Hi Thanks for the comment and interesting questions. For several months now I have forsaken CO2 technology in favourof trying to understand the intracasies behind diode laser technology where simple air cooling seems to be adequate. Howevere, I plan to resume my investigation into thermal control of water temperature with CO2 laser tubes. My initial investigation with the CW5200 was to prove how unsuited such a powerful "industrial" chiller is for such a delicate thermal problem. I have purchased very compact low cooling capacity chiller (approx 450 watts ) with the aim of trying to achive the flatline you were asking about. The problem facing any temperature control system is the finesse to which the pumped output temperature can be controlled. By it's very nature that finnesse cannot be achieved with any refirgrated system because by the laws of physics you need a significant thermal gradient to extract heat and thus any refrigerated system is a very crude tool. However there are other bits of physics that can be exploited to achieve the near flatline stability that the tube would apprecciate. Simply put, we need a large thermal water mass to buffer the dramatic temperature flucuations of the refrigeratied cooling system. By choosing a smaller refrigeration capacity I hope that I will be able to minimise that theremal mass to a practical volume. It will certainly be greater than the puny 6 litres used in the CW5200. I have several ideas I want to experiment with to control the referigeration and also the pumped output temeprerature. So watch this space.

@@SarbarMultimedia thanks for your answer and feedback. I agree regarding overkill of the cooling ability of the 5200. An intermediary water storage between the output of the cw5200 and input on the laser, with the cooler running based on the temp of that intermediate water site would largely smooth the temp curve I would imagine. That gives you I think a finer control because you aren't trying to manage what comes out of the chiller and into the tube, but managing that intermediary temp. Would be keen to hear your thoughts on that. Keep up the great work.

Hi Thanlks for the interest. Sadly no one else has made any kits. If you want to make some parts yourself then the drawings are here laseruser.com/k40-xtreeem-project-files/ I do have some long and short lightweight head blanks I can build if you wish to minimise the complications. You can also contactme at this websitre if you have more questions.

Hi John There is balance to be struck between pressure, airflow, orifice diameter and distance to the work. The priciple is much like ohm's law except electrical is not compressable whereas air is. For any given pressure DIFFERENCE across an orifice you will create a specific air flow, however, unlike current, water or oil, as soon as it escapes from the orifice, air instantly expands and just like paint spray it will form a huge cone. The greater the pressure difference across the orifice the more explosive the expansion will be instantly it exits the orifice. Yes, you will get more flow through the orifice with higer pressure but by the time it jumps across the gap to the work and expands it may be pretty ineffective, You will notice I checked the jetting effect of my orifice with a shallow lid of water. It is virtually impossibe to create laminar flow (a nice straight jet) with gas because of the expansion issue, so there is a compromise to be made My relatively low presure pump (3psi max) is probably creating no more than 1psi across the orifice so the gas does not expand rapidly upon exit to free air. Thus my cone of flow is narrow upon hitting the work and effective over a small zone. If you make the orifice smaller you will get less flow but more jetting for a short distance if you have sufficient pressure and ultimately a greater expansion cone. As I said, this is very much a compromise. I may not have achieved the absolute sweet spot but it's doing well as air assist and great as a lens protector. The priciple of adding more oxygen to the cut is used in metal cutting of mild steels as this aids the oxidation process within the cut (just like an oxy acetylene gas axe). However, metal does not ignite like any of the combustable materials we use on a diode laser. In session 20 I demonstrate what happens if you do as you propose.

@@SarbarMultimedia Thanks so much for the response. I agree there is definitely a tradeoff. Bridging the distance from the air / laser nozzle to the material (6 to 8 mm) and then getting the air down in the small gap is challenging. I was just thinking if you make that gap smaller with a nozzle design that was longer that may possibly be more effective in delivering the air to where the reaction is taking place. If you need more air for cooling that is really a separate issue that could be addressed with side vents. Love your content!

@@johnwagner7853 Hi John Thanks for the interest. I generally only fix issues that the designers of equipment have obverlooked or not understood . My solution here works for me but the principles I have demeonstrated can be adpted for your own equipment . Although my main goal is self-education on this little understood technology, I hope that a few, wanting to go futher than just fiddling with the Lightburn parameters, will be stimulated to explore their own machies in more depth. Yout thoughts already tell me that you are one of those few.. Salutations!!

