Diode Lasers....Under the Hood 25

[@alexcampbell492]

I feel that the time / spot size relationships are consistent with your CO2 laser findings and the intensity of the Gaussian beam distribution. I run a laser engraving business and teach this to all of our staff in the time/beam width relationships

[@SarbarMultimedia]

Hi Alex It's good to know that there are a few people that understand the finer points of laser technology rather than just fiddling with Lightburn settings.

[@jppalm3944]

Deep dive into diodes

[@MohamedHamed-sr3cn]

great video. Are you gonna do one about finding the perfect cutting settings? I have the same diode laser but in 60w

[@SarbarMultimedia]

In a futureb session I will be exploring the mechanism by which diode lasers cut materials because it is not as simple as a lookup library. In the next session you will be surprised to find out that your blue laser light cannot cut wood. That may suprise you, as I know you can cut through fairly thick wood with your 60 watts with a perfectly paralle kerf. Few people will understand why that can happen when A) the beam cannot cut wood and B) the diverging beam just 10mm below the focal point should produce a wide cut at the bottom....but it doesn't. Why? I know this may sound rather selfish but my videos are a record of me self-educating about this technology in great detail. Only if I understand what is REALLY happening can I make sensible logical decisons about how best to exploit the technology. I may at some future date be able to give general guidance about finding the best parameters for cutting and /or engraving but there are many detailed puzzle pieces to explore before I arrive at that point. Most diode users are encouraged to use the Lightburm Material Test Tool to detrmine the "perfect "settings for their machine. I happen to know that test matrix was designed originally for galvo fibre laser use. It is now being widely misusedby CO2 and diode users and will give nothing but "imperfect" settings unless used with mechanical understanding of what your machine is doing and adapted accordingly.. Here are a couple of videos I have done on this subject that may help you. Cutting kzbin.info/www/bejne/f5_Rpottl9Sse6M and engraving kzbin.info/www/bejne/hJKYkGmloLqsgck

[@patrickdjebar9225]

​@@SarbarMultimediaI can't wait to see the next video

[@wadhamga]

Random thought because I have just experienced the oval beam size with a border frame which I needed to be exactly the same size all the way around, it is wider on the x axis and narrower on the y axis which meant the border which was to be taped to look like a frame required modifying to hide the underlying material. My question is about the protective lens on a diode laser and whether it changes the Gaussian beam distribution?

[@SarbarMultimedia]

The simple answer is no. Are you sure you have found the best focal point? A few mm away from my focal point the beam quickly turns to an oval and then to a squarish shape as it defocuses . At the focal point the beam is virtually round. As I mention in this video the claim about there being a "wide" focal range is total rubbish. All the diode heads I have tested have a similar chracteristic except for the single diode 5 watt head. A thought about your X and Y difference in line thickness. I presume this is a drawn line border rather than something like a marquetry frame? If so then you could break the frame into 4 lines. The X wider lines could run at a faster speed because this will reduce the line width to match up with the Y axis lines. Experimentation required.

[@wadhamga]

@@SarbarMultimedia Thank you. Yes, a drawn line border. The confusion that I saw some months ago, was from one angle, is this observation below and another angle is the focal point/spot size/kerf and therefore the shape measurements need to be tested from another angle/perspective. At 9 mins onwards is the quickest to understand what I saw. kzbin.info/www/bejne/aqXNqHabfsZkqNU

[@wadhamga]

Another mind opening video and well balanced between data and proof, thank you! I have a burning question about why when I am doing images in any dither or grayscale does my laser change speed, slows when higher power and is faster when low power burning across x axis? No matter what speed setting or power setting it is visibly slowing on high power spots in the image and increasing on low power across the x axis. Could this be controller for diode is different to CO2 or your one? Atzer P20 that I use.

[@SarbarMultimedia]

Hi This is a fascinating issue that requres a sepereate investigation by you to tease the elements of this prob;lem apart. Your controller may well have a power/speed modulation function built into it. However, if you always use the max and min power set to the same value, then this function should only kick in as you decelerate at the end of a scan line, change direction and then accelerate back to your chosen speed. In principle a dither is a constant power mechanism for creating images. Once you have determined a power and speed to achieve the DOT size you require, EVERY dot will be burnt at these parameters, even if you have a min power set. It is the DENSITY of dots that gives the grayscale appearance to a dithered image and has nothing to do with power variation. Thus, logically, if there is no demand for power variation, then the power/speed function will not operate. Grayscale images are completely different in the way they ask the controller to operate. EVERY pixel may be a different shade of grey and based upon the 256 shades the controller detects it will set the power output (PER PIXEL!!!!) to one of 256 power levels between the max and min values you have defined. However, this only works properly if the SPEED is constant. I cannot believe that some software writer has been stupid enough to leave the power/speed modulation function operative for greyscale. So, I think you must try to decode your issue by creating some test patterns. A simple one will be to draw a series of dashes (in one line) where the dashes are 10mm long and the gaps are 10mm. Set the power (max and min to the same) to see if the zero power of the gaps causes a speed change. Basically you have got to determine with some simple tests such as this , whether the problem you are seeing is because the controller is sending signals to cause what you see OR is this caused by the mechanics of the machine, as I found out with my machine in the previous video (24)

[@wadhamga]

@@SarbarMultimedia Back to my basic question then is the controller your using a CO2 one or diode one? Is there a difference which means your unit is not functioning as a diode laser would?

[@SarbarMultimedia]

@@wadhamga As you can see from my machine, this is not a normal diode machine. It is a CO2 machine where I have disabled the glass tube and fitted a diode head to the XY drive mechanism. The controller is indeed different to a normal diode controller and allows me much greater ability to control parameters. The controller has a PWM signal output that is used to control a different CO2 source that is not a glass tube but is stimulated by radio frequencty (RF) rather than a high voltage (20,000 volts dc typically). You will find that your controller does not allow you to adjust the PWM fequency whereas I can adjust it from 1Hz to whatever the diode limit happens to be. My Two Trees head claims to operate from 1 to 5,000 hz. but I am pretty sure it can go faster. You are probably using Lightburn as your control software? This was originally written to copy all the features of my Ruida digital controller. The guy that wrote the software has tried to create a piece of universal laser control software and so he added many functions that are really only applicable to fiber galvo lasers. In the past 3 years he has added diode control to its capability.. t depends on which laser type you have and which laser controller you are running that determines which control functions you can adjust. Although it is an amazing piece of universal software , trying to make it tightly specific for each technology is a serious challenge. My controller is not the GRBL type used in most diode machines. So I have much greater control of both machine parameters such as accelleration as well a a wide range of control of the laser beam itself. I have no specific interest in reviewing one product against another, no, my very selfish interest is in self educating myself in the underliying priciples that make each type of laser technology work. My videos just allow you to follow my methods and processes for acquiring that knowledge. and are far too tedious for many diode users who just want to make items to sell om Etsy. The tremendous flexibily that my controller offers, is the perfect tool for my sort of investigation.. If you are still stuggling with your variable speed/power issues, you can take a video of the machine misbehaving and upload it to youtube as an unlisted video. You can then send me the link so that I can better understand your problem.