RDWorks Learning Lab 137 Compound lens Facts and Fiction
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- čas přidán 30. 03. 2018
- 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 - Věda a technologie
Hi Russ, i want to thank you for sharing the videos on youre channel. I am a teacher in the Netherlands and because of youre videos i was confident it was a good idea to buy a Chineese 40 watt printer for our school. My students love the machine. Youre information saved us from applying to much power while cutting and i got to understand why the laser tube broke down ( because of the frost) :) . Luckely i was able to fix this problem ( new tube ) with the videos and adjust the lasersbeam.
You are a great help for al of those who are working with this kind of machines. But you also made it possible for my students to work with the lasermachine evry day. They are able to be creativ and learn to work with digital production machines thanks to youre effort !!!!
A big thank you from me and my students, please keep going with the good work. You are a great instructor !!!!
Ben.
Fascinating discussion on laser lenses, I'm just getting started with laser engraving and cutting; these videos have been extremely helpful.
Hi Malcol
Thanks for your interest. and welcome to the fascinating world of laser technology. There are many experts (amateur and professional) that will tell you the best way to run your machine and the things you can do with it. None seem to take any interest in finding out how and why the technology works. The biggest problem I encountered that no one seemed able to answer (even laser physicists) was how it is possible to "burn" a deep parralel kerf with a beam od light that is expanding and loosing its intensity once it gets past the focal point see this thought provoking example which I sent to many optics and pysics professional.
czcams.com/video/vTEAm-01E1Q/video.html
I had zero meaningful explanations . I thought I understood a bit about lenses 6 years ago when I created this video. but in reality I understood very little. Yes I managed to find a magic combination of lenses to create a very small focussed spot but that lens type was rubbish at cutting....but why? I had to spend about 3 years of further experiments and observations before I fully understood how lenses and laser beams are really incompatible . However, despite this incompatability. manufactureres have been able to bolt proprietary items together in a way that wooks. I am convinced that machune builders are unaware of the real science theyare selling. A more upto date review on this subject can be viewed at
czcams.com/video/7N8Th1-IF4s/video.html
czcams.com/video/v7-VArJbJTs/video.html
There are no books or learned papers on this subject, it's all about experimentation and self education. Good luck for your journey.
@@SarbarMultimedia Sorting through the "so called experts" and people who actually know what they are talking about is difficult. I'm glad I found your website and appreciate your methodical approach, rather than the anecdotal information CZcams is rife with.
@@MalcolmProductions1
This technology is riddled with myths, and techno babble . I did a more recent series called CO2 & Diode Laser Myths and Misunderstandings mwhich you will find on this channel
Thanks for the great explanation.
I use a CO2 laser at work and was very annoyed that the focus point is only 2mm below the tip of the nozzle. Having the nozzle this close to the media you're working on leaves no room for uneven surfaces. I will take it apart and seen if there's a way to get the nozzle closer to yhe lens (or vice versa).
Awesome .Russ ..many thanks much appreciated
Great video as always, very interesting.
A great video - thank you for sharing. I'm only just starting my laser journey..
Cheers for the lesson. I learned a lot :)
A couple of ideas to try...
1. Make a final mirror that has a tiny curve to pre-focus the beam. (When milling the copper mirror set the pivot of the tool to the focal length you want.)
www.thorlabs.com/navigation.cfm?guide_id=2313
2. Insert a solid copper bock in the path just above the lens with a hole smaller than the beam to only allow the center energy to pass. (Blacken the surfaces to prevent reflections.)
3. Apply air assist to both the top and bottom of the lens. This will keep the copper block cool and the surface of the lens that's overheating and vaporizing.
You will be able to use higher power settings because you are throwing away the outer portion of the beam. You can even shape the beam by making a square or hexagonal hole in the copper bock. Soldering an etched copper disk to the top of the block would probably be the easiest way to form the shape.
My $0.02
Good luck
Hi Tim
I failed to make proper FLAT copper mirror, I had to pay to have them professionally lapped. Thus making specific shaped copper mirrors is way out of my capability. However, the principle of allowing just the highest density part of the beam through to the lens has some merit in my quest to find the smallest practical dot. I will certainly give it some thinking time. I have to be rather careful these days, because with only 2 grey cells left, they need exercise but not over exertion.
Many thanks for the thought
Best wishes
Russ
Can you help me in buying lens. I understand focal length. But why buy a 14 dollar lense vs 24 dollar vs 60 dollar. Confusing
Hi. Is there a better solution to use GaAs lenses to minimize the burned spot at the lens you shown at the end of the video?
Thanks for all your videos!
