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LCD type printer review by Tim Blythman & Nicholas Hannekum ANYCUBIC Photon Mono Resin-based 3D Printer Resin-based 3D printers have been around for a while, but it’s only in the last few years that we have seen them experience a boom in popularity and availability. We tested this model (available from Jaycar) to see how it shapes up, especially compared to filament-based 3D printing. W e previously looked at several filament-based 3D printers, including the UP! in August 2011 (siliconchip.au/Article/1132), the RapMan in the December 2012 issue (siliconchip.au/Article/450) and the Vellemann K8200 in October 2014 (siliconchip.au/Article/8040). The Vellemann K8200 was available from both Jaycar and Altronics as a kit. Since then, pre-assembled filament-based 3D printers are much more prevalent and can be purchased even more cheaply than the kits from less than 10 years ago. We also covered other 3D printing technologies in detail in January 2019 (siliconchip.com.au/Article/11367). That article covered 3D printers that siliconchip.com.au use a plastic filament, also called material extrusion, fused deposition modelling (FDM) or fused filament fabrication (FFF). It also described other technologies, including binder jetting, directed energy deposition, material jetting, powder bed fusion, sheet lamination and vat photopolymerisation. The last of those is also commonly known as resin 3D printing. Like filament 3D printing, the technologies needed for resin 3D printing have been known and patented for around 30 years. The recent expiry of these patents has allowed the unencumbered use of these technologies, resulting in machines that you can now purchase at quite reasonable prices. Australia's electronics magazine Resin 3D printing While the term vat photopolymerisation is a bit unwieldy, it does sum up how resin 3D printing works. The raw resin in a vat is photopolymerised, which means that it is hardened by the selective application of light. This is done in layers to build up the object (see Fig.1). Vat polymerisation can be broken down into three major subsets: SLA, DLP & LCD printing. The main difference between each type of printing is the type of light source used: • SLA (stereolithography) is the most common form, whereby a UV ‘laser’ is used to trace each layer of resin. July 2022  41 Cover Vat detail Z lead screw Platform securing knob Platform bracket Spout Printing platform Frame Vat retaining screw Resin vat USB port Fig.1: the basic principles of resin 3D printing are shown. Many smaller printers use an LCD panel to project an entire layer rather than scanning with a laser or DLP device. Source: “Digital Fabrication Techniques for Cultural Heritage: A Survey” • DLP (digital light processing) instead uses a single UV projector with the light selectively directed to process a whole layer at once. • LCD (liquid crystal display) is nearly identical to DLP except it uses an array of LEDs as the UV light source which is imaged via an LCD panel. There are quite a few parallels to filament-based 3D printing, including the use of ‘slicer’ software to process computer models into the printer’s working files. There are also several significant differences, which we’ll discuss in detail later. In practically all cases, the resin hardens when exposed to a UV light. The resin consists of photosensitive compounds which release free radicals on exposure to specific wavelengths of light. These free radicals cause other substances in the resin to combine into the final, solid resin polymer. A movable platform, analogous to the print bed on a filament-based 3D printer, moves away from the panel to create the third axis perpendicular to the platform surface. Anycubic Mono UV Photon The Anycubic Mono UV Photon is reasonably representative of the resin 3D printers that use an LCD panel. 42 Silicon Chip Touschscreen FEP film Power switch UV LCD screen (under vat) Fig.2: the main parts of the Mono. The FEP Film is a thin transparent plastic film that allows the UV light to pass through and cure the resin. Some larger 3D printers use the scanning laser technique, but otherwise, the parts and operation will be similar for the commonly available consumer resin 3D printers. We purchased our unit from Jaycar Electronics (Cat TL4422). Note that it will be discontinued as there is a higher-­resolution “4K” version replacing it (Cat TL4419). You might still be able to pick up one of the reviewed printers from Jaycar if you are quick. These printers are very similar and you can expect everything we say about the review unit to apply to the 4K version, with the benefit of finer details on the newer version. Returning to the printer we’re reviewing, It has a nominal print area of 80 × 130 × 165mm. Many resin 3D printers use a similar LCD screen to a mobile phone, which helps to explain those relatively small dimensions. The availability of off-the-shelf screens such as these is part of why prices for such 3D printers have dropped. The overall size of the printer is 222 × 227mm at the base and it is 383mm tall. So it’s quite compact. The nominal resolution is 0.01mm (10μm) on the vertical (Z) axis and 0.051mm (51μm) on the horizontal (X and Y) axes. The horizontal resolution is due