Plastic bender

Discussion in 'The Projects Forum' started by elib, May 17, 2016.

  1. elib

    Thread Starter New Member

    May 8, 2016
    4
    0
    Hello everyone,

    Introduction:

    I'm currently working on a project about food growing. In order to do it I need a bench to bend plastic (acrylic) easly to make the main structure. The goal is to bend plastic and also being able to make precise curvy bends.
    I have seen some DIY project that propose to heat up a wire of nichrome from a batteryy/variac and other..

    Here are some examples :

    - http://www.wa4dsy.com/robot/hot-wire-plastic-bender
    - http://www.instructables.com/id/How-to-build-a-Plastic-Heat-Bender/
    - https://www.youtube.com/watch?v=wVEf7PfuKxo


    Project:

    Here are some picture of where the project is a this moment.

    Picture 1: whole structure made of agglomerated wood, aluminium beams and small other pieces. 13238857_10153781752728440_7245404869062021601_n.jpg

    Picture 2: show hoz the structure is going to bend the plastic
    13178927_10153781752778440_5115166659484428056_n.jpg
    Picture 3: it's the area where the wire is going to stand and heat up the plastic
    13226925_10153781752818440_8037609706639782567_n.jpg


    Next:

    I'm novice in electronics and I need to find the best and safest solution to heat up the wire.
    Some possibilities:
    - Use a Variac : expensive but easly customable, electricity could be dangerous
    - Use a 12V battery 7mAh: less expensive but how long os the battery gonna last? Less dangerous with electricity as I would be playing with 12V
    - Use a voltage variator: look also dangerous because I would be playing with hight voltage. But cheap
    (http://www.befr.ebay.be/itm/REGOLATORE-DI-VELOCITA-SCR-3500W-220V-PER-MOTORI-AC-LAMPADE-DIMMER-TENSIONE-TEMP-/222057172918?hash=item33b3a38fb6%3Ag%3AkMwAAOSwMORW6-KO)


    What would you do?
    What nichrome would you use?

    Thanks in advance for your answer, I'm gonna give you the result as soon as possible!
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I think you'll find a heating wire disappointngly feeble for sheet-bending. Have you considered a commercial rod-type heating element such as one of these?
     
    Last edited: May 17, 2016
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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  4. Raikani

    New Member

    May 16, 2016
    14
    2
    If you want to use nichrome or other resistance wire for heating, I suggest picking up a small 12v power supply on the cheap. No need for expensive stuff like variacs and high voltages (other than mains going directly into the supply).

    I'm not sure about using batteries for this, I think you'll light your wire real quick.
     
  5. elib

    Thread Starter New Member

    May 8, 2016
    4
    0
    Thanks for your answers.
    Tapplastics solutions look dangerous as the wire is 120-220v and the risk of electric shock is high (Am I wrong?).

    After some research here is the solution I suggest:
    - Nichrome wire 0,5mm - 5,551ohms/meter (I use 40cm, 2,2204ohms)
    - 12v 7amps power supply

    0,5mm nichrome wire with 6A heat up to 760°c (http://hotwirefoamcutterinfo.com/_NiChromeData_files/1_Amperage.jpg)
    U = 2,2204 * 6 = 13,3224v

    So I could use this kind of power supply (12v):
    https://www.amazon.fr/Bloc-daliment...ie=UTF8&qid=1463613101&sr=8-1&keywords=6a+12v

    What do you think about this solution?

    Some questions:
    - 12v power supply while needing 13,3v what's the matter? Is it better to target 649°c with 5amp and needing 11,102v or even ?
    - Do you think 760° or 649°c is enough?
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Are you bending plastic or aluminum? Your acrylic will get soft at about 110C.
     
  7. elib

    Thread Starter New Member

    May 8, 2016
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    @GopherT : I'm bending plastic but the heat is about the wire and the plastic is about 1cm far from it. 110°c look low. I'm bending with hot air and it's about 300°c and need more than 10secondes to become soft.
     
  8. elib

    Thread Starter New Member

    May 8, 2016
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    0
    Do you have any advice about my proposition? I'm going to buy the material for it.
     
  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The narrower the area that you heat, the tighter your radius will be. Also, any metal at the heated bend will need to be at or above the bend temp or you will have a cold-spot (metal will suck the heat away from the area because it is a better conductor of heat than the plastic.

    Make sure you don't overheat (>250C) or acrylic unzips (de polymerizes) and makes flammable methyl methacrylate vapor - fire. A burning sheet of acrylic is a real pain to deal with. Depolymerization is complete and instantaneous at 300C.
     
    elib likes this.
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Its safe.. Its used with many commercial benders.. If you are concerned plug it into a GFCI outlet..

    But build your own if you want.. I just wanted to show a cheap off the shelf product intended for your exact use.. By the time you source a power supply,wire, plus your time its going to be more the $39.00 they are asking for that one....
     
    elib likes this.
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    And it will come with advice on heating time and setting for each thickness of acrylic sheet. You could easily go through $20 worth of sheet as you determine temp and time for each bend.
     
  12. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Or if you switch form acrylic(plexiglass) to polycarbonate (lexan) it can be bent cold in a standard sheet metal bending brake. Did it all the time at work for making machine guards.
     
  13. RichardO

    Well-Known Member

    May 4, 2013
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    I have also cold-bent polycarbonate. It was only 0.030 inches thick but still pricey.
     
  14. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Ours was 1/8", OSHA mandated all clear plastic guards had to be switched from plexi to lexan, because when plexi breaks it makes sharp dagger like pieces.
     
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