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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 ua-cam.com/video/ITQiwjAJysQ/v-deo.html 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 ua-cam.com/video/tvNfAg-cOLA/v-deo.html 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 ua-cam.com/video/jl6OYf3nJfA/v-deo.html ua-cam.com/video/j6eaUroujXg/v-deo.html 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 ua-cam.com/video/TVgmoN1wljs/v-deo.html. 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. ua-cam.com/video/vTEAm-01E1Q/v-deo.html 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. UA-cam 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 suki@cloudray.com 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 ua-cam.com/video/tvNfAg-cOLA/v-deo.html

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. ua-cam.com/video/vTEAm-01E1Q/v-deo.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 ua-cam.com/video/7N8Th1-IF4s/v-deo.html ua-cam.com/video/v7-VArJbJTs/v-deo.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 UA-cam 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

Yes there are several videosdscribing how a laser tube works . However let me summerise the facts because ther are many that create plausible techno myths to explain what they dont really understand The laser tube (rf or glass) is filled with a mix of 3 basic gasses. Crudely there is 10% carbon dioxide, 10% nitrogen and 80% helium.. Heluim does nothing except act as a heat conduction medium to carry the heat away from the pink ionized nitrogen. In a glass tube this ionization is provoked with high voltage and in an RF tube the ionization is stimulated by very high frequecy. In both cases the atoms in the nitrogen are made to vibrate very fast. so that collisions with the CO2 molecules creates the laser beam (I wont go into the physics this is just the crude principle). Lets change subject for a minute and look at the HV power supply used with a glass tube. 100% power is a misunderstood concept because it has nothing to do with WATTS. IF you look at the specification for your HV power supply you will find it has a maximmum current output. Let's say 28mA. The greater the current flow through the ionized nitrogen the pinker and more intense the beam will appear. So current flow is used to make the nitrogen vibrate faster. %power is a lnear measure of the current flow through the ionized nitrogen. and NOT watts. 100% power = 28mA for my example, 50% power is 14mA and 25% power is 7mA . The excited nitrogen is acting like a cue ball and supplies extra energy to the CO2 molecule as it collides with it. If you add sufficient energy to the nitrogen by increasing the current flow (%power) ithere is a critical point wher the nitrogen has sufficient energy to break away one of the oxygen atoms from the CO2 and changes it to CO and O (carbon monoxide and a free oxygen) Neither will produce a lasing action. So your carbon dioxide is like ink in a print cartridge . Yes the CO2 will eventually be consumed by this destructive action. However, the manufacturer advises on a current level that will reduce this destruction to VERY low levels and a typical glass tube can last for 5 to 8 years. The watts output is not linear and ther eis no fixed relationship between %power and watts. It all depends on the tube brand . Typically you may find that you will achieve 60% of the promised watts at as littlre as 30% power.....very non linear. So, in answer to one of your questions, yes, you can dramatically shorten a tube's life by "over driving" it with too much current .Stay below the recommended current and it makes little difference to the tube life even if you try to run at low powers. It may sound counter intuitive but running a tube at less than the recommended max %power can often result in faster cleaner cutting. IThis is due to the complex relationship between the intensity distribution in the beam and the shape of the lens you are using.. As you reduce the %power that intesity profile changes and there is an intensity sweet spot for each focal length lens that will rarely be at the full allowable power. You cannot overdrive an RF tube because it works with a different control principle A 30 watt RF tube has zero power adjustment. Instead it's like a light bulb, its either ON ( and delvering 30 watts ) or OFF (delivering zero watts). The ratio of ON to OFF is called the dutty cycle and for example a duty cycle that is ON for 50% and OFF of 50% is assumed to be doing 15watts worth of damage. The RF tube manufacturer has fixed the SAFE current flow to create 30 watts and you can do nothing about it. That is the main reason why Trotec and Epilog make silly life claims and comparisons between the two technologies. By the way diode lasers work in this manner also. If you know the safe current limit for your tube and you have an ammeter fitted, you can test the % power to find the number that allows the safe current flow for your tube.. There are fancy ammeters that allow you to limit the current so that you can use 0 to100% without overdiving your tube . However you can achive the same level of protection by setting the % power you discovered in the vendor settings of Lightburn or RDWorks.

