A Video Diary: RDWorks Laser Cutter Tutorials Series 03a

• Discussion of the strange links and discoveries that will eventually lead to 3D engraving success
• Discussion of beam energy distribution.
• Our beam is NOT a beam of heat but is a beam of LIGHT
• Energy transfer mechanism…… VERY IMPORTANT
• Etching stainless with MoS2, then sulphur powder then engine oil
• Observe the bright white “flame”
• A chemical reaction is occurring between the stainless and sulphur at very high temperatures
• White light is not for free . The Kelvin light scale says about 5000C
• Discussion of how wood burns, sublimating the carbon at something over 3000C
• Running a test matrix of varying power on MDF at different speeds
• Review of matrix results for 3 different lenses Trying to find. to determine how we can get a burn free removal of material.
• Discussion of how to linearize the power characteristic so that we get linearized power burn as we do our 3D engraving
• Source for 3D engraving images.
• How to use Photoshop to distort the greyscale levels to allow for the power nonlinearity
• How to use a laser cutter tutorial

• Discussion about the best resolution for the picture.
• Setting the SCAN parameters
• OUTPUT DIRECT switch must be set for greyscale engraving
• Multiple passes will be required. On this version of RDWorks as there is no option to run the program multiple times When you read this there may be an updated version that does allow repeats
• We take a look at a small, simplified matrix burn test pattern
• The first test with MDF. Pretty granular.
• Change to acrylic test material and run a matrix test
• Put the table down by 10mm to try and create a polished final cut.
• Did I get the calibration adjustment correct or could I make some fine adjustments?
• Matrix test with white maple
• White maple is still a bit granular
• I adjusted the calibration correction, and the results are staggeringly better
• Back onto acrylic with the revised calibration settings
• Soft wood proved to be very unsuccessful
• When the woods are washed, the results are amazing.
• Admission that running slowly may not be the best parameter. Running faster is actually better
• Review of what changes I made to get the better results in Photoshop. I.e., revised resolution and tweaked calibration graph.
• Final test with revised parameters.
• Comparison of 300 dpi and 600 dpi. With some great results
• How to use a laser cutter tutorial

• Making a crude mechanism to try and get steady (non-step) motion for moving acrylic under a fixed head/beam.
• The results are abysmal
• Despite the terrible results it does show up a sort of layering effect with horizontal striations.
• The horizontal striations are also there for normal stepper motor cutting
• Restatement of the energy transfer principles yet again.
• Demonstration of water being boiled by a beam of light
• Understanding a scientific definition of temperature
• An explanation of the energy transfer mechanism
• Proposed explanation for horizontal layer evaporation process within acrylic
• Possible reason for better striations with the stepper motor.
• Still more work to do on this.

• Revisiting the burning matrix test with three different lenses
• Comparing colour and depth of burn.in white maple.
• Observed depth of cut more with a meniscus lens.
• Demonstration of wood burning with a blowtorch and that burning effect reducing as the beam moves faster over the wood.ie the energy per unit of time gets less so the damage to the wood gets less
• Using an unfocused laser beam, we can demonstrate the destruction of cellulose in wood to leave a film of carbon on the surface.
• The carbon film glows white hot as its temperature rises to 3600 before it turns directly into gas
• Demonstration of wood removal without burning.
• Comparing burns prior to and after the lens.
• Speed and increment have significant effect on cuts.
• Possible explanation of why cutting with max power as fast as possible produces the cleanest non-charred edge..

• Anodized aluminium offers the prospect of high-resolution engraving
• Description of the anodizing process.
• What happens to the matrix burn test on anodized aluminium
• White is caused by evaporating the dye.
• Testing various parameters and resolutions …not too successful
• Using SPECIAL MODE engraving seemed to work quite well
• Using oscilloscope picture to show what special mode is doing.
• Single dots may not get full power.
• Beware the dangers of overdriving your tube in special mode.
• Microscope view of dots done in special mode
• Comparison with common mode dots
• Dots done with different lenses
• To be honest no results looked good with my dot test.
• Picture comparisons for different modes, resolutions, and powers.
• Running at 1000dpi seems to give a great result in special mode’
• A look at the numbers involved to create such an image.
• The scanning and resolution numbers don’t make sense when you examine the microscope images.
• Checking the scanning step with a digital calliper.
• The numbers don’t match but the pictures seem reasonable quality
• Once the dye has been removed the dot colour is white. Even if you burn the dot again it cannot get any whiter. Thus, unlike organic materials where multiple burns cut deeper and blacker, anodized aluminium is impervious to the effect and appears to be capable of 1000dpi images although in reality that cannot be true.
• How to use a laser cutter tutorial

