RDWorks Learning Lab 99 Beam Combiners Investigated
Vložit
- čas přidán 28. 03. 2017
- If you own a Chinese laser cutter this little series of videos about me learning how to use the free software provided, may solve the problem of trying to learn from a virtually unreadable manual.
I am nothing to do with RD Works, I am not an instructor and I am no expert. This series will document the essential bits of many hours of trial and error
Beam combiner • Visible LASER --- SPT ... - Věda a technologie
Great work, a good example of logical, experimental and professional.
Appreciate your time and explanation. I found your conversation style and methodology refreshing as it is complete. My learning journey is for a laser autocollimator for which most of the information applies.
Great video, thanks heaps. I bought a beam combiner and was stumped how to set it up and this video helped heaps in understanding. I managed to get the LED dot about 0.1mm away from the real location the laser hits - pretty darn happy with that, all thanks to this videos lessons
I love your channel. I'm learning so much about my own laser
Russ I love how your brain operates.
Nice work ! do you have the drawing in corel draw format so I can laser cut this rig? the one I bought on eBay doesnt fit my machine, and I dont want to cut it.
Thank you !
Hi
I investigated this subject but I have never fitted one to my machine. Great idea in theory, nothing but pain in practice. There are only two reasons you would want a visible simulation of your beam path.
a) you want a through-the-nozzle red dot pointer
b) you want to make beam alignment easier.
The biggest issue for me is the power loss that results from fitting this element in the beam path. You can typically expect to lose 3 or 4% power at each mirror and about 5% across the lens. These are ESSENTIAL elements and are already consuming 17% of your precious power Figures I recently acquired show about 8% loss for a combiner window.. That's 25% overall loss!!!! You don't need much power for engraving but if you are CUTTING, then you need all the power you can get
You must ask yourself
a) whether a coaxial red dot pointer is worth 8% power loss when there are other ways of doing it for free
czcams.com/video/3WO97D591js/video.html
czcams.com/video/Jm8syz6ARCY/video.html
czcams.com/video/30y6VTjG_t8/video.html
czcams.com/video/r4GfdS4GDqs/video.html
b) Can you justify a continuous 8% power loss for beam alignment reasons when this is a function you rarely carry out. I have tried many ways to simulate a TRUE beam path with my many attempts at a temporary red dot pointer. I stopped at Mk 7 because although all attempts were 95% ok, I still had to go back and carry out the scorch method to gain perfect alignment. With a beam combiner you have to set it up for that perfection and with the two beam combiners I have played with, I failed miserably. The only good news is that you don't need absolute perfection for the through-the-lens red dot.
One more issue to consider is lens material. My experimental work comparing lens shapes and materials shows the most efficient cutting lens will be gallium asenide. Gallium arsenide is opaque to visible light and will therefore block your red beam
So, there are many issues to weigh up before you commit to a beam combiner. For me the negatives far outweigh the positives. I REALLY thought I needed a red dot pointer (the external type) when I bought my first machine. I now have two machines and both pointers are removed. The dream was better than the reality.
My drawings are in DXF format and are structured for me to make a prototype. They do not include the mandatory heat sink block to catch the 8% reflected power so to that extent they are not a complete set of drawings. I was not using a CO2 laser for my testing so I did not need the heat sink. Attach your email to a comment and I'll send you what drawings I have and you can use them as a starting point for your project............if you still want to go ahead that is.
Best wishes
Russ
Kudos for sticking with it to the end. When I watched the original US trip video I could imagine how your failure to get the beams lined up irked you and the effort you would be putting in to solving the problem. Well done.
The SPT T laser looks interesting, I wonder what kind of cost it adds to the laser tube? ... I'll just go and have a quick search ..... Well it features heavily on their FaceBook page but not on their website. I have mailed an enquiry to them.
It's expensive.. mostly shipping. $603.99 shipped to the US for a 40W tube with 880mm length. The shipping costs $50 more than the tube.
BTW, this green LED laser you are using.. I read somewhere on the net, that there are no green laser LEDs around. Instead, infrared LEDs are used with a special lens or prysm that changes wave length to green light. I wonder if this little trick could be used with a CO2 tube to aid with alignment?
