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Thread: Anyone ever built a hot wire knife for cutting foam?

  1. #11
    Join Date
    Mar 2015
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    2,221

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    I like to use SS fishing leader wire

  2. #12
    Join Date
    Dec 2016
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    Helsinki, Finland, Europe
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    I got a piece of Rene 41 wire from ebay. Allows you to have the cutting wire real tight as its stronger at 1600F than stainless steel at room temperature or 10 times the Kanthal tensile strenght at high temp.

  3. #13
    Join Date
    Jun 2011
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    If you're looking for small pieces of kanthal or nichrome, hit a ecig shop. It's used for rewinding exit coils.

  4. #14
    Join Date
    Dec 2004
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    East Coast, USA
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    Quote Originally Posted by achtanelion View Post
    If you're looking for small pieces of kanthal or nichrome, hit a ecig shop. It's used for rewinding exit coils.
    Are those exit coils the coils that keep exit doors closed with magnet locks? Sounds like a trap...
    Work hard play hard

  5. #15
    Join Date
    Jun 2011
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    Ducking auto co wreck.

    That should be ecig coils.

  6. #16

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    Yep, used a transformer from an old stereo to provide isolation and step-down, (2) 12V output windings wired in parallel. Light dimmer to vary the line input power to the transformer. I used 0.023" mig welding wire and I made bows out of 1/2" EMT conduit for pattern cutting up to 48" wide. folded over and crimped the stainless wire in a butt splice, the other side crimped to copper 14ga to the transformer.

  7. #17
    Join Date
    Jul 2007
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    My only contribution is to use wires from an old electronic air cleaner. They are tungsten, about 0.010" and have terminations already installed. They are very forgiving of temperature excursions and surprisingly strong.
    Duffy, Gatineau, Quebec

  8. #18
    Join Date
    Apr 2010
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    Canada
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    I made mine from PVC pipe, due to the wire relaxing some when heated I created a automatic tensioner system based on the old bow saw method that had a string tensioner that you could increase tension at the rear.
    This automatically retains the set tension.
    I used a transformer and a Triac 'dimmer' controller on the secondary, and mounted it to the top arm of the cutter.
    Max.

  9. #19
    Join Date
    Mar 2010
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    1,043

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    For a power supply, I used a big old variac core that had lost it's brush assembly. The winding was still good, so I made a secondary winding of insulated # 10 copper wire wound through the toroid until got sufficient current for the constantan cutting wire. Varying the number of turns gave easy control of the current/temp.

    RWO

  10. #20
    Join Date
    Jun 2013
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    Skegness
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    I can only give info from a lack of technical knowledge but I used to work for a company that cut EPS shapes for packaging. We used nichrome wire powered by an arc welding transformer controlled by a toroidal transformer. We used wires of many different lengths for straight cuts and thicker wires bent to shape to cut profiles. The output of the welding transformer was low voltage so if a worker touched the wire they were burnt but not electrocuted! These worked successfully day in day out. I know that it is vague but it may be of help to someone who understands these things. I certainly don't!

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