GaAs is a very inefficient transmitter of IR light (about 60%) and ZnSe isa little better (about 70%). Both have reflective properties that accounts for these inefficiencies. However, that final performance of both materials can be improved to 95% + by the addition of a special anti reflective coating. There are a limited number of coating compounds that can achieve this magic. It is possible to achieve 98%+ with certain American secret formulations. This formula is not licensed and so you will see Chinese lenses mentioning US coating where as others use one of several other formulations that are widely available. Both GaAs and ZnSe are usually man made crystal salt materials that appear glass-like. GaAs is mechanically much harder and more durable and tends to be used for higher power lasers but......it's not the material that is the weakness but the coating. I damaged the coating on this particular lens because although perfectly functional at normal low energy densities ,when I focused the energy into one localized spot the coating evaporated. In that instance I was giving lens 2 a relatively easy ride with a 4" FL lens ahead of it. I have now done work for my next video with two 2" lenses and have not suffered damage ( yet). I was always aware of the possibility of damaging a lens or two or three but hopefully my curiosity and stupidity will answer questions and allow others to follow my success or steer clear of my mistakes.
Thanks for the suggestion
Best wishes
Russ
Hi boss and thanks again for your videos! I am looking for upgrading my laser with a 100 w high quality tube and good psu.. do you think i have to upgrade other electronic parts for best results? Thank you
Hi
Electronically and electrically you should need no more upgrading It depends on what your machine is now as to whether other upgrades are required.A 100 watt tube may have a beam out as big as 10 or 12mm diameter despite specifications claims of maybe 6mm so you need to make sure that your beam path can cope with a 12mm beam to captuea and transmit all of the energy. You will need 25mm diameter mirrors and ideally these should be solid molybdenum rather than some plated material. The bore of the lens tube must also be at least 12 mm or more and any retaining rings must have a bore of more than 12mm diameter
Best wishes
Russ
You’ve talked me into trying a compound lens. I purchased from cloudray. I have a 60 watt OMTech. I purchased the nozzle and the PVD (38.1) and the CVD (63.5) lens. I have 2 questions. Maybe 3.
1. Both lens flat side down correct?
2. The CVD lens goes in first followed by the PVD correct?
3. What is your cleaning process for the lenses? Same as all other lens? Just x2?
HiJosh
Yes you are right with all your assumptions If you scroll down the Cloudray web page there is a diagram that confirms the way the lenses fit. The top 38.1 lens is not exposed to fumes and will not need much attention. The airgap to the workwill be 10.5 to11 .5mm (depending on speed) so there will be little chance of fume damage to the bottom lens either but i do check regularly. Used for photo engraving, the main purpose of the lens, I suggestyou use low power in ther preionization zone for your tube.This zone creates an obviously noisy, hissy, cut. see this video for an idea of what I mean. czcams.com/video/S_2NOCpACVc/video.html
Hello ,
Thank you so much for your many many tutorial
I have a question about the beam diameter,
The reci tube 100w have a beam diameter 8mm
The Spt tube 100w have a beam diameter 5mm
A large beam diameter is better to have a small spot diameter no ?
But with a Small beam diameter we have narrow cone and so still have power when one deviates from the ideal depth of field ?
So to cut material, have a small beam diameter is better ?
Right ?
Thank you so much
Sorta... And it looks like you've been reading from Marco's post in the LO forums?
Anyhow while he briefly went over aberration he didn't cover anything about hz frequency, beam divergence or collimation, which all three considered play a larger roll in the end result of what he's testing. Specifically in regard to a gantry based machine that constantly moves the lens closer and further from the point of propagation from the tube. If cutting is what you want to do, then ideally you'd want a beam expander on a taller focal length lens. Just relying on a lenses focal length alone will change the useful length at which the focus travels in and out of the material, however the further it travels before converging, the higher the aberration effect. But this can negated somewhat by utilizing a beam expander, which further decreases aberration. A 2x beam expander will reduce deviation by 2, decrease the spot size by 2, and increase concentrated energy by a factor of 4, thus meaning with said addition of the beam expander you should see roughly the same spot size with a 4" lens as you do without the expander on a 2" lens. To decrease the cone width further, you could simply utilize a larger diameter lens/tube. Rather than the popular 20mm lens, you could go to a 25mm lens and get the same effect as he is getting without the need to stack two smaller lenses.
I have a Thunderlaser Nova24. It has a standard convex lens.
Hi
Always remember that these are not tutorials, you are looking over my shoulder as I learn. This is a journey of discovery for me. so by the time you arrive at session 145 , all will be clear.
czcams.com/video/OUkBObChgLo/video.html
Best wishes
Russ
ps a suitable size adaptor lens tube to fit your machine and a compound lens kit can be bought at Cloudray for about 1/10th the cost of a TL hi res lens
Hello, i am still wondering about the correct direction of the round lense site. Must the round site point UP or DOWN when the Lense is installed ?