• Review of power meters and how we measure watts
• The alternative DIY version
• The compromise you must accept for the DIY version.
• A better K type alternative thermocouple
• Look at the original K type cable.
• How to modify an existing dohickys to take the new alternative probe
• Daniel Roberts Arduino version of the e-dohicky.

• Review of what minerals are, and the properties required for successful production of dots.
• Geology lesson….yawn!!!
• Starting with slate we use a 2” meniscus lens and run a test matrix
• Also run a matrix test with Special mode
• Wide range of parameters will work for slate
• Marble seems quite good
• Limestone OK but not brilliant
• Granite seems to produce glass in one of its constituents
• Quartz, a man-made stone is bound together with some sort of polymer binder and burns black. However, the black brushes away . No good contrast.
• Cimstone, another quartz, man-made product needs further investigation under the microscope.
• Review of each material to see if there is a good colour difference to produce a binary image.
• Slate is the only obvious material that seems capable of picture work.
• Microscopic view of what happens when you engrave slate. It is not a sharding mechanism but a glass conversion process.
• How to use a laser cutter tutorial

• Before starting photo engraving on slate, we must find the smallest dots possible by choosing the best speed and power
• Microscope pictures help us determine what size dots we have achieved
• We must set the resolution to match the dot size.
• Although, again, because this is a binary material you cannot get over burning and it looks as though we can do hi-res pictures when in reality we are fooling ourselves.
• A look at different resolution results
• How a bigger picture at lower resolution appears to produce s better picture
• Testing with higher resolution but at slow speed
• Comparing hard Chinese slate to softer more expensive Italian slate
• A comparison with a fine granite. …a poor alternative
• We rejected man made quartz but there may be a way of exploiting its properties for certain applications
• Block engraving on green slate and granite will be successful where phots will fail.
• Photo engraving a piece of white man-made quartz material we rejected earlier. Wow what a surprise.
• How to use a laser cutter tutorial

• This time of looking at Max/Min power I understand more about the way the machine works and have my little USB oscilloscope to help me see what’s going on.
•  Look at the scope signals for cutting a normal square with max and min set equal..
• Look at scope pictures for some “magic” numbers
•  You can now see that there is a power ramping taking place which is proportional to speed as square drives in and out of each corner.
• As this first test shows, if the magic number for min power is too low then corners remain uncut
• Reset min to 10% and problems are almost solved
• Jump to 20% and all the benefits of min power a lost
• The range of setting for effective use of this min power is very narrow and will always require you to experiment with the material and lens you are using at the time.

• Quick review of matrix burn tests
• Can we get dark colour for organic engraving without charring?
• Repeat of the wood burning mechanism by IR light
• Understanding the difference caused by the high energy density core of the focused beam and the low energy outer part of the beam.
• We are looking to just scorch the surface with delicate control of power.
• More matrix tests with 2” meniscus lens, concave side down.
• Matrix tests with lens flipped upside down and focus reset to 3mm more.
• Results show the flipped lens has “softer burn characteristic
• Can we get an even softer beam using special mode ?
• Demonstration of the surface charring mechanism of a deep cut.
• Defocusing along with special mode shows great improvement
• Back to common mode with an out of focus beam but at very low power 13%
• How to scorch the surface without material removal?
• Maybe a 2.5” lens flipped will give an even softer beam.
• More out of focus, decreased power and speed.
• Finding the optimum speed for scorching
• Works well for MDF but not for card
• Faster speed and more defocus for paper is a bit better
• Great results overall.
• Demo of almost black depthless logo engraving on MDF

