RDWorks Learning Lab 163 Lenses Part 2 Lets Focus
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- čas přidán 15. 05. 2019
- If you own a Chinese laser cutter this little series of videos about me learning how to use the free software provided, may solve the problem of trying to learn from a virtually unreadable manual.
I am nothing to do with RD Works, I am not an instructor and I am no expert. This series will document the essential bits of many hours of trial and error - Věda a technologie
Russ once again good job and thanks for doin' this. lookin forward to where this is going to take us ….
Great job you deliver, Russ.
Hi
I get a gmail copy of your comment but strangely it does not correspond with this comment????
You ask about using two lenses. Yes, this is possible to achieve a smaller spot size and I have already done all the research into this subject over several videos.
See czcams.com/video/UxfC9jbX6PM/video.html
The end result of my work can now be bought as a compound lens kit from Cloudray
see www.cloudraylaser.com/collections/nozzles-lens-tube/products/compound-universal-engraving-nozzle?variant=13488869867571
I am in the final stages of looking for a "long" compound lens combination to increase the cutting depth/speed. This is exactly the opposite requirement to the small spot size challenge.
If you are planning to do your own experiments , you must be very careful with your combination and spacing. If you concentrate the beam from the first lens too much , the energy density will be high enough to burn the anti reflective coating from the second lens. . Believe me.... I have done it!!!
Best wishes
Russ
Welcome back my friend.
Very interesting video.
If you got a red laser that was defocused to a beam of 12mm or so you could do some experiments that were not invisible light. I really like the idea that if you could get all the power into a spot smaller than 0,1mm then you basically turn a 60 watt machine into 300 watts
Hi
Your idea is correct but the detail is a bit off. You must understand that we are NOT amplifying the watts but amplifying the DENSITY of the watts. If I was going to poke you hard with a sharp pencil and asked you first which end I should use, you will absolutely choose the blunt end because the same amount of poke force would be spread over a larger area and the DENSITY of the force will be lower. and the pain a lot less. If we assume that my 60 watt tube power was uniformly spread across the 12mm diameter beam, that would give the beam and energy density of 0.53watts /sq mm ( the blunt end of the pencil). If I now squeeze those same 60 watts into a spot 0.1mm diameter the energy density becomes 7,700 watts/sq mm (the sharp end of the pencil) The sole purpose of a lens is to amplify the light intensity because that is what we use to damage material. You can prove that it is still only 60 watts coming through the lens by measuring the power after the lens only to find that the lens has cost you 3 or 4% loss.
Thanks for the comment because I did say that getting your head around the concept of energy density would not be simple, so your question allows me to give additional information to help people understand.
Best wishes
Russ
Where do you have your various files/pdfs? Thank you for what you do here! VERY informative!!
Hi
If you go to www.rdworkslab,com you will find all my drawings lodged there for free download.
Best wishes
Russ
Hi. I greatly appreciate your work here. I've learned a lot, and I am in the process of buying an 80W Chinese machine for batch production cutting/engraving. I think perhaps there is a limit to what is attainable with optics here in terms of dot size. Have you looked at retro fitting a low cost 1 micron solid state laser? This would bridge the world of industrial quality cutting (the world that you came from) with a much much lower cost world that these machine cater to. Just a thought!
Hi
I really appreciate your comment and suggestion and I am well aware that different wavelengths of laser light can stimulate the same material to greater or lesser extents. As your are aware I a a retired engineer who bought a cheap CO2 laser as a retirement stimulus for my two remaining grey cells. The fact that there were no reference sources to help me though understanding the technology and that my other long time hobby was video production/editing allowed me to take on my own learning journey and share it. My goal has always been to understand the technology I bought at a budget price and to see just what the real performance envelope was. Could I make it in any way close to those VERY expensive big name products. I have applied my shed science to create simple pictorial models ( maybe not scientifically accurate) that allow me to glimpse into the physics principles that make this technology work. . I have never wanted to build my own improved machine, but just to understand to the fullest extent each part of what I already own. Lenses are right at the end of the beam path and where the final and most important but least understood part of the technology takes place.