Hi Matthias
The Chinese always supply their machines with the lens flat side up. I was told (and believed) that this was the wrong way and that it should always be flat side down towards the work. It was only a few months ago that I realized after some lens experiments that both ways are correct. If you have flat side up you get a sharper focal point ,which is great for engraving ,especially dithered photo engraving, whereas flat side down gives about 25% more cutting ability. I guess that in general most people are more interested in cutting than photo engraving, hence the myth that flat side down is the correct way is almost right.. Flat side down will make the focal length shorter by maybe 1mm or more so find that new focal point and make yourself a new setting gauge.
Best wishes
Russ
@@SarbarMultimedia Hi, thanks for the Answer...i will try the opposite direction of my Lense :-)
I wonder if the laser beam quality is also a determining factor. On the test you did around minute 15:00, its evident that the beam coming out of your tube is not TEM00. I'm used to have issues with that on my old EFR tube, my RECI tube in the other hand, has a consistent TEM00 mode. I say consistent because on my old EFR tube, the beam mode would change as a function of the distance to the laser output mirror. On paper for instance, cuts come out clean from my RECI tube, while they had that char halo on the old EFR, at particular areas of the cutting table, no matter how perfect the leveling was.
Hi Abraham
I think you may have misjudged my beam from that test. That was a very short very low power pulse because I did not want to "smoke" the 4" lense above. It was just to show that the beam was very small at that point in the beam path. I have done lots of mode burn tests into acrylic with this tube and it is nicely Gaussian.I know that you spend most of your effort on rapid cutting of card where edge scorching is the last thing you require, however, with dot engraving, no charring means no picture. That is the whole difficulty with this 1000dpi quest. Thunder Laser have made a claim which I find incredible because I don't believe a dot 0.025mm diameter will be visible on any organic material.....but that wont stop me trying!! Cutting and engraving have opposite requirements.
All best wishes
Russ
I'm going to buy this one from China Auto focus Gweike lc1390n 80watt. Do you recommend any other laser cutter in China beside this brand? I know they are the suppliers of BOSS LASERS.
Hi Robert
I have had correspondence from a couple of people with setup and alignment issues with their GKW machines. Remember that I get a lot of correspondence but it is skewed towards those folks with problems. I have had several from Bodor,Thunder Laseer and Boss users also, so no machines are always perfect. It depends on how closely you examine them and if any issues show up in normal working.
Before making a final decision I would inquire of
www.mektex.com/en/a6ea2ce4ecca4a1482d140bb81140582
and particularly kook closely at this
www.transoncnc.com/ts-cabinet-models/ts1390-co2-laser-machine.html
One of the great options is the servo motors. Rapid acceleration and deceleration plus absolute positional accuracy. These are still stepper motors but with the addition of positive feedback from a rotary encoder to ensue so there can never be any loss of steps.
Most of these machines are government approved designs for export and just assembled in factories from a huge list of standard components. Thus there will be very little to choose between the different machines and why they all look similar. Quality assurance is often something you have to add although to be fair most work straight out of the box.
Of all the issues I have to field, over 90% are from ebay machines, I never get to hear about good news so I have no idea what proportion of direct bought Chinese machines suffer problems.
Good luck with your purchase. You are taking the safest route with direct purchase. You may have choice of tube and power supply. Out of 6 Reci tube/power supply machines I have played with or help set up, I have not been impressed with performance. The Reci power supplies all seem rather sluggish until driven hard. That is bad news if you plan to do low power photo engraving type work. I came across a 7th Reci tube (W2)a couple of weeks ago that was driven by good quality non-Reci power supply. Wow it was good. I can only assume that because Reci only make high power tubes, they are basically cutting tubes where response time is never an issue. My opinion is that Reci are over specified, over rated and over priced, you will get better value from buying and EFR or SPT tube
Best wishes
Russ
@@SarbarMultimedia Thank you for your thorough input on the laser from China. I will look into the two you suggested tonight and hopefully make my decision. Btw just saw your channel the other night going to watch most your videos they are very informational. Keep up on the good content!
Thank You,
Robert
Have you tried adding an aperture?
