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I have a 3d printer that I am building which has a heated bed, as most FDM printers. The bed is about 25"x24" and will have (4) 12"x12" silicone heating pads anywhere from 500-700W each. Each heating zone will control to a temperature setpoint using a solid state relay and PID control.

The printer will be on 240V circuit with high amp capacity, so power is not an issue here. My question is because each of the heating zones are wired independently should I buy a big PSU and run 240V from the outlet to it and then to each heater? Could I get by with just wiring each heater in parallel to the 240V outlet.

As a side note, the motherboard, stepper motors, and all other devices associated with the printer are being powered by a small PSU that steps voltage down to 24V.

printer

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  • \$\begingroup\$ If I understood it right you don't need a PSU. Is there a reason you thought you needed one? And what would it even be? A 240VAC output? VDC? \$\endgroup\$
    – DKNguyen
    Commented May 20, 2021 at 4:22
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    \$\begingroup\$ Are the heating pads intended to be operated on 240 V? If so, you would wire them directly to 240 V - no power supply needed (but appropriate fuses and controls, of course.) \$\endgroup\$
    – Peter Bennett
    Commented May 20, 2021 at 4:25
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    \$\begingroup\$ Each heater has a controller and all controllers go into a power source , whatever you choose. \$\endgroup\$
    – D.A.S.
    Commented May 20, 2021 at 5:03
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    \$\begingroup\$ @tlfong01 it is a CoreXY printer, similar to a Modix printer, which is different than the printer referenced in the link. \$\endgroup\$
    – Feynman137
    Commented May 20, 2021 at 12:42
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    \$\begingroup\$ @Feynman137, many thanks for pointing out my wrong guess. Actually I know too little about 3D/Rerap printers to understand the differences. \$\endgroup\$
    – tlfong01
    Commented May 20, 2021 at 13:17

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You can wire the 240VAC heaters in parallel through an SSR or similar. How you do it is up to you, but a terminal block, spade connectors or even individual connectors (all properly insulated and rated, of course) might be options. I suggest fusing each heater individually.

You probably should include a series thermal cutoff or even two, as 2.8kW is a significant amount of power and might be enough to start a fire should the SSR fail 'on' or the sensor become dislodged. Since controllers are so cheap, you could consider a redundant sensor and limit controller, but simple mechanical thermal cutoffs are good to have in any case.

You would want the pads to be on a surface that spreads the heat (eg. thick-ish aluminum plate) and the sensor probably near the center.

The controller will adjust for minor variations in heat demand and mains voltage.

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  • \$\begingroup\$ The surface the heaters are attached to is 0.25in thick Mic6 aluminum plate. \$\endgroup\$
    – Feynman137
    Commented May 20, 2021 at 12:44

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