Jump to content
UltiMaker Community of 3D Printing Experts

Why not using AC to heat?

Recommended Posts

Posted · Why not using AC to heat?

Maybe this is a stupid question, but why getting a 250w DC power supply when a thyristor based device could use AC (with solid state relays?) to achieve this?

I mean, 75% of the UM2 power goes to the bed and nozzle heating, right?

And a 30$ low cost oven can reach 250°C and is like 1/3 the price of just the UM2 PSU

  • Link to post
    Share on other sites

    Posted · Why not using AC to heat?

    The UM2 power supply is designed to work with both 120VAC and 240VAC. If it was an AC heated bed you would have to either make 2 beds or use a transformer to lower the current. Also the USA Military determined that truly safe voltages must be under 60V DC or 30V AC. To make the bed AC power and also safe you might want to lower the voltage to 30V max. But now you have a heavy, expensive transformer to achieve this (and with a switch for 120V or 240V mains which adds more danger/complexity) and now it's just cheaper to use a DC power supply.

    This is my guess.

  • Link to post
    Share on other sites

    Posted · Why not using AC to heat?

    I am sure mine is not the only heated bed that runs on separate 120vac supply (driven with solid state relay). I don't feel it is at all more unsafe than other household appliances. As gr5 pointed out though, even higher voltage may not be safe. In Europe where a lot of UM's are sold, the AC line voltage is 230v and you'd be stuck running your heaters at that or add a costly step-down transformer.

    On the other hand, I don't think I would want my hot end to run on AC because of the nature of the head motion (wire travel and fatigue), and that I am touching the head quite often. If the nozzle heater were to short out, it would be easy to get shocked. Otherwise, the DC powered hot end and bed are already included in the new machines as they are shipped. I think only the UMO lacks a HB as stock.

  • Link to post
    Share on other sites

    Posted · Why not using AC to heat?

    Ok but, there is a lot of things working with AC that I feel safe with

    Think of your boiler, hairdrier (/hot gun), soldering irons which are almost like a nozzle or electric radiators which are almost like a heated bed...

    There is also hot glue gun, which is basically like an extruder, no expansive DC psu with this

    Don't think military US want all that to go <30V :-)

  • Link to post
    Share on other sites

    Posted (edited) · Why not using AC to heat?

    Think of your boiler, hairdrier (/hot gun), soldering irons which are almost like a nozzle or electric radiators which are almost like a heated bed...


    All those devices have to comply with a bunch of regulations. Those regulations are extra strict, if there are metal parts that could be touched. The devices you mentioned are all equipped with ground connections of metal parts, extra isolation and more.

    One can certainly modify the heated bed and/or the extruder to meet those regulation. But that means a lot of extra weight, cost in development and compliance testing and quite some production cost. For example, you might have to completely isolate the aluminum heating plate from accidental touching and you have to make sure, that even if this isolation brakes you still can't get shocked. That means a lot of extra material and engineering.

    Edited by Guest
  • Link to post
    Share on other sites

    Create an account or sign in to comment

    You need to be a member in order to leave a comment

    Create an account

    Sign up for a new account in our community. It's easy!

    Register a new account

    Sign in

    Already have an account? Sign in here.

    Sign In Now
    • Our picks

      • UltiMaker Cura 5.3 stable released
        In this stable release, Cura 5.3 achieves yet another huge leap forward in 3D printing thanks to material interlocking! As well as introducing an expanded recommended print settings menu and lots of print quality improvements. Not to mention, a whole bunch of new printer profiles for non-UltiMaker printers!
          • Thanks
          • Like
        • 24 replies
      • Here it is. The new UltiMaker S7
        The UltiMaker S7 is built on the success of the UltiMaker S5 and its design decisions were heavily based on feedback from customers.
        So what’s new?
        The obvious change is the S7’s height. It now includes an integrated Air Manager. This filters the exhaust air of every print and also improves build temperature stability. To further enclose the build chamber the S7 only has one magnetically latched door.
        The build stack has also been completely redesigned. A PEI-coated flexible steel build plate makes a big difference to productivity. Not only do you not need tools to pop a printed part off. But we also don’t recommend using or adhesion structures for UltiMaker materials (except PC, because...it’s PC). Along with that, 4 pins and 25 magnets make it easy to replace the flex plate perfectly – even with one hand.
        The re-engineered print head has an inductive sensor which reduces noise when probing the build plate. This effectively makes it much harder to not achieve a perfect first layer, improving overall print success. We also reversed the front fan direction (fewer plastic hairs, less maintenance), made the print core door magnets stronger, and add a sensor that helps avoid flooding.

        The UltiMaker S7 also includes quality of life improvements:
        Reliable bed tilt compensation (no more thumbscrews) 2.4 and 5 GHz Wi-Fi A 1080p camera (mounted higher for a better view) Compatibility with 280+ Marketplace materials Compatibility with S5 project files (no reslicing needed) And a whole lot more  
        Curious to see the S7 in action?
        We’re hosting a free tech demo on February 7.
        It will be live and you can ask any questions to our CTO, Miguel Calvo.
        Register here for the Webinar
          • Like
        • 18 replies
      • UltiMaker Cura Alpha 🎄 Tree Support Spotlight 🎄
        Are you a fan of tree support, but dislike the removal process and the amount of filament it uses? Then we would like to invite you to try this special release of UltiMaker Cura. Brought to you by our special community contributor @thomasrahm
        We generated a special version of Cura 5.2 called 5.3.0 Alpha + Xmas. The only changes we introduced compared to UltiMaker Cura 5.2.1 are those which are needed for the new supports. So keep in mind, this is not a sneak peek for Cura 5.3 (there are some really cool new features coming up) but a spotlight release highlighting this new version of tree supports.  
          • Like
        • 22 replies
    • Create New...