Here (quote): The 808nm infrared light from the laser diode is used to pump a Neodymium doped Yttrium Orthvanadate or Nd:YVO4 crystal which produces light with a wavelength of 1064nm.
The 1064nm wavelength light is then frequency doubled through a Potassium Titanium Oxide Phosphate (KTiOPO4) or KTP crystal. By doubling the laser frequency, you cut the laser wavelength in half producing a 532nm green laser light.
you are amazing thx for all your efforts
One term I came across while I was looking at this was a certain magical angle where beam loss through reflection was minimised called 'brewster angle'. For ZnSe, that angle is 67.4º. However, this may also selectively affect the polarisation of the beam. I don't understand (yet?) how these two things might happen, but it is somehting to keep in mind. However, since all the big boys do beam combining at 45deg and you are much closer to that brewster angle, it will probably not matter much...
Hi Jelle
I'm suspecting that this applies to RAW ZnSe which is about 30% reflective ie its only 70% efficient as a lens. They manage to raise this in normal lenses to about 95or 96% with an anti reflective coating. In HQ lenses they get a bit more (about 98%). It seem feasible that this Brewster angle is all to do with minimizing the reflection off the crystal structure. The beam combiner window looks remarkably just like a flat lens ie it may have a anti reflection coating on the surfaces for 10.6 micron IR but that same coating seems as though it's accidentally reflective to visible light. I've got to dig and experiment a bit more to see just how much energy gets reflected. Thanks for the information.
Best regards
Russ
How do I know what side a or b is on a beam combiner lense?
I am sorry if my annotation has confused you. I called them a and b so that I could talk clearly about the positions of the beams on a designated face . In reality both faces are equally transparent to IR but at the same time the coating on both surfaces is partially reflective to visible light. As you have seen from this video ,some visible light does pass through but there is sufficient reflected to allow it's use as a visible beam path replicator.. The biggest problem is finding a simple way to get perfect axial coincidence with the laser beam. Conventional beam aligners are a pig to set perfectly. I have been close but never succeded. As with all things that you put in the beam path, you can expect to lose between 3 and 5% power. I personally have always been rather cynical about the benefits. When I bought my machine I felt it HAD to have a red dot pointer. In reality it's an unnecessary feature that I soon removed from both my machines.
All best wishes
Russ
I really think you would have a hard time knitting a parachute out of wool that could take the stress of opening at speed.
is there a way that a red dot laser could be mounted on mirror 3 pointing straight down ?
Sadly no. I have thought long and hard about this subject, The red beam MUST be in line with the laser beam. If you punch a hole through mirror 3 it will take away the very reflective spot that the beam needs. The only way to make this happen is to mechanically introduce a red dot when the beam is not firing. Such a device existed mmanyyears ago but never found wide accetance. See
czcams.com/video/0gABmmm_aJo/video.html
I've been thinking about this. What if you used the beam combiner lens/mirror in the laser head.... as mirror 3. Then mount the red dot on top of the head pointing straight down?
Hi Jack
In my search for a red dot pointer I kept coming back to the possibility of using mirror 3 in some way, Sadly your idea will not work because the ZnSe combiner element is NOT a mirror for the 10.6micron laser beam, it passes through unhindered (except a 5 to 8% loss of power). It is only the much shorter wavelength red light that reflects off the surface.. Thus it cannot be used to replace mirror 3 . However the thought process is to be commended. I have often toyed with the idea of mounting a combiner about 10 or 12mm below mirror 3. My open lightweight head has made this a possibility but my counter argument always asks if the minimal convenience of a red dot is worth the 5 to 8% power loss.? The idea is not dead just a very low priority for when I run out of useful things to explore.
Best wishes
Russ
@@SarbarMultimedia Ahhhh..... well the thinking continues! I fear that if we run out of 'useful things to explore' it will be the non useful things that will get us. :-) Appreciate the input and your extensive work!
