3D Printing in a 100°C Heated Chamber - Lessons Learned

back behind me are three different frame types and three different movement systems for F F F or F DM fused filament fabrication or filament deposition modeling that's you know whatever you want to call it it's a the extrusion and sort of laying down of a bead of thermoplastic material and it's the low cost way to achieve 3d printing of course there's lots of other ways to do additive manufacturing so different has all those machines are we've got a Cartesian Mendel style frame we've got a delta very fast printer there and then we've got the sort of middle of the road which is your core XY so it moves more quickly than that one but it also has great accuracy which the Delta can sometimes lack so yeah difference as they all are they have one common problem and it's a big problem that is the fact that they print in the open air just look at that so if you are extruding plastic what you want to do is get it to its molten state and maybe maybe past its molten state where it's good and warm so that it really fuses to the layers down beneath it but then you want to freeze it and it's just like water right it's just like really viscous water it's in its molten state and it flows and then when it cools down to air or room temperature it's frozen so really you would like to be just below frozen just just across that frozen line so you're just above that frozen line to sort of lay it down and just below that frozen line and then you keep the whole part just below that frozen line pull the whole part out of the printer and let the whole thing cool down together and you would lose a lot of the problems that we have with these open framed printers with like you know peeling up off the bed or actual layer separation that happens as you get farther up the print so yeah hated chambers or even just chambers so like lots of people print and sign up a cardboard box they just make a box and they put that over their printer not only does it keep the eightieth ABS fumes out of your room where you're you know having to coexist with your printer but it also keeps the temperature there it keeps the little air drafts off your off your part there so yeah enclosures they're absolutely the most important upgrade that you can do it so why aren't we doing them well there's a good reason no company can sell an enclosure because Stratasys still has the patent and it was supposed to expire but they pulled some shenanigans with some sort of an extension with the Patent Office like they've all have had this patent for more than 20 years which you really aren't supposed to have a patent for more than 17 years it's it's kind of a gray area but it's somewhere between 17 and 20 but to get a patent to last more than 20 years is oh that's fishy like I don't know how they pulled that that stuff III have a patent myself I'm not against patents the problem is that patents are mostly just abused by large corporations who just use them to hold a monopoly and and and SiC their lawyers on other people so if I build a enclosure for my printer here in this video I am opening myself up to litigation from Stratasys they're not going to do that though because of the Streisand effect here on the internet and what does it gain them to come sue me some little tiny little youtuber who's already poor and just trying to eke out an existence here in this 3d printer community you know it's really not gonna benefit them but they could so they it's no joke they have a patent for a reason they really don't want people making heated enclosures but their patent will run up it will run out so when it does this is going to be the technique so let me show you guys everything that I've learned trying to make a 3d printer that can print polycarbonate without any issues let's get into it [Music] so let's go to google and see what everybody else thinks a 3d printer enclosure should look like so we see a bunch of clear plastic cubes that's pretty much what everybody wants and I think this all started here with this motif that you're looking at this is the IKEA lack hack which i think is this one here yeah so this is I think maybe the original DIY from 2015 so we've had these you know solids sighted you know plexiglass or acrylic sheets single wall IKEA lack AK from from quite a few years ago almost five years ago now if you Image Search and you go through it there's tons of these things look at this guy selling it on Etsy for money and this is a you know extrusions aluminum extrusions but again single wall and everybody does this and I don't understand why nobody has thought to make a double walled enclosure see this is the basically a cutaway drawing and picture of the glass that you find in your house any any modern home or skyscraper or whatever has double pane glass sometimes there's triple panes and it's actually the center pane is just a membrane but you have an outer pane and an inner pane and the air space in between insulates so why is nobody doing you know something like the IKEA hack only with two walls and so that's what I'm going to try to accomplish here but I don't want to be spending two hundred and sixty dollars on this enclosure it really shouldn't cost that much money so I'm gonna see what I can do to you know make this same motif or you know this this this is this is what everybody thinks of when they think of an enclosure so I'm not going to question the wisdom of the crowd too much I'm just gonna go with it but make the the glass double walled so to that end here is the design that I've come up with now I can click on this group here and move it and you can see there is my door and I'm not gonna put that on hinges I'm just going to have it you know pull out and then and then push back into place but you can see there's two panes of glass actually