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110 / 230 V~ PCB Heated Bed

Meet the Makertum MK1, a 500W PCB heated bed that runs from mains voltage

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The Makertum MK1 is a mains voltage heated bed for 3D printers with dual voltage support (230/110 V~), 500 W of heat output, 2 minutes heatup time (110 °C), power indicator LED and onboard thermal fuse. The beta test was overly successful, and preproduction boards are available now in the Makertum Shop and on Tindie.

IMHO, it’s pretty much nuts to convert down mains voltage in a power supply to 12/24V just to drive a large heating element, except that it „feels“ a bit safer. Also, it’s a false assumption, that a 12/24 V heated bed is actually safe, since in case of an unexpected malfunction it will still burn down your place - regardless of the voltage on the heating element. Using fuses, temperature feedback and considering failure scenarios cannot be omitted anyway.

Why mains?

There are some nice benefits of a mains voltage PCB heated bed:

  • high power output
  • cheap (no need for costly PSUs)
  • lightweight (no aluminium plate needed like in silicone heater pad solutions)
  • handy (reduces weight and size of printer due to smaller PSU)
  • versatile (any printing surface my be installed on top of it)
  • highly efficient (about 10 % less electricity cost over MK2+PSU with typ. eff. 90%)

Features

This implementation comes with a few more extra features:

  • super fast heatup time (about 10 times faster than the common MK2)
  • 230 and 110 V~ support
  • power indicator LED covered by tough transparent polycarbonate
  • no thermal breathing / flex due to double sided layout
  • extra mounting holes for three point leveling
  • compatible with RepRap MK hole spacing of 209 mm center-to-center

Safety

I did everything to make this the safest heated bed available:

  • fully insulated screw terminals
  • thermal fuse prevents overheating
  • current fuse prevents overcurrent
  • made from temperature resistant FR4
  • thorough stress testing on every manufactured batch

RFC

If you have any ideas or concerns about the design, please share your ideas in the comments.

  • 1 × PCB 1oz copper clad
  • 1 × LED cover (top) milled from clear polycarbonat
  • 1 × LED cover (bottom) milled from clear polycarbonat
  • 1 × piece of kapton tape or thermal compound for attaching thermistor
  • 2 × M2 screw length depends on LED cover config

View all 20 components

  • Kits Available Now, XXL Printing News

    Moritz Walter07/07/2016 at 08:30 0 comments

    Pure Awesomeness Available Now

    The Makertum MK1 kits from the pre-production are now available on Tindie and in the Makertum shop starting at €37 or $41, which includes free wordwide shipping.

    Just like in the beta-testing phase, the heated bed comes as a full-kit that contains all the parts necessary to get you up and running. The SSR is optional, just in case you already have one.

    Where to buy?

    Makertum Shop
    http://makertum.com/en/shop/recomended for EU customers
    - native payment in €
    - discounts for Bitcoin and Worldcore
    Tindie Store
    recommended for US customers
    - native payment in $
    - pure Tindie awesomness

    XXL Printing News

    So, where do we go from here? Well, it's a high performance 3D printer part, but it's main limitation is still size. The problem is, that if I just scale up the size of the PCB, it quickly becomes impossible to manufacture. I get a 90% yield from my current manufacturer now, and this number will go down dramatically on even larger PCBs, while at the same time, the product becomes more difficult to ship.

    IMHO, the only reasonable answer is tiling. Tiling smaller heated beds to a larger area is comparably cheap, and costs scale linear with print area.

    There are a few challenges to tackle, such as uniform heat distribution, temperature control, and mounting. So that's what I'm testing now. Large, tiled heated beds. Here a few impressions:

    Basically, I'm trying to mill out the edges..

    ..to let them overlap with each other..

    The result is a large heated bed. Hackaday Prize? I'll get a Nobel Prize for this!

    Of course, the layout would have to be adjusted to cover the gaps between the boards, and it would be nice if there was a power bus, as well as a bus for the temperature feedback.

    Print a whole leg prosthesis. In one piece. Because, why not?

  • Pre-production

    Moritz Walter06/30/2016 at 20:39 2 comments

    Good news everyone!

    It's been a while since the last update. In the meantime, I've sent the new design off to different manufacturers and waited for the results to come back to me. Then, I received an email from Mike Szczys and started writing for Hackaday, the blog part of it. Then the results came back. Then, I threw them all in the trash. It was a pretty sobering experience. See the wall of fail at the end of the post for details.