You might have a look at this video... he claims 1% loss - czcams.com/video/iO43PF3TZ_4/video.html
@@jackroberts8432
Hi Jack
Skepticism is entwined with my DNA. I am skeptical of almost everything, even my own results if they don't meet some common sense criteria I hope this shows through in the way I do my exploration. I stress often that my videos are not teaching material but most are exploration into things I do not know and that my methods are for my own benefit. I dont hide my failures and mistakes because that is naturally all part of the learning process. I show my method in boring detail so that if others wish to try for themselves (and maybe arrive at different answers) there is a point they can start from.It great that CZcams allows me to share that learning. I have done a lot of testing of mirrors and lenses (on and off screen) and in general everything has shown typically a 3% loss. Some lense 5% and some mirrors 6% I have tested two combiner systems from different sources (but probably the same reflective window) and both were showing 4% loss. Results from other of my correspondent in various parts of the world have maxed out at 8%. Obviously I cannot validate that extreme but it was tested with my dohicky power meter just before and just after the combiner. Even if the guy was getting incorrect power readings the RELATIVE difference expressed as a percentage is unlikely to be much in error.
Thanks again for your interest and as I said before this is not a completely dead subject even though I'm not enthusiastic, it's an interesting design challenge that others may wish to exploit.
Best wishes
Russ
I have a beam combiner (Edmond Scientific) at the laser head, and works well. I have a small adjustment and can get it right on. It has been working for 3 years without issues. The red beam only goes through the head not the whole machine. Less problems with the shorter distance. I just relocated the red pointer that was at the bottom of the laser head that aimed at an angle.
Hi Rich
I like your little fix. Much less hassle. However most people want to use the beam to set mirrors. For such a requirement the red beam must perfectly match the laser beam. The unit I was presented with was carefully described by Light Object as suitable for DIY project. Certainly not a piece of pro kit.
Thanks for sharing
Best regards
Russ
Rich Johnson I like this idea. I rather use it to locate my work area not to align the mirrors personally. Anyway we can communicate to get pictures of this setup.
This seems very close, but will be become a believer once I see it in a live machine (btw, your link at the end should have a bit to where you can click and goto the website..assume its the head mounted laser combiner video).
I hate keychains.
-Rob
Link says video unavailable
Will you sell your improvement ? Please
Did you say blissful plane?
Russ, you mention that the side mounted laser pointer is useless. I have to disagree as I've found two fantastic uses for it - well, one use which can check 2 different things. What I use it for is to determine if there is warping in 3mm ply that is outside the range that I get a full cut on the material or if I'm at the correct engrave distance for my lens. As it points at the board at the same angle, I can also use it to determine if my bed (blades) are parallel to my axis. As a production machine it also helps me set up repeat nesting patterns always running front-to back. I often use the passthrough feature with oversized stock so physical shifts are a necessity.
Hi Chris
This is obviously not a side mounted laser pointer but an attempt at creating a coaxial red beam for mirror setting.
From my point of view the little red pointer provided was noting but a pain. It was no a pinpoint dot but a blindingly bright red spot about 2.5mm diameter that left spots on my eye after studying it for a few seconds. it was so bright that I could not accurately line anything better than 1mm. Did I need it.? I soon discovered that because my nozzles are so close to the work (about 5mm gap) I could eyball to the same accuracy or better. If I need to VERY accurately line up cuts I use the pulse button to tell me EXACTLY where the beam will hit ( an example of this use is here czcams.com/video/3hFNAFb8uhA/video.html
No red pointer in the world would be accurate enough to do this spot on.
There are two pointer liear arrays the produce a cross haiir that are better but there is a very good alternative that does work well from Peter Jensen
see www.ebay.co.uk/itm/Laser-Cutter-red-dot-through-the-lens-position-indicator/192450569439?hash=item2ccef2a4df:g:CDkAAOSwbw1aHbn7
and
czcams.com/video/30y6VTjG_t8/video.html
Best wishes
Russ
I see your point - I'll check out the links as well. I'd like to send you a photo of what I mentioned before with plywood and pulses. I just took a photo of a failed piece - plywood warped upwards, dissipating the beam a little. at 45mm/s I counted 11 puncture holes regularly spaced across a straight line both across the grain and at about 60 degrees. 49.5Hz my friend! Is it PWM, mains droop, Air assist?