Your enthusiasm for mixing technologies is an interesting concept but, just like 3D printing, is not something that attracts me. However, when you have house trained your new Chinese dragon , i suspect you will be testing these ideas for yourself.
Best wishes
Russ
Thank's
Hi Russ,
Brilliant as always.
Question.
It would appear that based on 20% and 70% power levels that a smaller dot ( burn through ) is obtained with less power.
But you have to use these power levels in the real world to actually see results by burning material, every material has its 'power burn level'.
If there was a material that with a pulse length of 20 ms at power levels of say 5% showed burning,
then I would presume that the dot size ( burn through ) would be much smaller than you are obtaining now.
After all, when you do your multiple dots test to set focal length, if the material you used allowed a hole to be burnt through then the hole would indeed be very small.
Just ideas..
Hi Jerry
There are Three things you may wish to do with this machine. One is cutting where you must use max power normally (and quite slowly). Two is simple engraving of logos and text where low to mid range power is required and three is photo engraving where very accurate control of low power is required to make precise dots..
Lets start with dots. If you are an artist with a small paint brush you have the choice to make a small dot with that brush by JUST kissing it on the surface of your canvas, or to make a large full brush dot by pressing the brush harder. Our laser beam is a bit like that brush in that it has more power at the centre just like the brush has a point. If we just kiss that point of power onto our material we will BURN a small dot but if we leave the beam on that SAME spot for a longer period then the dot will be bigger.. So, the spot size of the lens is less important than controlling the power per dot ie a balance of power and time. I'm pretty sure that what you are seeing with this 20% and 70% difference is mainly that effect. However, this does raise the question as to what the REAL spot size is and I will be returning to this issue in a future part of this series. Theoretically ALL the light should pass through that SPOT (the focus point) therefore the spot cannot change size. So that means that even my charring diameter for 70% power is still not the spot size, because it gets even bigger when I increase the time from 20 to 50 ms. Alarming isn't it?
Best wishes
Russ
@@SarbarMultimedia Thank you for taking time out and doing such a detailed reply. very much appreciated...
( Your Laser series is responsible ( in a good way ) for me starting a small business designing and cutting out ( MDF ) wagons for 16 mm Garden Railways.)
Hi russ, me again 🤗 Another very interesting video thank you. Whilst waiting for my machine to arrive I have been reading up on and watching every video I can find on how to run these machines without causing irreversible damage during the learning phase of operation. Whilst cruising the ‘www’ looking for the correct mA reading for a 100w tube I came across an article that described using a small adjuster screw somewhere on the tube power supply in order to tune it so that when the controller is set at 100% the tube is at the correct mA thus giving you the full % range on the controller. I notice in your video you mentioned 70% being full blast for your tube and am now worried that there is a reason not to mess with the power supply, as I’m sure that if it was a good thing to do, you would have already done so.
Again many thanks for sharing all your hard work both on the machine and documenting it in sure a clear and concise way
Regards Jamie
Hi Jamie
Some power supplies have this screw externally available and others have it buried inside the case. If you have a 100 watt tube then generally it will be 24mA limit. However if it happens to be a named tube then 26mA will be the limit. If you look at the rating plate (or specification for your power supply you will find a 100watt unit will be capable of delivering 30mA. Without getting too technical the % power you feed into your program is NOT watts. It's percent of 30mA. That relationship is perfectly linear. whereas 50% power on a 100 watt tube is not 50 watts. the watts output is very non linear. I leave my power supplies with factory settings because
a) if I adjust it to 26mA I cannot plot the full calibration graph for the tube. It is necessary to over drive the tube to get this data , but you only do it for such a short period that you will not damage the tube.
b)Once I know what that max % I am allowed to use, my 2 remaining grey cells are enough to prevent me using higher values.
c)There is a quicker and easier way to apply a safety stop if you need it. Go to File, Vendor Settings, password RD8888. You will need your pc and machine connected (via USB?) so press the READ button to upload the data from your machine memory. Select the laser tab and there you will find a Max and Min tube setting limit. You can set the max to say 70% and press the WRITE button. Job done.
