Project Logs

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• [E1][P][M] 290L Barrel

  kelvinA • 07/20/2025 at 10:03 • 0 comments

  While jumping through Ebay's "similar items" section within listings, discovering "wood barrel ice-baths", I found out that there's one semi-common HDPE barrel that is taller than the 220L, blue and doesn't use a galvanised metal clamping ring: the 290L barrel. Like the previous barrel, this barrel was acquired to store things outside, thus it's beneficial that the ring is made out of plastic. For safety with a 450/405nm laser, blue or white is more ideal than red, dark grey or black. It's also got 4 convenient indents to carry the barrel.

  Cleaning the barrel

  The one I found happened to be local; the going rates for both 220L and 290L seem to be sub £40/ea when collected instead of delivered. 

  The black HDPE parts and the barrel's outside was scrubbed with a sponge and the inside was mopped:

  Modelling

  I let it dry while I measured things for 30 minutes, mainly the height. I know it's taller than 1110mm but maybe 1120mm or less. Nominally, I got 1115 - 1116mm. Then I went to the other side of the garden to try and get a full-size image as orthogonal as I could so I could import the image in Fusion:
  

  Taking a picture from so far away highlights how surfaces on the barrel aren't as straight as they might appear when closer. I left the lid on because I imagined that I could use its height as a reference, but now I think I'll just measure the height of the barrel's straight section.

  I then spent over an hour modelling the lid:

  It took ages to determine where fillets started and ended, and I had to use some 48mm tape as a spacer to be able to use my calipers to measure the wall's thickness and height. It's rare times like these where I wish I had a 3D scanner. Fusion's weight estimate is 750g and the real one is 100g less, and I believe some of that discrepancy is because I don't know the cross section of the seal. The HDPE lid alone is reported to be 600g in Fusion. 

  I have yet to model the other 2 parts.
  

  Trivia

  I also tried using Wispr Flow for this log, but ran into similar issues as when I tried Windows Dictation over 2 years ago. I have to think of the sentence, send it to my mind's Speech Processing Unit, say the sentence, read the sentence and correct it. The first 2 steps is the bottleneck because I don't think of sentences synchronously, so I generally have to think of the entire sentence in my mind, recite it, and then say it. 

  Maybe this workflow is a lot better for people who can literally just say what's on their mind? It's still better than Windows dictation because at least I don't have to worry about punctuation and the default CTRL+WIN shortcut is a lot less cumbersome than WIN+H.

  [July 30]

  Modelled the screw ring

  I've modelled the ring and kinda see how they're supposed to mesh together. It seems like it aligns with the lid modelled previously.

  Then I had to do some tricks here and there to properly design the custom thread:

• [R] 210L barrel?

  kelvinA • 07/09/2025 at 21:06 • 0 comments

  While I was writing the conclusion of the previous log, I came across this barrel that comes in 4 unique colours for some reason, such as light grey or turquoise:

  The dimensions are allegedly 500mm on the base, 660mm at the top and 940mm tall. It certainly looks like a more-ideal spread of those litres in terms of fitting components inside, and my opinion is that the light grey does look particularly home-like. Looking at the levels, the light grey is also even more reflective of blue than the blue barrel. 

  The obvious drawback is that the clamping ring is even wider, as well as the entire barrel, requiring even more space. It seems that the ring has a more curved shape and doesn't overlap when closed.

  The inside for the light grey looks nice. I don't think it would be all that much harder to clean the edges inside. I just wonder if it's as solid as the typical barrels considering there's a £20 price difference. The cost might be because the walls are thinner, or the seal isn't airtight, or perhaps it's simply that they can save on shipping costs because these cone barrels can be stacked.

• [P] 220L barrel and its steel ring

  kelvinA • 07/09/2025 at 20:21 • 0 comments

  One thing led to another, and an allegedly "new" barrel arrived:

  Barrel body and lid: 4.5 / 5 stars for suitability as an enclosure

  The inside of the barrel and the lid looked fine enough:

  That 3D line thing at the bottom is raised 1cm and likely remnant of the fabrication process:

  You can see in the video that it looks a lot floppier when the plastic is hot and going inside the moulds.
  