    Then, I got new quotes from new suppliers. Well, it's pre-production after all, and we're happily burning money on it. Better now than later. I finally found a manufacturer that delivered beautiful boards with an acceptable yield. From this preproduction run, I currently have 50 heated beds here for testing now. I still have to do a bit more testing on them, and if everything goes right, they will be available in the shop soon.

    This is how they look like:

    Wall of fail

    The first series of boards, the red ones that shipped out to the beta-testers, came from DirtyPCBs. They were awesome. I think it's worth mentioning that. When they fail, then they fail bad, but most of the time, they are simply amazing. Not so the manufacturers I tried afterwards. All of them had higher per-board prices, and all of them sucked hard. Some arrived with the Gerbers entirely misinterpreted (and yes, I quadruplechecked them), some had a weird flaky soldermask, and some just arrived virtually without packing and took serious damage. Here are some excerpts.

    Packing fail

    Gerbers WTF

    Black marker FTW

    These spots are quite common, although some runs had 50% yield due to these.

  • Dropping NTC pads; new silkscreen;

    Moritz Walter03/30/2016 at 14:14 1 comment

    NTC

    While fiddling around with the traces to squeeze in the NTC, it became obvious that adding the NTC to the board was not the great idea I thought it was, simply because I need to maintain a proper clearance between the high driving voltage and the low logic voltage to prevent arcing.

    How to not do it: Two 230 V traces between the pads of an 1206 NTC :)

    A friend helped me through the related norms, such as IPC2221B and EN60664, and it turns out that a minimum insulation distance of 2.3 mm would be required. Since most RepRap electronics are not sealed from touch, we have to consider a good safety margin on top of that, about 100%, ending up at 4.6 mm clearance. Of course, this large distance would also functionally affect the sensor, which should be really close to the heating traces in order to get responsive and accurate readings.

    So, if you can't do it right, don't. Because of this and until I get a better idea, I will drop the NTC from the design. The NTC can be mounted and insulated in many better ways, making use of kapton or mica, so there's no also need to compromise uniform heat distibution here.

    LED circuit

    As said, I dropped the LED overcurrent fuse, so the double sided cover will not be required any more.

    New silkscreen

    Alright, I know, this project log is not all that exciting :) But look at the new cool silkscreen. It has a lightening bolt on it to remind the user of the fragility of life.


  • Design changes; Approaching pre-production

    Moritz Walter03/26/2016 at 13:09 2 comments

    While beta testing is still ongoing and feedback starts coming back, I also spent lots of time evaluating the overall quality of the product in a large QFD, which, together with the feedback, will result in one iteration of design changes. Hint: It's going dark. This is how it could look like (the LED will stay onboard, don't worry :)

    Until now, I got overwhelmingly positive feedbacks with no serious complaints about the prototypes. However, I'm thinking of offering users more choices in terms of LED colors :) What do you think? I'd be glad to hear more opinions on this in the comments. I'f you're cool with blue LEDs, you might want to grab the last available beta testing kit :)

    Design changes

    Adding solder pads for NTC / thermistor

    On popular request, I'll add solder pads for an onboard NTC. If possible, they will be routed to the back to some pads for the wires. I originally omitted that, since I weighted the board area more valuable to be used for heating traces, especially when they might remain unused if the user prefers a thermocouple. Apparently it looks like virtually everybody uses thermistors, and nobody uses thermocouples on heated beds.

    Dismissing LED overcurrent fuse

    It has been pointed out to me by several engineers from the beta-testing group that the Picofuse which prevents the LED from overcurrent in case of broken heating traces is overcautious, especially since the corresponding failure scenario is highly improbable and would result in a fried LED at worst. Dismissing the fuse also allows for a single sided and more streamlined LED cover.

    New board color: Black

    The next generation of boards will have a black solder mask. I noticed potential quality issues with the red soldermask, which always tends to get a shade darker when reflowing and generally with time. Heat accelerates this process, and I guess users would prefer their boards to look the same all the time. Using black solder mask solves this.

    Pre-Production

    Once the design changes are implemented, I'll approach pre-production. I found a PCB supplier, who showed interest in the project and is willing to help me a bit with pre-production, which is usually frighteningly cost intense, simply because the setup cost will be the same as for a large batch but distributes only over a small batch.