Hi Benjamin I have to be honest and say I don't know for certain. LEDs in general have long but finite lifetime in the order of tens of thousands of hours . However . I know from my electronic inexperience that unless you limit the current flow through a light emitting diode it can have a lifetime of just a few minutes. I have heard from quite a few diode users that after as little as a year their products have died. Ouch, that can be expensive. Sadly, I will not be using my diodes for serious work or for any significant period to see if and how the diode fails. My goal is to investigate the pros and cons of the technology . I am sure you will find a sensible answer at one of the many diode user forums.

@@SarbarMultimedia thanks for answers. Yes i find this kind of information but if you have a light mesuring tool, i'll be curious if, for same current, the light power will be the same after time. From my personnal experience, after hours for cutting a big piece of wood, the diode loose a lot of power. However, i did'nt have tool for mesuring.

​@@benjaminbulle9199 I have had the same problem before. In my case, cleaning the lens was the solution.

Hi Kris You are perfectly correct about voids in plywood. The same thing happens with a CO2 laser where it IS relying on the beam to cut. In that case it is the fumes in the void that suck away some of the power as the beam has to "cut" though the micro particles of suspended tarry liquid before it can continue cutting. Wood is even less accepting of light energy at 1064 microns and in that case Borax, as well as table salt and several other metallic salts could be painted onto the surface to create enough absorbtion to scorch the wood and produce that carbon film. Carbon has a very wide spectral absorbance thus it allowed a fibre laser to engrave wood. Borax will accelerate the creation of the "tunnneling machine" bit it will do nothing therafter. So I dont think you will notice the difference except it will create a wider "brown" zone around the cut.

Hi Sadly there is no comparison possible because RF and Constant Current tiubes operate withcompletely different principles. The end result is the same in that both produce a stream of output photons witrh a 10, 640 nm wavelength. The glass tube uses a high voltage to excite the nitrogen in the tube which in turn stimulates the CO2 to create a laser output whereas the RF tube uses a GHz freqency with low voltage (about 40vdc) to achieve the same result. Because both systems are ionizing the nitrogen (producing a pink beam) they both pass throug a critical phase EVERY time the beam switches on If you take glance at this diagran you will see that phase defined as Townsend www.researchgate.net/figure/V-I-plot-of-a-DC-gas-discharge-7_fig1_327209884 This is a phase where the just a few free electrons (negative charge) in the nitrogen are stimulted to rush toward the anode (positive), crashing into other nitrogen atoms and freeing up more electrond to carry current. In the glass tube system there are two distinct functions for the power supply. First it has to create a high voltage to stimulate the gas to ionize. However, stimulating the massive release of free electrons means the potential for infinite current flow through the gas which is bad news, hence there is a secondary function for the HV psu and that is to limit the current flow to a few milliamps. This control of current is is achieved by a feedback circuit BUT this Townsend region is a phase of inoziation instability that we call preionization where the random nature of colliding free electrons can cause huge current flow spikes . In this phase the current feedback system cannot respond quick enough to manage the current flow. It is only when the ionization reaches the glow discharge phase that the current flow can be managed by thr HVpsu. In the case of the glass tube it is possuble to adjust the current flow through the tube to change the power output of the tube. The % power parameter is not controlling watts output but instead is is controlling the current flow through the tube in a linear manner, The output watts is very non-linear and will depend on the design and manufacturing quality of the tube. As can be seen from this video, it take several milliseconds to intiate a stable output from a glass tube EVERY time the beam switches on. The RF power supply works in a completely different way. When you first switch the power supply on the high FREQUENCY causes the nitrogen to pass through this Townsed reqion of preionization but it only ever does it once because there is internal circuitry that provides a "tickle current" to keep the system at the edge of the glow phase even before you switch the beam on. This means there is an almost intsantaneous power output the moment you ask ther beam to switch on. However, the biggets difference is the way the tube operates. It is controlled by a PWM system which means ther is NO VARIABLE CURRENT CONTROL. The current is fixed at a maximum that the manufacturer has deemed as a safe long life value for the tube Thus when you buy a 60 watt RF tube it can only do two things...... deliver 60 watts or zero watts. There is no power control, just an ON/OFF switching function The appearance of power control is acheievd by allowing the beam to be on for a variable period during each PWM cycle Thus %power is not controlling output watts with this tube either, instead it is controlling the PWM duty period and is ALWAYS operating at full current flow i.e.60 watts output The claim that RF tubes have a much longer life than glass tubes is very dubious because the current flow parameter that the manufacturer sets for an RF tube, makes it possible to predict operating hours with a reasonable degree of certainty (a bit like predicting ther number of print pages from an ink cartridge). The dissociation (degradation) of CO2 in a glass tube depends on the current flow that the tube is used at. The manufturer of glass tubes specifies an allowable maximum opearating current and a typical operating life but most people do not run at the max current and many laser operations (like engraving) do not require high power. So there is no way to compare liftimes. I personally have tubes that a 9 , 6 and 5 years old and all are still functioning as new. Just like an ink cartridge, when the CO2 runs out the power stops The cost of a 100watt RF tubei is 6 to 8 times that of a 100watt glass tube , so assuming a glass tube lasts 5 years, can you find an RF tube with a 30 year lifetime I have spent money and time buiding and testing an RF system in an attempt to find the "magic" claimed for the technology. Switching speed is it's only redeeming feature bcause that allows for precision engraving. It is necessary to manage the massive beam divergence characteristic with a beam expander , which in turn wrecks the beam intensity profile and makes it a very inefficient cutting machine. After years of decrying the cheap short lifespan glass tube technology, Trotec have had to accept the weakness of RF technology for cutting and are now selling a Q series procuct that integrates both technologies. One for engraving efficiency and one for cutting efficiency. Soory, there is no quick short answer to yout questions.