  I also learned that the sealing is done with a white o-ring instead of the flanges, as implied by the CAD model:

  Some of the measurements I noted down (in centimetres):

  • Body
    • >43 for bottom diameter
    • 46 for the bump diameter before the opening (see Eccentricity below)
    • >58, likely 58.5 for the widest internal diameter.
    • 59.5 or thereabouts for the outer diameter.
    • 36 for the vertical section
    • 95 from the middle line to the rim of the barrel
    • 94 if from the bumps
    • 46.5 - 47.5 for the opening (see Ovality below)
  • Lid
    • 48.5 diameter for its tallest feature (that looks like a wall)
    • 23 out from that wall-like feature as the handle clearance
    • 1.8 between bottom of body flange to the taper of the lid's flange

  The barrel has a slight amount of eccentricity, ovality and coning.

  Eccentricity: 

  Ovality: It's only 1cm. I think the lid flexes when it goes ontop of the barrel. 

  Coning: Like a standard plastic bin or a plant pot, the "straight" section of the barrel slightly cones out. Maybe the angle is 1 degree or something so that it can release from the mold. 
  

  All these things are kinda minor, and other than the seam line at the bottom of the barrel, it looks rather easy to wipe down. Its rigidity also inspires a lot of confidence. Furthermore, the roundness means that, while large, the barrel can fit in an outer corner:

  Clamp ring: 2 stars

  Unfortunately, I've sent the barrel back because the clamp ring was too hard to work with. It's super easy, barely an inconvenience to open the lever and take the ring off, but the other way required levels of force I just didn't have. My brother did, but he had to take a stance like some kind of superstrength superhero when closing the lever.

  One of the first issues is that all the hinges are loose-fitting and the ring isn't much taller than the thickness of the flanges. As seen in the below video (at 3m 0s), you need one hand pushed on the lever to expand the ring and then align the entire circumference so both flanges. With practice, it probably would be less of an issue.

   I haven't seen a close-up image of the barrel without the metal ring on the internet, so I took a picture. Below, you can see the kind of gap between the lid and the body flange, as well as artefacts in the body flange due to the manufacturing process:

  Another issue is that an additional 23cm of space from the lid ring to a wall is needed to have enough space for the lever:

  This wouldn't be an issue if I didn't have to put my entire body weight on the barrel to stop it from spinning due to the high angular force applied, meaning that the lever would have to be facing away from me:

  Read more »

• [R] Seal Detection

  kelvinA • 07/06/2025 at 12:06 • 0 comments

  Detecting if the barrel is sealed seems like most tamper-proof method of ensuring safety. This is because I remembered what was said in a BambuLab interview about the H2D:

  True story that one influencer tested the printer [and] write us a message to say:

  "I really want to open the door to shoot a footage of the laser engraving and I know you have some sensors on the door, so I tried my best to use magnetic to cheat your sensors, but uh somehow it didn't work. Could you tell me how to cheat the system to make the door open while the laser still works?"

  and uh yeah, we place lots of sensors, you know, to make sure even if the customer wanted to cheat the system, we won't, sorry. We won't allow you to, you know, light up the laser if all these security measures are not in place.

  And so, similar to encryption, whatever solution I come up with for a DIY strategy has got to be somewhat resilient to spoofing whilst the entire system is known. For example, a simple door switch can be bypassed by shorting 2 pins.

  With a pressure sensor, it both detects to make sure the lid is closed tightly and if air is unintentionally getting out, making the filtration less effective. My assumption will be that anyone savvy enough to program a microcontroller to send fake pressure sensor data also knows what they're doing.

  I guess trying to seal both a power inlet and pressure outport isn't too demanding. The issue is that it requires components that can move air out of the barrel and then re-equalise pressure when the print is finished, which costs money and space. 

  I'm also reading Electronics Protection: The Unknown Problem with Airtight Enclosures (PDF), wondering if the temperature differentials of the barrel and its environment could pose an issue, and it sounds like it. Their proposed solution was "expanded PTFE" but it allows gasses to move in and out, which defeats the whole point of the barrel.

