240v 300w Heated Bed

  • I am considering getting a Duet3D board for my new 3D Printer build as I am wanting to create a 600mm x 600mm build area that is going to be just over 1 meter in height. I already have a old heater that is 240v and 300w, obviously I can not just plug this thing straight into the Duet3D but using its current setup I would have no way to control the heat levels. It has a 100 degrees C thermistor that cuts out if it goes above 100 degrees C, I was thinking I could possibly use it to control the heat out put but think there must be a better way to do it. Any ideas that might help would be great.

  • Simply use a SSR for that.

    It´s athermistor ( to messure temperatur) or is it a temp fuse ( that cuts the line) If its a temp fuse most of them have to replace after it cuts out.
    If its a thermistor you can use it as normal

  • It is a Temp fuse.

  • @jmjcoke Thanks i'll look into those!

  • 300W is pretty low for a 600x600 bed.

    As a point of reference, my printer's 300x300x8mm cast aluminum bed with a 750W heater gets to 105C for printing ABS in 4.5 minutes.

    The normal way to switch line power to a bed heater is to use an SSR. The SSR can be driven by the Duet board. You will use the PID control built into the firmware with a thermistor mounted on the bed to regulate the temperature.

    You don't usually need a heatsink on the SSR.

    I don't know how accurate it is, but this site has a calculator that will give you some idea of the time required to heat to a specific temperature: https://jscalc.io/calc/uS8JYjYISgIvzJ1x
    It says my bed should get to 110C in 247 sec, pretty close to the time I have measured for 105C.

  • @mrehorstdmd Alright, I just tried out that website, it suggested it will take about 40 minutes to get to 110 Degrees C. which is strange as I have taken this heater from an old panel I had that heated my garage, it is able to hit 100 Degrees which is its maximum within 3-4 minutes on the same sheet of Aluminium that I will be using for my heated bed. I have a insulation foam layer under the heater also that retains a lot of the heat so requires less power to sustain the temperature.

  • Are you sure it's just 300W?

    Is the heater 600x600 or smaller? How thick is the plate?

  • and the temp fuse with 100° looks a bit low...some tolerances and some ABS printing ( 100-110°) and the fuse cuts off..and im sure in that moment you forgot that there was a temp fuse 😉

    300W seems really low...in my Dleta i use 300W für a Ø 300mm 8mm cated aluminium bed and its ok..

    External temp controller is ok..but not so comfortable, because you have input the wanted temp manually..another thing to forget before a large print..
    Most uses an SSR as a slave and the duet as controller... and pls dont forget to check the electric..i bought my heated bed uses..and the former owner have used it without ground on the aluminium plate..

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