let's let's just select those so you can see double wall thickness there with an air gap there between them and for the other material them and actually use you know that's where the expense comes in cuz I can make all these uprights here out of a two-by-four as well as all of the you know the cross members out of two-by-four as well and then these top panels you can see those right there I can make those out of luan and luan is just a really cheap and thin plywood so very inexpensive you could build this whole thing for I don't know 20 bucks so far and really the expense is just gonna come from those those you know plexiglass or actual glass sides but here on the Home Depot's website we can find a 4-foot by 8-foot sheet of mackerel on point oh three inches that's um basically 0.75 millimeter and it's 100 bucks so still pretty cheap because it's because it's thin you'd be worried about not being as insulated but we've got that air gap in between the two walls so really doesn't need to be that thick so I think this is gonna do a great job for this for this design so this is the plan and basically what I need to do is cut out a start by cutting these um these uprights and you can see I've got these slots cut into them to receive the the plexiglass or the the polycarbonate sheets so let's get to work in the real world doing a little bit of carpentry making this enclosure you guys know how 2020 aluminum extrusions are kind of like the paradigm that's the thing that everybody thinks of when they when they need to make a frame for something here in the maker community I consider two by twos to be kind of the same deal for but made out of wood and a whole lot cheaper you can get a 2x4 for like three dollars and that means that every 2x2 cost like a dollar fifty so they're very inexpensive they're a little bit flexible but for most things like boxes and shelves and whatnot you can easily engineer your project to you know to work just fine with them so you can see that on the table saw I cut out two slits and then I just used my chisel to actually cut the ends of the slit uh I did not want the cuts to go from end to end so I've got this terrifying little set of circular saw blades and I got this on ebay a year or two ago I think I plan to use them in my dremel tool but there that's why they're so terrifying they've got so much bite they just jump off the material you're trying to cut and they they slice your hand up so really not for a hand tool I don't know what the intended purpose is for these things but I came up with the perfect usage just now in this project this blade here is the largest one that came in the kit and it's one millimeter thick the the metal that it's made out of is ik exactly one millimeter which also happens to be the thickness of the clear plastic window so the polycarbonate sheet is one millimeter as well so cutting the grooves for the polycarbonate sheet to sit inside of with this blade as it gets a perfect fit which is awesome so I've currently got this all set up with this fence you can see here and it basically just ends up being like a table saw on its side [Music] and Here I am cutting the loo on the thin plywood cover for the top and the base you know the floor and the ceiling of the chamber and you can see by the beard that I had in this clip that I recorded this footage quite a few months ago this project has been ongoing kind of in the background it's not been a major priority for me but I have been working on it and actually I've had it running here for a couple of months but I just got around to making the video for you guys recently anyway yeah this is the the construction technique you know it's basically a hollow core door this is I mean I don't have the paper normally Holley corridors have this like sort of honeycomb shaped paper on its edge that that really stiffens the center and if I was going to do this project again in the same construction technique I might fill the cavity there with some expanding foam like some great stuff something like that and Here I am cutting the polycarbonate so this is gonna be all of the windows yeah that's you know two two by two so two double pane windows everywhere so that's that's how I made those shapes okay so the first sheet of polycarbonate is installed into this bottom which is actually the top because this is currently upside down so it's insulting the slot where it's supposed to be there at the top and what I'm trying to do at the moment is slide it into the vertical slot here that it's supposed to go into and I'm having a very hard time getting that to go in there so these slots just as I planned are a good friction fit and that was to make them so that they are airtight so that I have a really well insulated box to print inside of and well the difficulty sliding that in is only the beginning because this is just the first piece this is a double layer so when I can grab both sides it's challenging enough but what happens when I'm doing the the piece back behind there and I can't even grab both sides of it so and then it's even worse than that because eventually I will have six of these pieces in there so three sides each with two pieces and I will be trying to slide down the bottom wood piece over the over onto that so I will have six pieces with the grooves here that I'm trying to line up all in one perfect moment and it's it's not gonna happen so I've got to redesign this enclosure for build ability well you guys I didn't document the process but this is what I ended up with I basically didn't want to scrap the entire build so instead of using a poly carbonate windows on all four of the sides I just ended up using some sheets of luan so I was able to kind of salvage the 2x2 construction and I don't recommend anybody duplicate this chamber there are better ways to do it for