  It seems that the simple and inescapable choice is to maintain a detectably negative pressure with a compressor and electronic valve, where every 30 minutes or so, the print pauses, makes sure the air is clean and then equalises the pressure before recreating the negative pressure. The assumption is that the inside of the barrel will be hotter, thus the negative pressure will slowly increase.

  Some bargain bin pump is unlikely to pass my low-noise standard, especially since the pump will be going out to 1 bar. The air pump below went up from 66 to over 80 dB when pumping into the open air:

  
  

  The "fixed" pump at 37s in the below video is still much too loud when pumping into open air:

  Car tyre compressors aren't much better:

  It seems that, on the inside, a piston system is used:

  Perhaps the good old-fashioned way is to get the Y axis to push a manual bicycle pump? There was a graph in The Unknown Problem with Airtight Enclosures I mentioned yesterday where the pressure decreases and then equalises. The rate this happens will be enough to tell if the barrel is sealed enough or not.
  

  An idea could be to have a pump that is pressed when the effector goes to the bottom, which it typically would have to do when selecting the cartridge to clear the resin so that the laser can work on the printed part.

  When it comes to the actual sensor, I was a bit worried when AliExpress started off with sensors costing over £20 each, but with the help of Gemini, it sounds like I should be fine with a low-cost barometric sensor such as the BMP180:

  whereby

  The BMP180 measures absolute pressure in the range of 300 hPa to 1100 hPa (or 300 mbar to 1100 mbar).
  1000 mbar (ambient absolute) - 50 mbar (gauge) = 950 mbar (absolute).

  As you can see from the graph above, the drop to -52.5 mbar 

  The listing also has the BMP280, which is cheaper. Turns out it's also the newer sensor with twice the...

  Read more »

• [M] 3D sketching in the 220L barrel

  kelvinA • 07/03/2025 at 10:44 • 0 comments

  I've unintentionally put in upwards of 9-hour days for... checks notes... 7 days to get the above solution which achieves multiple desired goals. As you might understand, the first complication is that I need to work within a cylindrical area. The second is that it's not a pure cylinder but curves at the top/bottom similar to a filleted chamfer, meaning some things only fit at certain heights. If you look at the top-down angle above, that's the reason why there are 3 concentric circles to denote the perimeter of the barrel at its widest section, about an inch from the opening and the opening itself.

  Printers I've seen, like the Ender 3, have the screen on the right side. Thus, that's why the print volume is more leftwards. I plan to have the screen on the inside and perhaps a status LED on the outside.

  Most of the time was on the motion system. Considering that, unlike FFF, this application calls for very precise movements that don't need to be particularly fast, it's probably no surprise that most of my research was on ball screws. Considering my work on delta belt tensioners, I've decided that I'd rather not deal with belts and the design/manufacturing time that comes with it.

  Day 1

  One of the first things I saw was the below video:

  Then I went on AliExpress to see different options and how much extra length is needed for an axis. The lowest I found was 119 - 120mm.
  

  Day 2

  I found out about non-captive stepper motors:

  I was also asking Gemini about some questions about the build plate material. Both it and I believe that a typical aluminium bed will interfere with the charged-plate responsible for attracting uncured resin back onto the film.

  Then I found out about enclosed sliding tables, which look as sleek as the Windstorm S1 I mentioned a few logs back:

  I thought this would be particularly useful for the Z axis. If kept in the orientation seen above, the build plate would be vertical and exhibit no counter-lever sagging, unlike the typical orientation for 3D printers having the build plate parallel with the ground. This was one of many reasons for keeping the barrel upright. However, this orientation risks resin falling onto the ballscrew. Hence, that's why I thought this enclosed module would be beneficial.

  Then I found a forum post titled Ballscrew Basics where the OP mentioned some interesting things. notably:

  "But what about accuracy?? Isn't that the primary reason to use a ballscrew?" True, accuracy can be extremely high, but ACME screws can be ground and with a correct, matching nut, can exhibit identical accuracy to the finest ballscrew.

  This claim both tracks with the video above and the Prometheus MSLA designers testing both a lead and ball screw. One of the bigger factors is efficiency:

  A typical ACME threadform has an efficiency of roughly 40%, whereas a ballscrew's efficiency can easily top 90%.

