done anything like what we have with laser diodes, that I'm aware of.

Jeff

[John Champlain]

Engraved today. Same settings as the Gene Autry image.
John Champlain

273916

[Jeff Woodcock]

Very good job John!



Hiya John,


Unless the beams are combined (from a physics standpoint) there will be little to no benefits of using two diodes.(In reality there are quite a few drawbacks that will increase losses rather than reduce them by having two focussed at the same point)


cheers


Dave



The problem with an angular attempt at combining beams is the phase spaces will overlap and cause interference and noise leading to much bigger spot sizes and lower power density.(The cancellation effect will also be much more pronounced)


The cancellation effect is used in industrial lasers to prevent damage to the optics from reflected beams so can in some cases pretty much wave any of the gains having two beams may provide.


cheers


Dave


Dave,


I sure am not a physics expert, but I have decided to suggest this based on the experiment I did. It's my opinion, that theory needs to be thrown out the window! I know me and my son spent allot of time on focusing and aligning these two 445nm LD's when we set it up. We recently did a test to see if the two beams are actually slightly off from each other. What we did was lasered in one spot on black anodized aluminum at full power for 10 seconds and then scanned a .500" square @ 4800 DPI. I then imported it into my Cad program and made sure it was to scale. I zoomed in on the burnt spot and measured it and what we have discovered is, the beams are not burning at a slightly different spot which means there is no phase stacking issue or any interference occurring. The burnt spot measured .004" X .0045" which corresponds with the size of the burn line we have been getting when engraving.

John is using the same 2W 445nm laser diode with the same 3 element glass lens as we are and he is getting a .004" burn line also with it. We also determined that using the two LD's focused to the same spot, the burning power did not double, but actually quadrupled. We are able to engrave twice the feedrate as John and we only need to use half of the total power on the same type of material. I know this does not seem possible, but I can only say it has to do with heat, not phases. There is a big advantage of using two laser diodes focused to the same intersecting point after all. :cool:

Jeff

[Dave Sheldrake]

Hiya Jeff,


It's my opinion, that theory needs to be thrown out the window!

Ummm unless quite a bit of generally accepted Particle Physics has changed and the entire Quantum mechanics models change I have some doubts that the theory is wrong.


the beams are not burning at a slightly different spot which means there is no phase stacking issue or any interference occurring.

You can only measure this kind of thing with a DWC, going by spot sizes and a cad program is nowhere near accurate enough.*If* the beams are focussed on exactly the same spot you WILL be getting phase problems and interference.


I know this does not seem possible

As a function of two spots it's not possible.


but I can only say it has to do with heat

Laser beams have no specific heat as such, they induce molecular excitation in the target medium, that is what we measure as heat. So we go from light energy to heat energy. The ability to heat any given material is a property of the material and not the laser. To suggest a laser has a specific heat is like saying a moving rifle bullet that has kinetic energy also has an inherent temperature.


There is a big advantage of using two laser diodes focused to the same intersecting point after all

What you are claiming to have achieved is polarised multiplexing but without the use of either Dichroics (in the case of two diodes with different outputs) or a beam splitter (for diodes in the same wavelength).

What you are making is a basic causality error, because B *follows* A it does not mean B was *caused* by A.

cheers

Dave

[Dan Hintz]

the beams are not burning at a slightly different spot which means there is no phase stacking issue or any interference occurring. The burnt spot measured .004" X .0045" which corresponds with the size of the burn line we have been getting when engraving.
Focusing at the exact same spot with two separate beams that are not phase-locked essentially guarantees a lack of phase coherence... it's basic physics for waves.

On a side note, you're achieving CO2 levels of resolution (5 mils) with a light source capable of sub-fiber levels of resolution (<1 mil). You'd do significantly better if you used proper optics.


We also determined that using the two LD's focused to the same spot, the burning power did not double, but actually quadrupled.

Again, this goes against basic physics... even if we remove the coherency issue from the stage, soubling laser power does not equal quadruple power at the focal point.

Before you go making bold statements like you have made in this thread and your prior one when you first tried to introduce us all to your "better method", you need to understand the basic physics you seem to be ignoring.

[Dave Sheldrake]

Hi Jeff,


I sure am not a physics expert, but I have decided to suggest this based on the experiment I did. It's my opinion, that theory needs to be thrown out the window!

Brian Dunning calls this "Appeal to lack of authority" and "Proof by anecdote" and goes on to say the following.


Appeal to Lack of AuthorityAuthority has a reputation for being corrupt and inflexible, and this stereotype has been leveraged by some who assert that their own lack of authority somehow makes them a better authority.

Starling might say of the 9/11 attacks: "Every reputable structural engineer understands how fire caused the Twin Towers to collapse."
Bombo can reply: "I'm not an expert in engineering or anything, I'm just a regular guy asking questions."
Starling: "We should listen to what the people who know what they're talking about have to say."
Bombo: "Someone needs to stand up to these experts."
The idea that not knowing what you're talking about somehow makes you heroic or more reliable is incorrect. More likely, your lack of expertise simply makes you wrong.
Proof by AnecdoteMany people believe that their own experience trumps scientific evidence, and that merely relating that experience is sufficient to prove a given claim.