  • Beta testing is going on right now

    Moritz Walter03/13/2016 at 19:36 0 comments

    With only few boards left in the Makertum MK1 beta-stock, testers from US, UK, Haiti and Germany have now taken on the task to test the hell out of the prototypes from the beta production batch.

    Some are already still prepping their wires, others are already printing. Stefan from Hamburg has completed his fresh Proosha IIIo 3D printer build with a Makertum MK1 and is sharing his printing experiences in a live stream right now.

    AstroPi case timelapse:

    Heart gear timelapse:

    And also @BPop has his board up and running, sharing a stream for us of a cool project beeing printed:

    http://69.244.131.202:8081

    Thanks to all testers and happy printing everybody!

  • Beta testing phase has started!

    Moritz Walter02/14/2016 at 15:44 0 comments

    Yay!

    Beta testing has started, in fact, the first testers have already installed theirs and print diligently @Attraktor Makerspace. There are still enough available to send out. To simplify the process of getting one, I setup a little webshop in my blog.

  • Beta testing about to start shortly

    Moritz Walter02/10/2016 at 10:48 0 comments

    Good news everyone: Eventually everything came together, the PCBs, the electronic components, the machining of the plastic parts, and the writeup of the assembly instructions, so the beta testing phase will start soon, possibly by February, 15th 2016.

    Update

    The hardware kits are now available here!

    The beta testing hardware kit

    PCB (top)
    parts and electronics
    PCB (bottom)shrinking tubes

    About beta testing

    In the beta testing phase, I'll give out 15 hardware prototype kits to interested beta testers. Beta testers are kindly asked for a contribution of 39 € (incl. SSR) or 32 € (w/o SSR) plus shipping to obtain a hardware kit. I know that's something you don't see when beta testing in the software world, so to smoothen things a little, beta testers will get a 50% discount on a PCB from the final production line of the heated beds.

    Who can beta test?

    You need to own a compatible 3D printer. Besides that, everybody with sufficient knowledge about mains voltage electrical wiring and mains voltage safety precautions can take part in the beta testing. However, you'll have to agree to a legal liability disclaimer that leaves you with the full responsibility of all your actions and all the outcomes when testing the prototype.

    How to get in

    You can now order the kit here.

  • PCBs, dirty PCBs, and statistics

    Moritz Walter01/14/2016 at 16:31 0 comments

    OK, you can't really do good statistics on a batch of 20 units. BUT I recently tested all the received boards I had manufactured from dirtypcbs.com for resistance and functionality, with interesting results ;)

    Yield

    5 of the 22 boards I received (20 were ordered) arrived defective. I contacted dirty for the issue, and they refunded me for 3 boards (since i ordered 20) within a day. The defects are kinda interesting, since they seem to be were similar, close to identical on all defective PCBs. Here are some:

    Resistance variation

    The rest of the boards was fine, and I could measure the resistance of them:

    minaveragemax
    Rtop61,169,478,5
    Rbottom58,467,8690
    Rtotal124,4137,28160,1
    Ptotal @ 230 V~330,4387,4
    425,2

    There resistance varies about 30 %, and even though this is a lot, for any normal PCB layout this wouldn't be an issue. Since the resistance of the traces simply defines the maximum power output of the heated bed, they're perfectly useable and a good proof of concept.

    Small quantity prototyping

    If I would have let the prototypes be made with a german board house, I would have paid about double the price, since even though the boards itself are about 4 times cheaper from dirty, the shipping of the large boards eats up most of it.

    If I'd do this again, I'd probably use the german board house from the start. Even though I got a refund on the failing boards, shipping is not refunded, and somehow I lost my trust in their e-test ;) However, high-RPM prototyping services like dirty (or similar) chew through individual small quantity orders at an amazing rate and for an incredible price, they're still the best for their 5x5 protopack.

    Manufacturing

    For preproduction and final manufacturing I'll work with a high reputation PCB house from Germany I've had good experiences with in the past. I've already received quotes from them (and others), and given enough interest in the board, maybe this project will get eventually get there.

  • milling LED covers

    Moritz Walter01/14/2016 at 12:28 0 comments

    Yesterday, I was able to mill the polycarbonate LED covers for the heated beds on our mill at Attraktor makterspace. They turned out way better than I hoped. The necessary screws and nuts haven't yet been delivered, but once they arrive, the parts for the first beta test kits are complete.