to the LCD itself, while Australia's electronics magazine the motion hardware limits the vertical resolution. All of these figures are much finer than commonly found on filament-based 3D printers. We’ll refer to it as the Mono, as Photon is the name Anycubic appears to give to all its resin 3D printers, and we feel that the UV label is implicit. It’s called the Mono because it uses a monochrome LCD panel. Many other similar printers use commonly available RGB panels, resulting in longer print times as the RGB panels do not pass as much light as monochrome panels. Fig.2 shows the main parts of this type of printer. In operation, the Z lead screw moves the platform vertically. The hex screws on the platform allow it to be adjusted correctly when the Z-axis is at its bottom home position. During printing, the Z-axis moves upwards as successive layers are exposed. One side effect of this motion is that the object is printed upside-down (compared to a filament-based 3D printer), leading to some subtle and interesting side effects. Setting it up Naturally, we dove straight into trying the 3D printer out. Here’s our experience of starting to use the Mono. siliconchip.com.au We expect many similar printers are much the same. We started with a 500mL bottle of Anycubic clear resin (Jaycar Cat TL4427) as the clear resin would let us inspect the interior of 3D printed parts. We also printed some parts with grey resin, as you can see from our photos. We had no trouble with the quickstart guide, although the instructions are brief. There are a couple of presliced files on the included USB stick, so you don’t even need to install the software to start printing. We simply plugged in the USB stick to the Mono. We later switched to a shorter USB stick so that it didn’t protrude as far from the printer’s body, reducing the risk of it getting damaged. We found that even a 1GB stick was ample, with most sliced files coming in under 10MB. After unpacking and assembling, the essential preliminary step is to set the platform using the four hex head screws. There is a piece of paper included specifically for this purpose. Like a filament-based printer, the ideal gap between the platform and the UV LCD screen is about the thickness of a sheet of paper. In the case of the Mono, this gives space for the thin film of the resin bath. There aren’t too many functions on the Mono’s touch screen, so it’s easy enough to navigate. Still, the “Home” option, which we expect would be used regularly, is quite deep in the menu structure. After the platform is homed, the hex head screws are tightened to fix this positioning. The instructions say to press the “Z=0” button before continuing. After this, the platform moves up to allow the resin vat to be inserted. While it appears that the thin FEP (fluorinated ethylene propylene) membrane of the resin vat would be a suitable thickness for calibration (and we did use it on occasion when the vat and platform were wet with resin), we can see a good reason for removing the vat. A common catastrophic failure mode is for the platform to be driven into the UV LCD screen with something solid hidden in the resin. This cracks and damages the LCD (fortunately available as a spare part). This is more likely than you might think, as many failed prints result from the printed object detaching from the platform and falling into the resin. Even using clear resin doesn’t help siliconchip.com.au much, as a transparent object is practically invisible in clear resin! Accessories and safety The Mono includes several tools in the box. There are two scrapers, a plastic mask, some gloves, a handful of filter funnels and three hex wrenches (Allen keys). The manual also notes that safety glasses should be worn when handling the resin. The mask, gloves and filter funnels should be considered consumables. There is some discussion online that the mask supplied (which appears to be the type used for protection against dust) will not block the resin fumes, and we found that to be the case. The most common advice is to work in a well-ventilated area, such as near an open window. However, consider that sunlight (which includes a significant amount of UV) should be kept away from the printer to prevent the resin from being prematurely cured! The gloves and glasses are to prevent skin and eye contact with the resin; the MSDS lists irritation as a side-­effect of skin contact. We didn’t notice any discomfort when we did get resin on our skin, although this will vary from person to person. Thorough rinsing and washing with soap and water is the recommended way to remove resin on the skin. The most extreme cases of exposure involve the resin being retained in the skin and slowly hardening. We imagine that this would be nasty if you got it in your eye. Fortunately, the resin is safe after it hardens, so the general advice for disposing of surplus liquid resin is to leave it in the sun to harden. not necessary if you take care, but you must wear safety glasses as this is when the resin could easily splash. The inside of the vat is marked with graduations in millilitres as well as a MAX marker. Filling above the MAX marker might cause the vat to overflow when the platform is lowered into the vat. The slicer program reports an estimate of