diode 16
Vložit
- čas přidán 20. 06. 2024
- My belief that diode lasers were great at engraving has taken a knock. In certain circumstances they can be fabulous but most folks do not understand what those limiting circumstances are. Getting a result of some sort by fiddling with Lightburn parameters makes most people happy.
I was always very sceptical about a laser diode's ability to cut. As expected , it was VERY slow and required multiple cuts...what a waste of a life. HOWEVER, Used with understanding of the beam properties, and with lots of patience, I was suprised at the cut precison but not impressed with the charring of wood products or the "textured" surface of black acrylic.
Mixing the cutting properties of this beam with grayscale control of power, results in amazingly crisp (but slow) 3D engravings. - Věda a technologie
This was very interesting Russ. I recently did some cutting tests with my new 45W Opt laser, and noticed some huge differences in cutting performance with different focal heights. Your video gave me some great ideas on how to test the cutting performance vs. focal height. Its back to the shop for more testing :-)
I love all your videos, amazing information. Do you have a site or group where you can order your Dohicky still? I had some laser power issues and am not replacing my mirrors and lens using your videos and would like to get data using your dohicky so I can track my work.
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
Hello Russ,
I really enjoy your videos, i am getting better in letting my laser machine do what I want with each video i watch.
So just an idea for a possible learning journey in the future:
Galvo-type CO2 lasers
There is plenty information out there regarding fibre lasers, but next to nothing engineer(ish) regarding their CO2 brother.
It's the same as with diode lasers, nearly no info that isn't marketing related.
The few independent sources mostly characterise these machines by their speed they whip through material and of cause their rather big spot size. But again, nothing really scientific or in a way an engineer would approach it.
Therefore I would be more than happy if you could bring light into the darkness of combining an RF-Tube with the strange behaviour of F-Theta Lenses, just as you did in this series.
According to what i have seen even a 30W unit can do outstanding "damage" compared to much more powerful gantry-type CO2 lasers, let alone units of the same power.
And all of that at multiple times the speed, since 2000 mm/s isn't unusual for a 30W galvo-machine engraving wood.
I would be more than happy if you could take this machine-type into consideration for future videos.
These machines are comparatively expensive though, mainly because of the RF-Tube i guess.
Anyways, great work with the diode lasers and revealing their secrets!
Kind regards
Max (Germany)
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
Dear Russ,
I agree with the methodological concern of JerryIrwin41 concerning the beam anisotropy.
The answer should be visible on the circular cuts where the beam is at "every" angle with the cut direction.
So is there any visible difference on the cut aspect over the circle perimeter ?
Thanks again for your efforts
Jean
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 Russ,
Assuming the 2 beams are converging / diverging along the X axis...and the speed is same....
Then cutting along the x axis when the beams are 'out of focus ' then it will behave as though there are 2 cuts at 5 watts happening ? and therefore cut deeper
if gutting along the Y Axis then when the beams are 'out of focus' it will appear as 2 x 5 watt lasers side by side..? and therefore cut shallower.
It would have been interesting to have seen when you did the cuts into the 10 mm along the X axis to have also seen cuts in the Y Axixs. at the same settings ?
Or am I completely seeing this wrongly ?
As always.. your videos do promote thinking..Thanks...Jerry
+
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