# Nichrome Wire Calculations for 1x1 meter Reprap

Posted by KontinuumReprap
 Nichrome Wire Calculations for 1x1 meter Reprap July 30, 2012 05:43AM Registered: 10 years ago Posts: 19
So, we are building this large Reprap and we want to use nichrome wire to heat it's 100 x 100 centimeter print surface. However, we have a problem calculating what size nichrome wire we need. The calculator on this site (http://www.jacobs-online.biz/nichrome/NichromeCalc.html) generally seems really helpful but it only goes to 90 centimeters in length and that will obviously not be enough for us.

We plan to tape the wire with kapton tape to a plate of approximately 0.6 cm aluminum to spread the heat evenly and then have a 0.5 cm sheet of glass on top of that to make sure the print surface is perfectly even.

The glass needs to be heated for PLA temps (so at least 60 degrees Celsius), we are using a 12 volt powers supply, and we think 11 meters would be an adequate length (lengths of 100cm, spaced 10cm apart).

Can anyone help us find out the approximate diameter (Gage) of the wire or point us to some calculations that we can work with?

Best regards
 Re: Nichrome Wire Calculations for 1x1 meter Reprap July 30, 2012 06:53AM Registered: 11 years ago Posts: 643
All you need are the basic formulae of electric circuits - ohms law, parallel resistances, and P=IV. Also, find a table of resistance vs wire gauge.

But you aren't going to be able to run this from a 12V supply, you would need over a hundred amps to get it up to temperature. This needs to be a mains powered hot bed. Start with a 1.5Kw target. At 220V that implies an overall resistance of 1.6 ohms. As a single 11 meter length, that would require AWG5 wire. Or you can use, say, 20 parallel wires of 32 ohms to get the same overall resistance using one meter lengths of AWG32 wire
 Re: Nichrome Wire Calculations for 1x1 meter Reprap August 06, 2012 04:16PM Registered: 10 years ago Posts: 19
Thank you SO much. That was really helpful.
 Re: Nichrome Wire Calculations for 1x1 meter Reprap August 14, 2012 01:37PM Registered: 9 years ago Posts: 369
i did some paper planning for a bed about ur size. its a huge huge thermal engineering thing !
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