Bed Heating troubles for ABS
I received my i3 Mk2S kit about a month before I expected it, assembled it, and I've been having a great time printing and learning.
I'm an absolute novice to 3D printing, and the Prusa i3 Mk2S has been an absolute delight.
I tried printing ABS for the first time the other day.
I tried Benchy, setting nozzle temperature to 255C and bed temperature to 100C.
Here's where I ran into trouble.
I observed that the bed heating LED was constantly on and the bed temperature reached as high as 95C, but never hit 100C.
The first few layers printed fine, and I noticed that the bed temperate slowly declined, then the print operation stopped,
the LCD reported a bed heating error, and the nozzle and bed heating settings reset to zero.
The ABS adhered well to the bed, so that wasn't a problem. The few layers of ABS that were printed seemed laid down nicely as well.
First, I think the ambient temperature was probably too low (maybe 18C to 20C?), so that probably didn't help matters.
Second, the system would not allow a preheat operation, reporting bed heating error on the LCD.
I shut the printer off for a few minutes and tried again. The system then preheated okay for PLA and I could
unload the ABS filament.
So, I assume there is a PTC fuse in the power supply that had overheated.
I've read recommendations in the forums that the voltage from the Power Supply to the heater connector on the RAMbo could be increased by
adjusting a trimmer potentiometer in the Power Supply.
However, I would like to know what official advice might be offered before I take that route.
Is there a particular range of ambient temperatures versus bed settings that are recommended?
Is there something that I should do to ensure the bed is getting enough power to reach bed temperature settings?
Re: Bed Heating troubles for ABS
Well you are very unlikely to get official advice here.
The posters on these forums are 99.99% users of the printers.
You need to ask PR support team who can be contacted via the shop pages. Or you could listen to us users who tend to give more practical advice 😉
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Bed Heating troubles for ABS
Thanks Peter.
Like I mentioned, I'm an absolute novice to 3D printing and I'm figuring out information sources.
Your note and direction are much appreciated and I'm looking forward to hanging out in the forums.
Dwayne
Re: Bed Heating troubles for ABS
Thing is, all the electronics are fine up to 24V, the fans will tolerate 15V and the motors are current limited.
You only need to increase the PSU output voltage by 0.5V to significantly increase the heating ability of the bed (and nozzle) and that work-around has been carried out many times by users here without problem.
Printing ABS requires absolutely no air flow around the printer and consistent ambient temps. Therefore an enclosure is the best option for many. However some of us will not print with ABS for a few reasons, including the toxic fumes and its lack of biodegradability.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Bed Heating troubles for ABS
Full disclosure: I have a self built clone of a MK2S, and two different clone MK42 beds.
I think the MK42 is a bit marginal on power.
The extruder cooling fan blows air on the bed in the early layers, and this is much worse in the MK2S extruder design because of the way the PINDA mount was redesigned.
This cooling is enough that when you print a small model in the centre of the bed, the bed can't keep up because it's not powerful enough. Prolonged cooling when the bed is powered causes the thermal runaway error.
Options are:
- move your small print away from the centre of the bed so that the print isn't over the top of the thermistor. Then the localised cooling won't be reported back to the printer.
- disable thermal runaway protection. (Probably not the safest idea)
- increase the bed power.
Increasing the bed power can help a bit. The bed is approximately 0.8 ohms and an extra half bolt will add about 15W of power. Probably not enough to make a difference. You could probably add a bit more voltage. The component that is least able to stand the increased voltage is the extruder cooling fan. YMMV.