Hi I really appreciate it whan people take the time to watch and comment on what they see. Thanks for sharing your persona;l experience.which may depend on the brand of laser you are using and its focal distance. I never experienced issues with the 5 and 10 watt diodes but 20 watts seems to have an eklevated fire risk. I think you have misinterpreted my kitchen towel demo. The idea was to show that glowing red hot carbon cannot be blown out like a candle but by adding extra oxygen (air assist) you exacerbate the exotheric reaction and make the carbin glow nearly white hot like the campfire you describe. On the other hand there are parts of the cutting process that do benefit from the cooling effect of air flow. You will recall the end of the session where I posed two questions for you to think about. One was about the effects that air assist had on apparent cut width. It may seem impossible but the extra heating effect of air assist can also exist alonside a cooling effect. I will answer this conundrum in the next session. In the meantime I'm not sure you have understood the importance of carbon in the cutting process. The main costituents of wod are cellulose and lignin with about 10% of other non-structual materials like resin, oils/tars. Both cellulose and lignin are almost transparent at 455nm wavelenght see these graphs kzbin.info/www/bejne/f4W0mqqgdq-sqbM www.researchgate.net/figure/UV-Vis-profile-for-a-Kraft-lignin-without-initial-lignin-and-the-same-sample-after-the_fig3_337842474 If they will not respond to 455 nm light they are technically as transparent as glass or clear acrylic. However, it is the 10% of other stuff in wood that can be stimulated by the light to heat up and cause the surface to darken and eventually create a carbon film. This carbon film then acts like a tunnelling machine because it rapidly absorbs the light energy thus heating the carbon film to near white hot. It is this white hot energy transfer film that precedes the cut and vapourizes the cellulose and lignin ahead of it., The laser beam is NOT cutting the wood. Understanding this mechanism of cutting illustrates the risk of fire if you keep the heat in one place for too long. In the next session I will investigate if there is any. cutting speed/depth advantage to jetting air into the kerf. Thanks again for your interaction on this subject as it does allow me to explain things in a way that my video may have skipped over. I am amazed at how complex cutting with a diode laser happens to be and I have never seen any scholarly works or manufacturer videos explaing how their product actually works . It's always just brands handing out free equipment to let others do their demonstrations/promotion for them.

@@SarbarMultimedia Thank you for your detailed feedback. And yes, there are not much detailed information about it.

@@TorteTS Hi I must alogize because I sent you an incorrect link. The top left graph is the one I wanted you to see. www.researchgate.net/figure/UV-visible-absorbance-spectra-of-the-aqueous-phase-after-a-cellulose-films-and-b-PHB_fig5_322879134#:~:text=Additionally%2C%20the%20absorption%20peak%20at,at%20304%20nm%20%5B29%5D%20.