• Quick review of how the machine creates single black engraving dots for dithered images.
• Response time of power supply is key to rapid single dots
• Summary of what in store for this video
• Lightburnsoftware.com for 30-day trial
• Create a scanning offset test program
• Use this pattern to assess the response time of your HV power supply
• Step through the Russ Formula with small modifications to allow for the NEW response speed of the power supply
• Close look at the dot test with 2.5” lens to get the best focus/power/speed.
• Microscope examination of results comparing different card types for testing
• Results just mediocre so change to 2” lens
• Microscope results better but still not good. Swap to 1.5” Lens
• Much better dots even at 200mm/s so the calculated response of the power supply seems to be proven.
• Quick look at the Lightburn software and its great features, especially the photo engraving features.
• Examination of the various dither options available in Lightburn
• Emphasis on getting the right DOT quality for the material you are using BEFORE you attempt any photo engraving
• OOPS……Forgot to correct the scan line offset that we used to assess HV power supply response speed. This MUST be corrected, or the dots will be mis-registered line by line and creating a fuzzy image.
• It is important to set the test speed to that of the scanning speed you plan to use for your image scanning
• You will need to go to Config, System setting to add the Scanning Reverse Offset factor and then repeat the test until you get near perfection.
• First picture comparison is pretty good. Just the right tone
• Further review of factors in Russ Formula to test an increased resolution.
• Comparison with an RDWorks image.
• Close examination of all the dither types
• The magic effect of picture size
• Microscope examination of the dots for each dither system
• How to use a laser cutter tutorial

• Hi res photo engraving relies on producing VERY small crisp black BURNT dots with our laser technology.
• Single lenses seem to hit a brick wall at about 0.2mm i.e., 127dpi…..a fairly low resolution
• A quick look at different lens mounting systems, i.e., in nozzle or tube
• A look at lens shapes and the reason why a meniscus lens may be the best for producing small dots.
• Small dots may be produced by just kissing the very high density at the centre of the focused beam, but the chances are there will still be low energy around it to produce a scorch halo.
• Certain materials cannot be over burnt or scorched.
• Thunderlaser sell an expensive compound lens assembly claiming to be capable of burning 1000dpi, but I have no idea of the lens combinations used, or the internal spacing configuration
• I have designed my own special nozzle to experiment with combinations of two different focal length lenses. The principle being to use a 4” lens to reduce the beam size before it passes through a second shorter focal length lens.
• We are now hunting for the smallest possible clean burnt dot.
• Using acrylic with my standard dot test to see if we can produce halo-free dots
• With experimentation with speed and power and a meniscus 2” lens it seems possible to get 0.1 dots (just)
• Can we find a better result with Special Mode?
• Yes it seems better, so I use Lightburn to run a 254dpi picture
• Testing with cast and extruded acrylic the results were disappointing
• Change to Newsprint dither pattern at 254dpi Results look good
• Then at 508dpi for pretty good results
• Move to wood for testing. At 508dpi
• Slightly different woods and different grain directions create massive final image differences
• Did I damage the 2nd lens by concentrating the power to a high energy spot?
• I have not been able to get anywhere near the Thunderlaser 1000dpi claim
• Challenge to Thunderlaser owners to make 0.025mm dots with their HR lenses.
• How to use a laser cutter tutorial

• Trying to give some visual cues as to exactly what a 0.0254mm dot (1000dpi) looks like.
• Review of some background tests that I had conducted changing lenses and distances between lenses.. Shorter spacing gave better results.
• Testing the idea of obscuring the low energy part of the beam and only allowing the higher energy central part to reach the lens.
• Quick and dirty results with various size orifices indicate the obscuration of any sort does not help get better dots.. The smaller the orifice the worse the dot.
• More dot tests using acrylic. Results showing great 0.1mm dot consistency.
• A closer look at newsprint dithering and why it seems to work at twice the predicted resolution for a given dot size.
• Comparison of picture on different card types. and different dithers and different parameters.
• The promise of an owner’s Thunder laser lens loan may allow us to solve the claim.
• How to use a laser cutter tutorial

• In my search for the smallest dot, my normal methodical approach seemed to have been hijacked by progressive small successes.
• I recognised a pattern of decreasing dot size with decreasing distance between lenses.
• Review of the Parallax Technology treatise on lenses forces me in another direction .
• Demonstrating the refraction effect and how Snell had created a law to calculate it. It is the basic principle of how rays pass through a lens.
• With zero previous experience, how hard can it be to calculate rays for different compound lens configurations?
• After a few hours some interesting patterns begin to emerge
• It requires another special nozzle design to house the revised lens configuration.
• Trying to find the new focal distance and the best parameters by using the dot pattern
• We are starting to get better dots real 0.1mm diameter or a bit less.
• Test this new lens with a more demanding picture.
• This is an amazing image at 254dpi and makes you wonder why you would want 1000dpi?

