Silicone Heated Bed



  • Hi , I'm thinking of using a 220v AC Silicone Heated Bed for my 440x420mm 6mm bed which will be use for pla and petg so 70 c max should be o.k.
    ( Now I`m using tape cold , which works most of the time, but need the heat to be able to use glass.

    But not sure what wattage would be need to get it up to temp , minimum wattage ?
    For most of the time I would only be using the middle 300 x 300mm of the bed I was considering a 300x300mm 300 watt heating bed but not sure if this would work.
    Can`t find many 220v Silicone Heated Beds in the UK most look to be 110v or a wattage over 1kw .





  • If you want reasonably fast heating to around 100C for printing ABS, then a good figure to use is 0.4W per square cm of bed area.

    300 * 300mm (e.g. large Cartesian or CoreXY printer): 360W

    So 300 to 500 watts look to be in the right ball park ?



  • I have 300x300 750W keenovo heater from aliexpress, it heats up faster then my hotend :D.


  • administrators

    Both Keenovo and Shenzen Ali Brother Technology will make silicone heaters inexpensively to your own size, voltage and power specifications.

    Don't forget to order a heater a little smaller than the aluminium bed support, to leave room for fixings around the edge.



  • I was hoping to find a UK reseller , but it looks like I may have to go by the slow boat from china route.
    Due to never ordering from outside the EU before I`ve looked into the customs / duties / tax etc I would have to pay extra for anything from china.
    Which being under £135 I think would cost me just VAT on top ?



  • @peter247 said in Silicone Heated Bed:

    I was hoping to find a UK reseller , but it looks like I may have to go by the slow boat from china route.
    Due to never ordering from outside the EU before I`ve looked into the customs / duties / tax etc I would have to pay extra for anything from china.
    Which being under £135 I think would cost me just VAT on top ?

    Cannot tell for UK though as I live in Greece and I usually buy from banggood. Nothing has gone through customs so no any additional charges. Anything more expensive will go through Netherlands and it will seem like being sent within Europe. There are usually three shipping methods available. The cheapest one and slowest, the airmail priority and a third more expensive and fastest one. Picking any of the first two won't go through customs. Additionally, anything that goes through customs apart from the VAT you will have to pay an additional customs' fee.

    I wonder if there is anyone here who can confirm for UK.

    I have a 30cmx30cm heated bed at 750W and it takes approx 2:54 minutes to reach 70c



  • Living in the UK I ordered a silicone heat bed from aliexpress (400x400 750w) and was pleasantly surprised by the speed of delivery, 8 days and no additional charges.

    It was sent via epacket as that was the free shipping option.

    Hope that helps.


  • administrators

    @peter247 said in Silicone Heated Bed:

    I was hoping to find a UK reseller , but it looks like I may have to go by the slow boat from china route.
    Due to never ordering from outside the EU before I`ve looked into the customs / duties / tax etc I would have to pay extra for anything from china.
    Which being under £135 I think would cost me just VAT on top ?

    Typically I have to pay VAT, plus a surcharge to the delivery company of £10-£20 for collecting the VAT.



  • As an aside to shipping speeds, I ordered a bed from Keenovo off eBay. Living in Canada, overseas packages can take at minimum a month to arrive, occasionally over two full months. My keenovo bed was at my door just over a week after I ordered it.

    They'll also work with you to make a custom bed for your printer, so if you have an oddball design they're definitely the ones to go with.



  • If you order from Keenovo, I'd recommend asking them to include a bimetallic switch in your heater. Costs something like 2 dollars, makes the whole thing a lot safer. I've ordered mine with a 155 °C cutoff temperature.



  • @mike definitely, that's a great idea too, with the inherent dangers running an AC bed something as simple as that could save your bacon if your SSR fails and your heater ends up on thermal runaway.



  • @mike Wouldn't a bimetallic switch just cycle on and off if the SSR fails? A thermal cutout would guarantee a shut off. Or are the Keenovo bimetallic switches the manual reset kind? An automatic one would be unsuitable, and the one-shot kind would render the heater useless if it's buried within the silicone?



  • @klcjr89 A resetting bimetallic may reset, but not a problem if the bed is designed to take upto the switch point. In addition the abnormal behaviour of the heater should be detected by the duet and power supply to the heaters killed when the PSU_ON signal drops.



  • @dino also how many 12 / 24v P.S.U have you seen which is capable of 500 watts or more, that`s unless to go for some sort of ATX psu.



  • @peter247 I don't quite understand what you mean. When using an AC heated bed you can get away with using a much lower wattage PSU than if you are using a large DC heatbed.

    Since the power from the wall is AC it doesn't need to be converted to DC by the PSU. Therefore the PSU only needs to power fans, control board, steppers, hotend heater and anything else.

    My AC heatbed is connected to the IEC where I get mains power for the whole printer. I'm considering switching my PSU to a lower wattage passively cooled one since the mean well SP-320-24 has a loud fan and has a ton of overhead.



  • @klcjr89 It'll end up cycling - usually these switches flip back on at when the temperature drops by 10-15 degrees. I was previously using a thermal fuse caked onto the heater surface with some RTV silicone, but if this one trips, you have to rip it all apart and solder a new one in it's place.

    So I much prefer the bimetallic switch. It will still prevent my arguably massively overpowered heater (500 W for a 200x300 mm bed) from reaching dangerous temperatures if the worst (SSR fails closed) happens. And besides, even in this case the Duet will still post an error message, so I'll eventually see it and shut everything down.



  • i recently installed a 200x200 110v, 500w Keenovo on a glass bed and it will go from 25c-160c in less than 2 minutes. I'm pretty sure it will easily hit 200c but have yet to find the need to try it. Pretty cool when you can create a puddle of molten plastic with your bed. At the same time I also added a 12v 50w cartridge heater to the hotend and it takes less than 3 minutes to get from 25c to 400c. Wish I would have done this years ago.



  • What controls have you got for the environment of the machine? Enclosure or is your machine made out of a low thermal expansion material? With a linear thermal expansion rate of 23.1 * 10^-6 for Aluminium I work that as a 0.23mm expansion per metre of extrusion for a 10C temp change.

    There's something to be said for a slow warm up as it gives the rest of the machine a chance to warm up and settle before the bed probe. The expansion itself isn't so much of a problem - you can tune / change procedures to account for it. What is a problem is the bits closest to the heat sources get hot first, then conduct heat away taking a while to reach equilibrium, geometrically changing the chassis in a non-linear manner over a longer period of time than it takes to heat the bed.

    I've been meaning to ask if there is feature request for some sort of average duty report on the heaters or a warning of under powered heaters for the chosen set point. Having whinged about the negatives of big heaters I have to conceded my bed heater is lacking.


  • administrators

    @doctrucker said in Silicone Heated Bed:

    I've been meaning to ask if there is feature request for some sort of average duty report on the heaters or a warning of under powered heaters for the chosen set point. Having whinged about the negatives of big heaters I have to conceded my bed heater is lacking.

    See the M573 command.


 

Looks like your connection to Duet3D was lost, please wait while we try to reconnect.