    Cutting polycarbonate

    Polycarbonate is a tough and temperature resistant material and can be processed similar to wood. Large cutting teeth on normal and circular saw blades usually give good results. On the mill, you'd probably use a not too small single tooth acrylic or similar milling bit.

    But those LED covers are quite tiny and I wanted the finish of the milling pockets as nice as possible. Since our mill doesn't feature a tool changer, I also wanted to mill them all in one go, which means the milling bit cannot be larger than the small screw holes (ø 2.2 mm). So I contacted the people from vhf camfacture to help me out with the right milling bit and parameters. They're very dedicated and supportive people and their unique milling bits are worth the money. Eventually, a ø 2 mm polished flute single tooth milling bit was used.

    I had to experiment a bit with the right size of the attachment bridges. Polycarbonate is quite tough, so it definitely needs strong bridges, however, they are also hard to remove.

    So, that worked. I was in a hurry and later on found the photo below came out blurry, but I'll soon post better pictures of the completed kits anyway!


  • comparing power consumption I

    Moritz Walter01/14/2016 at 11:35 0 comments

    I wondered how the power consumption of the mains voltage heated bed compares to the MK2 while holding a certain temperature, assuming that the PSU will cause significant losses. However, not having two trusted electricity meters at hand, I tried it with a pair of OWON B35T bluetooth multimeters. The csv-export functionality of the app is flawed with bugs, so well, it did not work. Also, I suspect some of the readings were bad.

    I will have to redo this, but however, I was able to capture the readings for full-on and idle, and they're still interesting.

    The setup

    I wired the MK2 in default configuration, with the heated-bed power rail of the RAMPS 1.4 powered through the PSU shown in the photo below. The other power rail of the RAMPS 1.4, which powers the Arduino and logic is powered by another PSU that is not seen in the photo since it belongs to my 3D printer. This way, I ensured that the logic power consumption does not influence the measurement.

    The current that goes into the above PSU and eventually powers the MK2 is shown on the left multimeter, the current that goes through the SSR and eventually powers the mains voltage heated bed is shown on the right multimeter. Since both are attached to a common 230 V~ mains line, I can compare the power consumption, even if (lacking a third multimeter for measuring the mains voltage) I don't know the power consumption exactly.

    Idle

    The idle power consumption is not surprising, since the PSU has the fan spinning and has to maintain some idle current on all its power rail, it must consume more power than an open switch.

    Turns out the PSU draws about about 0.69 A, which results in an idle power consumption of about 16 W. The mains voltage heated bed is very savy here, since it's just off, but the SSR appears to let through a small idle current of 6mA. This idle current is suspiciously high, I expected this to be only a few µA. Another reason to redo the measurement: It's a potentially crappy multimeter, maybe just a bad reading.

    Full-on

    The full-on current surprised me a bit. Even though we are comparing a supposed 120 W heated bed to a 400 W heated, the current draw of the 400 W heated bed is only 54 % higher than the current draw of the MK2. Which raises the question of how much power is actually lost in the PSU. I will probably have to do some more measurements on this matter, measuring output current and voltage of the PSU as well. Eventually, the MK2 consumes 260 W of electricity through the PSU, while only half of this reaches the bed in form of heat.

    Maintaining 100 °C (measurement failed)

    As said, this failed. I wanted to graph the data of current consumption of both boards over a period of time while they would maintain 100 °C, but the CSV export of the data failed. I also couldn't get steady readings from the app for the mains voltage heated bed. The first problem is a bug in the csv-export of the OWON B35T smartphone app, and the latter is just because multimeters are not electricity meters and their true-RMS window is just to small to capture enough half waves from the SSR. On the smartphone app you can spot a yellow graph (MK2) and a red graph (mains voltage heated bed). The yellow one is ok, but the red one's just too noisy. I also didn't take a better picture of the graph since I expected the csv export to actually work. I'll try better next time :)


View all 18 project logs

  • 1

    Check received parts

    You should have received:

    • 1 pcs PCB
    • 1 bag with screws
    • 1 bag with electronics
    • 1 bag with cable lugs, screw joint and cable fuse holder
    • 1 bag with polycarbonate LED cover
    • 4 pcs shrink tubes (+ 4 spare)
    • 2 meters of heat resistant supply cable
    • 1 SSR (if you chose the SSR option)

    As shown below:


  • 2

    SMD soldering

    Take the bag with the electronic parts, some of them are very tiny, so don't lose them. We dropped the Fled from the design, so don't worry if it's not there:

    Top side

    As long as the bottom side is still unpopulated, lets solder the 0805 SMD LEDs to the top side:

    Unpack them carefully and mind the polarity of the LEDs:

    If you do not own reflow equipment, and must hand solder the parts, it's recommended to first add a little solder and flux to the right pad (if you're left-handed: left pad) of LED1 with your soldering iron:

    Then, hold LED1 in place with tweezers, mind the correct polarity (see below) of the LED. Melt the pre-applied solder with your soldering iron until the LED has good solder contact with the pad. Be careful not to overheat the LED.

