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  • RobertKuhlmann commented on RobertKuhlmann's instructable 3D Printer Heated Bed25 days ago
    3D Printer Heated Bed

    I agree. Until now driving my heatbed with the SevenSwitch driver is extremely reliable.The heat from the copper wire always gets "cooled"by the aluminum heatbed. Even the sections of wire not in direct contact to the aluminum don't heat up to critical temperatures (critical in the sense to make the insulaiton fail), because the heat within the wire is distributed through the copper wire to its better cooled sections nearby. Also the insulation stays stable, because it would only degrade if heated far above 200 °C (withstands up to 400°C anyway) over longer time, which never happens in this setup.If you look at a transformator coil, overheated sections are not cooled by nearby heatsinks, but the wire in total heats up much more and can lead to electrical insulation failure.ric...

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    I agree. Until now driving my heatbed with the SevenSwitch driver is extremely reliable.The heat from the copper wire always gets "cooled"by the aluminum heatbed. Even the sections of wire not in direct contact to the aluminum don't heat up to critical temperatures (critical in the sense to make the insulaiton fail), because the heat within the wire is distributed through the copper wire to its better cooled sections nearby. Also the insulation stays stable, because it would only degrade if heated far above 200 °C (withstands up to 400°C anyway) over longer time, which never happens in this setup.If you look at a transformator coil, overheated sections are not cooled by nearby heatsinks, but the wire in total heats up much more and can lead to electrical insulation failure.richfiddler11 wrote: In theory, you could power a heater like this this with AC line voltage.That would of cause be daedly dangerous. Why should I bring line voltage to a part I will have to touch with my hands? There is no need for high voltage here and DC is more easy to control (and with cheaper parts), than AC. And a breaking AC line wire isolation beacuse of the movements of the bed, would be dangerous too. No need to risk your life just to get power to the heatbed.

    Here you find instructions to build one: https://reprap.org/wiki/SevenSwitch_1.2It's very easy to build.I would not use RAMPS for that, because in case of failure it is expensive to replace, while SevenSwitch can be repaired or even be replaced at very small costs.

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  • RobertKuhlmann commented on RobertKuhlmann's instructable 3D Printer Heated Bed9 months ago
    3D Printer Heated Bed

    What kind of short circuit problem do you mean? If the insulation of the wire failed while having contact to the aluminum at the same time, something really went wrong, because the wire should never get so hot that the insulation fails at all.Maybe try a different wire type.

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  • RobertKuhlmann commented on RobertKuhlmann's instructable 3D Printer Heated Bed3 years ago
    3D Printer Heated Bed

    It may scale up. You should use several heating fields under the platform and supply them in parallel (the aluminum spreads the heat very evenly). Of course you need a sufficient power supply for that, or several supplies in parallel and, more important, you should use several switches (e.g. SevenSwitch) in parallel, because their abilities are limited too. But if you scale up everything in parallel it should work like charme.

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