Starling: "Every scientific test of magical energy bracelets shows that they have no effect whatsoever."
Bombo: "But they work for me, therefore I know for a fact they're valid and that science is wrong."
Is Bombo's analysis of his own experience wrong? If it disagrees with well-performed controlled testing, then yes, he is wrong. Personal experiences are subject to influences, biases, preconceived notions, random variances, and are uncontrolled. Relating an anecdotal experience proves nothing.

B Dunning - Skeptoid.com (Logical Fallacies)

cheers

Dave

[Jeff Woodcock]

Focusing at the exact same spot with two separate beams that are not phase-locked essentially guarantees a lack of phase coherence... it's basic physics for waves.


On a side note, you're achieving CO2 levels of resolution (5 mils) with a light source capable of sub-fiber levels of resolution (<1 mil). You'd do significantly better if you used proper optics.






Again, this goes against basic physics... even if we remove the coherency issue from the stage, soubling laser power does not equal quadruple power at the focal point.


Before you go making bold statements like you have made in this thread and your prior one when you first tried to introduce us all to your "better method", you need to understand the basic physics you seem to be ignoring.


Thanks Dan,


The lens that we are using is the best that is available (cost wise) that gives us a small enough spot for our analog modulation line engravings. I'm happy with the results we are achieving with it.

Thank you Dave,

Who in the heck is Brian Dunning? Oh, wait a minute, who cares?

Jeff

[Rodne Gold]

I have reservations on the utility of such machines , as what they achieve in 3 hours , I can do so in 10 minutes or less and do without lasers in an even shorter time.
Essentially they are reinventing the wheel , their machine is a laser on a XY table , as are all of ours.

I don't see the commercial advertising aspect in their posts tho

[Jeff Woodcock]

But as my favorite band Rush once sung, "You can change perceptions, but reality will not budge."

Wasn't there lyrics LSD induced and why they were considered an Acid Rock Band? I believe they were referring to an Acid trip when they sung those lyrics. I'm curious, why would that be your favorite band??

[Dave Sheldrake]

I don't see the commercial advertising aspect in their posts tho

Simple way to advertise Rod, post about a "development" of an all "New" system on a forum that has thousands of users.

If say Mike Null or Scotty Shepperd had posted, "Hey guys have you seen this idea?" with a link to the pictures or web site then that would be one thing, but ramping up statements about the validity of a product anybody has a financial interest in by the person with a financial interest bears scrutiny.

If people had read such by Mike or Scott and then followed on to buy the item, Mike and Scott would not benefit financially or physically (their only perceived benefit would be a few people saying "nice find" or "cheers guys we bought one of those") but when the person making claims about the wonders of a product is the one getting paid to provide it (when nobody else does) it's questionable as to the motives behind it.

Thankfully most people do read into things these days before buying and should be able to see that any suggested benefits of a twin diode system is flawed from the very start and all they will be getting (as you rightly say) is something most of us already have that is already 10 x faster.

cheers

Dave

[Dan Hintz]

I decided to send my comment directly...

Rodney, your PM box is full

[Jeff Woodcock]

Thanks Dave,

I have done another test with my Coherent brand laser power meter in the past where I de-focused the beams slightly and shot them at the thermopile sensor and got a reading of 10W output. When I did this with my single 1W diode laser engraver, I got 1W, so I feel it's fairly accurate. I have no way to check calibration on this unit unless I send it out to someone that offers that service. I just can not imagine it being off 6W on this meter in the 0-10W range when this meter is rated up to 100W. I could take pictures of this, but what good would it do me when I will just be accused of fabricating the outcome or you will say there is errors in that test also. Since this is just a Hobby, investing in a DWC would be a waist of money. Even if I did have one, no one would believe the outcome of it anyway.

You know when I come up with an idea, I don't start searching the internet trying to find out who claims or why it will not work, I just try my best to make it work. This build has exceeded my expectations and I will leave it at that.

Jeff

[Keith Outten]

I have removed several posts in this thread because either the intent or the direction they were taking violates our Number One Rule.....Thou Shall Be Friendly.

I will also leave the following as a reminder of our policy concerning signatures:

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.

[Dave Sheldrake]

Hi Jeff,


I just can not imagine it being off 6W on this meter in the 0-10W range when this meter is rated up to 100W.

It's unlikely to be off more than 0.5 watts to be honest, they do suffer from creep but not by much. To get 10 watts from 2 x 1watt diodes though suggests something is very wrong. What mode is the sensor working in?
If two diodes are radiating 1 watt of energy each then you would expect to get just under 2 watts on the Pile (there are some losses to take into account so 2 watts total is unlikely) but to get an over unity of a factor of 5 suggests something is going tilt somewhere. I'm not familiar with the Coherant system or how they measure but if I fire 2 x 250mW 532's at a thermo I get some funky readings as well.