    Now, that the LED is held in place, you can easily solder the other pad. A little flux helps spreading the solder. Careful with the heat!

    The LED2 just goes like the first, add a little solder and flux to the right (left-handed: left) pad..

    Then place the LED with tweezers. Again, mind the polarity (see below), since LED2's polarity is inverted to the polarity of LED1. Melt the pre-applied solder again until the LED has good contact with the pad. Careful with the heat!

    To complete the top side, solder the second pad of LED2:

    Bottom side

    I recommend to start with the 0805 SMD resistor:

    Unpack the resistor carefully:

    Then solder it using the same technique as with the LEDs. Be careful not to overheat the resistor.

    The next thing to solder is the 63 mA pico fuse "Fled". If you ordered a pre-production board, you can skip this part, since the Fled was dropped from the design:

    The fuse "Fled" needs a bit of preparation, use pliers to bend and cut the wires as shown below to make it surface-mountable:

    Then solder it to the PCB using the same technique as with the other components. Be careful not to overheat the tiny fuse.

    The last component on the bottom side is the thermal fuse:

    This fuse also needs a bit of preparation. Use your pliers to bend and cut the wires to make the fuse surface mountable. Make sure the fuse's body can have good contact with the PCB when mounted.

    Start by applying solder and flux to the right pad. Then hold the fuse in place and melt the pre-applied solder. Make sure you don't overheat the temperature sensitive component. Check if the fuse's body touches has good contact with the PCB before you solder the second pad. If you can't align it just right, you can use thermal compound between the fuse and the PCB. The solder connections on both pads must be excellent, since they will have to carry the operating current.

  • 3

    Install polycarbonate LED cover

    The polycarbonate cover protects the user from touching the LED pads, which conduct mains potential. Make sure it's installed properly at any time. Pre-production boards come with only a single-sided cover.

    Start by peeling of the protective film from both halves of the cover:

    Take the two M2 screws and nuts from the bag with the screws and start assembling the cover as shown below:

    Put the M2 screws through the top half of the cover and through the PCB.

    Turn the PCB arround and install the bottom half of the led cover. Counter the screws with the M2 nuts.

    Make sure both screws are tight, use Loctite if necessary.

View all 9 instructions

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Discussions

wywywywy wrote 01/18/2017 at 15:20 point

Is this project still being developed?  We haven't had any news for a while.

  Are you sure? yes | no

Maurice Nonnenmacher wrote 12/03/2016 at 08:09 point

Hello,
Where could I get one of these please ? If it hasn't been released yet, I would like to become a beta tester please.

  Are you sure? yes | no

BPop wrote 07/27/2016 at 15:57 point

My Beta board just died today. I probably only have 200-250 hours on it. I just started to heat it up for a print, and as it hit 60C, it stopped heating. I noticed the LEDs were no longer flashing either. I connected it directly to 120v and it still won't heat up. I am thinking that the thermo fuse blew, which is weird since it was at such a low temperature. I'm going to temporarily jump a wire across to see if that helps bring it back. If so, I'll just have to order a new fuse. If not, then I guess I go to plan b and hook the old 12v bed back up.

  Are you sure? yes | no

BPop wrote 07/27/2016 at 16:02 point

As a quick update. A jumper wire, with the fuse removed, and the bed is heating again. Going to go hit a local electronics store to see if I can get a similar replacement today. 

  Are you sure? yes | no

BPop wrote 07/28/2016 at 03:15 point

Luckily my electronics parts store happened to have some thermal fuses in stock. I had to go with 141C fuse, but I figured it was close enough. Now it works like nothing ever happened!

  Are you sure? yes | no

Moritz Walter wrote 07/28/2016 at 16:05 point

Hey there! Glad you could resolve this already. The beta kits shipped with a 121 °C fuse for good measure, which may have been a bit overcautious: Of the 15 beta kits that shipped, two (including yours) had this issue until now. The pre-production boards ship with a 133° C fuse.