• Upon reflection, maybe there is another way to get a fine dot and that is to filter out all the low energy fuzz at the focal point by grossly exaggerating the spherical aberration rather than cancelling it.
• Stepping through the thought process and logic for my new direction.
• Using a meniscus lens as the second lens
• Lots of test patterns …..very boring but showing some great results.
• Testing again with the demanding image . Superb results at 363 dpi. (0.7mm)
• Dot size is king and determines the resolution of the picture, however different materials will give different dot sizes and require different parameters
• Don’t attempt a picture until you have found the correct focus and parameters with the dot test
• THE DOT SIZE DETERMINES THE PICTURE RESOLUTION
• Repeat the picture on acrylic so we need a negative image.
• Reason for reversing the image
• Amazing result for acrylic
• Now to test a piece of glass. Not bad
• The Mk2 compound lens pushes the dot size to 0.07mm
• We seem to have proved the principle of exaggerated spherical aberration as a power filter.
• How to use a laser cutter tutorial

• You can make a 0.2mm dot on most materials but not all materials allow dots as small as 0.1mm or less
• Main aim is to see how well I can photo engrave on some foil covered PETG and Acrylic
•  The first sample failed its focus/dot size test and had to be abandoned.
• Second sample just a bit better so decided to run it at 127dpi
• A satin finished gold foil scored very highly as did a black woodgrain foil.
• Silver foil on a white background posed and interesting positive or negative engraving question,
• Photoengraving test on Formica Wow. Superb at 245dpi
• Why do we need to chase 1000dpi?
• How to use a laser cutter tutorial

• Recap on the disruptive principles I am pursuing to produce a halo-free dot
• Explanation of the reason why I would want to put a 1” focal length lens to guide light into a meniscus lens
• Finding the new focus point and power settings.
• Measure the ramp line to characterise the lens
• Measuring the dot test looks as though we can achieve 0.05 dots on acrylic
• Now to test on anodized aluminium.
• In the absence of anodized aluminium, I am trying to simulate with black painted marble. Not too successful.
• Maybe it would perform better on my 1mm thick beer mat card
• Change of colour as the picture progresses would indicate that the lens is becoming fogged.
• Lens examination proves that is so.
• Lens cleaned and colour restored. Comparing the 350dpiresults with our best 254dpi picture still leaves that lower resolution as the best compromise.
• One final lens configuration produces even better 254dpi results
• The new combination puts the meniscus lens and the plano convex touching each other.
• In summary even though a 0.05 dot is achievable on certain materials it is so weak that is not of any real benefit. 254dpiwith 0.1mm dots id the real practical limit and cam produce stunning results.
• How to use a laser cutter tutorial