Thanks for your comment and concern about my laser head overheating. Although the airflow may be reduced by about 20% it is also travelling across the endface of the heatsink body which it would not normally do. I have been testing the body temperature regularly and it stays at room temperature. I therefore think I have not compromised the module cooling. As for extraction, you may have noticed that this is not a normal diode laser machine but a an RF CO2 laser that has been temporarily converted to test these heads. The extraction is VERY efficient , even with the cover open (have you seen the frame by frame video at the end to see the extraction efficiency?) I am pleased that you do not have problems with your setup but I made these changes because the tar residue along the cut edges was present with or without air assist. I am not advocating this change for everyone, I am just illustrating my problem and how I went about solving it. I had no such issues when testing the 5 and 10 watt heads but that was because the long focal distances meant that the gap between nozzle and work was large. In the case of the 20 watt head this gap is about 6mm.

Hi This is a common issue because people fail to save their vendor and user files when their machine is working well.. However, don't panic because therevare several ways to get back into action.. The easiest is to go to forum.laseruser.com/viewtopic.php?t=6302 Sign on to be a member to gain access to many different machine files. If for any reason that fails, then contact me privately with this contact form and I will help you with the problem. forms.zohopublic.eu/ndeavorlimited/form/K40XtreeemLaserCutterContactRussSadler/formperma/k2Cn0QN5ChpazfTMAUw25lZ-FKpjZa96TQWHjv3ntOg

If there was any movement (wobble?) then I would expect to see it on all the other "spots" a maybe fuzziness or ovality.. At this point in the testing I had no notion of how the individual optical paths were arranged but I would say its more likely that there is insufficient intensity in two of the diodes to complete the doughnut, Hence the C shape. In practice it is never going to be an issue because who would use the beam 10 or more mm out of focus? At the time of making the video I did not consider the "lazy" diodes idea so thanks for your suggestion because my thoughts may still be wrong. Everything I do is new and unrehearsed so you are live learning with me.

I agree. My understanding of air assist is to stop soot landing on the lens and causing damage as seen at 2:36. I would have an air filter on the air intake too.

Hi Marcus I really appreciate your interaction with this air assist issue and some of the things you point out are relevant. However. I have spent many years with CO 2 lasers and fully understand the reasons why and when not to use full air assist. In general, you need air assist for cutting to blow the fumes oiut of the BOTTOM of the cut because with CO2 you never try to use multi cuts. If there is no bottom way for the fumes to escape they, by default, must run along the blind kerf and rise out of the material surface whereupon they meet a downward rush of air assist ( or in this case the significant cooling airflow) and stick to the edge of your cut. The fumes are not solid particle but micro droplets of hydrocarbon tarry substances (like steam) that will condense on your work if blown downwards. If you can't cut in one pass then it is better to let those fumes rise out of the kerf and carry them away with cross flow air before they get a chance to settle. Yes you do need to protect the lens (or in this cae the protective window) but it requires only a small positive pressure inside the nozzle to do so. Because that nozzle orifice is so large (about 6mm) there is never going to be a JET flow to aid cutting i.e. forcing large volumes of air into a kerf that is about 0.1mm wide. Thus the resason for the nozzle must be just for lens (protective window) protection. Yes, fumes do absorb laser energy but not to the extent you imagine. If you Google the absorption spectrum for various hydrocarbon products you will find that they are maybe only about 20% absorbing at 450 nm So, although it is a sensible precuation to get them out of the cut area as quickly as possble it is not a huge issue because the wood you are trying to cut is even less efficient at absorbing 455 nm light energy (about 10%!!!). However, use that 10% absorption to create a surface carbon film and all of a sudden the carbon is almost 100% receptive to 455 nm wavelenght light and so the cutting process begins.This is a completely different cutting mechanism to that which occurs at 10,640nm with CO2. The problem with many myths and ideas about air assist is that they are not rooted in fact. One good example is the risk of wood cuts catching fire. Remember I mentioned the carbon cuttinig mechanism, well that leaves a film of carbon on the kerf walls. If you observe your cuts carefully you will see the walls glowing red as the laser beam stimulates the carbon. Let me ask you to carry out this simple experiment. Take a piece of kitchen towel and twist a corner into a littl sausage shape. Light the end and wait a few seconds before blowing out the flame. You are now holding some glowing carbon (as per your kerf walls). Now try adding air assist (blowing on it) and then ask yourself about the wisdom of blowing on glowing carbon? ( "cools down the work piece"?) I will be devoting a complete session in the near future to the way that air assist works with a diode lasers because as the power increases so single pass cutting become more viable. Fitting a flame detector to your machine is like putting a sticking plaster on a broken leg. Understanding how and why a fire can start, allows you to adjust your usage stategy to avoid the risk.