the resin volume needed, although this will vary with resin type, temperature and even the degree of exposure selected. We found that we needed an excess of at least 10mL to avoid running out. Since there will be an excess of resin needed in any case, we found it easiest to be generous, as the resin can be later reclaimed using the filter funnels. The printing process The “Print” menu item simply lists the available files on the USB stick, including a name and a thumbnail that looks like the view from the slicing software. Play and pause buttons control the process. A remaining time display is shown Adding resin The last step before printing is to add resin to the vat. Wearing gloves is probably This 3D printer also comes in a 4K resolution model called the Mono 4K (twice the standard resolution). Australia's electronics magazine July 2022  43 during printing. We found it was pretty accurate but consistently underestimated by about a minute for every hour of printing time. What you have read so far may lead you to believe that resin 3D printing is quite simple. Of course, there is some subtlety to the way the Mono (or, we expect, any other resin 3D printer) does its job. ‘Exposure time’ is a critical parameter for resins. It varies from resin to resin and needs to be longer for thicker layers. Critically, it is not the only time that is spent by the printer on each layer. The default exposure time for the Anycubic resin is two seconds per 50μm layer. But the actual cycle time per layer is on the order of 10 seconds as other things need to happen. When the printer is ready to start its exposure time for a layer, it passes the image to the LCD, turns on the UV backlight and counts down the exposure time. It then turns off the backlight and clears the LCD. There may now be an ‘off’ period, where everything is left as-is for a few seconds, allowing the freshly exposed resin to settle. Both the absorbed UV light and the chemical reaction it triggers can generate heat, so this period also allows the heat to dissipate. The printer then lifts the platform to detach the freshly printed layer from the FEP film. While FEP is a similar material to Teflon, the resin still sticks to it quite well. The tearing/popping sound it makes is disconcerting, but perfectly normal. The Mono’s default setting is for a lift of 6mm at 4mm/s, so it takes a few more seconds to lift the platform clear of the FEP and then reposition it for the next layer. The platform returns to a point that is higher by the layer thickness, to allow the next layer to be printed. After the printing sequence, the platform is moved upwards, although items close to the Mono’s height limit might not clear the resin vat. The printed object can be left to allow any excess uncured resin to drip for a few minutes. Fig.3: these small, inexpensive UV nail lamps work well for the final curing step. As with any UV source, we recommend wearing eye protection while using such devices. the bed, any supports are removed; that is usually enough for most designs. For a resin printer, the part needs to be removed from the platform and then any excess liquid resin must be rinsed off by solvent washing and possibly mechanical cleaning. After removing the supports, the part undergoes further UV exposure to ensure that the resin is fully cured and hardened. Not only are there more steps, but they are also much messier due to the sticky liquid resin. Anycubic also sells a ‘wash and cure’ machine, which can help with some of these steps. It’s at this point that gloves are needed. An organised (and, if possible, spacious) workspace is imperative, as you do not want to be moving things around while wearing sticky gloves. We recommend employing a large work area with a lip (to contain liquid resin) to remove the part from the platform, alongside two containers of cleaning solvent and next to another open area where clean parts can be placed to dry. We kept the Mono on a large plastic tub lid to provide a ‘catchment’ for leaks. It certainly helped with the occasional drip while removing parts Post-processing from the printer. One crucial way the resin 3D printThe most common arrangement uses ing process differs from filament two tubs of cleaning solvent. One is 3D printing is in the manual post-­ used for the first pass, to remove the processing steps. For a filament 3D bulk of the excess resin, and the secprinter, after removing the part from ond to finish. The solvent from the 44 Silicon Chip Australia's electronics magazine second tub can be recycled to be used in the first step. We’ve even seen some people use a third tub to clean the platform, keeping it out of the way while the parts are cleaned. So despite it being a small machine, you’ll probably still need a good amount of nearby space in which to work. To remove the printed part from the printer, the screw on the platform is loosened to detach the platform, and the platform is rested on its edge. The metal scraper can then be used to separate the part from the platform. Substantial force might be needed, potentially making this step messy if the part flies off. The part is placed in the first solvent tub, which is agitated to remove the uncured resin. It is then moved to the second tub to remove any remaining resin. It’s then