Yes. At differernt positions and and many different sizes. Nothing gets rid of that low power halo around the dot. However, more patient testing with different lens material/shapes/focal lengths and I discovered a magical combination. See czcams.com/video/UxfC9jbX6PM/video.html
You can now buy this kit from www.cloudraylaser.com/products/compound-universal-engraving-nozzle?variant=13488869867571
Best wishes
Russ
I just ordered a thunder laser and when I get the nozzle I'll let you know how's work
I have every confidence that your TL machine will be plug and play. Sturdy well built machines. I will be fascinated to know how the TL 1000dpi can achieved. Perhaps its something like an Argon cover gas that prevents the scorch effect? Your assistance will help us all. Many thanks
Best wishes
Russ
you're very welcome what's your email address ?
Check your you tube messages (maybe possible spam folder) for my email address.
Thanks again.
Russ
this is my e mail address
tridenttrikes.eu@gmail.com can you give me your dots picture I also have some other info for you ')
I would like to prove your dot pattern and try it out in my printer. how do I contact you?
Hi Diego
Just add your disguised email address in a way that confuses those bots trawling for email addresses. for example maybe break it up like this ( Diego.semi=====) Hi Russ thanks for reply ++++(at gmail dot com????). I will reply and also delete the comment
Best wishes
Russ
Hello, thank-you for this very interesting video. I’d like to know wher it is possible to buy good meniscus lens ? Thank-you in advance. :-)
Hi Daniel
I have bought from these first two links and confirm that they are meniscus.
www.ebay.co.uk/itm/302408621765?euid=117c331ad97248d2b4d8b5846f604afe&bu=43020994255&cp=1&sojTags=bu=bu
www.ebay.co.uk/itm/253085972561
I have lenses from here also but I have not received them yet so I cannot verify that they are meniscus.
www.aliexpress.com/item/Free-shipping-for-China-laser-mirror-20MM-50-8/32498877973.html?spm=2114.search0204.0.0.224b4eb5pJMfln
Cloudray advertise meniscus lenses but they are not!!
Best wishes
Russ
Thank you very much. :-)
For the china blue is it 18mm or 20mm? I think it is 20mm you once said but I can't remember (power supply is on its way via UPS). Of course neither of those links ships to the USA. Bummer.
China Blue is 18mm diameter lens
Thank you. 25mm on the mirrors and 18 on the lens.
Very first ha! Great video mate.
Doesn't matter, sparky.
The Best Stooge i know what i am saying dude :)
Okies, I am glad that you do, Sparky.
Why not just use a 16mm camera lens that focus with no distortion?
Hi
I wish life was that simple. The 10.6micron wavelength light we are working with has very limited properties. ALL metals reflect it (mirrors). A VERY small selection of special salts allow it to pass (lenses) . EVERYTHING else absorbs the light energy. Thus normal glass is in that last group and is totally opaque. Fire the 10.6micron light at glass and it will just heat up and damage it. Thus normal lens materials will not work.
Best wishes
Russ
Did anyone ever get back to you with any success making a .025 dot?
Hi Eddie
The short answer is no. I am pretty confident they never will. It all comes down to material physics as I originally thought and has been confirmed the more I research into lenses and the way they focus the LIGHT energy onto the material. This theoretical thing called spot size is just that as far as we are concerned. Whatever lens material, shape, orientation or focal length I choose I have never been able to achieve a burn to match the spot size. Typically it will be 50% to 100% larger. I recently came across a compound lens combination from one of the big optic companies claiming a spot size of 0.02mm. Excitedly I tested the combination only to be disappointed. I will discuss this in my next video as It may have other merits which I have yet to test. 0.05mm is the limit I bounced off and that was VERY difficult to achieve and only on very special non-standard material (Laser Tile). I have been speaking to an Epilog owner who was going to run my 254ppi dot test and report back. 3 months of silence says it all.
Best wishes
Russ
@@SarbarMultimedia I just tested my Thunder Laser NOVA35 with a spot size of .025mm separated .25mm apart. The results are okay, but not perfect. I'll send a photo to your email address(I have it form past discussions).
I have an Epilog laser with a meniscus lens. If you want, I could run your dot pattern on that to see how it compares to what you are running.
Your Epilogue laser is probably powered by an RF tube. and already has a very small 3mm diameter beam?. I will be happy to send you the dot pattern if you private message me with your email. I expect that your machine should gobble it with speed and power and because your tube is "always on" there will be no signifinat response speed to worry about. It should be more controllable to get the "tip" of the beam to give reliable small burns (dots). However, with organic materials I suspect you will still have a scorch halo.
Many thanks for your help
Russ
BTW, for my 1.5 lens, I use this www.lightobject.com/381mm-Focus-Lens-Adapter-for-XLE-XY-Stage-P953.aspx nozzle, works superb.