Best wishes
Russ
The power of your grey matter was never in question, only my own. Now If my understanding is correct (it usually isn’t) the pwm output of the controller is scaled in 256 bits between 0 and 100%, if never set over 70% max or under 20% min are you not effectively only leaving 128 bits of working pwm range thus reducing the resolution of grey scale engraving. I get the need to over drive the tube for testing but surely never 30% could you not leave just a 5% or 10% margin as over drive capacity? I know this is a flawed statement in that 100% power is never used for engraving but it is the resolution of the pwm signal that we are calibrating
@@jimmer147
Hi Jamie
PWM is very confusing on this controller. If you look on CN5 terminal group you will find an AN1 terminal.This is an analogue power controller that can be used instead of the PWM. Your % power appears on both these terminals as a 0 to 5vdc signal representing 0 to 100% of the max output power of the HVpower supply. This DC signal from the controller leaves the controller either as a digitally encoded PWM signal so that it does not get affected by spurious rf interference or as a simple analogue signal depending on which terminal you have connected. When that signal arrives at the HV power supply IN terminal it passes through an rc filter that either let's the analogue 0 to 5vdc signal straight through or intercepts the PWM signal and turns it back to an analogue 0 to 5vdc. It is the value of this dc voltage that actually controls the current allowed to pass through the tube.
PWM has nothing to do with grey scale, that is a completely different story.
When you import a colour photo to RDWorks, it imports as a grey scale image where every pixel is mapped for its coordinate screen position and its shade of grey (0 to 255), When you select the SCAN parameters you will select the OUTPUT DIRECT switch and that will now activate the grey scale decoding in the controller. Before you start scanning you must set your Max and Min powers. Max power=0 (black) and Min power=255 (white). Now when you start scanning the controller will output a power signal for EACH pixel according to it grayscale value.
I hope you can now see that PWM and grayscale are not related. In the controller manual, it actually recommends the analogue output for glass tubes and PWM for RFtubes.
Best wishes
Russ
Understood, I think my incorrect terminology and mixing of processes has confused things. Disregard the mention of engraving and the 256 step pwm and it’s irrelevance. If the controller output is between 0 - 5v and the untuned laser power supply is, for ease of math, 0-35mA then we have 0.07mA per V, if tuned to max out at .25mA then the output is .05mA per V is this finer control resolution not more desirable?
@@jimmer147
Hi Jamie
It's finally all down to one's level of OCD. The only time you need tight control of power is for dot photo engraving. I have a 60 and 70 watt tubes. Your ( Reci W4?) may only output about 80 watts. The power can be selected in 0.1% increments and I have NEVER had to resort to that last increment of control for dot engraving.. For cutting, the nearest 5% will be fine. So I think you are worrying needlessly.
Best wishes
Russ
My question is if I need a Voltage regulator on my machine to garante consistency of power?
Hi Yanko
Most electrical equipment is very tolerant of voltage changes. I think it would have to be at least a 30% drop before you noticed any changes. I speak with many people from all parts of the world and this has never arisen as an issue.
Best wishes
Russ
Hi Russ, there is a thing that bugs me... Assuming the beam has this bell shaped intensity profile, why don’t we get a smaller and smaller hole as we move out of focus after a certain point? In your tests the hole widens and widens and suddenly disappears. It could be that the tapered part is in-between two samples but there is no trace of it in any one of the different cases. Any thoughts?