A 141 °C fuse still protects you from a thermal runaway, so that should be fine. These fuses typically allow for about 20 °C overshoot, so the maximum temperature of a 141 °C fuse can be as high as 160 °C.

Just shoot me a reply to the order confirmation e-mail and I'll refund you for the fuse!

  Are you sure? yes | no

john wrote 07/10/2016 at 22:04 point

I'm still using my Beta version PCB with great success. Although I just updated the gantry on my printer (Eclips3D) to accommodate the Titan extruder. Unfortunately now the cooling fan duct now hits the  top LED cover on the PCB. Can I remove the upper cover and keep the lower part attached to safely cover the bottom parts?

  Are you sure? yes | no

Moritz Walter wrote 07/11/2016 at 08:23 point

Hey there! The beta boards should be just fine for further use. I stopped testing the beta-batch at 5.000 hours continuously at 110° C without issues. That's 7 months non-stop. About the LED cover: The LED pads carry mains potential. You probably won't die if you touch the exposed LED pads in operation (no guarantees however, please don't touch them). Yet, you printer logic might be less forgiving if the nozzle crashes into the pads and scrapes over them for any reason, which is why I made the cover fairly thick. Unless you can't replace the cover with something thinner but equally protective, I suggest you just hang your nozzle fan a little higher.

  Are you sure? yes | no

john wrote 04/29/2016 at 21:55 point

I am bench testing right now and it seems to be working well. I noticed a couple of tiny bare spots of the traces on the bottom, so I covered the bottom & top with a large Kapton sticker 20.32 cm square for safety.

  Are you sure? yes | no

Moritz Walter wrote 04/30/2016 at 08:29 point

Hi John! The PCB should not be exposed to the touch when in operation, so the Kapton is certainly a good idea. Please don't print directly onto the Kapton, though: In case of a malfunction the nozzle might still plow through the Kapton into the traces. A 2-3mm sheet of borosilicate glass on top of the PCB may prevent both touch and damage. About the spots, sorry to hear that! Feel free to contact me via email (answer to order confirmation) and get some $ back!

  Are you sure? yes | no

john wrote 04/30/2016 at 13:38 point

Yes I have borosilicate glass on top of the PCB. Thanks

  Are you sure? yes | no

Sancho_sk wrote 03/05/2016 at 21:24 point

Hi. I wanted to buy the bed on your webshop (it said 5 in stock), but when I click checkout I am redirected to initial page. I tested both German and English site, the result is always the same :(

Can you, plz, advice, what's wrong?

  Are you sure? yes | no

Moritz Walter wrote 03/05/2016 at 22:51 point

Hi, sorry for the trouble. It should work now! Kind regards!

  Are you sure? yes | no

Sancho_sk wrote 03/01/2016 at 18:45 point

Hi. Any chance you would be able to share the PCB in a bit different format? I don't like to install wine programs just to open the PCB layout... Thanks in advance.

  Are you sure? yes | no

Moritz Walter wrote 03/03/2016 at 12:05 point

Hi! Gerbers can be found here https://github.com/makertum/Makertum-MK1

  Are you sure? yes | no

Sancho_sk wrote 03/03/2016 at 13:30 point

Wow, thanks a lot!

  Are you sure? yes | no

Moritz Walter wrote 03/03/2016 at 13:37 point

You're very welcome, I'll be very happy to see more of them out there!

  Are you sure? yes | no

Sancho_sk wrote 12/24/2015 at 22:29 point

This looks like a briliant idea. One question frim a total noob. I would think of something made out of the heating element of a hair-drier, ssr and thermistor. I would unwind the wire of the heating element on some 20x20cm kapton sheet and organize it evenly. Then i would stick it to the bottom part of my glass bed. Is it too crazy idea?

  Are you sure? yes | no

Moritz Walter wrote 12/24/2015 at 23:39 point

Thanks! You gotta be *extremely* careful if you actually persue something like that, even small hair driers typically run at very high wattages above 1kW.

  Are you sure? yes | no

BPop wrote 12/21/2015 at 03:15 point
I would be very interested in buying one if they work out. Feel free to contact me if you need a beta tester, or if they become available for sale. Best of luck! bpopilek@yahoo.com

  Are you sure? yes | no

Moritz Walter wrote 12/21/2015 at 08:56 point

Thanks! I will notify you as soon as it becomes available!

