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    Securing bed heater to bed plate

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    • Phaedruxundefined
      Phaedrux Moderator
      last edited by

      https://www.canadiantire.ca/en/pdp/imperial-high-temperature-silicone-red-304-ml-0642712p.html

      User's-Manual-Keenovo-Flexible-Heaters.pdf

      The sealant should be more than enough to hold, but if you want a physical backstop just try to keep it from making much physical contact to the heater itself.

      Z-Bot CoreXY Build | Thingiverse Profile

      jens55undefined 1 Reply Last reply Reply Quote 0
      • jens55undefined
        jens55 @Phaedrux
        last edited by

        @phaedrux, thanks.

        I am still inclined to want to provide positive pressure somehow but the issue is that if you provide too much clamping force then you could in theory distort the build bed a bit. Seems silly to buy a cast tooling plate for the bed and then proceed to distort things.
        Interesting that you are not supposed to use acetone to clean the plate ....

        Dougal1957undefined 1 Reply Last reply Reply Quote 0
        • mrehorstdmdundefined
          mrehorstdmd @jens55
          last edited by

          @jens55 I think a combo of silicone adhesive backed up with some mechanical clamping is probably the ultimate in safety and long operating life. It doesn't take much clamping force, so I think it can be done without distorting the bed plate. If you include some mechanical clamping, you can mount the TCO on the plate instead of the heater.

          https://drmrehorst.blogspot.com/

          zaptaundefined 1 Reply Last reply Reply Quote 0
          • zaptaundefined
            zapta @mrehorstdmd
            last edited by zapta

            This is the recomanded Voron way. He uses JB Weld RED Hi-Temp RTV.

            https://www.youtube.com/watch?v=vZx4vfevwx4

            jens55undefined 1 Reply Last reply Reply Quote 0
            • jens55undefined
              jens55 @zapta
              last edited by

              @zapta, thanks for posting that. I am starting to feel like I am doing too much worrying about the sandwich arrangement.

              zaptaundefined 1 Reply Last reply Reply Quote 1
              • zaptaundefined
                zapta @jens55
                last edited by

                @jens55 said in Securing bed heater to bed plate:

                @zapta, thanks for posting that. I am starting to feel like I am doing too much worrying about the sandwich arrangement.

                That's understandable. I am sourcing parts for a new printer and plan to have two thermal fuses, one on the aluminum and one on the silicon, also reduced the Keenovo header standard 500w spec to 300w.

                jens55undefined 1 Reply Last reply Reply Quote 0
                • jens55undefined
                  jens55 @zapta
                  last edited by

                  @zapta, what do two thermal fuses get you other than if one falls off you still have another ....
                  I also happen to think that 700W is just right for a 300x300 bed. I am too impatient to wait for a 300W heater to bring the temp up before printing.

                  zaptaundefined 1 Reply Last reply Reply Quote 0
                  • Nuramoriundefined
                    Nuramori @jens55
                    last edited by

                    @jens55 this is exactly the way I built my bed. From top to bottom, this is my assembly.

                    Pei or garolite LE
                    3M 468mp adhesive sheet
                    Steel spring sheet
                    Staymag magnetic sheet
                    3M 468mp adhesive sheet
                    325mm x 325mm Mic6 aluminum bed

                    300mm x 300mm Keenovo 120v/750w silicone heater with adhesive sheet - edges sealed to mic6 plate with RTV sealant

                    3mm silicone insulating sheet.
                    3mm aluminum compression bottom plate secured to mic6 bed with spacer sleeves threaded into bed at three points to ensure compressive positive contact and prevent delamination failure.

                    Thermal manual reset fuse attached to mic6 bed that trips at 150c.

                    jens55undefined 1 Reply Last reply Reply Quote 0
                    • jens55undefined
                      jens55 @Nuramori
                      last edited by

                      @nuramori, that is exactly what I was contemplating with the compression plate screwed to the MIC6 plate.
                      I would be using thermal insulating material (rock wool maybe) rather than the silicone insulating sheet you are using.
                      I was thinking that rather than fixed spacers, I would use springs to limit the amount of pull on the bed plate. Maybe have some slop in the mounting so as to allow differential expansion.

                      Nuramoriundefined 1 Reply Last reply Reply Quote 0
                      • Nuramoriundefined
                        Nuramori @jens55
                        last edited by Nuramori

                        @jens55 That's why I used spacers, so there's just enough contact to keep it in contact in the event of a delamination, which would not really happen with contact eliminating any gap. The spacers allow for preventing warping from over tightening, and the "pull" you state via a consistent distance. Since I mount my bed assembly to a support frame, it allows for decoupling mounting strain from the bed itself. By mounting the bed assembly by the bottom plate, it also thermally isolates the bed from the frame or any support, with the only thermal bridging occuring through three small M3 screws, yet a repeatable and consistent distance from the extruder that rarely needs calibrating.