Thanks. It somehow makes the word what it is. I'll leave it as is.

Thanks for your detailed list of valve options. I will examine those valves on Amazon because all knowledge is good knowledge and I have not encountered these brands before. However no matter how "full bore" a valve is, the limiting flow resistance is either the fitting into the nozzle or the orifice in the nozzle itself. There can be no less resistance than removing the valve all together, which I have done for test purposes. The free airflow from the nozzle that I see on my flow meter is little different. The disadvantage of any motorized system is response time. One of the air assist options available on my RDC 6445 controller is to have the valve opering with the beam on and off. A poppet solenioid has about a 10 ms response and can match the laser switching. If you just want to select air on or off for a layer where switching only happens once. then slower response options work well enough.

Ihave demonstarted a completelyy different method to that usually advocated b the Chinese and everyone that speaks of beam alignment, See this more recent video as it should help to solve your problem kzbin.info/www/bejne/qqexl3SdYsiCgqM Best wishes Russ

@@SarbarMultimedia the video doesn’t show which mirror you adjust when checking the front left corner. This is where i am stuck now. I have all corners on point except for front left. With which mirror do i continue here for adjusting?

I will send you the standard data pack that accompanies the video but this was created a long time ago and I have learnt so much more since. Here are a couple ofe recent videos that bring you more up to date kzbin.info/www/bejne/oJ2ZgIycaNN9nKM kzbin.info/www/bejne/oGfIkoiopNqdjsk I discovered the secret to photo replication many years ago and the basic method has not changed. This early work forced me to understand the basic principles of digital imagery and how so much of it depends upon fooling our eyes Dithering an image into a binary format relies on our eyes averaging the black and white areas they focus on to create the appearance of grayscale when none actually exists So many people use the great graphic toolbox in Lightburn to create photo engravings that are pale shadows of the original. Giving me a box of paints and brushes can never make me an artist. This understanding of how dithering works ie black dots on a white background (at least for the print industry) forced me to investigate how lenses work and how materials get damaged by light intensity In my optical ignorance I experimented with the many lens I had amassed and created a compound lens combination that burnt a reliable 0.1mm dot on most materials with no halo. This means that I could copy a 0.1mm pixel ie an image resolution of 254ppi Under special circumstances I have been able to push the boundary to 508ppi (0.05 mm) dots see kzbin.info/www/bejne/iofKnqKEZtyfoNU. If you are a photographer you will know a lot about lenses, however I must urge you to forget all of that optical knowledge because little of it is transferable to the laser world Transmitting IMAGES with light is what lenses were designed for, using those same lenses to focus light iINTENSITY is a completely different application and produces some surprising results for example see this short video and explain how this is possible when the beam gets weaker after it passes through the focal point. kzbin.info/www/bejne/rIWocqBjZZZ4Z7M I have experimented with lenses and laser beams a lot since my initial foray into photo replication and there are several relevant videos I could point you towards if your interest goes that far. I had no idea I was only scratching the surface of this technology when produced my first video on the subject Many people have requested the info pack but without a contact email I cant send it. KZbin is clever at detecting email addresses and blocks replies. However, the algorithm is not that clever so you can try to encode your address in a sentance like this I will be meeing bdotsmith at the big g company This is utter nonsense to an algorith but we can usually decode it. Igf that fails I have a private contact form that will get to me forms.zohopublic.eu/ndeavorlimited/form/K40XtreeemLaserCutterContactRussSadler/formperma/k2Cn0QN5ChpazfTMAUw25lZ-FKpjZa96TQWHjv3ntOg