• I have designed a temporary linear non-stepping drive system so that we can create silky smooth head motion for test cutting acrylic
• The previous attempt was rather crude and misleading.
• Using a piece of acrylic, I run a speed test. The power is constant so if we get a level bottom cut it proves that we have uniform speed.
• Breaking the front face of the cut away allows us to see inside that test depth cut. There are obvious striations on the cut face but why when the speed was absolutely constant?
• Demonstration of the energy density profile of the laser beam and how it is only the low energy outer part of the beam where the liquid phase of acrylic can exist.
• Demonstration of what appears to be an unexplained and weird property of acrylic. Despite the beam expanding and losing its energy density below the focal point it can drill a virtually parallel hole deeper and deeper into the acrylic
• It has been suggested that this phenomenon is due to the laser beam being internally reflected (as in an optical fibre)
• Demonstration of how I think beam drag is generated. Done in discrete steps to simulate the action of a stepper motor you can observe gas/liquid dynamics happening within the cut and the settlement of and cooling of liquid on the wall of the cut to form marks that may be the mysterious striations.
• Now a look at punching 20ms pulses into a block of acrylic at different distances above and below the focal point.
• Using a piece of thin card, we can see the high energy core of the beam at the same 20ms pulse, create a 0.2mm diameter hole. That same 20mm pulse creates a 0.5mm hole in the acrylic.
• Break for a physics summary about how light transfers its benign energy into hear energy by stimulating molecular excitement in the material it impinges upon.
• A reasonable explanation of the hole difference between burning card and burning acrylic is a gas scouring that takes place around the beam to make the acrylic hole oversize.
• When the beam moves there is no immediate solid to erode so the cutting action is by definition intermittent. And it is the artefacts of this intermittent NATURAL cutting action that leaves small striations.
• How do we “hide” these striations? Buy leaving heat in the cut.
• Lots of cutting tests on cast and extruded acrylic without and with air assist.
• To try and emulate the high frequency pulsing of “expensive” rf driven machines I am running dot mode to produce pulse cutting.
• I now fool the machine into thinking it is engraving. That way I can invoke Special Mode where I can use the PWM signal to turn the beam on and off at 20,000times each second. This is a close simulation of an RF driven tube.
• Looking at all the samples . All have the same fine pattern of striations despite there being no stepper driven cause. There is little difference between with and without air assist. There is a noticeable difference between cast and extruded acrylic, but all have these fine striation pattern.
• Summary: Those that insist that striations are stepper driven are partially correct BUT take away the steppers and we have clearly demonstrated that there are still natural striations .generated during the cutting of acrylic.
• How to use a laser cutter tutorial

• Apologies for not continuing with acrylic fest part 2 but decided to remake the head mounting bracket while it was off to refix the belt I had previously removed.
• Never been in love with the existing head so I have designed my own Mk1 design made from ACRYLIC sheet!!
• Cutting and assembly of the pieces
• I even make a new mirror plate from acrylic
• I have made a set of pre-set lens tubes
• Mounting the new head
• Quick re-polish of my copper mirror
• Setting aids to ensure precision Z
• But first setting procedure for X axis i.e., mirror 2
• Having set X axis true to bearing rail we need to move the head (on its adjustment bracket) so that it “catches” the beam onto the target centre.
• Now comes the VERY important Z axis setting procedure
• Having set the beam perpendicular to the table We can now adjust the whole head to catch the beam onto the mirror 3 “sweet spot”
• It is crucial that we set the beam to pass through the axis of the lens.
• One final check at the 4 corners to sees us requiring small resets in X and Y
• That in turn requires a final adjustment in Z
• 1.5” lens cutting 10mm plywood for a final test.
• Sticky tar residue (condensed fumes) that would normally stick to your honeycomb table
• Instant table cleaning with acetone
• Mk1 lens module demonstration
• Quick review of advantages of the new head design
• Is this it? Or will there be a mk2?
• How to use a laser cutter tutorial

• I watched a Thunder laser video about how they claim to be making 1000dpi images with their 1000dpi HR lens system
• I choose a difficult image to process and load into RDWorks
•  IMPORTANT!! A pixel appears on a computer screen and a dot is what we burn onto a surface The first is defined as PPI and the second as DPI.
• To get faithful reproduction of the NON-OVERLAPPING pixels on the screen, we must have NON-OVERLAPPING dots also
• Therefore, if the best dot size you can make is 0.2mm then the resolution for your picture must be 25.4mm/0.2mm=127PPI
• Choosing dot graphic converts a greyscale image into a binary image with various density dot patterns that fool the eye into mixing white and black to simulate the greyscale that was there before.
• Now that it is a black dot pattern on a white background we only must copy the square pixels with same size round black dots
• Ok, lets reset the picture resolution to 1000PPI.. This time we will use Net Graphic to process the picture into a binary image
• Playing with the conversion parameters as Thunder laser do. We arrive at a picture that we cannot copy. Simply put, the dots in this processing system are various sizes and that cannot be copied by our “one size dot” laser machine.
• Lots more analysis of the way the Net Graphic system works .
• We know we cannot burn much better than 0.1 dots on most materials so let’s see what Thunder laser are using for their lenses.
• They have 3 lenses 4” , Standard ( which turns out to be a 2” lens) and HR.. The 2” claims a dot capability of 0.1mm which without overlapping dots will give 254dpi.. They claim a capability of 500dpi. The HR lens system claims a DOT size of 0.05mm (508dpi) for which they claim phot engraving to 1000dpi (not ppi)
• Having created their 1500ppi image thunder laser dump you and do not advise you how to set the scan interval because any attempt to scan at other than 1500 lines per inch in Y will result in aliasing patterns
• This is clearly demonstrated with several pictures at different scan intervals
• So, the 1000dpi photo engraving claim is misleading and impossible.
• How to use a laser cutter tutorial