Since this is just a Hobby, investing in a DWC would be a waist of money.

It's astounding how much information a DWC provides, any kind of beam combining almost requires them to be used for experimentation.If the opportunity comes along to get one I'd highly recommend it, they will pay you back ten-fold in time alone.


I just try my best to make it work.

Admirable sentiments, commitment to purpose above all things often yields results. All I'd suggest is getting something on paper to support any claims, it's useful for others and can often lead to developments that aren't apparent in the initial idea.

best wishes

Dave

[Jeff Woodcock]

Hi Dave,

The Diodes we are using is a 1.6W Nichia NDB7875, but we are pushing them with higher amps then the max ratings. A good heat sink is key when doing this. Max amps on these are 1.7 and we are running them @ 2.1A max each which should be landing us in the 4W+ range total and that is why I said it was 6W off. The 1W one I referenced is our first single 445nm diode build on our mini router engraver that we tested with the meter.

I'm not sure what you mean by mode, but here is the meter we have.

Jeff

[Dave Sheldrake]

Hi Jeff,

Nice diodes (Nichia are amazing) there are some legacy issues with multiple non-combined beams being shot at some meters, I just tried 2 x 250mW 532's and got over 4 watts as a read out. I'm looking into why at the moment but have a feeling it will be to do with time/energy calculations between the head and the meter. If possible and you have one to hand, can you fire a third diode at the head at roughly the same spot and see if the readout gets even more funky?

cheers

Dave

[Jeff Woodcock]

Dave,

This is what I determined. The Range switch for changing it from 1W-3W-10W-100W is flaky. When we did this test before (months ago) we set the range to 3 for the 1W diode and it read 1W. When we tested the two Nichia's, we set the range to 10W and when we projected the two beams it jumped to 10W.

This time, I set the Range to 3 and I have two Aixiz 1W 445nm lasers and no matter if the two beams were overlapping or not, it read 2W. I then set the Range to 10W and projected the two Nichia's at a farther distance then the focal point so it would not burn the thermopile, it jumped to 10W. I then fiddled with the knob for the Range and it dropped down to 4.5W and stayed there. The switch has an intermittent problem with it, so my initial test we did months ago did have an error.

Even though the initial meter test did have an error, we have done over 200hrs engraving time since with this setup to still stand behind that it does have 8 times the burning power as our 1W machine based on feedrates and power settings on Birch Ply. Our 1W engraver can only raster engrave at 50IPM at full power, but the dual Nichia can raster engrave at 225IPM+ @ half power. 4.5W should be in the 225IPM range @ full power if the difference was linear. One thing to consider also, we were able to get the focal point down to .004". That's .003" smaller then our 1W machine. Theoretically the burning power should be more intense because of this, so that may be the contributing factor in the difference.

Jeff

[Dave Sheldrake]

Hi Jeff,


down to .004". That's .003" smaller then our 1W machine.

That will make a huge difference to power density


Theoretically the burning power should be more intense because of this, so that may be the contributing factor in the difference.

That could be the principle reason for the difference,

1 SqCM is 100 SqMM's

1 watt / 0.007" (0.1178mm) gives an area of 0.0248 SqMM's, 100 / 0.0248 * 1 watt gives a PD of 4,032 Watts per SqCM

Now moving to a single 1.6 watt Nichia on a spot size of 0.004" we get

1.6 watts / 0.004" (0.1016mm) gives an area of 0.0081 SqMM's, 100 / 0.0081 * 1.6 watts gives a PD of 19,753 watts per SqCM

So it follows that power radiated over area would be 5 times more using one diode (there are some loss calculations to include but for clarity they don't really matter at this point) even when radiating at 1.6watts, get that up to 2 watts and the numbers jump again by a pretty large amount. (100 / 0.0081 * 2 = 24,691 watts per SqCM) or roughly 6 times as much ERP / area.

Granted you don't actually have 25kW's available but the differences are for illustration (given that increasing the spot size also had an equivalent increase in ERP when going up to 1 SqCM etc)

Some other factors will affect it like focal distance (focussed laser beams have a depth of field) and the reflective index of the material as well as a few other considerations I'm not surprised that a 2 watt diode with a much smaller spot can engrave at 6+ times the speed of a 1 watt with a larger spot. This in part, is much of the reason Western made machines like Trotech , Epilog etc can achieve more with 25 watts of power from an RF source (very high beam quality and stability) than a Chinese DC glass tube can achieve with 60 watts +.

What would demonstrate the differences in a more visible way would be vector cutting a thin material (Paper?) with a single diode compared to twin diodes. When cutting the power / time differences will show up much more noticeably. Engraving is a 2D effect (you are only working on N depth) but in cutting you have the third axis that has a yield point that can be calculated for power requirement / time.


burning power

Yup, defined as induced energy / time. I'd maybe suggest looking at better optics to achieve a smaller spot size (Edmund Optics or maybe Thor Labs) and you will likely find much more benefit than adding a second non-combined beam to the mix.

cheers

Dave