  Hypothetically, wear is another one I've read in multiple different locations over the years, but in all my 8 years of scanning the entire internet for 3D printing information have I seen something along the lines of "my T8 lead nut wore down and I needed to replace it".

  A specifically important part are the bearings though:

  A C0 ballscrew is worthless if it is supported by a single, standard radial ball bearing.

  Moving on, I found this 201mm curing lamp but I'm likely just going to use a 240LED/m 405nm strip:

  Up until this point, I hadn't even really started to think about the cartridge situation. I had the great idea of 

  • having each cartridge be 44.45mm tall (the same as 1U in a server cabinet)
  • a cam system such that the Y axis could select what cartridge is pressed onto the film-covered LCD, 
  • designing a dynamic system such that trades Y print space for cartridges. 
  • The X length of the LCD is a tad shorter than 3 cartridges, so the adjustment would essentially be a range of 2 -...

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• [T] Use Halot-X1 display assembly?

  kelvinA • 06/25/2025 at 12:23 • 0 comments

  I just found out that Creality just uploaded a rather interesting video about replacing the UV light board:

  I have a feeling a lot of good information is in here. It's basically a teardown video of their moving display module. Unlike other MSLA printers, this one is designed to move, and thus it's the most compact solution I've ever seen:

  And, as mentioned in previous logs,

  • the backlight has local-dimming zones for higher longevity / lower power consumption and
  • the screen is both 
    • approximately the same width as A4 scanner sensors (the minimum for the X axis, for where an A3 is the maximum) and 
    • extremely high resolution, so it's more future-resistant (though unfortunately with 3:4 pixels instead of 1:1 square).

  Thus, this solution feels star-aligning. The local dimming is the best part, because the whole screen wouldn't be exposed to UV when only a small section needs to be, which is a case that's even more likely with the SlimeSaver than a typical MSLA. I don't think even Creality knows just how long it will last though because no numbers have been reported.

  The Y dimension of the panel is 118.37mm, so it makes the most sense for the Y axis to be 4 times that at 473.48mm since it's rather close to the 480mm I was considering. Maybe some overlap would be required and it would be closer to 472mm.

  So, what's inside?

  The first thing I noticed was that they're using much more LEDs for the light source than usual. I counted 19x28/9pcs on the mesh grid under the lenses to block LED light from straying away. There's only 92 dimming zones, so there is likely some electronic reason why the engineers couldn't've done 542 zones. The product page claims 6.5 mW/cm2, which is more than double that of the Anycubic Mono 4. 

  I'm also starting to notice that more printer manufacturers are starting to incorporate cast metal (aluminium perhaps?) into their products:

  I believe it's also used as a bit of a heatsink as there are fins in it. There are also two blower fans; could they be curving around, or are they to exhaust the warm air? The product page suggests that they use the heat energy to warm up the enclosure.

  That orange cable goes to the LCD. Interesting that the signal goes through 2 different boards, with the input being notably smaller. Perhaps it's something like eDP or HDMI that is then converted to MIPI for the screen?

  Seems that the LEDs run on 24V and there are 2 ports on opposing sides. Perhaps the electrical path goes through one and out the other? Maybe each port controls half the board? this is an aluminium-backed board, so Creality is likely limited to a single layer, though I do wonder if any of those larger resistors are 0 ohms to jump over tracks. The board is certainly a lot fancier than what I had in mind, which may allude to the reason why it says V21 on the bottom.

  There also seems to be some copper (heatpipe?) rows that leave and go somewhere:

  At least this angle allows for a better look at the control panel. The 4 fan ports are obvious, but all the tables are unfortunately a bit more cryptic to me. I think, like with the Q8100-60002 scanner sensor I... still haven't talked about on Hackaday (whoops), the table is just referring to the names of each of the components in the densely packed sections. Is there some kind of regulatory or debug requirement to put each and every component name on the silkscreen? There's also some TX/RX pins; are they for a chip on the other side of the board or exposed from the input ribbon cable?

  I punched in "ze096da-01a" and one promising result I got was the YI2410A0-1:

  I presume that the dyed polarizer is to further improve LCD longevity?...

  Read more »

• [T] Pivot?

  kelvinA • 06/24/2025 at 16:15 • 0 comments

  Pivot to 3D printing services?