                        jens55undefined 1 Reply Last reply Reply Quote 0
                        • jens55undefined
                          jens55 @Nuramori
                          last edited by

                          @nuramori said in Securing bed heater to bed plate:

                          Since I mount my bed assembly to a support frame, it allows for decoupling mounting strain from the bed itself. By mounting the bed assembly by the bottom plate, it also thermally isolates the bed from the frame or any support

                          You lost me there.

                          mrehorstdmdundefined theruttmeisterundefined 2 Replies Last reply Reply Quote 0
                          • mrehorstdmdundefined
                            mrehorstdmd @jens55
                            last edited by

                            You can get a pretty accurate estimate of bed heat-up time here: https://jscalc.io/calc/uS8JYjYISgIvzJ1x

                            https://drmrehorst.blogspot.com/

                            1 Reply Last reply Reply Quote 1
                            • Dougal1957undefined
                              Dougal1957 @jens55
                              last edited by

                              @jens55 said in Securing bed heater to bed plate:

                              @phaedrux, thanks.

                              I am still inclined to want to provide positive pressure somehow but the issue is that if you provide too much clamping force then you could in theory distort the build bed a bit. Seems silly to buy a cast tooling plate for the bed and then proceed to distort things.
                              Interesting that you are not supposed to use acetone to clean the plate ....

                              Reason for not using Acetone (this I assume is to clean a plate that has already had Glue or 3m adhesive attached) is that £m 468 and acetone is a very bad mix the 3M just turn to mush and becomes very difficult to remove I guess that it may also leave a residue that effects the 3M as well. IMHO If I was to order another one it would be without the 3M Adhesive. I also like to get them with a small 10mm diameter hole in the middle so that I can fit my own temp sensor to the bed.

                              Doug

                              1 Reply Last reply Reply Quote 1
                              • zaptaundefined
                                zapta @jens55
                                last edited by

                                @jens55 said in Securing bed heater to bed plate:

                                @zapta, what do two thermal fuses get you other than if one falls off you still have another ....
                                I also happen to think that 700W is just right for a 300x300 bed. I am too impatient to wait for a 300W heater to bring the temp up before printing.

                                I plan to connected the two thermal fuses in series that that if one of them burns the heating will stop. Using a 200x200mm 300W 110VAC Keenovo on a 250x250x8mm bed.

                                Not sure about adding insulation at the bottom since it's a Voron 2 which has a closed chamber and thus needs to be heated.

                                1 Reply Last reply Reply Quote 0
                                • theruttmeisterundefined
                                  theruttmeister @jens55
                                  last edited by

                                  @jens55

                                  I think @Nuramori means, don't use the tool plate printing surface as the mechanical attachment to the machine.

                                  What works really well for me is:

                                  Print surface (MIC6 plate, which has magnets and gets a flex-plate type surface on top)
                                  Silicone Encapsulated heater (mine has a thermal fuse built in, its a 200C one). Attached with PSA.
                                  4x squares of VHB or any decent adhesive (in the corners, huge areas of glue can cause compounding issues), might even be epoxy... can't recall.
                                  Sheet of 6mm Nylon foam (from McMaster in the US, but its made in the UK).
                                  4x corner bits of glue.
                                  1/8" aluminium sheet (not fancy MIC6 or anything).
                                  The printer,

                                  That 1/8" sheet carries all the weight and is what is attached to the printer. The MIC6 plate is held in place by the adhesive, there's no need to add mechanical fasteners. You just need to allow enough adjustment in the mounting between the final sheet and the printer to get the MIC6 surface reasonably square and true to the gantry.
                                  Because I'm not using mechanical fasteners I don't have to worry about thermal expansion, conduction or durability.
                                  I have multiple machines built in this way that have been working without issues for several years.

                                  Isolate, substitute, verify.

                                  jens55undefined 1 Reply Last reply Reply Quote 0
                                  • jens55undefined
                                    jens55 @theruttmeister
                                    last edited by

                                    @theruttmeister, interesting arrangement !

                                    theruttmeisterundefined 1 Reply Last reply Reply Quote 0
                                    • theruttmeisterundefined
                                      theruttmeister @jens55
                                      last edited by

                                      @jens55
                                      It probably wouldn't work with anything other than that nylon foam. If you can find it...

                                      Its cheaper than silicone, excellent insulation value, actually sticks to glue and its rigid!

                                      If I couldn't get that foam I'd probably go with something involving shoulder bolts in slots to let the MIC6 expand, with the heater sitting in a cutout in the mounting frame, and a retaining plate below that (to support the insulation), attached to the frame not the plate. And just use PEEK washers or thin spacers to insulate between the frame and plate.

                                      Isolate, substitute, verify.

                                      1 Reply Last reply Reply Quote 0
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