instance you could get polyurethane foam you can order it from the Home Depot or Lowe's or maybe they have it in stock and that that polyurethane foam has a foil backing to it so it would be more temperature resistant and I even flame resistant than the wood that being said what is more flame resistant than people give it credit for it I don't pray with this thing unless I'm in the room with it and I have a fire extinguisher close by so anybody who wants to raise safety concerns yeah blah blah blah I'm DIY I'm experimenting this isn't a final product there is some fire danger with this thing so yeah don't do it like this but this is working and it's a great proof of concept and the key and this is the point of the whole video this is what I want to get out to everyone when you build your chamber and you absolutely should build chambers you would get much better results out of your higher temperature plastics in a chamber and when you build your chamber it needs to be sealed sealed so don't let air come in and out of it it needs to hold all the air inside of it and also it needs to be insulated so think about those really fancy coolers who are they made by Yeti and I think there's a bunch of copycats now why are those you know three hundred dollar coolers so much better than your $20 you know roto-molded crappy igloo coolers or whatever you want to whatever brand names attached to those and the reason is just because they seal really well they're very tough and strong and stiff and those lids have a ring and down they cut those like ah that's basically glorified the rubber bands to really hold them to the base the lid holds to the base and so you don't get any air leakage so air leakage is huge so yeah that's what it comes out to insulate it and make it sure that it's sealed whatever chamber design you end up with so that's how you design the box and for me because I kept that same sort of front door in order to seal and I just used some of this foam gasket material that I had in my garage from when I was sealing my my truck and canopy to the pickup truck bed so that works out quite well yeah and so it is working but there's more to a heated chamber than just the box so let's talk about the other components that you're going to need on this you're gonna need a heater of some sort you're gonna need the printer obviously it's the whole point and well there's some considerations there we'll cover it in a second and you're gonna need a way to control the heater with your printer so yeah each of those things are her and how pile of worms or yeah I think that's the same box of worms whatever that's it's that each of those things is an issue that's going to take some of your time to figure out well three years ago when I first decided to make a heated chamber you can see one of my very first videos I was talking about making a printer that was heat resistant enough to put in a chamber I knew I wanted to do this from when I very first started this channel it's just been a long road to get here and when I first thought I was going to do this project this is what I bought I bought a bunch of these well three of these AC I think these are AC you have 220 volt AC heater cores and the idea was just to put one of these 120 millimeter fans and blow across these heater cores here and use this LC 25 or something like that arduino little PCB to somehow get in arduino because background I was running marlin so it's gonna get another Arduino to sort of work as a the chamber heater brain and somehow talk to Marlin and I didn't quite know how I was gonna do it and this is rather convoluted right is quite a DIY in-depth way to do it but there's a much easier way this is a Harbor Freight special cheap cheap cheap heat gun basically a glorified hairdryer don't use it as a hairdryer you'll let your skin on fire it's got two settings it's got hot with a high fan and it's got kind of hot with a lower fan and the amazing thing about this unit is just how incredibly value engineered it is it has no electronics to speak of it's got what is it Schottky diodes that's it Schottky diodes and a motor and a and a coil there's no brain to it there's no microchip or any of those it's just a switch and some Schottky diodes I burned up one of those actually the one that I had was about 15 years old I'd already sort of abused it and it it was a questionable life anyway but sticking it here in the chamber and running it at high heat so on the high setting with the chamber up around 100 degrees Celsius was just too much for it to handle so lesson number one if you're gonna use one of those those heat guns yeah you only want to run it and about at the 50% power now here's the way that that machine works you can see the Schottky diodes which are basically one-way valves for electricity and so if you think about the the AC coming through you're you know the power outlet here in your house it goes it flips the the two lines flip positive negative you know 50 times a second 50 or 60 I think it's 50 here in the United States so yeah that means that if you were to only use the positive from one side you would have half of the positive so instead of always having positive coming from either one connection or the other you only have positive voltage coming in from one connection so it's basically like a very cheaters way of doing 50 percent pulse width modulation so with using what is this for for Schottky diodes so inexpensive you a cop logic so now all you need is a switch that decides whether or not you're going to use both phases of the AC current or just the single phase okay so that's how it's accomplished and that's why those things are so inexpensive but with the original heat gun that I was using in the in the chamber I was holding it like this and over here on the handle with some wire which I