  Are you sure? yes | no

ecloud wrote 12/19/2015 at 09:31 point

I always thought it's kindof funny to use copper for a heater, figured it was just an expedient when Makerbot came up with it, because for a printer bed you want it to be flat.  But I think there's a reason real heaters are made from nichrome wire.  Copper likes to oxidize, for one thing.  There are precedents for cheap flat heaters too, like the bed heaters for pet reptiles, although those are not intended for such high temperatures.

Likewise, fiberglass is not such a great conductor of heat, right?  And I wonder if it outgasses.  It just happens to be what PCBs are made from, and it does need to be an insulator.  

So if we try to rethink the whole concept, what we need is a good conductor of heat which does not conduct electricity, and can be made into flat sturdy sheets which aren't too brittle.  Ceramic would be nice except for being brittle, but there are a few which are strong enough.  And we'd like to embed nichrome wire into it, or apply etched or cut nichrome foil to the surface.  (EDM could be used to cut the traces, if you can get foil in the first place.)  And then come up with a cheap and easy manufacturing process.

But I agree, using line power makes a lot of sense.

I was trying to think how I could make a heated bed for my AIO Zeus, which has a glass turntable that is not meant to get hot, because there are some plastic parts underneath.  So the bottom side of it would have to be insulated with some very-flat material which does not conduct heat.  It doesn't really have to be round though because the turntable doesn't turn during printing.  And I'd need a separate thermostat because the controller isn't intended to control any extra heaters.  But that's the easy part.

  Are you sure? yes | no

Alex Rich wrote 12/19/2015 at 17:13 point

your comment just made me think,  why don't they print conductive ink on to the bottom of glass printer beds.   Would work like the rear windshield heaters on cars 

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Moritz Walter wrote 12/21/2015 at 09:32 point

@ecloud and @Alex Rich Dudes, I'm not trying to rethink the hell out of "heating" here, I just look at what works, look at what sucks, and try to improve the latter. The windshield heater idea is totally awesome, though.

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Alex Rich wrote 12/21/2015 at 12:11 point

Yeah like you said pcbs are cheap, you're proving a different concept. Would be cool to try a heater printed on glass, I wonder how much heat it could take without peeling off. 

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K.C. Lee wrote 12/21/2015 at 16:29 point

@Alex Rich
You can get Polyimide heating film with PSA and stick that on to a glass surface.
http://www.omega.com/pptst/KHR_KHLV_KH.html

There are other cheaper supplies.  Not cheap, but it is probably the easier way for single quantities.  

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Alex Rich wrote 12/21/2015 at 16:54 point

@K.C. Lee Good idea, it wouldn't really help me test the concept of using conductive ink on glass though.  Those look like ready-made flex-PCBs, I'm sure they would work just as well as a standard PCB.  I just read up on this for a second, apparently conductive ink can just be screen printed.  The question is would it be cheaper than just using a PCB or flex circuit.  If it is cheaper it might be worth trying, if it isn't cheaper I don't see why it would be better in any way.  They do it on car windshields so you can still see through, that's not a requirement for 3d printing beds.

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K.C. Lee wrote 12/21/2015 at 18:46 point

They are rated for 200C and designed for industrial applications. Unlike PCB heaters, they are not a hacked together solution.  The conductive film is sandwiched between the polyimide protecting/insulating them.  PCB have TG of 120C or 160C depending on the type.  Old PCB tends to turn white initially, then yellow/brown over time if there are hot components mounted on them.

The traces for the 120V/230V heaters are much thinner than the 12/24V, so I don't know if the 7mil copper have good adhesion when they are operated at high temperature during operation instead of a couple of minutes during a reflow.  The solder mask helps a bit on the adhesion.

As for conductive ink, I don't know enough for those and not sure if you can get an even application of them for DIY.  The areas with thinner ink will get hotter due to higher resistance.  Also you have to make sure that the ink can handle the high temperature and doesn't crack under heating/cooling cycles.