Hi Christopher
Check your you tube messages for my email. Always intersted.
Best wishes
Russ
good explanation! i bought the left type on the picture at the beginning. its crap. you will never get this adjusted - as you explained very good! but the main problem is the wobbly and unstable housing of the chinese laser machines. while i was trying to adjust the mirrors and combiner lense i noticed a hugh shaking or „dancing“ of the beam around the previous adjusted point while moving the laser head on the y axis. so, if the red pilot laser beam is dancing around the co2 beam will do the same. so the power at the focus point will always change or lost while movement of the head - crap! now i understand why good laser machines cost eur 15.000 and more....
Hi
At the time of doing this video I had no data about the power loss that using this unit incurred. I have since corresponded with several people who bought them already fitted to their bigger machines If you look at the solid black anodized plate on the left of these pictures, that is a heatsink/protective shield to absorb the reflected energy. In two cases, the factory fitted combiner was mounted the wrong way round right adjacent to the tube but with the red pointer sited to the rear of the tube and pointing out of the rear cover. In itself this is inconvenient for adjustment but not terrible. The serious, almost criminal act, was to remove the heat sink. This resulted in the beam (from a 150 watt tube) reflecting some of its energy at whatever/whoever was behind the machine at that point. One correspondent measured the power loss across the device as 6%. Another guy could not understand why his wall 5 foot behind the machine had a scorch mark on it!!!! The Chinese only build these machines, I'm convinced they do not understand the technology involved.
Best wishes
Russ
Thanks for all the info! No idea how frustrated I'd be with my little K40 machine without being able to look over your shoulder occasionally.Your laser tube fixture inspired me to design my own. I included a beam combiner but now that I see the problems it can create, I'll likely leave it off. The solution I'm working on now is to shoot the pointer up through the laser head and hit a target on the front of the tube. The problem there is that you have to remove the lens each time. But, compared to aligning an invisible heat beam, that's less risky, I suppose.Keep up the good work!
Hi
Several people have suggested the same thing and I point out that the AXIS of the laser beam coming out of the laser is the important aspect that your method does not take into account. You may have set up a beam path through all the mirrors but you now have to mess with the tube alignment to set the beam onto the path you have just set up. Good luck with that task.
Best regards
Russ
came across this :
blog.gafu.de/?p=1579
instead of moving the lens, this guy moves the laser with servo motor! Blew my mind!
I think beam combiner are not only for alignment but also a safety factor to see that the mirrors positions are not messed up due to a knock on the machine or something like that....
Hi Pete
It sounds like you may have one on your machine and are making an excuse to keep it. I have two machines and unless I go out of my wat to change a tube or upgrade parts I never need to touch the mirrors Even a gentle clean maybe once a year will not disturb them. A quick blip on the pulse button soon tells you if the beam is hitting the side of the nozzle although I have never encountered the problem, All mirrors have lock nuts but mine are all unwound fully because the tension on the springs automatically keeps them locked in. Once you have set your mirror , tightening those lock nuts messes up the alignment. position.
My test results and feedback from other correspondents tells me that a power loss of 5% to 8% is the penalty for having such a piece of unnecessary kit. I would ask you to reflect on how often do you REALLY use it . My experience with 3 machines is that once set, the beam (mirrors) are VERY stable.
Best wishes
Russ.
@@SarbarMultimedia I have not, I am currently building up the machine. But I know one person where a mirror fell out and the beam startet perforating the wall panels. I do not think anyone tests the mirror setup before cutting so this would be a visual indicator that everything is fine. But I am no evangelist in this topic, just thinking there might be additional use for it despite the points you mentioned👍
Hi Pete
Just a quick note on mirror security. Place an O-ring behind the mirror before you clamp it. That evens out the clamp pressure and adds springiness and friction to overcome that issue you imagine.
Best wishes
Russ
How much power loss do you think these combiners waste please
My findings showed 5% loss but others have tested and found 8% loss. That's a lot of waste for a red dot pointer in my opinion.
Best wishes
Russ
SarbarMultimedia have you considered using two small line laser pointers to create a crosshair effect. Aimed at an angle but shining down a vertical plane, the cross point will always be directly below the laser. You can now get very small ones that would not add more than a few grams. I might try this myself.
