With Russ Sadler
In this Series, Russ has purchased a new 500 x 300mm, 50W laser machine from eBay. With a view to modifying and upgrading it. In fact, he rips out the glass laser tube and high voltage power supply. Then he replaces them with an RF laser source and PSU from Cloudray. Find out how the expensive RF laser source upgrade compares to a glass CO2 laser tube. Prepare to get your hands dirty!
If you are considering purchasing a CO2 laser machine with an RF laser source from one of the big boy suppliers. I would suggest you check out this series before making a decision!
Video 01: Welcome To A NEW Learning Adventure (16:21)
Looked at from my point of view, I am a very lucky guy because Cloudray have VERY generously sent me some rather expensive equipment to upgrade one of my machines. Hmmm. If I succeed, it could spawn a whole new generation of low cost, high speed, engraving machines.
You must admire Cloudray for taking that gamble. HOWEVER, I am expecting either a bribe, or a visit from men in black suits. Demanding I desist from showing you how to make cheap fast engraving machines!!!!
Video 02: Catching Up With China Blue (26:27)
(Editor) Russ is carrying out some destructive work on his Tangerine Tiger. This is before starting the rebuild to bring it to the same standard as his modified China Blue machine. By replacing the belt drive system. First he cuts a side access hole for the stepper motor. Then he replaces the stepper motor bracket and 2nd mirror assembly with an all-in-one assembly.
This assembly includes a rack and pinion replacement for the drive system. Next up is removal of the cable chain and fitting of the lightweight laser head.
Video 03: More China Blue Catch Up (26:13)
I continue to be brutal with this machine as I manufacture a whole new tube mounting enclosure to prevent cutting fume ingress. Lots of cutting/grinding, sweat and swearing (edited out) and ripping out wires, sees good progress as things begin to take shape
Video 04: Fixing The Wiring (54:31)
Rewiring parts of the machine to remove surplus switches and functions and rewiring to add auto air assist and a time delayed extraction switch off. re-siting the limit switches and REMOVING THE DANGEROUS LED LIGHTING.
The new belt drive bracket arrives, and the X axis returns to action with its flexible rack and pinion drive principle. Details of the RF laser source upgrade tube are here.
Video 05: We Have Lift Off (44:45)
This is a milestone video where we finally have a fully functioning machine available for testing. As usual there are many hurdles and mistakes to overcome.
Video 06: Beam Expanders Decoded (11:01)
A quick footnote to the last session where the discovery of a rapidly expanding laser beam brought home the importance of understanding what technical parts of the specification actually mean in the real world.
Video 07: Let’s See What We Have (20:16)
Having established that an RF laser source upgrade beam is not as parallel as the beam from a glass tube system, it was found necessary to add some correction optics. Here we test the power cost and the effectiveness of this addition and finally get the beam setup. I impatiently take a peep into the future.
Video 08: Let’s UNDERSTAND What We Have (39:09)
Having more or less completed the build (there are a few small detail issues still to be resolved) and beam alignment completed, we know that the machine works and is usable to carry out initial tests.
These tests include analysing the beam profile, recording the RF laser power characteristic and using an oscilloscope to verify how the PWM signal controls the laser beam power.
Video 09: Where Is The Magic? (44:57)
The way this technology has been hyped by the big companies, I was expecting to discover some magical properties from this type of beam control and generation. Glass tube technology allows control with just power and speed parameters.
It is simple and intuitive for people to comprehend and use. RF technology adds frequency to this list of control parameters and power is no longer an intuitive parameter. The complex interplay between these 3 parameters now requires a degree of mental gymnastics to optimise performance.
I can begin to understand why the sellers of these machines hide that complexity behind menu driven software. This video attempts to separate and explain the effect of each of these 3 parameters and then demonstrate how they mesh together to produce a predictable result.
Video 10: What Is The Point Of HYPERDRIVE? (23:39)
I am beginning to question high speed engraving with an RF laser source upgrade. The underlying principle seems to be limited by the power available. The higher the engraving speed the more power is required to match the damage threshold of the material you are marking.