had screwed to the lid here at the top and at a hundred degrees Celsius these components around this cheap cheap hot hot air gun those are not high temperature plastic components and they started to warp and the wire was cutting into him and that's no good so I had to remove all the plastic components from this heat gun while still keeping the the functionality of it and so we'll show you in a minute but that's basically what I was able to achieve now that thing has a fan on it to blow the air past the the hot coils but that fan isn't really enough to truly circulate the air inside this chamber so what I've done is I've put a fan here at the top that blows down so it catches the air from the from the heat gun there at the back corner and the air is kind of blowing over to this front corner anyway and then it blows the hot air down which kind of makes this loop of hot air and keeps the hot air well distributed in the whole chamber to to measure the temperature of the chamber I've just got another thermistor bolted to that side of the bed artha of the wall of the inside of the chamber and yeah inside of this chamber now I have my original end or three this is not the pro version this is just the normal under three with some ultra base as my print surface because it's glass and I just trusted it more in the heat right that that extreme hot environment inside there's really really hard on all of the components but the end of three seems to be doing pretty well with the Delrin pulleys these are definitely getting softer in the heat but they seem that the motion system seems to be doing okay I did have to strip away a lot of the other functionality the most important thing that I had to strip away and this is super interesting you guys it's the BL touch sensor I found out that BL touched up Burt sensors will no longer work at 50 degrees Celsius so the BL touch sensor says smart on it and that is because the BL touch sensor nobody tells you this it has the same functionality as the pinda probe on the Purusha because of BL touch sensor is using a magnetic sensor just like the Pinta program uses only instead of measuring the the actual bed itself the BL touch measures a little magnet attached to the probe which is touching the bed so yeah I'm out with the sensor I have to go back to the original way to level the bed on an under three and that is manually using the knobs underneath but I've replaced those big plastic knobs with these little metal knobs actually this is an old printer it might have come with those little metal walls to begin with but everything that's plastic is suspect and it's likely to warp and so you really want as much metal for the components that matter as you can get in there yeah so a better printer would have been this one here which is my is this the two trees sapphire printer and you can see this one's really neat cuz all the electronics are underneath this subfloor so this is this is kind of like if you were going to put this in the chamber you would want the floor of the chamber to come to right here because I've got my stepper motors which are then controlling these rods and that's awesome the stepper motors are below the floor as well and then the entire motion system is metal linear motion rails so you have bearings metal bearings on metal rails none of this Delrin plastic running on rails so this is actually I think a better candidate for reverting inside of an enclosure than the ander 3 but I just I didn't want to risk my more expensive nicer printer on this first experiment so I used at the end of three and I'm getting just find results and part of the reason for that is the fact that I have moved my electronics underneath the printer here and from the get-go like I said I've been wanting to do one of these chambers for some I started this channel and to that end when I first built up my under three here I made the power supply and the board into a tower which was separate like the wires were extended off to the side just so that I could accomplish this task of putting the power all of that underneath the printer and you can see that in other videos I'll link the playlist in the in the description but yeah so this is it's all working great the electronics are isolated outside the box there are some stepper motors in here that um that do get hot they get hot but stepper motors do okay up top - they're doing fine at 100 100 degrees Celsius they're too hot to touch the entire frame there is really uncomfortable to touch if I have to open it up and get in there but um but it all works and there's something really interesting to tell you guys about and that is the fact that the heated chamber is the same as a filament your hair right at 100 degrees Celsius that's a really quite warmer even even printing at 50 or 75 degrees so that filament that polycarbonate roll in the open air I just set that on top of my printer here they're top of the box and just leave it overnight yeah it'll it'll be that quickly it absorbs the water out of the air and it starts printing terribly the little snap crackling and popping you get from wet filament but as long as I keep it in the chamber while I'm printing it's drying even further every time you know as I'm printing in this hot chamber so really cool stuff if you build a heated chamber you've also basically got a filament dryer as well what else what else yeah I'm using one of those cree allottee dual drive capstan extruder mechanisms I found that that was actually kind of important I didn't have very good luck with my old-school metal one which was like again like a two or three year old design maybe a newer metal design would have worked and I didn't need the double gears but it's nice to have it peace of mind because you really shouldn't be breaking into this box once it starts printing it's