Thank you Russ for the detailed explanation. So, my 30 watt Trotec will not be negatively affected by operating it at 100% power - I believe the tube is a Synrad brand - will have to look inside to verify. There is no setting to adjust my power by mA. It does not operate using Lightburn or RDWorks. In my Trotec Job Control settings, I can adjust the supposed power (by percentage) but also the PPI/Hz. So would this mean that in reality my settings only allow an on or off condition which can be XXXX number of times within a particular distance -? For example, a 1 inch long black line would have all pixels "on" when set at 100% power but only half of the pixels "on" when set to 50% power? Presumably my black line would not turn out as black at 50% power unless there was sufficient DPI to cause overlap of the "on" dots? I should probably revisit your videos on dots and pixel size and PPI. Incidentally I can also separately set a fixed number of dots per inch within their print driver while in Corel Draw, such as 125, 250. 333, 500, 600, 1000. Corel Draw then sends this info to Job Control.

@@DesignCutters Hi You are correct. Your RF tube has no current control because that is set to a VERY safe level by the manufacturer. Your tube can ONLY EVER deliver 30 watts or nothing depending if it is switched ON or OFF. The ON/OFF is controlled by the PWM system and 100% power means it is ON for 100% of every PWM cycle. Remeber that there are two basic types of scanning (engraving) If you have vector letters for example. for every scan line the controller knows where thre starting edge of the letter is and turns the beam ON until the other edge of the letter tells it to switch off. If you have your %power set at 100% , then regardless of the PPI, there will be no pulses in the burn signal because the duty cycle is 100% (ie a continuous burn). In normal graphic terms PPI =pixels per inch but on a Trotec machine I have heard the machine demonstrators describe this parameter as PULSES per inch. This brings me to the other type of engraving that involves a BITMAP image . Such images are made up of individual pixels Let's assume your image has a resolution of 254 PIXELS per inch. First of all, PULSES per inch is meaningless if you specify 100% power. You can only get pulses if you specify 99% power or less (99% ON and 1% OFF). I suspect you have no control of frequency if the PPI means PULSES. The 254 PIXELS per inch example means that each pixel is 25.4/254 =0.1mm square. Looked another way that is 10 PIXELS per mm If I want to engrave this image at 200mm/s. If I want to run my image at 200mm/s then I need to create 10 X 200 = 2000 BURNS per second but only if they are PULSES that are switching the beam on and off 2000 times per second. ie the PWM is set to 2kHz. At 400mm/s the PWM needs to be set to 4kHz. This calculation may be confusing for many people so I think Trotec has bypassed this issue by asking you for the image resolution. If you say 254 PIXELS per inch and a certain speed then Trotec appears to be calculating the ideal PWM frequency to create 254 BURNS per inch. Single isolated pixels are the most difficult things to create but in theory the PWM system is capable Here is my little test pattern to see how good yoiur machine is at creating 0.1mm dots from o.1mm pixels. workdrive.zohopublic.eu/external/32aaa1ca80215714ed29e7eb1ed473de1c276af9b9cf88d21fd7bad49dc391d7/download Change the %power (pulse width) to see how this affects burn size.. I am sure you will be surpised. (by the way set your PPI to 254) Note your concept of how PWM works is incorrect as this pattern will demonstrate. 50% power does not mean you will lose half the pixels They will ALL be there but will be shallower (thus thinner) becuse you have halved the EXPOSURE time for each burn. Also your thoughts about PIXELS per inch in CorelDraw are also leading you astray. You can specify1000ppi in CorelDraw (that's a pixel siize of 25.4/1000 = 0.025mm square) but If you use a typical dither pattern such as Jarvis, Diffusion or Stuki then you will just get an overburnt mess. If you use newsprint or halftone then the image will be much cruder but may work. It certainly will NOT be a 1000ppi image That is why you must understand what your machine is capable of. Sadly there is one big issue with an RF beam which you will see with the dot test. Do the test in the corner nearest to the tube and then run the same test with the same parameters at the diagonally opposite corner of the machine. Are they the same?

