3 hours and my onyx bed is only at 89c

[clarks]

Any idea why it won't go higher? Can this be sped up w/o a lot of complicated electronics?

my build platform is Onyx+1/4" aluminium heat spreader + kapton tape

Is there any adjustment I can make in firmware, or on the RAMBO?

thanks,

clark

[Polygonhell]

Any idea why it won't go higher? Can this be sped up w/o a lot of complicated electronics?

my build platform is Onyx+1/4" aluminium heat spreader + kapton tape

Is there any adjustment I can make in firmware, or on the RAMBO?

thanks,

clark

I'm surprised you get it that high with 12V and 1/4inch of AL on it.
What you really have is an enormous heat sink on top of it.
It's a big bed, with 12V I get a bit over 90 with a glass bed on top, the best solution is to increase the voltage slightly.
Having said that I print ABS on mine with the bed set to 80.

[clarks]

oh, that makes sense. How do I increase voltage in the firmware, or are there pots that can be adjusted on the RAMBO? My multimeter measures the voltage at the heat bed points as 11.33v

thanks

[Polygonhell]

No you need a higher voltage power supply feeding the heated bed input.

[clarks]

and the RAMBO board will be okay with a higher voltage power supply plugged into the bed ports?

[cambo3d]

as long as you keep the current in check, remember the rambo has a 15amp fuse for the heat bed circuit.

also, how did you wire your heat bed?

[jetpad]

I added this power supply to just power the bed. http://amzn.com/B006QSOF60

Now the bed heats up to 90C about twice as fast as the hot end heats up.

[Eaglezsoar]

Hey, Jetpad - glad you got it working. Cambo3d is one of the first to use a 24V power supply with good results.
He is a trail blazer and you should read his entire build log.

[Broose]

The Rambo board can handle the 24V, but you need to be really careful about the connection to the board. If the connector or wires have too much resistance due to a bad connection, the connector can heat up to the point of melting. I suggest if you use that Amazon 24V power supply, that you turn the voltage adjustment down to the lowest level. It does work really well and I have no problem getting the bed temp up to 110C fairly quickly.

[clarks]

thanks, i'll try it.

clark

[clarks]

@Cambo3D,

my heat bed is wired with 18 gauge.

clark

[geneb]

You might try adding another set of 18ga wires to it and a fourth wire from the power supply to the heated bed connector on the RAMBo.

g.