really hands-off you don't wanna you don't want to get any drafts of cool air in there to mess up your the prints all right well the final thing to talk about before we start sending some test prints for you guys to see is how you control all these components together so I'm sure there's a way to do it with Marlin but it's gonna be convoluted and you guys know I consider my time to be a little bit valuable at least and I've fought with Marlin for too many hours of my life I fought with crappy Chinese electronics for too many hours of my life so I like to go with the solution that I just know will work and it just it's easy and it gives me all the flexibility to make the project happen the way that I want to and that is a duet Control Board so duet Control board's have a chamber heater chamber functionality built right into them in the the RepRap firmware and then of course there's the plugs on the actual hardware to accept those those those things as well the problem is RepRap firmware it has some thermal runaway protection encase your printer catches on fire it automatically shuts off which is a good safeguard but as a normal user I can't get into the backend code I mean I could I could really it's all open source I could really go in there and try to fight with it and I make my own build of the firmware but I'm not I'm gonna do the workaround anyway so the the it stripping a thermal runaway protection error basically it thinks that the chamber heats too slowly with just a single one of these you know heat guns I might be able to put two of these heat guns in there and it would heat up quickly enough that I wouldn't trip that error but with just a single one I have to get the chamber up to temperature before I turn the control over to the duet board and to that end I've got a switch under here where I can just turn wrong we can see I've got it set to only be able to run the the slow setting that's the you know 50% long but the pulse will be pulse with modulation half with that with the Schottky diodes it's only 50% on but I'll run it like this for I think it gets up to 50 degrees in about 5 minutes 75 degrees in like 10 minutes and it takes a while to get it to 100 degrees if I had foam or better insulation it might go more quickly but here's the interesting thing the the metal of the frame of the printer is the controlling factor here the the metal you have to get it up - it's like a radiator itself or heat so you have to get the metal up to 100 degrees and then your chamber will stable will stay stable so it's kind of easy to get the air up to 100 years but you'd be surprised how sort of well this thing holds heat once it's been at temperature for a certain amount of time yeah so then once I've done that and looking at my you know the control on the computer and I can see that it's at the temperature I want it to be then I can turn on the the functionality for keeping it at that at that chamber temperature that I want it and it will turn the the heater gun the heat gun on and off you know as it needs to to maintain that the chamber temperature that upset so yeah there you go that's my chamber project that's quite functional so let's jump on the computer I'll show you the interface for a quick second what you're looking at here is the the interface the web interface to the duet control board which is controlling the the chamber heater and and the the under three in the chamber itself so obviously you've seen this before if you're watching my channel you can control how hot the nozzle is how hot the bed is and I've built in you know my activating in in the the firmware configuration file I've activated the chamber heater so I've currently got it set to 82 degrees and I could drop that to 80 degrees and it would stop cycling I'm hoping you can hear that hope it comes through this Mont this microphone it's cycling turning itself on and off in like a very slow pulse width modulation cycle and I've been doing this manually but you can certainly build it into your your slicer software where it keeps the chamber at a certain temperature as well so now let's jump over to the printer itself and talk about what I've just made you can see in there I've got a print which is finished there on the bed and just listen to that hum the fan unit so that's back there in the corner we'll see it glow red here in a second [Music] anyway so I'm ready to pull that part out of there but I wanted to show you guys a couple of things first of all I have this switch in there attached to the wiring still and they have this nice sort of spring actuated plunger that melted you can see the mountain right there so that's switch failed on me just to give you an idea of the stuff that happens in a hundred degree chamber I really need to this is just the iteration number one proof of concept there is a lot of work before this is ready for primetime alright let's take a look at that print so I'm using these cloth covered rubber bands kind of like hair ties to hold the door closed and then you can see the print in there and it's fully stuck to the bed there's no delaminating or peeling of that part and I'll show you here in a minute I mean what you can see the length on that part imagine trying to print that out of ABS and know that ptg is just that much worse and warping than ABS so you can see the reflection on the base there then it's a perfectly flat part by the way this is that blade holder in action and you can see that it does a really good job I'm holding a regular utility knife blade these two pinned rivets are just made out of some copper wiring and then here it's held on with an m3 screw into AM what is that an insert you know it's an aluminum insert that's brass plated when you go to ebay to buy these things you get them really cheap because they're not completely made out of