placed on a flat surface to allow the excess solvent to evaporate. This last step is critical. It should be left until no shiny spots remain. Resin mixed with solvent stays sticky, even after the next curing step, and can only be removed with further solvent processing. Solvent options We tried three different solvents. While some people swear by isopropyl alcohol, we found that they all were quite capable of doing the job. Isopropyl alcohol was actually the last we tried because it still appears to be in short supply and, where available, it siliconchip.com.au least compared to the Anycubic resin. It tended to end up with a slightly yellow tint and did not seem to be as dimensionally stable as the Anycubic resin. We suspect that is due to the heating and expansion that occurs during the UV curing process. Some resins also expand as they solidify. On the other hand, we found that this resin needed slightly less exposure time, so we could print a bit quicker with it. The cured eSun resin also had a very odd bluish cast in sunlight. We suspect that is due to the photoreactive compounds present in the resin fluorescing in the presence of UV light. Resin exposure range finder Fig.4: a sample print of the Resin exposure range finder (R_E_R_F) test file. Different parts are printed with varying exposure times to hone in on the ideal exposure setting. There are several different features to compare, and your choice might depend on whether you are printing coarse or finely detailed objects. is much more expensive. We first tried methylated spirits as it is the cheapest. It worked fine for dissolving the leftover resin, but leaves more residue that takes longer to evaporate. We suspect this is due to the additives or the small amount of water usually present in methylated spirits. Still, the results are satisfactory as long as the part is left to dry completely. We also tried acetone. It’s much more aggressive than either of the other two solvents and also evaporates quite quickly. Being more aggressive, you should ensure that your gloves can withstand it. Because it evaporates so quickly and thus cools, we suspect that water was condensing on the parts when it was humid. That water needs to evaporate before the part can be cured. The isopropyl alcohol works much the same as the methylated spirits, although there’s a bit less residue and, as we noted, is more expensive at the time of writing. fingernail polish and gels). They run from USB power, and the style we purchased costs around $10 from a local eBay seller, shown in Fig.3. The UV lamp has collapsible legs that can make it taller than small parts, and the timer runs for about 60 seconds. We found that using this lamp for a minute on each side of the part was enough to cure it fully. Resin choices There are a rapidly growing number of resins now available. Apart from the obvious choice of different colours, different material properties are also possible. Many quote strength, density and hardness, although the standard resins often seem to be the strongest. Subjectively, we felt that the standard Anycubic resins gave the best results. We tried the eSun eResin-PLA from Jaycar, also in the clear variety, although it comes in a handful of colours. It claims to be ‘low smell’, and we found that to be the case, at One of the files on the USB stick is called R_E_R_F.pwmo (.pwmo is the file type of the ‘sliced’ file used by the Mono). This special file is used to help calibrate the exposure time. When this file is printed, different parts are printed at different exposure times to allow the optimum time to be found. Fig.4 shows a sample print of this file, and you can see that the part at lower right is obviously underexposed. Not as evident in the two adjacent parts is that the small pillar features are missing, so the optimum setting is towards the middle of this print. See the later panel for further discussion on what resins are available. Software At a bare minimum, you will need to use the Photon Workshop software to ‘slice’ models into a format suitable for printing. There was a version on the USB stick, but we downloaded a later version, 2.1.24, from siliconchip. com.au/link/abet It’s common to work with .stl files, but .obj model files are also supported, as well as several sliced formats (see Fig.5). We found this handy when trying a model from www.thingiverse. com in the .obj format. Curing The last step is to use UV light to fully cure the resin. The wash and cure machine has a turntable that evenly exposes the part to UV light, but we found that simply leaving the part outside in the sun for half an hour, while turning it over occasionally, was adequate. We also tried a small UV lamp of the type sold as a UV nail lamp (for curing siliconchip.com.au Fig.5: raw mesh files in .stl and .obj formats can be loaded into Photon Workshop, as can pre-sliced files of the various types shown. Loading pre-sliced files will not give as many printing options, as you cannot change aspects such as the layer height. Australia's electronics magazine July 2022  45 Fig.6: the Photon Workshop application, showing a 3DBenchy loaded. The 3DBenchy test object (by www.creativetools. se) can be downloaded from www.thingiverse.com/thing:763622 At left are the various transforms