Hi Joseph. As you work through my videos you wll seet that at one stage I tried to amplify the inensity effect of a beam by using various pairs of different focal length lenses. In the case of creating a super small clean dot, I succeded but when I tried to use two lenses for increasing cutting speed/depth I came across a brickwall. Lenses are designed with a focal distance based on the assmption that the rays entering the lens will e parallel. If you use one lens to focus the beam down to a smaller size then two issues ensue. First the rays are now converging at the second lens so this automatically reduces the focal length of the second lens. The smaller beam hitting the second lens is now not a Gaussian distribution (because of spherical aberration) and is being poorly focused by the less refractive geometry at the centre of the second lens. If the lenses are touching (as with the short focussing compond lens system I designed for photo engraving) this effect is not important, however putting distance between the lenses does not have the expected intensity amplification effect you would imagine..

Ok I have a question: What type of lens ie. ZnSe,GaAs,Ge,CVD-ll-vl Znse for photo engraving is ideal.? I believe 1.5 is a good length but don't understand the types. Do you have a video on this subject. Thanks Joseph

@@josephlovell6951 Hi Joseph Yes there are several videos on lense but it is all summed up in these two videos. Forget germanium as a lens because after about 12 watts the power changes the crystal stucture of the lens and it becomes opaque for CO2 light. The lenses we can buy for our machnes regardless of price or material, ALL possess an unbeatable physics property called spherical aberration. In normal lens use for telecopes . projectors, camaeras etc the light is always uniform intensity as it hits the lens.with parallel rays. Under these circumstances the standard laws of lens theory apply. However.we are not sending a uniform intensirty beaminto the lens and we are not trying to project/capture an IMAGE. Instead we are tring to intensify the intensity of the bean to damage material. An the golden rule for damaging material is " the greater the INTENSITY the FASTER you can do damage". There are two lens forms we can buy. One is plano convex which has significant spherical aberration properties and is designed to be used flat side towards the work. The second type is a meniscus form where the lower face of the lens is concave,. This reduces the spherical aberrationeffect by about 90% and produces a pretty small concntrated spot size. This form of lens is ideal for engraving whereas the plano convex form, with its HORRIBLE optical properties. is actually more efficient at cutting. There are basically only two types of lens material we can use . 1) Zinc Selenide All ZnSe material is poor at transmittong CO2 light (about 70% efficient) and is toxic to handle. However, in the same way that you see a blue/mauve hue to camara and binocular lenses which is there to improve light transmission, so it is with ZnSe lenses. They are coated with several layers of exotic materials to provide an anti reflective coating to improve light transmission to 98% or better.. Althnough ZnSe can occur naturally it is always grown in a laboratoty (jusyt like silicon chips) The Chinese use a manufacturing technique called Physical Vapour Deposition (PVD) whereas the USA uses a process called Chemical Vapour Deposition (CVD). The PVD materal is limied to about 80 watts whereas the CVD material can handle up to about 200 watts . The ll-lV material is always CVD material and has a slightly more efficient anti refection coating. ..... but you pay a lot more for that 1 or 2% transmission improvement. Remember that ALL these lens types are designed and made according to factors defined by conventional lens theory so there is no significan difference in the GEOMETRY between any of these ZnSe lenses, they all perform the light intensification function in exactly the same way regardless of manufacturing process or price. By the way, the AR coating on the ZnSe makes it safe to handle but be careful if you break a lens. 2) Gallium Arsednide This is a weird material because it is black and you cannot see through it. So you wonder how can it work as a lens? Light is equally unfathomable because at 12.640 nm wavelength this black material is transparent and allows the light through. This materail is even less efficient at transmitting light (about 60% efficient) but by adding exotic materials to produce an anti reflective coating, the transmission efficiency is again about 98% However there are two properties that sets this materiial apart fro any of the ZnSe products. First. it is mechanically stronger and will easily handle powers in excess of 500 watts . Second, it has a different refractive index that means that for a given focal distance the shape of the lens geometry is "flatter". As I show in these two videos. the focussing effiiency of a lens is not constant, it depends on the INTENSITY distribution in your beam. For your RF machine the situation is very complex because your beam is being modified by a beam expander as soon as it exits the tube. This basically destroys the nice Gaussian intensity distribution and what is sent aroind your machine is an unpredictable intensity mess, The RF machine is pretty efficient at engraving (if you find out how to control your dot size) but it is very inefficient at cutting (yes I know it cuts) but the spherial aberration property of the lens can only be exploited by a decent Gaussial intensity distibution. Finally if you are looking to produce the smalles dot you need a special compound lens with a very sort focal length (about 20mm) that I develoed and is on sale at C;loudray see this www.cloudraylaser.com/collections/nozzles-lens-tube/products/cloudray-n04-universal-compond-engraving-nozzles and scroll down to see lots of detail. Sadly , Trotec have locked you into a rather expensive and inflexible lens mounting design and a high definition lens arrangement was never on their design radar. This means doing the best you can withthe shortest focal length lens available and see if it can be of meniscus form.