@@Snagglepuss1952
If you REALLY need a red dot indicator of where your beam will land then then two line lasers are the best of all possible options. Despite weighing only a few grams each, the mountings and the cables also add mass. If you are trying to create a high speed engraving machine then any extra weight is bad. It is even worse if you mount it down near the nozzle as I see so many individuals and Chinese builders doing . This just adds to the pendulum effect that you create on the head mounting bracket. It's a laser line and will work just as efficiently if you mount it high up directly off the head bracket. Just remember two things. The sharper the laser lines , the more intense the light and the more it will "burn " into your eyes and creates a falsely wide line. Unless you have a minute spot of light (or crossover point, your laser landing point (about 0.2mm diameter) will be lost in the uncertainty of a much bigger red dot.. As I have mentioned to others, I felt that a red dot pointer was an essential feature when I bought my first machine. I was wrong and have survived more than 5 years without one on either of my machines. A quick blip on the pulse button and I know exactly where my beam with strike. If your beami does not remain PERFECTLY on the sweet spot of mirror 3 as you move your head around the table, the resulting beam landing point will not remain in the same place . Until you have tried it and tested how accurate it is/is not, you will not understand how untrustworthy a red dot is.
Best wishes
Russ
SarbarMultimedia Good info, I appreciate you taking the time to share, and your videos are a gold mine of information. Stay safe and cheers from An EX-pat in NZ
My machine has been apart for weeks because I stupidly decided I should align my mirrors then I decided stupidly I could use the beam combiner to help me align my mirrors . This is wonderful if you're an engineer like you. But I'm totally screwed ! Because when you buy Chinese you're on your own !
Sounds like you may have one of those backward mounted beam combiners. Criminally unsafe!!!! I would remove the combining window and do without the combiner. That way you can set the machine with the tape and scorch method that I use. It may seem crude (and I hate it) BUT it works to get you perfect beam alignment,
If I had your email I would have sent you this procedure as a document but here is the logical way to set your mirrors
The principle is very simple . and easy when you have confidence. I know that fear of never getting your machine to work again. I had it the first time I took a mirror off to modify it.
Set your max power button to about 15%. That way when you press the pulse button you will not blow a hole in your target. The aim is to scorch a mark so it may take two or three pulse pushes to get the mark.
Aim your laser beam at the CENTRE of mirror 1. The angle and alignment of the tube is not too important because mirror 1 is able to deal with the error. Now concentrate on mirror 2.
SETTING THE Y AXIS
Step1 SITING
Drive mirror 2 to the front of the machine and adjust mirror 1until the burn mark is somewhere near the centre of the mirror (it does not have to be perfect, within 2 or 3mm is OK) This isjust to make sure your beam hits the mirror.
Step 2 TARGET BURN
Fit a new target. Bring mirror 2 close to mirror 1 and produce a scorch mark This is your TARGET.
Step 3 MATCH THE TARGET
Drive mirror 2 to the front of the machine and adjust mirror 1 until the scorch mark coincides with the TARGET.
You will find it difficult to achieve this first time so repeat steps 2 and 3 until you achieve near perfection. Once you have achieved this YOU CANNOT TOUCH MIRROR 1 again.
Hopefully if the Chinese have set your machine correctly the burn you have on mirror 2 will be within 2 or 3 mm of the mirror centre. If not, we will have to discuss the options of how to get that burn mark to the centre of mirror 2.
SETTING THE X AXIS
I am very sure that your number 3 mirror is poorly designed just like mine and many other gold heads I have encountered. If you look at my videos you will see a black line across the entry hole to the head. If you aim for the centre of the hole you will find the Z axis will be very wrong. Draw a line about 3mm above centre and that is where you will be trying to aim your beam. Lets call that point A
Step1 SITING
Drive mirror 3 to the far end of the gantry and adjust mirror 2 until the burn mark is somewhere near A This just to make sure your beam hits the mirror.
Step 2 TARGET BURN
New target. Bring mirror 3 close to mirror 2 and produce a scorch mark This is your TARGET.