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Moritz Walter wrote 12/21/2015 at 23:29 point

Thats an excellent criticism @K.C. Lee, PCB material is not a material where common sense suggest it should be used as a hotplate. However, I've been using FR4 PCB heated beds for almost 4 years straight at 110-130 °C, ridiculously overdriven at 65 W/sqin in countless heatup cycles, and they still look like brand new. No decoloration, no cracks, no delaminantion, literally no issues at all. And that is probably because FR4's safe continuous operation temperature is 130 °C, while its temperature index suggests that 140 °C should be no problem either. The board I am suggesting has a 130 °C thermal fuse on board, preventing it from harmful temperatures without solely relying on the microcontroller. I'm not saying it has aircraft approval, but it's far from being a hacked together solution. There is a thermal and an overcurrent breaker and the datasheets have been read.

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K.C. Lee wrote 12/22/2015 at 00:12 point

Since you are using the copper for heating, you are intentionally heating the copper traces far beyond the usual industry acceptable temperature and current limits.

IS400 material http://www.isola-group.com/products/is400/  is what Eurocircuits spec for their regular PCB (UL-ML) for up to 130C.  The actual Tg can actually be anywhere between 110C to 150C.  (see datasheet linked in the page)  That's a very wide range and the 130C is only a typical value only.

>The Glass Transition Temperature (Tg) is one of the most important properties of any epoxy and is the temperature region where the polymer transitions from a hard, glassy material to a soft, rubbery material.

So unless you are pretty sure that the Tg min guaranteed from your PCB supplier is above your *long term* operating temperature, then I think that can potentially be an issue of pushing the material.  Specifying a higher Tg PCB material would give a bit more margin.

I treat personal stories the same way as anecdotal evidence.  The heater doesn't need to follow mil spec, but until it is UL and/or some other safety approval, there is an issue putting it inside a consumer product or release to the crowd at large.

Also the way the LED is attached... What happens if the traces in the PCB that is parallel to the LED were to break?  You do not have anything limiting the current to a safe value going into the LED branch.

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corry lazarowitz wrote 12/18/2015 at 20:37 point

not sure how cheap you're talking...silicone Heston element $50 8x8.  SSR $8, aluminum plate precut $10.  Used pub heater my printer came with to guide drill holes to mount the heater to, and pwm control even with zero crossing results in highly stable temps.  Not that expensive and works quite well

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kc8rwr wrote 12/17/2015 at 22:09 point

Now you have me thinking... if this is a good idea for the bed then why not for the hotend?

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Moritz Walter wrote 12/17/2015 at 22:18 point

Yeah, why not, would cut another 40W from the psu bill, just by replacing the heater cardige.

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MECHANICUS wrote 12/17/2015 at 06:00 point

simple easy and resistivity can be tuned with more or less coats of paint.  you can just use micronized graphite and you wont have to process into graphene.

Get a ssr and a tempcontroller off of ebay for around 15-20 bucks.

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TTN wrote 12/07/2015 at 03:57 point

Wouldn't it be easier/simpler/cheaper to get a 110 or 240 volt silicon pad heater with a cheap SSR all from aliexpress?

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Moritz Walter wrote 12/07/2015 at 07:45 point

Totally - if you only buy one. But in moderate quantities PCBs are really, really cheap. Also, you'll need something to mount the silicone pad to. Cha-ching.

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TTN wrote 12/07/2015 at 07:47 point

Indeed, as I'm finding out at the moment. I guess someone's gotta pioneer that first one and after that everyone is better off :)

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Nick Sayer wrote 12/05/2015 at 16:12 point

Rather than using an SSR you might consider rolling your own control circuit with a triac and an opto-isolated driver. You could probably surface-mount that right along side the input area. I made a reflow oven that way and it works really well. 

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Moritz Walter wrote 12/05/2015 at 16:44 point

A custom driving circuit would definitely be a great improvement over those dumb SSRs, it also would allow us to control the RMS power output. Having the driving circuit inside the heated chamber on a heated plate sounds a bit risky though. It's probably safer to keep the driving circuit and logic external in a cool place.

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Nick Sayer wrote 12/05/2015 at 18:27 point

The really temperature sensitive part will be the driver triac. In my case, I used a through-hole part with a heat sink, but in my case I was driving more like 1 kW. In your case, a heat sink would be indicated to keep it away from the hot plate. The rest probably could be kept cool enough just by being a inch away (on FR4) from the heating traces. 

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Szabolcs Lőrincz wrote 12/05/2015 at 12:29 point

Now that's some badass 3D printer part! I you could get it to manufacturing, I'd definitely buy one!

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Moritz Walter wrote 12/05/2015 at 13:19 point

Thanks for the feedback! Once the design is somewhat safe I'll have them made and see how they perform, so stay tuned :)

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