Hi Thomas
This test work was the beginning of a two years set of tests and experiments to try and estobisk exactly why lenses cur. Everyone spends a lot of time concentrating on the focal point because that is where the lens manufacturers concentrate effort.. Their goal is to get all rays passing through a single smallest spot size. and that is what we have all been taught. What happens after that focal point is YOUR problem and not within the lens manufacturers remit. There is another widely documented energy density "fact" based on this theoretical spot size. The spot size change between a 1.5" and 4" lens is dimensionally very small; but when you convert those dimensions to area then the differences are large. Lets just say that the area of a 1.5" lens is 1 unit then as the focal length increases to 2", 2.5" and 4" their areas change to approximately 1, 3, 6 and 18 times. Thus if I had a 100 watt tube then the energy density of a 1,5" lens is 16 times greater than that at the focal point of a 4" lens. . This implied that a 1.5" lens would cut a lot better than a 4" lens. My experiments showed the opposite to be true and thus I began my hunt to try and find the real truth about how lenses cut..
What you see in this video was my first foray into the subject convinced that there would be some evidence /patterns that I could use as a guide for my next step. The only thing I proved was that I could never get ANYWHERE near those theoretical spot sizes
I am literally only just finding out thal truth I have been seeking. So you might like to jump to
czcams.com/video/WwsjwUmeCFI/video.html
and
czcams.com/video/ITQiwjAJysQ/video.html
Best wishes
Russ
hello russ I have a question on my laser when I send my work to the laser it shows up backwards I don't know if I hit a wrong button thank keep up the good work
Hi Richard,
Not sure where your problem is from your description
1) It could be your settings in RDWorks. Your drawing will always look OK but if not matching your machine 0,0 will produce a mirror image when sent to the machine for cutting.
Where does your machine run to for it's datum when you switch on or RESET. .. It depends on which issue of RDWorks you have. If you go to Config System Settings you will either find
A) a picture showing 4 dots to represent the corner that your head runs to. If so make sure the correct corner is chosen.
B) If it is an older issue then it will ask about mirror X and mirror Y. . It is a certainty that your head runs to one of the back corners in which case mirror Y will need to be ticked. If X runs to the left corner then leave the X mirror unticked. If it runs to the right than tick the X mirror
The final check is to look for the two blue arrows in one corner of your RDWorks work area. They MUST match the corner where your head sets 0,0.
2) If this is not your problem then maybe your picture displays on your machine keyboard incorrectly. If this is your problem then press your ZU button and the bottom item in the menuu is SCREEN ORIGIN Play away!!!!
Best wishes
Russ
it would be nice if every lens was sold with these maps. standardized to CO2 lasers at a specific power and pulse time.
Hi
The maps in themselves are interesting but have little practical meaning until I relate them to performance. I am just designing tests to check that feature now.
Best wishes
Russ
Hello sir we all learn a lot from you can you point me to your video were you share how to maintain steady power on the machine?
Hi Yanko
I am a little puzzled by your question because the only thing that our laser tube does is to output constant steady power. Can you explain your problem a bit more so that I can try to understand the issue you are fighting with.
Best wishes
Russ
Hello, I really like what Russ is doing in his videos. Literally professional. I bought a double head laser machine with 130 watts of power. I want to make money with this machine. I want to cut mdf and engrave my lover's photo on mdf :) Like you do. Those who came to install the laser machine did not give me enough information about how to use it. Probably not as good in themselves as you are. I have no technical knowledge. How many inches of lens and what brand should it be for image engraving? And can you tell me what to look out for in the engraving process?
Hi Murat
It's exciting to get a new machine but if you have no previous knowledge of laser machines I'm afraid this s no like hooking up a printer to your pc and learning a few keystrokes to make it perform. With some basic knowledge you can make the machine work but the real problem is that no two machines are exactly the same so after learning a few basics you will have to tune your practices and parameters to fit what your machine can do. It can do two basic things, cutting and engraving. These two processes are completely opposite in their parameter requirements. There are lots of myths about lenses and there is so much more to lenses than most people ever bother to know. Initially I would suggest using a 2" (50.8mm) general purpose lens. You claim to have a 130 watt tube which will be too powerful for good photo engraving but my guess is its actually less than 100 watts . I can send you a datapack on photo engraving but it requires some knowledge of image editing as well as an understanding of your machine's capability. Just add your disguised email address to another comment and I will send the information to you and also delete your comment/email address from public view.
Best wishes
Russ
36:05 "Depth of Cut"