that can be applied to rotate, move and scale objects, while the slicer settings are at right. Supports can be created using a second tab on the right. If you are designing your own files for printing on a filament 3D printer, much the same process will apply, except for using a different slicer program. For example, we use OpenSCAD to design .stl files for filament printing, and you could use those same .stl files on the Mono. As long as you can export .stl files from your 3D design package, you can import these into Photon Workshop. Fig.6 shows the Photon Workshop software. Most of the transform options on the left will be familiar to those who have used a slicing program from filament 3D printers. These allow loaded objects to be rotated, sized, moved and adjusted. At right are the exposure and printing settings. The program defaults to two-second exposures for 0.05mm layers, but we mostly used five-­second exposures with 0.1mm layers to speed up printing slightly. Note how the time more than doubles going from 0.05mm to 0.1mm, presumably due to the UV light being attenuated as it passes through thicker layers. We also did some prints with much thicker layers to improve the printing time and found that 0.3mm per layer, with around 15s exposure, tended to be the limit. After this, the lift and peel 46 Silicon Chip time becomes less significant. In any case, 0.3mm is getting into the layer heights commonly found on filament printers, resulting in prints with noticeable jagged layer artefacts that begin to show the resin curing unevenly. Fig.7 shows a pair of test cubes, one printed with a 0.3mm layer height and the other with a 0.1mm layer height. Resin printing specifics Supports are common in filament printing, but are used in a slightly different way with resin printers. The general advice is that all resin 3D prints should use supports. This is primarily due to the way that parts adhere to the platform, but also because of the high forces that occur on each layer lift. Using supports means that the part can be printed on a detachable raft that can bear the scraper’s brunt while the part is being removed from the platform. The raft can also be expanded to provide a greater area to affix to the platform, reducing the probability of it detaching mid-print. Another factor is that the first layers (by default, six with the Mono) are overexposed to ensure good platform adhesion. This means that they will Australia's electronics magazine tend to be over-dimensioned unless compensation is made. Using supports means that the actual 3D model does not start until these early layers have been printed, meaning that they do not suffer from overexposure. There are some artefacts at the points where the supports contact the object, but we found that they snap off quite cleanly, and a light touch with sandpaper removes all traces. Fig.8 shows a part with a raft and supports; you can see how the supports taper to narrow points that make for clean breaks. siliconchip.com.au Fig.7: the left-hand cube was printed at 0.3mm layer height, while we printed the right-hand cube with 0.1mm layers. The staircase effect is much more pronounced at 0.3mm. Note how it is more prominent on the top half of the object. This is due to the way that the resin cures more the closer it is to the UV source, producing unevenness within thick layers. The holes visible are part of the punch and hollow features which can be used to reduce the amount of resin needed. We should point out that while Photon Workshop can produce supports and a raft, the ones shown in this image were done by a separate program. We tried PrusaSlicer from Prusa Research (www.prusa3d.com). Prusa Research has a substantial background in filament printers, but they also design and sell resin printers. Importantly, PrusaSlicer can export a 3D model (such as an .stl file) with supports added, allowing the now-­ supported model to be sliced by Photon Workshop. We just had to choose an appropriate Prusa Research printer, and the SL1 has a similar build size. Fig.8: the narrowing of the support pillars near where they join the model means they snap apart easily. Removing supports from resin prints is easier than on parts printed with a filament printer. It isn’t evident that the raft has an angled edge, which makes it possible to wedge the scraper underneath it to help remove the part from the platform. It might seem like an unnecessary extra step, but we found that the supports broke off more cleanly, and it was also a bit more intuitive to manually place support points using the PrusaSlicer program. Hollow and punch In the world of filament 3D printing, a partial infill is very common, with figures around 25%, allowing parts to be both light and strong. Various patterns are used, with trade-offs in print speed, strength and, in some cases, interior support. With filament printing occurring in the air, air fills the voids and it is trapped when the top layers are printed. Since resin printing occurs under the surface of a liquid resin bath, empty spaces are liable to be left full of the same. So the reasons and strategies for infill treatment are very different for resin printing; simply choosing an infill option is not enough to guarantee a hollow part. Both Photon Workshop and