@@SarbarMultimedia Wonderful! Thanks

Hi Chris Thanks for the reply. I suggest you cut your teeth on CO2 technology and the complexities thatvare involved with it. Having used RF CO2, Fibre laser of several types and and now diodes, the most useful and flexible is still glass tube technology for many reasons. However, despite my neglecting diodes for many years (what's the point to downgrading ?) I am equally aware of the onrush of these simple devices that are now the enty level machines whereas it used to be K40. The marketing shows all the wonderful things you can do with the technology but fails to explain any of the material limitations of 455nm technology or howmslow it can be. Yes there are many "tricks " that can be used to achieve some sort of results with unsuitable materials but the sort of people buying these machines seem uninterested in how they work, they just want to use Lightburn to fiddle with parameters and earn some pocket money on Etsy etc. I am not making videos for them, instead these videos are just a record of MY learning journey into this technology. It may interest a few serious viewers but I do not monetize so numbers are unimportant to me. Understanding and reverse enginnering is important to me and some of the issues I find are interesting and help to keep my two remaining grey cells exercised. 7 years ago when Cloudray strted as a very small business ,I was approached with a view to selling my designs for a profit share. I declined because my retirementtax affairs were nice and stable and income from China would have unsettled my situation. After some research into the new company and its owner, I made the decision to GIVE any of my designs to them for free.. In that way my products would probably be available to the community after I had been called to fix St Peter's big laser machine!!! I also provide technical help to Cloudray. especially on glass laser tubes. With nothing more tha a friendly gentleman's agreement, if I needed items or equipment for my expeimenta and research ( Cloudray would get in-depth product knowledge from my research) then I only had to ask and it would appear. We have no formal relationship it is personal between me and the owner. On special occasions such as Chistmas or their 7th anniverasry I will recieve a little package of gifts as a token of their thanks. In this anniversay year they sent me 3 T-shits which are nice quality and I wear them a lot off camera. I can suggest that you email [email protected] to see if it's possible to get one or mre. She is the sales manager Best wishes

@SarbarMultimedia Hi Russ, I do own a Cloudray 7050 55watt CO2 laser. I love it. It has served me well, except I haven't been able to hook their rotary attachment to it yet and it work correctly. Other than that, I watch your videos and try out some of the things I learn from you. I know you said one time that making videos was another of your hobbies, so I guess I can be grateful for that. Otherwise, we wouldn't be seeing these great videos that keep my two remaining grey cells working together. I, too, am retired and have no interest in making a living playing with lasers. It is purely a hobby that I thoroughly enjoy. I started out on a 5 watt diode and then a 10 watt diode. The only thing I use the diode laser for is engraving names on small velvet bags that we use to place the spent cartridges in at Veterans funerals. We then present them to the family. I won't say I don't do anything for pay because I have been approached to do some engravings where I have to purchase what I will be engraving on. Thanks again for making the videos, I do appreciate it.

Hi Yes I stil sell the dohicky power sensor.. You can contact me through this contact form and I will send you all the information. forms.zohopublic.eu/ndeavorlimited/form/K40XtreeemLaserCutterContactRussSadler/formperma/k2Cn0QN5ChpazfTMAUw25lZ-FKpjZa96TQWHjv3ntOg