@@SarbarMultimedia thanks that is helpful

Hi Joseph How lenses and laser beams interact has taken me a long time to understand. Thus my knowledge of lenses from 5 years ago has changed a bit. You may like to update by looking at these videos ua-cam.com/video/7N8Th1-IF4s/v-deo.html and ua-cam.com/video/v7-VArJbJTs/v-deo.html

@SarbarMultimedia I have watched many of your videos over the last week. I love how you keep digging into them . Although sometimes your concerns are not clear. But I get it you need more data before you can make that leep. I did subscribe so I can stay up to date. I just got an older co2 laser 50w that I have updated to 70w tube and power supply. But looks like the controller is very old so I need to learn RDWorks

@@josephlovell6951 Hi Joseph Always bear in mind that these videos are not rehearsed and that you are looking over my shoulder as I experiment and discover. This is a record of a learning journey and as such some sessions will be very much "follow your nose". It may take many sessions to arrrive at a sensible conclusion. It took me about 3 yeas to discover exactly how lenses managed to focus the beam to produce a deep parallel cut. There is no need to learn RDWorks if you are used to using Lightburn. Lightburn was created 7 or 8 years ago because a very capable software programmer who was also a laser hobbyist, became aware of the limited capability of RDWorks and it's very clunky interface. He set about reverse engineering RDWorks to create Lightburn. So with just a few exceptions, everything in Lightburn is in RDWorks but the usability and features of Lightburn are from a different planet.. Lightburn has now been developed into an industry standard package where it can be used with any type of laser or laser controller using Linux. OS or Windows. RDWorks is still Widows only.

@SarbarMultimedia thanks for the information I have a morn 3050. It has a RDL8082 B main board. That I can find any thing on it. So unless I can contact to it. Witch I have not tried at this time. Because I fear I won't have the driver's for it. So I will cross that bridge when I get there. I have parts on order to fix the cooling system. Just trying to get as much knowledge as I can for now. I'm hoping I can make it work and not have to spend 400 for a new contractor. Still think your work is brilliant. I bit surprised at some of the rezol

@@josephlovell6951 Hi Joseph I think your machine will be fitted with a RDC6442 controller see www.google.com/search?q=RDC6442&oq=RDC6442&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIGCAEQRRhB0gEINTEzNGowajeoAgCwAgA&sourceid=chrome&ie=UTF-8 If so then either Lightburn or RDWorks will be OK and there is no need to upgrade.