Step 3 MATCH THE TARGET
Drive mirror 3 to the front of the machine and adjust mirror 2 until the scorch mark coincides with the TARGET.
You will find it difficult to achieve this first time so repeat steps 2 and 3 until you achieve near perfection. Once you have achieved this YOU CANNOT TOUCH MIRROR 2 again.
Now you will identify a major problem. The dot is not on A You immediately think to adjust mirror 2 to put it into the right place WRONG. YOU CANNOT TOUCH MIRROR 2 again. You must stop and think how to get the dot onto A. I have modified my head mount so that I can move the head to put A into line with the beam. I suspect your head is not adjustable. The only option is to go right back to the tube and move it so that the beam finishes on A. That is a VERY tricky setting and why I made my head adjustable. Do you keep fiddling with the tube position or make the head adjustable? Your choice. I think this is a major design fault with these machines.
Mirror 3 and the Z axis alignment is the most important one you have to make. Most think this is the easy axis but it is the most difficult.
First understand what the "sweet spot" is for mirror by watching
czcams.com/video/eSjNsK2sjNo/video.html
Take a look at this from about 24minutes
czcams.com/video/jVGByifge_Q/video.html
This will step you through the important principles for setting the Z axis
Best wishes
Russ
You're good
By the way one of the days while I was adjusting my mirrors I found 2 bullet holes on the screen of my laptop! This is not a toy!
:D been there done that
I decided not to use the combiner because I don't like the idea of reducing power of laser ray. Instead, I am going to make a little jig: the idea is that which is used in SLR cameras: it's easier to lift the LED laser out of CO2 laser way instead of combining beams and doing numerous adjustments. What we basically have to do is combine their rays at start and, say, at 2m distance. That will guarantee they will be coaxial along the 3 mirror system too.
czcams.com/video/Jm8syz6ARCY/video.html This is how I did it.
Hey Russ,
Amazing video!
I Found this the while looking into beam combiner:
blog.gafu.de/?p=1579
Don't know if you've come across this before, just running it past you.
Hi
Apart from my attempts to copy the beam path to make beam setting easy ( I got close but never 100% suceeded) others have taken a less ambitious approach and decided to just use the lase rbeam as through the lens pointer. A beam combiner is continuously losing you 6 to 8% power and in my opinion (from test work I have done) will never completely simulate the beam either. The only time you really need a red dot pointer is when your beam is not on therfore several attampts have been made to achieve this, I refer you to these videos
czcams.com/video/0gABmmm_aJo/video.html
czcams.com/video/30y6VTjG_t8/video.html
czcams.com/video/r4GfdS4GDqs/video.html
czcams.com/video/Jm8syz6ARCY/video.html
There are other earlier designs that I cannot easily find at present but these might set you thinking.
Best wishes
Russ
So the red pointer is worthless when you purchase the machine because it never points at anything. And the pointer is worthless in the combiner. Truth
Hi Mark
I have tried many times (and gave up at Mk7) to emulate the path of the laser beam ACCURATELY. Unless you can get that exactness it will only allow you to set your beam approximately. . Firstly the beam combiner continually gobbles about 8% of your output power, 3% is lost via the ZnSe window and the other 5% is reflected off the window because it sits at 45 degrees to the beam path. I have seen several machines where the beam combiner has been factory fitted the wrong way round so that when you open the back tube cover the 5% can be reflected at YOU. If you really want a well set up beam combiner because it is essential to have a through the lens red dot then look at the SPT tube
www.cloudraylaser.com/products/spt-laser-tube-tr90-tr100?variant=12801293189171
The red dot pointer that is usually supplied is pretty useless (I have removed from both my machines) They were either too bright and caused spots in the eye as you tried to locate with them or the dot was almost 3mm diameter and I could guess better that that by eye, They are very height sensitive because they point at the work from a 45 degree angle . Some have fitted two linear pointers to produce cross hairs which are not height sensitive. and there are other methods as well see
czcams.com/video/30y6VTjG_t8/video.html
czcams.com/video/r4GfdS4GDqs/video.html
If I ever need a really accurate beam position I just blip the pulse button.
Best wishes
Russ