brass they're just brass plated but they do the job and actually this knife works pretty well too so I've got a couple of these that float around my shop so you know I never know where I set them down there's always one that I can find somewhere so that worked but let's let's talk about test prints a little bit more here for a minute I made this print here in an attempt to get a failure to occur that I could then show the the heated chamber addressed and fixed but if you go back and you watch my older video here about printing at 310 degrees you'll see the failures that I was getting on those polycarbonate brace and how do you get any of those failures on this print here which is printed in the open air meaning I took the lid off I took this front the front door off but it still enclosed on five of the six sides of the cube so even just five sides and closed still gives you better results than printing in the wide open air so because I couldn't get a failure to occur I couldn't show you guys before and after I wasn't about to unbolt the printer out of that enclosure just to get a crappy print so that I can show you that it was better because trust me it's better anybody who's ever printed with ABS knows the struggle if you try to make large parts on your bed they will peel up unless you Lou you use like a slurry like an ABS slurry which just really keeps them attached to the bed but you're still getting all those internal stresses trying to peel that up and so you're likely to get layer separations where it can't peel up off the bed so instead the part itself sort of cracks in the middle of the part so heated chamber it's the way to go it's the ticket for any of these higher temperature resistant plastics polycarbonate PE ek abs if you want good results make a heated chamber and your heated chamber needs to be sealed and insulated and also I think that I'm onto something with the the hot air gun you know modules it's it's kind of a already made fan heating element module for like 14 dollars why would you try to make your own it's very effective now I am printing a lot of parts for my other printers on this printers because I want that the heat resistance of the polycarbonate but um I'm printing it 330 degrees now which gives me really good layer adhesion and oh my god polycarbonate is the best material I've ever printed with you can just feel the strength in the parts it's is significantly stronger than everything stiffer stronger all of it I ordered some what is it carbon fiber impregnated polycarbonate that stuff's gonna be amazing so I've got the ability to make some seriously engineered parts now because of this chamber but I really would like to make another version of the chamber the outside of the wall here I think I measured it like 45 degrees when I'm printing at like 80 degrees so it's about half the the chamber temperature in there that's what the skin of my my wooden box here measures so with an actually the insulated chamber not just these like double wall you know luan plywood structures the heated chamber idea is a winner however I do now have a new problem and that manifests here on the new knife that I printed and that is pillowing and you can look up pillowing most of you probably know what that that problem is on 3d prints on your top layers yeah so part cooling is not ideal I was printing this at 88 degrees the chamber absolutely gets up to a hundred degrees but you know even at 88 degrees I was getting pillowing with with part cooling at full blast so I need to lower the chamber temperature to a level where I don't get peeling up off the bed and yeah I get good part cooling so it's gonna be lower than 88 degrees I don't know maybe it's sixty degrees maybe it's 75 degrees but you know I definitely am fighting with that that peeling this is an older version of the knife that I printed up and I printed this when the printer was an open-air printer and I had two layers of the brim material and the brim was like you know a centimeter and a half wide across that whole thing with two layers and I could not get it to stay down peeled up just so much forced about wanting to peel it up and there isn't a slurry like you can do with ABS there isn't a slurry for polycarbonate so I absolutely need the chamber to be at a certain temperature to get that to stay down and yeah I need that part cooling so either I'm sort of jetting in outside air for the park cooling that's an idea but then you're you know diluting the the chamber and you're making it cooler as well whereas the sealed and insulated you know that's the whole point is to keep the heat inside there so it's a it's a delicate delicate balancing act for sure as I was editing this video the best solution to the problem occurred to me and that is to just use a larger part cooling fan or multiple part cooling fans just to really get a whole lot of that 88 degree air blowing across the part because the freezing point of polycarbonate is well above 88 degrees so as long as I can just get a larger volume of air to strip away that heat from the from the part then I think I will no longer be having this issue but you know in further experiments I'm sure I will get it to a level of where it's it's perfect but I'm gonna definitely be remaking this this box at some point in the future for now though it's working just fine and I couldn't be happier with the parts that I'm getting from it so that will do it for this video here's a link to another video that YouTube thinks you want to watch and there's a link to my patreon account please go over there and toss me a buck it really helps out see you next time thanks for watching

Channel: Design Prototype Test

Views: 229,383

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Id: 79r5D9nCQfM

Length: 36min 23sec (2183 seconds)

Published: Fri May 22 2020