Thanks for the reply.

Sorry for more stupid questions, I just like to know why.

Is it because it's not electrically possible or because of a firmware limitation?

Regards,

Les

It's not electrically possible, it was not designed for this, the traces are not thick enough, etc.

Thank you for the clarification. :-)

I ordered this very big MOSfet for my 400W bed, it works well for me:
I can't put a link, so google:
"3D printer parts heating-controller MKS MOSFET for heat bed/extruder MOS module exceed 30A support big current"
It has opto-coupler so you can use it at different voltages and it is <10$
SSR are better for much higher voltages (>100V)

I was kinda thinking of doing the same thing. I have some VBFM (very big friggin mosfets) i was using to build monsterous ECig mods at extremely high amperage, was considering hooking up one of those. (should EASILY support 24v at 20 amps (can take truly massive amps without heatsink). Much cheaper than a 30 dollar SSR.

Might be a little overkill… but I really want the spindle controllable via smoothie. Think the hardest thing is gonna be figuring out how to wire it up and what size resistor I need on the legs to drain it when switched off.