  As alluded to in the conclusion of a recent Coaxial8or log, I'm currently wondering if it makes more sense to spend the time and money designing SlimeSaver parts that are printed via SLS or MJF services. I'm not living in 2018 when such services were rare and expensive. The benefits would be more design freedom, higher durability end-use parts, a BOM that doesn't rely on the builder already having a 3D printer and myself not being further delayed working on FFF -- a technology I still believe is ""legacy"" the same way any recent PC won't boot from a HDD but still good as an external storage medium.

  The main concern is being slowed down by checking over CAD files multiple times to ensure they're good enough to be printed.

  Pivot (back to) to 210mm, non-motorised X axis?

  Understandably, I still want a printer that is large enough for me to print the #T^2 Tiles [gd0095] (192mm?) and #Teti [gd0022] (205mm??) and other than the Y axis being in the 400 - 500mm range, my justification for going larger just seems kind of weak at the moment .

  On the flip side, there are 3 notable complications I'd avoid. 

  First would be engineering/programming/testing a slider. I know there's still the laser slider that needs more or less the same things, but every little helps. 

  Secondly would be getting the 4-segment intersections to line up. The shortlisted pixel sizes are merely 0.04mm and smaller, and it's probably already going to be an interesting thing to get entire rows to line up. XY tiling is likely an unnecessary complexity. 

  Thirdly would be the CIS scanner sensor. A while back I found a sensor for "MFC-6890CDW MFC-5895CW MFC-6490CW" that is 291mm wide but, as you might expect, there are many more A4 sensors to choose from.

  What's extremely convenient is that the Halot X1's 10.1" screen is 211mm, meaning that the print area and scanner will be very well matched. The SlimeSaver doesn't necessarily need to use the 16K screen, but it would help massively for longevity to use its local-dimming backlight, negating the higher price of screen replacement. I think I've mentioned this in a previous log, but users are seemingly happy with the quality at 35 microns, meaning that the screen chosen needs to be 6048 pixels wide.

  While researching prices (around £95 - 115+ on AliExpress), I found out that the Saturn 4 Ultra has the same screen, as well as 8G of RAM. The Saturn 3 is mentioned to use Linux whereas the 4 is a "self-developed system". Could it be possible to hack a Saturn mainboard instead of buying a £130 NanoDLP computer and £30+ HDMI driver board?

  The minimum Z height target should be slightly longer than X to be able to print something cylindrical with supports.

  Pivot to 150L barrel and/or place on its side?

  Me remembering about the 150L barrel is partially what spurred me to consider the smaller build volume above. It's a slightly shorter, slightly rarer and notably narrower version of the 220L barrel:

  I'm wondering if it's a better user experience to fit such a barrel under a bed and get to the print like opening a drawer. I've also got concerns on gravitational forces exerted on the print itself during printing, but I don't really have any concrete evidence.

  220L barrels do seem a lot more common though, and now I've even found an ebay listing for a 220L for merely ~£5 difference. Therefore, the real question is if the 90mm smaller diameter is enough of a difference.

  I guess it depends on factors like:

  • if the entire printer cylinder needs to be able to come out of the barrel.
  • the space requirements of the laser axis. 

• [T] Build volume of 28*48*28cm?

  kelvinA • 05/13/2025 at 18:57 • 0 comments

  So, 3 years after the start of this project, I've finally simplified the project description:

  One of the points is the build volume. I've been sketching some rough measurements and I believe that 28 * 48 * 28cm (XYZ) is a reasonable goal to aim for.

  This build volume is similar to a CR-10 (and its clones), but the Z axis isn't the longest. If anything, the Z axis will be the shortest if additional space is needed for internal components. Part of the reason is due to the shape of the barrel, but it's mainly so that the slowest axis isn't also the longest axis, which is usually the case in the MSLA industry.

  The X axis is limited by the fact that PET cake collars max out at 30cm wide. It sounded reasonable to use a 30 * 50cm build plate and have the XY build area be a 1cm margin within, hence 28 * 48cm. Due to BambuLab, it's also wise that the X is at least 25.6cm so that Makerworld models fit. To allow for the printing of vases and other large, cylindrical objects, it would be ideal if the Z axis matched the X, hence a height goal of 28cm.

