This is our deep dive into The Russ Formula for Successful Photo Engraving. See Russ Sadler's original work (on which our tests are loosely based) at the end of the article. We are also incorporating a viewer's feedback on our interpretations of the Russ Formula.


TABLE OF CONTENTS


Intro

We recently produced a video, Crash Course - Photos In LightBurn, in an attempt to help with preparing photos in LightBurn, and after receiving some feedback and constructive criticism from a viewer, we realized that without having a firm grasp on how your laser behaves first, you really won't know how to 'dial it in'. 


So we graciously decided to accept the challenge of delving into how speed, power, focus, and all of the other factors specific to your laser, can affect the output. This is our deep dive into The Russ Formula for Successful Photo Engraving

See Russ Sadler's original work (on which our tests are loosely based) at the end of the article. There is a video and links to files and resources utilized in this article.


Viewer's Feedback On The Crash Course Video


Hi Team


  Let me start off by saying that I already own 3  Chinese laser machines and have been self educating on the machines, the technology and the Chinese laser  industry  for the past 6 years. From my early days I would always go to the Thunder Laser website for good information to help me get started. Not only did I greatly respect their openness but as a retired engineer I could appreciate the high quality of design and the superb engineering  that went into creating beautiful machines.


A couple of years after I started my learning journey, I became aware of the efforts of a dedicated individual who was in the process of writing a much better version of RDWorks. It was obvious that this guy was a professional programmer because he really understood user interfaces.  As Lightburn started to become more than a beta  version I got involved with helping to iron out some issues with the graphics section of the package 


Prior to this work with Lightburn I had spent  a lot of time trying to decode how  a black and white paper printing technology  (which is what you see coded into Lightburn)  could be faithfully reproduced with  a CO2  laser machine . The concept is simple: 1 pixel=1 dot  but the execution is very difficult.


Lightburn, 1-Touch and Photograv  will only ever produce cartoon-like images  or BBQ'd wood because none take into account the ABSOLUTE importance of understanding what the machine is capable of.  These softwares have no knowledge of your power, your lens focal length, your nozzle type or air assist, the accuracy of your focus, the material you are using or its flatness.


My intention is to help you to properly understand the capabilities of your machine and software ( because I am an admirer of both).


I will ask you to try and run this very small test program (dotSize.bmp is attached at the end of this document) on one of your machines. you will need a magnifying glass because it is only 10mm wide and 5mm high. It is  a 254 ppi bitmap so make sure you match your parameters. It takes about 2 seconds to run. Look at the example  image I have provided and aim to copy #4


 Let me make 2 predictions:


1)  Lightburn will  produce the  dashes  but not the dots. You will have to use RDWorks initially.


 2) You will struggle to get a pattern that matches #4


Try different materials.


Sincere good wishes


Our Take On The Feedback

We always shoot people straight and expect the same in return so this is exactly the kind of feedback we like to see. If we can do something better we want to know about it and we are very pleased that this user felt us worthy of his time. We are excited to jump right in and see what we can learn along the way so, here we go! :)


Our Initial Tests

Here are the results of what we found so far.  These are performed on a Nova 35-80 with stock 2" II-VI lens. C-90 SPT tube, MYJG100 LPSU, CW5000 constant setpoint of 20c. ruida 6442. Firmware: v8.07.64


Here are some reports on the dot size (not spot size) that can be achieved between the 2" and HR BeamBuddy head. The original report conducted by Thunder Laser China Engineering, which includes the Thunder OEM HR head as well as the 2" and the Beam Buddy, is attached at the bottom of this article: Dot Test-2” vs. US-HR (Beam Buddy)

Dot Test Focal Prep



Dot Test Focal Burn - Stock 2" Head



Dot Test Speed Matrix - Stock 2" Head




Viewer's Feedback On Our Initial Tests


 Considering I gave you a challenge and almost zero clues, I would say you are at about 9/10 with your success so far. If you switch off  Lightburn PASS THRU you may be a bit surprised at what the test does and that may make you ask a few questions. Switching on pass through bypasses all of the Lightburn graphics software and sends a raw bitmap image to the machine, exactly as RDWorks does.  OK so you navigated that man trap!!!!