That is a simple physics fact. So is high speed engraving with RF a bit of an illusion where the engraving speed is actually low but the acceleration is high. This video shows how slow speed and high accelerations can yield faster cycle times under certain circumstances and that depth of cut (colour) disappears as speed increases.
RF refers to the means by which the beam is generated and not the manner in which the beam is controlled.
That control is managed by a simple fixed amplitude PWM signal that allows only duty cycle and frequency control. I will go hunting for some POSITIVES in the next session. Response speed promises to be one.
Video 11: Making Dots, How Hard Can It Be? (31:15)
Dots are the basis of dithered photo engraving. The simple rule is 1 dot = 1 pixel. This machine has pulses at its operating heart so therefore must be fast responding, Fast response should give the capability of producing crisp clean dots….that’s what I have always imagined of RF lasers, It turns out the opposite is true. That fast response prevents crisp ROUND dots.
Video 12: Dotting Impossible, So What Now? (36:49)
This session proves beyond doubt that RF technology cannot produce round dots, they will always be oval. The switching capability of the technology is so fast that when combined with PWM control system, it actually prevents single dots with any useful power. Thus the simple 1dot=1pixel rule cannot apply. Instead, I look at other compromise strategies for photo engraving.
Video 13: Let’s Compare RF And Glass Tubes (45:35)
I was very excited by the prospect of creating a very fast RF laser engraving machine to match the performance of those very expensive commercial machines. A few months into the project I now have a lot of detailed learning about how this different technology works, I discover there is no magic in it after all just lots of smoke and mirrors.
This session lays the published facts about glass tube and RF systems side by side so that it is possible to make realistic judgments on the merits of each.
Video 14: Photo Engraving Myths (45:27)
Claims to be able to burn 600 to 1000 ppi images with and RF laser engraver have always intrigued me. How is that possible when the technology uses the same laser beam and lenses as DC glass tube technology? There must be something magical happening when the beam pulses at high frequency!
Not only can it produce dots thinner than a human hair, but DEEP and DARK images when the physics dictates this is not possible. Now that I have a puny 20-watt RF laser source I hope to discover the slight of hand tricks that are being used to convince us that there are holes in the laws of science.
Video 15: Is Ordinary Engraving Another Disappointment? (20:41)
Ordinary engraving is one of the areas where the almost instant switching capability of this technology should excel. In this session we explore the superficial properties of this high-speed engraving capability.
However, with only 20 watts of burning power, just how fast will that allow us to go. We know this machine is currently capable of at least 1400mm/s but does that mean faster cycle times? Caution…. there may be two limiting factors that will prevent this speed being usable. First is POWER, just how thinly can I spread 20 watts and get acceptable results? Second is ACCELERATION, the faster the linear speed, the longer it takes to accelerate and decelerate.
We have already seen how this second factor can have a HUGE effect on cycle time. Hence, the headline speed capability of a machine maybe impressive but without sufficient watts and motor power that number may be meaningless.
Video 16: What Can We Cut With 20 Watts? (40:43)
Is my understanding of how PWM controls this RF laser source upgrade tube flawed? I think there are major differences about the way PWM can be used in glass tube lasers and RF tubes. I compare the two technologies and demonstrate that with RF technology it is the raw PWM that is driving the beam switching.
Certainly, for a low power 20 watt tube, like I have, CW (100% power) is the only power I can ever imagine using and that means I am bypassing any PWM control. Cutting efficiency is dependent on 4 main factors. Assuming I use full power, they are: – lens focal distance, cutting speed, beam expansion factor and the correct application of air assist. All are demonstrated in this video.
Video 17: Beam Setting To FIX The 4th Corner Problem (16:32)
The eternal problem with beam setting has been the “4th corner”. There is a well tried and tested beam setting procedure that works well in principle. In practice there are many instances where after setting 3 corners perfectly, when you check to see where the beam is landing on mirror 3 at the 4th corner, you discover that there may be a significant error of several millimetres. T
HIS IS NOT A MECHANICAL PROBLEM. But an issue where the beam has been deflected to a different path. For several years I have pointed to the flimsy mounting bracket at mirror 2 as the root cause of this problem. When people fix that problem (usually be adding an extra fixing screw) or re-fixing the cable chain, the problem can be cured.
