Heater bed can't keep up

I have been having an issue with my heater bed keeping up with a print anytime I have any kind of fan going. I was able to block the air (from the extruder fan) from hitting the bed and that works. When I install a fan for the nozzle though, the air from that cools the bed and it shuts down the print. Does anyone have some tests I can run or have a seperate psu idea for the bed? It's for a folgertech prusa i3.

I can't even get an auto tune to work. It times out because it can't reach its target. Seems like it's not getting enough power or something?

you need if not already have it a funnel to direct the air only at the nozzle, lots of them on thingiverse, you can also I believe change how fast the fan runs in slic3r so just turn it down some until you do not have a problem.

I got the auto tune to work and input the new values. The only time turning down the fan works, is if its off or so low that it doesn't cool like it should be. I have had to but the printer in an enclosure, which has helped, but not enough. It feels like if I even breath on the bed the temp goes down. We will see if the new values work and then I will update.

New values didn't work. It gets to target heat just fine, but the second I turn the nozzle fan on, it loses heat and can't get back to target. It remains about 5 degrees below target. Any other ideas?

What voltage is the heater getting? Perhaps the wrong FETs on the RAMPS card not turning on all the way?

- Tim

Edited 1 time(s). Last edit at 04/30/2015 10:09PM by tadawson.

1) Make sure that you are using heavy gauge wire to the bed, as in 14 AWG minimum.

2) 24 volts to the heated bed (via SSR) will certainly fix the problem.

I'm feeding my 300mm diameter Onyx with 19V from a de-tuned 24V supply, and it has no problem holding 110C or getting there from cold in 5-6 minutes.....