Prusa­ Slicer have a “Hollow” option that allows a wall thickness to be set, which is simple enough, leaving the remaining space inside the model hollow. Fig.9: the narrow pillars in this model boat are 0.3mm in diameter. You can just make out the 0.1mm layer lines below and the aliasing due to the 0.051mm pixels. With such fine details, the extreme forces that occur during each layer lift mean that such delicate parts must be designed with care and with an appreciation for the printing process. siliconchip.com.au Australia's electronics magazine July 2022  47 What resin is available? There are quite a few different resins available to use with the Anycubic Mono. The default type of resin is sold by Jaycar and comes in a 500g bottle with black, grey, clear, blue and green as available colours (Jaycar Cat TL4425-9). Anycubic also sells a more expensive, plantbased version (made from soybean oil) in 1kg bottles. It’s marketed as having less odour and shorter curing time at 50-60s exposure for the bottom layer and 8-10s exposure for other layers. It comes in translucent green, clear, grey, black and white colours, and it can be purchased online from websites such as Amazon. Third-party resins In terms of third-party resins, many should work if they’re suited for DLP or LCD printing and are rated with a UV wavelength around 410nm. We have only fully tested the eSun range, which is available from Jaycar. They sell a standard 1kg resin (Jaycar Cat TL44439), and PLA (polylactic acid) resin (Jaycar Cat TL4433-9) which can be cleaned with isopropyl alcohol. Both are available in red, yellow, white, black, grey, blue (sky blue for the standard resin) and clear. There’s also a water-washable version, which has the highest density range of the eSun resins, but in exchange has the lowest tensile strength (Jaycar Cat TL4450-3). Sadly they don’t list whether any of the above resins can be painted over, as that can be a nice feature if you’re assembling a garage kit or similar. Your best bet is to use clear resin when available as it should have less pigment, making it easier to paint. Monocure 3D from Australia also make resin that is suitable for the Photon Mono. You can find a list of compatible products on their website: https:// monocure3d.com.au/printers/photon-mono-x/ While not directly related to this printer, Formlabs have a very nice document listing all the different types of resins they sell along with their specifications; you can find this document at: siliconchip.au/link/abeu You can also find a general guide on 3D printing by Formlabs at https:// formlabs.com/asia/blog/3d-printing-materials/ But the model then needs to have holes added so that any liquid can be drained out of the model after printing. It’s possible to leave the resin inside, but that has no real advantage over simply printing the model solid in the first place. Since some resins can expand on curing, this could cause the model to swell and rupture if curing continues later. The “Punch” option adds holes, and they are simply placed by clicking on the model’s surface. More holes should be better, to allow air to enter and excess resin to leave, but they will also mar the model’s surface. Wall thicknesses of around 3mm are the default, with a similar size for the 48 Silicon Chip punched holes. The test cubes shown in Fig.7 were printed with 3mm walls and 3mm punched holes to test these features out. Draining the liquid resin from a model is another messy step that is added to the process, followed by the need to rinse and drain the cleaning solvent. We think that if it makes sense for you to print hollow objects, the best results will come from designing them to be hollow from the start. Most of the objects that we printed were relatively small, so the potential resin savings were not worth the trouble and effort. You’ll also find that objects printed in clear resin will show the outline of the hollowing, so there might also be Australia's electronics magazine cosmetic reasons why hollow objects are undesirable. Dimensionality We found the dimensions of printed objects to be very accurate, which is to be expected when two of the dimensions are created from a fixed-sized LCD screen, and the third is set by the steps and pitch of a worm gear driven by a stepper motor. One test model we printed had a 5mm square hole and a series of different sized holes. We found that the post had to be 4.9mm or smaller to fit in the hole. This is around two pixels of difference on the LCD screen! Unsurprisingly, the pixels tend to spread by a small amount. If they didn’t, adjacent pixels wouldn’t merge to become a solid object. But this effect is relatively minor. Fig.9 shows a printed model with some fine details, including pillars only 0.3mm across. Of more serious concern are the forces that distort an object as it is printed. As we mentioned, there are substantial forces involved as each layer is lifted up and away from the FEP film. The fine pillars in Fig.9 have only been printed successfully as they are vertical and the handrail is horizontal. Such fine elements would probably not have printed well if they were not aligned with the axes. You could add supports to the side of objects, but they will be of limited use on such small objects. We found that a