Sagging Heated PCB

Discussion in 'Calibration, Help, and Troubleshooting' started by Chase.Wichert, Apr 18, 2016.

  1. Chase.Wichert

    Chase.Wichert Well-Known Member

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    It doesn't seem normal, however I haven't heard of too many people having this problem. What is the best fix? I saw someone said a piece of foam underneath..
     
  2. Kick2box

    Kick2box Well-Known Member

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    As there is alread cork underneath, I'd print something (like a cross or X for example) to support it against the whole platform, it would be a clean solution and not look too ugly.
     
  3. Chase.Wichert

    Chase.Wichert Well-Known Member

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    I stuck a ruler under it for now, I guess that will be my next print... Only problem is that it kind of needs to be adjustable to allow bed leveling...
     
  4. Kick2box

    Kick2box Well-Known Member

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    I'd take some of these self adhesive PUR-stripes (for windows) and put it on top of the print.
    Or make some threaded holes and use screws for adjustment...
     
  5. Alex9779

    Alex9779 Moderator
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    I thought about using PUR foam but the problem is the heat resistance... I dunno how hot the bed can get under the cork.
    PUR foam can resist up to 80° C so far know, I found some which can resist +130° C for a bout an hour but thats all.
    What if printing HT, maybe some are printing ABS with 120° C, I assume 80° C are possible...

    Maybe a "sandwich", soft foam topped with something heat resistant, maybe a printed part in X shape or just some other plate...

    Now that I am missing the clips on the left and right side the bed is about 2mm away from the glass in the middle... Though it gets hot but I dunno how hot and how long it takes until it the top of the glass has that temp...
     
  6. Kick2box

    Kick2box Well-Known Member

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    It's a solution to put the PUR stripe below the print instead on top, but I can still touch mine from below when it has 110°.
     
  7. R Design

    R Design Well-Known Member

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    I've been using foam under the bed.

    Actually, I started with a spring jammed in right in the middle.

    ;)

    My bed's only been up to 80C but underneath it seems a lot cooler.

    However, I'm concerned about the poor heat distribution on the top side - it's a LOT cooler at the edges - and so am thinking about involving a sheet of aluminium between the PCB and the glass.

    That could sort out the sagging problems too.

    Anyone have any experience of that?
     
  8. Kick2box

    Kick2box Well-Known Member

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    Yes, but this should be milled to be flat and will be pretty expensive. The PCB will be to weak to heat that up.
    If you want something nice, I recommend this guy: http://forums.reprap.org/read.php?335,501747
    Also selling complete solutions with PEI and heater. Pretty cheap for what you get, if you really need that.
     
    #8 Kick2box, Apr 18, 2016
    Last edited: Apr 18, 2016
  9. Ephemeris

    Ephemeris Well-Known Member

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    If you want a flat thermally conductive layer, use MIC6 cast aluminum tool plate. It comes already ground very flat. It's easy to cut to size because it's relatively soft. Most importantly it's made specifically not to warp when machined (it lacks internal stresses). Plates of MIC6 are readily available and pretty cheap. Easiest way to get it in the USA is

    http://www.mcmaster.com/#aluminum-alloy-mic-6/=121e6x4
     
  10. R Design

    R Design Well-Known Member

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    Thanks guys, that's good information.

    I'm going to look into this.

    "Need"?

    Basically, the one time you don't need a part to detach is when you have a very FULL build plate, have gone to bed / lunch /....., and need to have it all ready for some deadline.

    Yet with the current heat distribution it would seem very likely that's going to happen.
     
  11. Kick2box

    Kick2box Well-Known Member

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    For me it's only a hobby, so I don't have deadlines. :)
    If you wan't something really perfect then I suggest you ask gonzohs via email for a complete heatbed. Additionally you probably will need a SSR and a bigger power supply.
     
  12. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    I have noticed the hot bed sagging before I have it mounted. Thought maybe the clips on the sides would "bend" it back up. I like the idea using a spring. Finding ones that fit without pushing too hard and maybe more of them.

    I'll be following this thread :)
     
  13. Chase.Wichert

    Chase.Wichert Well-Known Member

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    So, I found some springs, and am printing out some spring pads, that I will put in various locations around the bed to keep it up, It should look good, and not affect anything, they are large in diameter but rather small in wire diameter. So they should work very well, and I can take out the ruler that it is sticking out the front 6 inches.
     

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