Fuse on Ramps 1.4 not sufficient for heated bed, need advice

Hi guys!

Last year I build a CoreXY printer from scratch as part of a university project.

I have a aluminium plate as my print bed and a silicone heated bed with 12V/ 250W. My power supply has DC 12V 50A 600W. When I tried to get my heated bed to work, the fuse for the heated bed got hot and the bed shut off after about a minute. By now I know that the fuse is not sufficient for a heated bed with these specifications.

I was able to print PLA fine without a heated bed (thanks to a PEI Sheet on my aluminium plate) but now I want to start printing ABS and I need the heated bed to work.

What do I have to change on my board? What kind of fuse do I need?

Any advice is appreciated.
Thanks!

Cathleen

Edited 1 time(s). Last edit at 03/20/2018 08:31AM by cthzi.

For a bed of that power, you would be much better off using 24V power. Then the bed wires, bed mosfet, and fuse (if you need one) need carry only about 12.5A instead of 21A.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hi,

Thanks for your answer.

I thought about that but the heated bed is for 12V only.

In that case you will need to use a good DC-DC SSR (not a SSR-40DD, those are no good for this application) or MOSFET switch to control the bed heater. And very thick wires between the PSU, SSR or switch, and bed heater.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hey,

Yes, I will do that. I read about SSR yesterday and you're right. Thanks for the advice with the DC-DC SSR.