hi In the past three yearsI have learnt a lot more about the interaction of light waves with various materials and I now understand how this effect happens. In fact I recently reproduced the same bubble effect during experiments with a diode laser see ua-cam.com/video/pvNKf2T-op4/v-deo.html from about 20 minutes The bubbles are random (ish) because there is a zone of light intensity either side of the focal point which is sufficient to ineract withthe few acrylic molecules that happen to be in the path of the photons

My apologies for late reply, I am currently on a vacation. However to get all the data (and more) you need to contact me privately so that I can send you what you requested. Please use this contact form forms.zohopublic.eu/ndeavorlimited/form/K40XtreeemLaserCutterContactRussSadler/formperma/k2Cn0QN5ChpazfTMAUw25lZ-FKpjZa96TQWHjv3ntOg Best wishes Russ

@@SarbarMultimedia Hi Russ. I send a message few days ago on yor private conatc. I did not get any respond. Thx anyway. Dex

hi The simple answers are yess. all brands have this beam alignment issue but there are a few machines that have now tried to deal with this setting issue by making the head mounting bracket crudely adjustable in Z but the emphasis here is on crude.. However, one company did recognize the merit in all my modifications and the blue machine you see me using is a prototype machine that Cloudray designed , that is a copy of my original modified 300x500 machine.. My original machine did not have a programmable Z axis but this Cloudray version has a super smooth table mechanism. see this product www.cloudraylaser.com/collections/laser-cutting-machine/products/flash-sale-cloudray-cr-series-russ-oem-70w-co2-engraver-cutting-machine-with-working-area-20x12 This is exactly the machine you see me using. ;

I am not a chemist but from everthingi know and have experienced, acrylic is very analagous to H2O. At room temperature it is a clear solid just like ice. At 1C ice changes state to lquid water . At 160 C acrylic changes from solid to liquid acrylic. At 100C water boils off into micro liquid particles (steam). In the same way, liquid acrylic boils and evaporates as Methyl methacrylate, micro particles . Steam recondenses on a cold surface so does acrylic . If you blow it back onto the material surface with air assist the hot vapour will stick to the surface as it cools to a solid . Under the correct circumstances it is possible to cool the acrylic vapour before it hits the material surface and ithen just settles as a thin film of solid dust that can be wiped away with a dry cloth. I know that you can use acetone to dissolve acrylic but an not aware that any by-product of acrylic decomposition creates acetone. Quite the contrary. Acetone is used in the prodcution of acrylic (MMA) and is therefore most unlikely to return as a decomposition product.. Acrylic is basically a hydrocarbon and if you reheat the vapour to higher temperatures then it decomposes into combustable products. Great question Thanks

Hi Max and Min are equal because this is not normal constant power cutting. Enen though you still slow down forthe corners, the very short high power pulses do not cause burning because they are always instantly vapourising the card. Reducing acelleration to achieve staright cuts sounds like a mechanical issue. If you wish to contact me privately so that we can try to sort this with email and pictures/video then use the following form forms.zohopublic.eu/ndeavorlimited/form/K40XtreeemLaserCutterContactRussSadler/formperma/k2Cn0QN5ChpazfTMAUw25lZ-FKpjZa96TQWHjv3ntOg

Hi I understand your frustaration about UA-cam videos. Everyone want's to share what they can do with their laser but nobody is taking the time to understand even the basics of what makes the technology tick. Having spent many years experimenting to self-educate myself on various types and wavelength lasers, I am a latecomer to 455nm lasers because they are low power, slow and have a very limited range of materials they can damage. They seemed very uninviting and I thought it would be simple to trasnsfer my other knowledge to this technology. However there are still some surprises that I did not expect as I dig deeper into how these devices actually work. Lense and laser beams are like a marriage made in hell. On the surface they seem to work ok but when you understand what is really happening, things are far from efficient. I am still a student exploring so I will let you catch up with the series to find out what I have discovered so far. Thanks for the interest

. Two problems with your thought. First you would have to flip the program and second how would you guarantee perfect alignment with the first cut.

I hope it works as well for you. Special problems require special solutions