hi everyone, i’m tom, and two days ago,i wrecked my voice. i’ll try my best to be comprehensible today, but, as always, ifyou’re having trouble understanding my spoken words, feel free to turn on subtitles, thoseusually have the full script i use / in there and should be pretty accurate.but anyways, today’s topic is going to be heated beds, that has been one of the mostrequested topics, so today i’m gonna tell
how is 3d printing used, you all about them!so, heated beds have one very obvious main purpose: and that is to get the surface ofthe print bed up to a temperature where the print will stick to it better and, as such,will not come loose from the unavoidable warping forces that the layer-by-layer printing processgenerates. but a heated bed has a second side
effect that can help reduce warping at thesource, and that’s because the radiated heat will help keep the print warm. you see,that largest factor in how much a print is going to warp is, roughly speaking, the differencebetween the plastic’s glass transition temperature and the “cooled down†temperature duringa print. so either, you have pla with a low glass transition temperature of 50â°c andlet it cool down to 20â° with an unheated bed, or you use abs with a glass transitiontemperature of about 100â°c and just make sure it doesn’t cool down as far. the extremecase of this would be a heated chamber, which keeps your abs print at 60 to 80â°c, so you’dend up with the same 30â° temperature difference. heated chambers or at least enclosed printersare extremely nice for the high-temp plastics,
but that’s an entirely different topic.now, because of those two effects, i still haven’t found a plastic that is not easierto print with a heated bed. i mean, sure, you can print pla on blue tape and some ofthe soft plastics onto glass and such at room temperature, but even for pla, having theoption of heating the bed surface and printing straight to glass is just so much more convenientthan having to pry your prints from blue tape. of course, heated beds are absolutely neccessaryfor some plastics, like abs, which can be printed onto a cold surface, but that involvesa whole new level of kludges. as far as the heated beds themselves go, thereare two basic types that you can get. one is the classic pcb heater, originally designedby joseph prusa, which was the first heated
bed that you could buy. along with the prusamendel, it basically established the mid-size form factor of a 200 by 200mm build platform.you can still get heater pcbs that are very close to the original design, some of themcan now be switched from 12v to 24v, others have different form factors, like the roundbeds intended for delta printers. but there’s two issues i personally have with heater pcbs,and those are, one, it can be pretty hard to get them to make good contact with whateversheet material you put on them, which becomes necessary, because, two, they have a tendencyto warp and bulge, especially the cheaper and thinner ones. as the controller appliespower to the bed, the side with the heating tracks heats up much faster than the oppositeside, the pcb expands on the hotter side,
and in the process of that, bows the entireprint surface. in fact, one of my first big mysteries with my back then prusa i2, wasthat the second layer just wouldn’t stick onto the first one. and as it turned out,because i was reducing the heated bed temperature for all layers but the first one, the heatedbed would shut off for a while until it reached that cooler temperature, and, you guessedit, bowed away from the nozzle and basically left a huge gap between the first and secondlayer. so, the other option, which i like a lot more,are heater mats that you can stick onto the bottom of your print sheet, in my case, aluminumbecause i also use an inductive probe for bed auto-adjustment. you can get these heatersfrom a few resellers in europe or the americas,
but you can also get them directly from theguys that make them, at any size, voltage and power rating. for example, i had thisone made as a 150mm square with 150w, which will take it up to 150â°c. more than enough/ even for printing polycarbonate. i also have a 300mm round bed incoming that is madeto run at 230v mains power, since shoving 600w through a power supply is kinda pointless,and it’s pretty hard to wire everything properly at those currents anyways. but, please,if you are using mains power anywhere, be careful, make sure everything is unpluggedbefore you start working on the wiring and ground your printer frame through the protectiveearth rail. i’ve heard from a couple folks that thesilicone heater mats tend to give up after
a while, but i haven’t had any problem withmine so far. and i’ve been torturing it quite a bit.if you're wondering what kind of power you need for a certain size, it's relatively simple:you need at least about 0.6w for every square centimeter of heated area to get to 120 degreesfor abs or about 0.2w to get to about 60 degrees forpla, but if you want save some time during heat up, you can also go up to 1w per squarecentimeter. just make sure your electronics can handle it. most electronics are limitedto 10 or 15 amps of output current, which means that they can just about power a prusapcb heater at 12v or something a bit more powerful at 24v. read the specs for your boardand make sure none of the transistors or connectors
burn up when you’re heating it up for thefirst time. now, as far as sheet material for heated bedsgoes, again, there are main two choices. you can either use glass and clip that to a heaterpcb, or use aluminum in the same fashion or directly stick a heater mat to it. i preferaluminum, it’s cheap, it won’t break, ever, it will distribute the heat from theheated bed extremely evenly and it will ensure that the surface temperature is exactly whatyou want it to be. and you can directly use it with an inductive sensor. for smaller beds,flatness doesn’t matter as much, but for larger ones, you can get milled, planed aluminumsheets at almost any size and thickness - this guy for example will end up on top of thataforementioned 300mm heater mat in the cerbrisreborn.
