DIY budget heated bed December 23, 2013 04:54AM |
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Re: DIY budget heated bed December 29, 2013 07:54AM |
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Re: DIY budget heated bed June 18, 2014 09:44AM |
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Re: DIY budget heated bed August 17, 2014 11:29AM |
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Re: DIY budget heated bed August 19, 2014 07:20AM |
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Re: DIY budget heated bed August 29, 2014 12:54PM |
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Re: DIY budget heated bed August 29, 2014 01:28PM |
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Re: DIY budget heated bed August 29, 2014 03:09PM |
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You're right. I forgot to mention the cooling of the MOSFET, which I will do too, of course. I didn't need a heat-sink until now (driving 18A though), because the MOSFET is in the direct air-stream of the fan of my power-supply. But adding a heat-sink will be no problem.Quote
dc42
There is no way that the mosfet will switch 150A, despite its theoretical 150A rating. Assuming it is driven by a 5V signal (i.e. from 5V RepRap electronics, not the new 3.3V Duet electronics), then the maximum that you should ask the the mosfet to pass is 32A (the value at which Rds(on) is specified for Vgs=4.5V). At that current, it will dissipate about 4W and need a modest heat-sink. In fact, you should put a heatsink on the mosfet if you want to pass more than 16A through it.
I think I don't need a uniform current flow, because the aluminum is a good heat conductor. This is my experience from my current heated bed, where the positions of the heating-wire-loops are not that important. Even if there would remain some minor temp-differences, these are not very important, as long as the lowest temp (which should be basis of the thermistor-measurement) is high enough. I couldn't see any differences in adhesion of prints to the bed between 130°C and 110°C for ABS (plain aluminum with hairspray).Quote
dc42
Bear in mind that to get uniform current flow (and hence uniform heating) through a sheet of aluminum, you will need to bolt strips of copper sheet or much thicker aluminum plate to two opposite edges, and feed the current to the plate via those.
Re: DIY budget heated bed August 29, 2014 03:13PM |
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Re: DIY budget heated bed August 29, 2014 04:08PM |
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Maybe I wasn't exact enough: The "sheet" is 220mm x 220mm x 3mm.Quote
dc42
... Where do you get the figure of 0.3 ohms from? I make the resistance between opposite edges of that sheet about 10 microohms.
Re: DIY budget heated bed August 29, 2014 05:55PM |
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Generation 7 Electronics | Teacup Firmware | RepRap DIY |
Re: DIY budget heated bed August 30, 2014 05:10AM |
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