• Testing of Laser Tiles
• The importance of having a responsive power supply before attempting dot work
• Comparing typical response specs from top to bottom of the price range
• Quick calculation to show that ANY power supply cannot deliver 1000dpi pulses unless you scan at very slow speeds
• The importance of using the right lens to achieve the smallest dot size, which in turn relies on a critical combination of speed and low power.
• Microscope pictures of compound lens tests on the Laser Tile
• Examination of the first test picture at 300dpi to see what success my settings had.
• Black areas were not as black as they could be more of a grey halo.
• Just change resolution to 500dpi
• I draw your attention to the white light emitted during scanning, and indication that the surface temperature is exceeding 2000C
• Thoughts on how these Laser Tiles are performing their magic. It’s all to do with ceramic wizardry.
• Proof of the idea by heating the glaze to red hot without it turning black.
• Microscope pictures of the 508dpi image.
• Still not black enough, really needs to run slower to allow more power per dot and stay within the power supply response rules
• Sadly, running at 50mm/s means the stepper motor is setting the head into resonance and .causing strange patterns.
• How do we unravel this puzzle? By making the lines wider and darker by increasing the power.at 100mm/s from 14% to 16%?
• WOW!!!! LOST FOR WORDS
• So 508dpi IS achievable but under very special circumstances.
• This is truly the brick wall. So where does this leave the Thunder laser claim?
• How to use a laser cutter tutorial

• Having used the MK1 head very successfully there were many requests for the drawings. Upon reflection and with a 3D model in front of me to, I decided that making special lens capsules was not the right way to proceed because everything was bespoke.
• Mk2 was required but and would be based on standard lens tube and nozzle technology.
• Cutting and assembly of the Mk2
• Note. This design is only suitable for machines with an adjustable table
• How to use a laser cutter tutorial

Although this design uses standard lens tubes it still requires a special nozzle and modifications to the lens tube.

• Fitting the MK2 head to the machine
• Demonstration of flex in the head mounting bracket
• Attempted acrylic replacement bracket turned out to be junk
• However, without this junk bracket the strange test pattern results I saw earlier on my Mk1 head may have been harder to track down.
• Continue to set the MK2 head in Z as we have demonstrated with the Mk1 head
• We now carry out the focus test with the Mk2 head and get even worse wobbly test results
• The acrylic bracket and the new aluminium bracket are the culprits.
• Need to design a steel stiffer bracket system.
• While the bracket is being made I have remade the head so that it is projects a little lower and also bodged a stiffening bracket for the original aluminium system that runs a nice steady dot test.
• New bracket arrives and is fitted.
• Go through the Z setting procedure again
• 2 more days have passed and more thoughts about how you will be able to make this for yourself have been troubling me.. Oh dear, I feel another change is coming!!!
• Welcome to the Mk4!!!!!!
• How to use a laser cutter tutorial

It uses a standard UNMODIFIED lens tube system.

• Review of a bit of lens and beam theory
• Different lens mounting systems and nozzles
• Where to buy lenses and what material should I choose?
• What are those materials used for lenses?
• Now lots of tests to look at what sort of dots each lens will produce
• How to use a laser cutter tutorial

View some interesting results under microscope comparing each to an ideal compound lens reference.

• This session is all about assessing the % power transmission through the lens
• Look at the method I am using
• Look at the calculation strategy I am using to assess transmission efficiency
• A close look at the gallium arsenide lens very shiny anti-reflective coating makes you wonder if this can be true, surely something so shiny must reflect?
• An analysis of the results puts gallium arsenide as best performer and a few other surprises.
• RDWorks laser cutter tutorial