  I expect the laser-accessible Y length will be around 10cm shorter. An area of 28 * 38cm is still plenty for PCBs, especially if they're printed such that the thin side is against the plate like standing dominoes.

• [R] Laser reduction of copper (oxide) nanoparticles

  kelvinA • 05/05/2025 at 23:34 • 0 comments

  This is another log I moved out of the quick comments because it's starting to snowball.

  For a point of reference, the resistivity of pure/bulk metals are approx:

  • Copper: 2 μΩ cm
  • Brass: 4 μΩ cm
  • Iron: 10 μΩ cm
  • Stainless: 90 μΩ cm

  Finding "Copper Composites and Laser Sintering: Novel Hybridization Method for 3D Printed Electronics"

  On April the 24th, I found this open-access paper that's 2 years old: 

  • https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/admt.202201900

  Two notable quotes are below:

  PLA-based composites with 90% and 80% (wt.%) copper loading [with] a 5.5-W 450-nm blue laser with various combinations of parameters to “sinter” the surface of the samples. [...] The copper particles became oxidized during the process, and none of the samples yielded a conductive result. 
  
  Instead of partial melting, sintering (i.e., bridging adjacent particles) can be achieved by chemical reaction that causes deposition of a native copper layer on copper particles [...] using copper formate, which [...] spontaneously decomposes at approximately 200 °C to form native copper and volatile compounds. [...] However, copper formate, formic acid, and ethylene glycol are all incompatible with the temperatures associated with FDM printing (200–250 °C).

  They reported a resistivity of 400 μΩ cm and included a video showing a 5.5W blue laser adding a new trace to a printed, active circuit:

  Finding loads more papers

  Because I don't have the limitation of FDM, and my hypothesis of sintering particles suspended in matrix possibly disproven, I started looking into what the aforementioned paper was talking about when they mentioned native copper formation. 

  It seems that it's possible to use a laser to "reduce" copper (oxide) nanoparticles to copper at a temperature low enough to apply circuits onto PET, for example. General reading gives the impression that copper oxide nanoparticles are more stable than copper nanoparticles.

  1. One-Step Fabrication of Copper Electrode by Laser-Induced Direct Local Reduction and Agglomeration of Copper Oxide Nanoparticle (2011)
     1. 31 μΩ cm
     2. Laser: 1070nm 0.4W 25μm at 30mm/s
     3. "There are two types of copper oxides: CuO and Cu2O. The band gap of CuO (∼1.2 eV) is lower than that of Cu2O (∼2.1 eV). Hence, Cu2O is reported to have a high transparency with a slightly yellowish color and usually absorbs wavelengths below 600 nm, while CuO strongly absorbs the whole visible spectrum range and is black in appearance."
        1. So it sounds like a 450nm laser should be fine. I expect all the researchers are using lasers that their uni had on hand, and high powered blue lasers are relatively new.
  2. Photonic Sintering of Composite Pastes with Copper Oxide Powders Using Different Light Sources (2021)
     1. 8 μΩ cm on PET substrate
        1. It seems only a single layer is formed in these experiments, so the substrate its on affects the resistance.
     2. Laser: 638nm 1W
  3. Direct Writing of Semiconducting and Conducting Microstructures by Using Selective Laser Sintering and Reduction of CuO Nanoparticles (2024)
     1. 88 μΩ cm
     2. Femtosecond Laser: 800nm 0.04W at 0.004mm/s
     3. "The cupric oxide (CuO) nanoparticles are air stable, cheap, and easily available materials; they are also good precursors for fabrication of Cu micro/nanostructures by using selective laser reduction."
        1. So I guess this is why they're common in academia.
  4. Fabrication of Flexible Copper Microelectrodes Using Laser Direct Writing for Sensing Applications (2024)
     1. 62 μΩ cm
     2. Laser: 1064nm 0.955W* at 60mm/s
        1. *This laser was defocused because it's minimum power was 10W for a 42μm spot size was too much.
  5. Direct laser writing of copper and copper oxide structures on plastic substrates for memristor devices (2023)
     1. They only mentioned ohm/square measurements
     2. Laser: 1064nm 4W 15mm/s
  6. Additive...