good rule of thumb was to align an object so that it has a long vertical axis. Such alignment ensures a small footprint and thus suffers less lifting forces. This will also tend to result in the longest printing time. On a similar note, we found that thin sheet-like areas (even vertical) did not always print well. We suspect that the lifting forces cause stretching, leading to deformation as subsequent layers are printed and joined together. One upside of the whole layer being printed simultaneously is that multiple objects can be printed in the same amount of time as a single object, provided they fit in the print area. Impressions At the time of writing, we’ve used about three litres of resin, and the FEP film is looking noticeably worn and siliconchip.com.au scratched, although this doesn’t seem to be affecting the print quality. Spare FEP films for the Mono are available (Jaycar Cat TL4502), as are complete resin vats (Jaycar Cat TL4504). The LCD screen used for projecting the UV image onto the resin is also available as a spare part (Jaycar Cat TL4506). We’ve heard figures of around 1000 hours of operation before replacement is needed; that works out to about six weeks of continuous printing. It appears that the UV light eventually degrades the LCD to the point that it no longer blocks the UV light and needs to be replaced, although we haven’t seen any signs of this happening. Resin printing with the Mono is simple enough, although it can sometimes get messy. The resolution and detail are impressive. As you can see from our photos, the finish of the prints is very matte and almost has a texture like velour, although the layer and pixel artefacts might be visible, depending on the lighting. So models printed with the clear resin will not have a glassy finish, although a gloss lacquer can generally improve transparency on clear models and hide layer lines. Summary We’re impressed with the fine detail that the Mono can produce and how easy it is to use. Printing with it can get quite messy, but with the proper space and tools, it is manageable. There are a few consumables involved, and we suspect that the cost of these will add up after a few years. The print volume is smaller than most filament 3D printers, but we expect that the fine detail will appeal to those making smaller miniatures and other parts. We’ve found at least one other use for the Mono – see our panel on “3D Printing PCBs… sort of” for more information. We suspect there are other UV reactive substances (UV ink is one that we know of) that might be used in combination with the Mono. We haven’t tried it, but it might also be a handy way to erase EPROMs in a pinch! As noted earlier, the Anycubic Mono UV Photon resin 3D printer and select spare parts are available from Jaycar (www.jaycar.com.au/). SC siliconchip.com.au 3D Printing PCBs... sort of We covered using 3D printers as part of a home workshop process to make prototype PCBs in our “Modern PCBs – how they’re made” article from July 2019 (siliconchip.au/Article/11700). That article mentioned techniques like printing a thin layer of filament onto copper-clad fibreglass to act as an etch resist, or even directly printing conductive filament onto a substrate. But YouTuber Thomas Sanladerer demonstrates another use for a resin 3D printer that actually comes very close to how the professional PCB fabricators work at https://youtu.be/RudStbSApdE The technique uses the 3D printer’s UV LCD to selectively cure the photosensitive resist on a coated copper clad board, before the resist is fixed, and then the board is etched in the usual fashion. The results are both fast and remarkable. The photo below shows his first test PCB using this technique. That video screenshot also demonstrates the importance of the difference between positive and negative resist boards! He notes an exposure time of 60-90 seconds, although that will probably vary between printers and resist compounds. Given that the Mono’s resolution in the horizontal plane is around 50μm, 10mil traces (which are about the minimum that we typically design for) are about five pixels wide. In other words, it should be possible to create very fine PCB detail with this technique. The trick is converting Gerber files into something that the slicer program can process for the printer. Our Making PCBs article has more information about Gerber files. We don’t have access to the software that Thomas uses. Still, it appears that there are numerous ways to convert an image file to an .stl file, including via several online tools, so it shouldn’t be an insurmountable obstacle. Thomas also shows etching an image of a leaf onto a piece of copper-clad board, so it appears that there are many uses for this technique. With the existence of UV-curing inks, it may be possible to ‘print’ PCB silkscreen overlays too. This is something we’ll be trying out soon. Perhaps it won’t be long until we’re all making factory-quality PCBs ourselves! YouTuber Thomas Sanladerer (https://youtu.be/RudStbSApdE) shows how to use the UV LCD of a resin 3D printer to selectively cure photosensitive resist, producing home-made PCBs. Like him, you will have to be careful of the differences between positive and negative resist boards! Australia's electronics magazine July 2022  49