Hi If your spot is just burnt on fumes then soak it for a few seconds with IPA and try to remove the spot with circular rubbing using a cotton bud. The antireflective coating is pretty duarable. Howver, if the debris has ben on there for a few minutes then the debris will absorb laser energy and heat the surface of the lens. That process could bake the fumes into the AR coating and the lens is likely to overheat with use and a cental star crack will happen. Lenses are the most vulnerable part of your machine, thus you should always have a spare lens. The 50/60 watt tube supplied with your machine may not be what you think. . A typical 50 watt tube will be 1000mm long and 50mm diameter. It may claim to be 60 watts because that is waht it was test at innthe factory .... but that is not for you to use as it will shorten the tube life, 200mA is the max to run a 50 watt tube at. However, that 50 watt tube is almost certainly a B grade tube with a poor intensity profile. B grade does not mean crap but if you watch part 2 of this video you will see me running a B grade tube in one of my machines. Because I now understand how lenses and laser beams interact I have paired this 70 watt beam with a 2,5" GaAs lens and it cuts very well. Your question about tube upgrade is an intersting one. AS the power of a tube increases so does the beam diameter. This could mean the the intesity gain is not proprtional to your expectations. I have found that the best "jack of all trades " tubes are in the 70 to 80wttt range. Steer clear of Reci (despite their good reputation). I have ssen far too many that are rubbish at low power Why pay twice the price for something that does not deliver across the range. Amongst the rest, Yongli, EFR and SPT, I would rate SPT as the best value for money. You can buy an A grade SPT rebadged (officially) as a CR70 or CR90 from Cloudray.. Fof a small kerf on thin material I would use a 1.5" (38.1mm) meniscis lens. There are all sorts of "opinions" about lenses and getting what you pay for, The facts are simple, The geometry of a lens logically has to be the same no matter who makes it and how much ir costs. Cost is generally related to the quality of the material and the materials manufacturing process, USA on a lens description means it is made with CVD ZnSe which is bright yellow and can withstand power in excess of 200 watts. The brown honey coloured material is Chines manufactured PVD ZnSe which ir rated at about 80 watts. That's another reason for staying below 80 watts with your tube, you can use cheap lenses. I have tested the power transmission and cutting performance of almost every lens available and higher cost does not get you better performsnce, One final point (myth) about lenses. A bright yellow CVD lens looks crystal clear to our eyes whereas the brown Chinese PVD lenses look rather dull and unexciting. OK. if that is your judgment of lens quality, how do you explain the BLACK galliun arsenide lens? We "see"in the 400 to 700nm wavelength range the light passing through these materials is at 10,640nm. So what you see is not what is actually happening. At that wavelength my black gallium arsenide lens is transparent Weird? Best wishes Russ

@@SarbarMultimedia Thanks Russ. I rarely hit 18 mA on mine and have the power turned down to 80% max at the controller, so 100% in lightburn is 80% at the machine. Tube still going strong 5 years now. Reason to step up to 100W is to cut thicker material in the 1/4 to 3/8" range for some projects. Also great info on Reci tubes, so I will look into the other tubes at Cloudray. I also replaced the Chaser lens soon after watching your earlier videos on lenses, and put a lot of what you taught to practice. Right now I just want to get a tighter cut for a couple projects, so will look into the 1.5" setup. Will also see if that is just a surface spot or actual damage. Going to tie the pressure switch into my relay setup that turns air on and off, so the tube wont fire if there is no air pressure, I missed that somehow. I've also put your acrylic cutting and etching to good use, and yes, keep the machine clean, don't want a grid fire. I appreciate all the work you put into these videos.

Hi Malcolm I never stop learning or stop searching for better ways to do things. In a more recent video I have found there is a logical flaw in the way we have all been taugh to set machines. I modified my machines many yeats ago to make the heads adjustable in Y and Z. The principle I demonstarte in this video works for all machines , however if you do not have the adjustments that I have it will be more difficult to achieve. see kzbin.info/www/bejne/qqexl3SdYsiCgqM

Hi Jean Even though I am supposed to be retired, I have been involved with paid work for the last several weeks and my hobby has been on hold. Howvere I am now back on the diode learning journey and am in the middle of video 17. which deals with some loose ends that I created in this cutting video and the grayscale video. I will take a few moments to carry out the test that Jerry and yourself would like to see. Best wishes Russ