Hi Abraham
I have always had 1.5"capability on my China Blue But the lightblade machine lens system had to be modified
to take the 1.5". Mine uses a the standard nozzle modified whereas Lightobject have come up with a strange design that hampers visibility of the work area. This looks like another piece of Chines design by someone who has never used a machine.
Thanks for the link it made me smile
Best wishes
Russ
I really love your videos but it takes hours to watch which I Dont have can you compartmentalize and simplify
If you jump over to my Lightblade Learning Lab series that I did with my Thinklaser machine , it is not experimental but much more a demonstration of machine capabilities. see
czcams.com/video/kx4vmDguCyE/video.html
Best wishes
Russ
My eyes are rolling back in my head obviously I don't have a tenth of the brain matter you have as have can you simplify
Hi Mark
Trust me, my two remaining grey cells need continual exercise or they will atrophy along with the others that I once had. This compound lens study for producing micro dots was fascinating and my final conclusion defied all the lens theory I could find. However great this was for photo engraving, the main reason why people buy these machines sd for CUTTING.
I am currently in the middle of preparing a huge body of work about lenses. I have spent far too long believing all the theory about lenses so I have decide to ignore the theory and try understand just what is useful for our machines from the very practical point of view and why some work better than others. I have opened a Pandoras Box with this topic and it is massively bigger than I anticipated.. I hope to give reasoned and demonstrated examples as to why you should or should not spend your money on expensive lenses. At this moment I would advise to spend at the $15 level for ZnSe if you have a sub 100 watt machine and if more than 100 watts then go for GaAs material. Both will be plano convex lenses and used flat side down will give good cutting performance. I shall be testing cutting performance with lenses in both orientations in an attempt to help people with exactly your questions.
Best wishes
Russ
Let me help you out so you can make a very small beam size. Use a collimator. And fit it at the beginning, before mirror 1. Get one that can be manually collimated. Or get a software controlled one. Then you can control the beam diameter with ought changing lenses. There are collimators that can increase or decrease the beam diameter. All depends on the type of lenses use inside the collimator. And try tjslasers.com they might be able to make it for you as well. The last I used was them 10 years ago.
Many questions. How much are they?How big are they? How many lenses are there within? Are they available for 10.6micron wavelength? Do you have one or is this just an idea? This sounds like another element that has to be precisely aligned in the beam path like a beam combiner system? What would be the advantage over controlling the beam diameter at the last point in the light path. I mention this last point because from what I have read, beam divergence increases as the diameter decreases. A good argument for delaying diameter change to the last minute?
Truly interested if you have facts/links please.
Best wishes
Russ
SarbarMultimedia There are usually built to order custom built. They have been around since 1985. I have three in three of my machines. But mines are up collimators. They are available in 1064nm. You can make your own. Where easy to make. You can purchase the lenses from Controllaser.com. Or any other lens provider. You can even install it just before that focusing lens, inside the focusing lens housing. I wish I had the time to do a diagram for you. But you have a pretty good understanding of lenses now and how they work. Or you can call Controllaser.com and see if they will make one for you. Get ready for the price. Each lens will be around $250.00 or more. You need a minimum of two lenses in some cases four lenses. Don’t get the uncoated once get the coated lenses. The the lensers have be able to move in and out. So you need two cylinder slivers. And each lens has to be mounted on the end of each cylinder one cylinder being larger than the other cylinder so I can slide in and out allowing to focus the beam size. Make it out of aluminum. Now that you know little bit about collimators you can do the rest of the investigating on Google. And you will see. There are auto collimators. Which can be used to align the laser beam path as well. Using a camera on the end of the lens head, with an auto collimator built in it.
Way overly complicated and far too pricey by the sound of it.
The Best Stooge You can get all the parts from China for about $60 bucks
Everything already made? On our China Blue machines the hooking up part sounds very complicated but maybe if I had something to read showing how it was done it might not be. What would the dot size become?
Very interesting video. My question is a bit off topic but I'm still a novice so forgive my ignorance. I think you show the insertion of lenses, curve side up, however, I've watched other videos where the opposite is shown, specifically here:
czcams.com/video/Eg6THrEdleo/video.html
At around 13.22 he says curve side down. Who's correct?
Simple answer is both. Although these are specifically sold as ENGRAVING machiones,most people want to cut with them Cutting is done more efficiently with the flat side down but the focal distance will be anything from 1 to 2mmless (you will need to test this for your lens) But you get a better focus for engraving with the lens flat side up. The Chinese always supply machines with flat side up but most experts will tell you flat side down is "correct" . There is no absolute correct way, it depends on your need. You can engrave quite OK with flat sidedown for most applications but fine detail and small text are when you need to flip your lens.
Best wishes
Russ