Recent design changes I created for the mirror 2 mounting bracket have made it so stiff that I MUST have fixed this issue for ever. Wrong. I have had to go back to absolute basics and try to understand just how it is possible for the beam to be deflected so much after what appears to be perfect setting. It turns out that there is a vital setting step that is missing from this long established procedure. Add this step and it will fix your 4th corner problem.
Video 18: RF And Glass Tube Cutting Comparison (29:10)
Thinking that my RF laser source upgrade was just 20 watts (with a bit of extra power for warranty purposes). I was surprised by the initial cutting tests on 3mm Baltic birch plywood. Perhaps there was something “magical” about the cutting power of an RF tube after all!!!!.
Were the “big companies” marketing claims correct after all? We require the truth. In this session I set about comparing an RF tube and a glass tube running at exactly the same watts and with the exact same test conditions. Let’s see if I am confirming facts or shooting down myths.
Video 19: Greyscale Engraving (43:36)
Grayscale engraving has two main uses, well…., one and a half. The flaky HALF is for replicating greyscale images onto organic materials that will “scorch”. The more solid ONE is for 3D engraving of materials that will erode, such as wood and some safe plastics.
This session deals with the most fragile application, photo engraving, and examines the issues that prevent it ever being serious competition for dithered laser engraving. The RF laser’s rapid switching capability makes it a perfect tool for doing such a task, however, here we discover the weak link in the process
Video 20: 3D Engraving With Greyscale (58:27)
The RF Technology’s ability to almost instantly switch to different power levels, makes it well suited to creating a variable depth scan line. Add all these scan lines together and proper 3D engraving is the result. I have successfully mastered the process on my glass tube machine, but the PWM manner of tube control used by the RF technology appears to offer different challenges. I explained the process of “burning” wood with a laser beam in the previous session and showed that with well-chosen parameters it was possible to excavate a significant volume of wood and NOT leave a charred surface behind.
Video 21: Pulse Width Modulation (PWM) And Cutting (50:39)
In reading operating manuals for some of the “expensive” RF machines I find instructions for using different PWM frequencies for different materials. This session investigates just how/if PWM duty cycle and frequency affect cutting I cannot see how frequency is related to specific materials because as I explain in the video the frequency to excite the various molecules is dramatically different to the PWM range of frequency.
Just looking at most of these expensive machines, tells me the designers had scant understanding of just how important efficient air assist is to cutting. Is messing with frequency an attempt to compensate?
More Video Series
Why not try out one of our other video series such as:
The Lightblade Learning Lab is a series of videos that Russ did for Thinklaser Limited based on using the Lightblade 4060 Laser Cutting and Engraving Machine. The Lightblade 4060 has a 400 x 600mm bed size and was supplied with a 60W EFR laser tube.
The Fiber Laser Series is all about Russ’s adventures and investigations with a 30 watt fibre laser, loaned to him by Dean at Lotus Laser Systems. If you are looking for a laser solution to engrave metal, without the fuss of using coatings such as Thermark, Cermark or Molybdenum Disulphide spray, then this is the series for you.
The K40 Xtreeem Laser Cutter Upgrade Series is a series of 6 videos covering how Russ, strips down a generic K40 laser. He then designs and builds a number of new components and completely upgrades and overhauls the K40 into a high specification K40 Xtreeem Laser cutting and engraving machine.
The Lightburn Software Series is probably the best generic laser cutting software available (I use it for almost all of my laser work). This series has tutorials, hints and tips as well as the occasional speed comparisons between it and RDWorks. My thanks to the team at Lightburn for allowing me to embed their videos.
The Top 10 Ranked RDWorks Learning Lab Videos
Recommended
Check out The Concise RDWorks Learning Lab Series that condenses all of Russ’s work into an easy to follow encyclopaedia of laser knowledge.