Hi Max I was loaned a 20 watt MOPA fibre laser for about a year by a local company that builds bespoke laser systems for industry It was about 5 years ago when such lasers were rather rare and the company didn't have recources to explore the limits of the technology. That had a galvo head and an F theta lens. It was during thr period when I was trying to understand how a normal single lens with an expanding beam below the focal point could burn deep parallel cuts.. Ther F there lens was only ever designed to keep the OPTICAL focal point on a flat plane over a very limited area. Such machines are designed for MARKING the surface of materials and never cutting although deep engraving is possible to a limited extent. In nprinciple this lens is a brilliant idea because it means the beam can be made to scan across the material rather than trying to move the material acosssa static beam. As I said, this was long before I fully understood the weird relationship between laser beams and various lenses. or the fact that the OPTICAL focal point that all lenses are designed for is not the same point as the INTENSITY focal point. In the same way that speed and power change the position of the most efficient focal distance with a single lens, I noted the same characteristic witht the F theta lens. I had not yet understood the concept of spherical aberration and therfore this issue was just something I noted for future investigation. There are several bits of optical trickery used in fibre and RF lasers to modify the beams before passing into the final focussing lens. One such device is the beam expander, an optical device invented by Kepler and Gallileo in the 15th century to improve telescopes. The principle being to change a small non-parallel beam of light to one which is bigger and more parallel.. This is an essential requirement for expanding the very small output beams from RF and Fibre laser soiurces. I draw your attention back to Diode Laser video 03 where you see me demonstrating the effect of UNIFORM intensity sunlight focussed through a normal lens. You can clearly see that the outer part of a lens is where the spherial aberration effect is LEAST and the refraction concentrates the light into a single focal zone. The central part of the lens still refracts the light towards focal points BUT those focal points are spread beyond what we see as the OPTICAL focal point and because they are not acting in unison they are not concentrating the light INTENSITY sufficiinetlyto do damage. Lenses are designed to transit images and not to concentrate INTENSITY so we can do damage with it. The RATE of doing damage to material is directly related to the intensity ALL laser sources have an output intensity profile that is near Gaussian. That means the area around the beam axis will naturally be the most intense and most damaging.. Howewver send this beam through one or more lenses and at each lens , spherical aberration takes its toll and eventually destoys any semblance of a Gaussian intensity distribution . WE are almost back to a very low but UNIFORM intensity. Logically this means that in the same way that I was not using at least 50% of the sunlight to damage material, I am probably wasting 50% of the laser beam's potential with the optical trickery BUT the end result is a concentrated SOPT that is great for engraving/marking but useless at cutting. Although my interest in the diode laser was close to nil as a useful technology, the optics for harnessing the very low power of the laser beam is fascinating . It appears that designers are exploiting the many spread out and useless focal points that result from the low refactions around the lens axis but are stacking multiple lasers beams through this area to efficiently increase the intensity of the poorly focused small diameter. I am unsure if this is designed or accidental based on all the tedchno babble I read or hear as they try to sell these devices. Yes, it works but there are also many cosequential negatives that happen as well. It has turned out to be more interesting that I had originally imagined. Best wishes Russ

+ Hi Jerry Your ideas are thought provoking but you must not lose sight of two important facts of physics. First, light travels in straight lines or to imagine it another way, the little photon bullets are travelling in straight trajectories. Secondly, it is only the density of those bullets (light intensity) that can cause damage. Although we have two cones of light coinciding at a point those cones are not filled with uniform intensity light.The light is weakest at the surface of the cones.. Imagine those two cones just touching each other then where they touch will be a vertical beam of two combined weak rays.. Logically it must be these combined vertical stream of photon bullets that are responsible for the deep narrow straight cut. This is just a concept, in reality the cones are overlapping but it must still be some combination of VERTICAL photon bullets that are responsible for the cut. There will be some small element of non vertical photons that aremaking it through the cut entrance are causing the balloooning erosion effect near to the top of the cut. Watch the circular cuts and you will see no evidence of cut width change or cutting loss depending on the direction of the cut. I will try to do the test you are intersted in and send a picture via email (is it still "homecall"?) Best wishes Russ

@@SarbarMultimedia yep its homecall. That's very kind of you but don't let me interfere or take up your valuble time.. a small amount of time is all we have left .... Jerry

of course , if the beams are not aligned along the x axis or Y axis but are canted along the nnw or the ssw direction then cutting on X and Y direction will show the same. but as Jean describes far better than myself it would show up doing a full circular cut. I envisage it as the system the dam busters used to get there height correct using converging light beams.. Jerry

@@JERRYIRWIN41 Hi Jerry Yes the dam bustsrs heigh detection system is an exact analogy . However the fact that I cannot getthe beams to perfectly merge to a thin line means there is some "crud" of alsmost equal intensity at that intersection point that prebvents an ideal focus. . In a weird an fortuatous way that may help to "fatten" my dots when it comes to ditherdengraving.. Something I will be exploring futher in session 17.

@@SarbarMultimedia Many thanks again for your in depth replies. Jerry

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. kzbin.info/www/bejne/rIWocqBjZZZ4Z7M 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 kzbin.info/www/bejne/bX-bhZtnYq55atU kzbin.info/www/bejne/rGiQh3Sof8d9itU 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 KZbin 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