PLA burnout furnace + DIY controller build

Discussion in 'Furnaces and their construction' started by Negativ3, Sep 22, 2017.

  1. Negativ3

    Negativ3 Silver

    Last edited: Dec 3, 2017
  2. Jason

    Jason Gold

    WOW those are dirt cheap.. Are they any good?
     
  3. Negativ3

    Negativ3 Silver

    The plastic is abt 3/16" thick all round, the lid fits nicely with the body and the o-ring seems to function well.

    So cheap I bought two, the second I plan to do a little testing for moisture ingress.
     
    Last edited: Dec 4, 2017
  4. Negativ3

    Negativ3 Silver

    And so the build begins...

    [​IMG]

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  5. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    -3, remind me, what was the upper operating temperature you were targeting for the burn out oven? Is the idea just to set investments on a rack or somehow suspend them above the heating element?

    Best,
    Kelly
     
  6. Negativ3

    Negativ3 Silver

    Kelly,

    The ceramic fiber blanket and board are for my main melting setup, with enough ordered to line the container shown for PLA burnout.

    Maximum op temp I envision will be 750 C on the burnout.

    Yes, I will have a sturdy stainless rack with a catch-plate at the bottom.
     
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    There were a couple build threads started here and at AA that contemplated using stove elements and I'm interested to see how well they handle furnace heat. At first it seems like quite a stretch given cooking temperatures but I've seen stove elements bright red hot so given the temperature that color suggests, maybe the elements themselves can hack it. You may need to give some thought to that electrical connection....

    Best,
    Kelly
     
  8. Negativ3

    Negativ3 Silver

    I am willing to give it a go. Plan b is to design and fit a stainless steel tube drilled with many holes and formed into a circle to provide a burner. Then I will look for proportionally controlled needle valve for gas regulation.
     
  9. Jason

    Jason Gold

    I was curious about those heating elements too.... Might work.. Hope so! I'll let Neg be the guinea pig on this one.
     
  10. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Or just buy or wind your own NiCr coil designed for the intended power level and use your existing control scheme. There's really not much to it and electric will provide better control and ability to program burn out schedule.

    Best,
    K
     
  11. Negativ3

    Negativ3 Silver

    Thanks Kelly, that is now plan B. I have a length of NiCr on the way to fabricate a foam cutter.
     
  12. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I may have posted this before but here is a link to the Kanthal design handbook for resistive heating elements. I used it to design my coils. It gives recommendations on maximum power density per unit of furnace wall and coil surface area. It also provides guidelines on recommended ratio of coil diameter to wire diameter and coil spacing. You can use Ohm's law and the published resistance for a given wire to design to the desired target power level. You want to use the max gage wire for durability that packages well within the design guidelines for your furnace requirements.

    Kanthal is a good choice for upper temperature limit but alloys like NiCr 60 retain more hot strength albeit at modestly lower max operating temps.

    http://www.hi-tempproducts.com/pdf/the-kanthal-furnace-mini-handbook.pdf

    Best,
    Kelly
     
    Jason likes this.
  13. Negativ3

    Negativ3 Silver

    Thanks Kelly, it's a good resource.
     
  14. You are right. That's about an 11 on the cool factor scale...but aren't you afraid that you are just contributing ti A.I. taking over the world?
    Haven't you seen "Terminator"?:eek:
     
  15. Negativ3

    Negativ3 Silver

    Finally some time to hook up and test some components.

    The ridgidiser I am using is blue out of the bottle, turning dark then the ceramic board turns white after curing at temperature.

    [​IMG]

    Back to work tomorrow for 12 days, hopefully back for christmas.
     
  16. Peedee

    Peedee Silver

    Is that element from a fan oven? They don't like getting too over heated - may cause you longevity issues. Not trying to be negative just had experiences with them.
     
  17. Negativ3

    Negativ3 Silver

    Yes, it's an element from a fan oven. Got the shell finished this afternoon and gave it a run up to cure the rigidizer.

    [​IMG]

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  18. Jason

    Jason Gold

    Is that 753 degrees celsius??? If it is and that's not Fahrenheit, you have some bad ass insulation going on there. Colors being goofy on the net, it looks almost orange... so 700 C roughly.
     
  19. Negativ3

    Negativ3 Silver

    753 C in 12.5 minutes.
     
  20. Jason

    Jason Gold

    I'm impressed. That's bad ass. AND FAST. Wonder what it could do with a 2nd smaller element parked inside the first one. Melt bronze?
     

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