  Read more »

• [R] NEJE 60μm lasers

  kelvinA • 04/22/2025 at 22:33 • 0 comments

  Table of 450nm Laser Modules

  	A40630	A40640	E40	E80	VF20	K30	P2 33W
  Size (mm)	40*50*85	40*50*85	40*48*145	41*56*113	50*80*80
  Weight	210g	204g	280g	600g	360g
  Input Power	12V 3A	12V 4A	12V 4A	24V 5.5A	24V 5.5A	24V	24V
  Optical Power Min / Max (W)	6 / 7.5	10 / 12	10 / 11	20 / 24	20 / 22	30	33
  Claimed Spot XY (mm)	0.04 0.04	0.04 0.06	0.06 0.06	0.06 0.06	0.08 0.08	0.16 0.19	0.08 0.10
  Power Density (W/mm^2)	3750	4166	2777	5555	3125	987	4125
  Focus	Adjustable	20 - 70mm	Fixed	Fixed	Fixed	Fixed	Fixed
  Cost (incl VAT)	£60	£132	£110	£312	£200 - 300		£430

  450nm Research

  So... don't be alarmed (I'm mainly talking to the mirror here) but I've been looking high and low for the ZBAITU VF20 and every listing I find allegedly cannot be shipped to my address:

  However, I just found the NEJE E80 which is a 20W laser that currently costs £312:

  I lowkey wondered why NEJE didn't seem to make anything more powerful than their A40640, which I didn't pay much attention to since it's a 10W (continuous) laser and I had been looking for 20W ones. I think it was one of the most expensive at the time. The lowest I've seen is under £135 now.

  What I didn't know is that NEJE focuses on making sure their spot sizes are 0.06mm or less. For example, compared to a typical 0.08*0.08mm ZBAITU module:

  • the E80 is 0.06*0.06mm, thus a 77% higher power density.
  • the A40640 is 0.04*0.06mm, thus 167% higher. 
    • Yes. This 10W laser has power densities equivalent to an VF20 outputting 27W

  Back to the E80, it seems that the engineers feel like it was best to keep their 20W offering in the oven for much longer than the rest of the industry. Here's some of the quotes (slightly edited for grammar):

  The focal point of NEJE E80 0.06x0.06mm, and the power density reaches 6666W/mm², Compared with *tool 40W module with power density 5000W/mm² (0.8x0.1mm, 8xLD).
  
  E80 is much better than that of similar 20W and 40W laser modules, with smaller focus, smaller angle, XY symmetry... The complexity is more than 3 times higher than that of ordinary 20W modules.
  
  We did not choose 8xLD or 6xLD to release new products relatively quickly for marketing gimmicks.

  I also found it interesting that all 4 diodes are on the same plane and mounted onto a copper heatsink:

  Anyway, I found this pic of multiple modules beside each other to get a better idea of size:

  I started compiling the table at the top of the log and the laser that stood out the most was the A40630:

  This is the smallest laser in multiple different metrics. It's the smallest cost, smallest footprint and a dot size of 0.04*0.04mm, merely 5 microns a side larger than a pixel on one of the 6.X-inch 4K displays, yet still has a power density exceeding the VF20. The only concern is that this doesn't agree with the wiki page, which states a focus of 0.13*0.13mm which is muuuch larger. It's literally the only one that's been tested in the wiki:

  
  Additionally, there's a forum thread from 2023 where one user said:

  I have the E80, and the spot size is about .08 x .10, the same as most 20W lasers. 
  
  The only lasers I have ever seen that actually have a spot size smaller than 0.08 are 1.5W - 2.5W... 0.06 x 0.07ish under the microscope.

  Thus, without 3rd party evidence, I probably shouldn't blindly rely on NEJE's claims. At the same time, Metal Base seems to be getting results from a Laser Tree 30W laser, which has a notably lower power density. 

  Laser Tree also has a K10 module that has a quick focus adjustment feature to toggle between engraving and cutting. It seems that 0.03*0.04 can be obtained for the shorter focus:

  Thus, perhaps NEJE's claimed spot sizes are at the absolute...

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