 Reverse scanning offset has no effect on the results of this test, only when you come to do the engraving.  It looks as though you are using black anodized aluminium?. This is one of the easy materials to conduct this test.  BUT  I note the halos around the dots and wonder if this is something like Rowmark. Things get much more difficult with  organic materials.


Focus is a moving target because it changes with speed. You are trying to achieve the thinnest dashes on the test top line. so if you  settle on your "best" speed (experience has told me this is between 400 and 600mm/s) and then start concentrating back onto your focus  you will probably find that raising or lowering it  by just 0.5mm will make a noticeable difference..


The way a glass tube machine works is VERY dependent on the response speed of the HV power supply. Most HV power supplies have a response speed spec of "less than1 ms to reach 90% of your demand current"   Lets see what  that 1ms means for what you are trying to achieve.


The pattern is 254ppi  ie 10 pixels per mm. However the most demanding switching you will ever encounter is on the bottom line of the pattern where  you are trying to put 5 black dots and 5 white "dots" per mm


 A white pixel tells the tube to switch off and a black pixel tells the tube to switch on. Thus after it has switched off, the software will not switch the tube on until it "sees" the leading edge of the next black pixel. It now takes a max of 1 ms to reach power to burn that pixel. Hmmm that seems  like a serious speed limitation. 


Let's assume it MAY take as ;long as 1.5ms to burn a black pixel  i.e. 1 ms rise time and 0.5ms to burn the dot. For the time being let's butt 10 black pixels (1mm) against each other and that would mean 15ms/mm. 1000ms/15ms= 67mm/s.. So that is crap because we know we can engrave  faster,  but why?  

Firstly,  all A grade  HV power supplies can work at least twice that speed but once you start running at faster speeds, something interesting happens. 


When you encounter a single white pixel at speed, there is not enough time for the power supply to switch fully  OFF . Thus it requires less time to switch on and reach the  required output power. for the following black pixel. Thus achieving a DOT with a glass tube system is very much a balancing act and the actual speed you can run at is a UNIQUE property of every single HV power supply.  


Run too fast and the dots slur into each other as you discovered when you ran at 1000mm/s..  Now you can understand why.  Did you also notice how the dashes were thinner  (observation, observation and observation  then question, question, question)


 You cannot achieve a dot with an RF tube because the switching is instant. You will always get 2 pixel wide sausages.  Thus a glass tube has much greater engraving quality if you get it right,

 

Currently with  anodized  aluminium ( I'm sure that's what you are using) the smallest dot  you can achieve is 0.2mm diameter  That limits your image resolution to 127ppi


 Ok so now swap your standard 2" lens for the HR lens tube/nozzle  that Thunder laser sells and give that a try. 


 Send me your results and then when you have matched my  #4 we can have a session of how to move forward with photo engraving.   I hope you can now see that there is no point in using all the fancy facilities in Lightburn if you have no idea what BASICS  your machine is capable of.


Testing Round 2

Here are some reports on the dot size (not spot size) that can be achieved between the 2" and HR BeamBuddy head. The original report conducted by Thunder Laser China Engineering, which includes the Thunder OEM HR head as well as the 2" and the Beam Buddy, is attached at the bottom of this article: Dot Test-2” vs. US-HR (Beam Buddy)

 

Dot Test Focal Burn - HR (Beam Buddy) Head

coming soon

Dot Test Speed Matrix - HR (Beam Buddy) Head

coming soon



RDWorks Learning Lab 115 The Russ Formula

You can get the PDF here: https://support.thunderlaserusa.com/helpdesk/attachments/65005412262 and it is attatched at the end of this article. This video goes through the process step by step. We will be performing similar tests but we have not watched this video as of the Round 2 Testing :)