which i hope i’ll get to build over christmas,but it looks like the ball ends for it aren’t going to arrive on time. anyways, the othermaterial you can use is glass sheet, and that is pretty much always perfectly flat due tothe way it’s made. many people use borosilicate glass, which is similar to pyrex and madeto resist temperature shocks, but i’ve found that regular 3mm window glass works just aswell. even when i heated up one side of my double heated bed to 120 degrees and leftthe other side cold, it never flinched. 2mm is too thin and has a huge risk of breakingjust from the force it sometimes takes to pry a print off.also, if you're planning on using a heater mat instead of a pcb, i'd definitely recommendaluminum. the heater mats are hand made and
can be a bit irregular in their heat output,which alumium helps smooth out, but also, if you stuck it to a glass sheet and breakthat, well, you can probably trash the heater, too.on top of whatever sheet material you may choose to use, you can use different toppingsas well. but for many plastics, you don’t have to. many users print directly onto clean,and this is important, absolutely clean glass, many plastics will directly stick to that.then there’s kapton and pet tape, which are nice for abs and other higher-temp materials.and there is the glue section of glue stick, diluted pva glue and hairspray, each of thosehaving their own unique properties, and, as always what might work for everybody elsemight just not work for you. so there’s
definitely some trial and error involved,but there’s always some way that works out. most of the surface choices lose their stickynesswhen they cool down, so prints are going to be much easier to remove or pop right offif you wait for the bed to cool down after a print has finished.one last thing i want to talk about is thermistors in heated beds or # for heated beds. becausethey are always somewhat awkward to place if you want a good reading. if you tape oneto the bottom of the heated bed, the top might end up being much cooler than the spot you’reactually measuring, if you put it on top of the heated bed, you obviously have the riskof running into it with your printer’s nozzle. either way, you should really make sure thatit is well-insulated from the air around it
and gets good contact to the spot you’retrying to measure. some newer pcbs have a spot in the center to place a thermistor,which is actually a really decent place to put it. the silicone heaters, on the otherhand, can be configured with a thermistor built-in, but i’ve found that it reportstemperatures that are way too low. either way, if you have a thermistor in a spot thatisn’t exactly where you need the temperature, i’d at least recommend waiting a bit afterheatup before you start the print, that way the heat has some time to soak through theentire construction you have on there. or, if you have an aluminum bed, you can alsouse the e3d v6 method and clamp a thermistor into the aluminum plate, that way, you’llget exactly the temperature the bed actually
is at.so, i guess that’s got to do it for today,
if you have any questions left, please feelfree to leave a comment and i’ll try to answer those. i’ll see you next week, untilthen, i wish you all a politically correct happy holidays - i don’t care much aboutwhat you do or don’t do over christmas, but everybody gets a few day off, and that’sgotta be worth something. au revoir!
