My 2nd hot end does not seem to be getting up to temperature.

My 2nd hot end does not seem to be getting up to temperature. Both hotends are set to 250. The heated bed is set to 95 and is slowly getting up to temperature. Any advice? Oh…and what the heck??? My printer has shut itself off twice now. It Just quietly decides to power off. The power supply fan stops and all lights go out.

Power supply not up to the task? Any wiring/connectors getting hot? Polyfuses on a RAMPS? Selected the right thermistor table?

sounds like a brown out, your printer is either drawing more current than the psu can provide, or there’s a short somewhere, from the sounds of your 2nd hotend you probably have a dud heater cartridge/resistor

This is a Rambo board. It has a 15amp fuse (automotive style). I have used the 2nd cartridge via the 1st extruder’s heater wiring before and it seemed to work OK. It could be that the heated bed draws too many amps since it has always taken a bit of time to heat despite the number of wire sets powering it.

How about heating the bed up first before the hot ends? The bed draws the most current initially and then tapers off.

It seems that heating up the nozzles before the bed will let the nozzles reach temperature, but it shuts off. It seems that heating up the bed first will not let both nozzles get to temp, but it just turns off the temperatures instead of shutting the whole printer off. I do not care to try the tests out too many times to see if the results are consistent.

Still could be the power supply. It the bot draws a lot of power the usb will be taxed also and then loose connection.

Power supply ,power supply & power supply

I now remember that back when I was considering the dual extrusion, I did math and figured out that my RAMBO board might not be able to supply enough power to run everything without blowing the fuse. It is a 15 AMP fuse. The heater cartridges are 12V 40W. The heated bed is an Onyx heating bed (probably earlier than version 5) and is 12V or 24V, but I do not know how many W it is drawing. It may be that I am lucky my power supply did shut off instead of just going up in smoke.

Does anyone know how to properly measure the Watts being used by each piece without damaging the circuits or getting myself electrocuted?

Use an ammeter in series with the loads, then, P=U*I. At just 12V, there is zero risk that you’ll electrocute yourself. You can connect and disconnect heater leads while the board is powered up without the risk of damaging it.
The Onyx is rated at 10A (so 120W, as are most other heated beds), and each 40W heater draws another 3 to 3.5A. So you’re ok with just one heater, but two are pushing it.

So…I guess this means I may be using 120+40+40+5*12=260 WATTS of my power supply assuming my steppers are 12V at 1A which I think might be an exaggeration.

I will have to check the power supply to see what the specs are. It was a good power supply compared to most. I do not know if the RAMBO can handle it all, but I suspect the 12A fuse would blow if that was the case.

My power supply is a 480W one.

Is that an ATX supply?


Especially the cheaper ATX supplies don’t like it when you’re only loading the 12V rail(s), since it might increase the voltage on the 5 and 3V3 rails above safe limits and trigger a shutdown (group regulation). The usual fix for that is loading the 5V rail with a (pair of) load resistor(s) that draw a total of about 0.5 to 1A.

@Thomas_Sanladerer or attach something like a fan to it?

@Thomas_Sanladerer oh heck…I could move my raspberry pi and fan onto the 5v connectors.

That might already be enough to keep it from tripping. Since it’s been working just fine for you with one hotend, it’s likely that the second one is just barely pushing the 5V rail past its limit, so anything from a fan, RasPi, or maybe even the Arduino should be enough to get it back on track.

@Thomas_Sanladerer Thanks much. You may have saved me alot of stress. Now my only concerns are finding the 5v wire sets, doing PID training of the hotends again and possibly changing the maximum power setting because I think my first hotend likes to overshoot the temperature on the heating cycles. Those heater cartridges pack some punch.

Oh yeah…and I have to wonder if the amperage that the controller will pull will blow the 15A fuse. With the hotend, 4 motors, and heated bed, I really do not understand how all of that could be under 15A. Maybe I am misunderstanding the point of that fuse.