Heated bed failure  

Re: Heated bed failure

Simple fix; replaced cable with wire rated at 15 amps; noticed thermistor wire was also wearing through, so fixed that at the same time.

Back printing. Amazing thing was that I didn't have to adjust the bed after re-assembly. Did a check and it was still spot on.

Peter

Re: Heated bed failure

Good thing you were able to find the solution so fast!
And that graph makes me think I need octoprint myself 🙂

Re: Heated bed failure

Yup, it could have taken a while to find and fix.

Octoprint is brilliant; have it (with webcams) on both printers. I am currently working on powering the Pi from the printer PSU. I have a couple of buck converters which I will be building into a Pi case with a webcam bracket.

Peter

Re: Heated bed failure

Good info Peter!

THanks!

On the subject of OctoPrint, i was looking into getting it for myself. Is there a way to setup multiple prints with one rasberry Pi? Or will i need a PI for each?

Re: Heated bed failure

You will need one pi for each.

I have got my pi powered from the Rambo itself. There is an addition 5v header on the board that I ran to the 5v on the GPIO header of the pi. It is actually powering it, the pi camera and and led light strip.

Re: Heated bed failure

Good deal, Looks like im in the market for 2 Pi's then. I also backed that kickstarter for the PINE64, (another mini computer) dont see any reason why i cant make it run Octoprint, for my 3rd printer.

Thanks!

Re: Heated bed failure

For some reason, one of my Pi's is drawing over 2 Amps from the 5V PSU. I know this because the power LED on the Pi is flashing occasionally.

A strip of LEDs running on a 5V rail will draw 20mA per LED. Richard, I think you may be very close to the limits for RAMBo.

Ideally, a LED strip should be run off a 12V supply, with a number of sets of 3 LEDs in series, plus a current limiting resistor. I prefer not to blow up another RAMBo, hence why I will be also powering it from the PSU via an efficient regulator.

In fact, I was thinking about lighting as well, but controlled by Arduino with an ultra-sonic sensor to detect when I am near to the printer, so it kan turn the lights on when I am close and save money when I am out the office.

Peter

Re: Heated bed failure

Yeah, I'm pretty sure I am close to the limits of what the Rambo can provide power wise. The led strip I am using is usb designed for 5v.

I'm thinking of pulling the pi power off the Rambo and getting a power strip that I can plug it, the printer and the light strip into so that I can power them all on/off with a single switch. Not quite as neat as just having one power lead for everything but I don't want to stress the Rambo more than necessary.

Re: Heated bed failure

Hi Richard

USB lighting is not the most efficient available; 40% of the power is wasted as heat. Also bare in mind that a USB light can take up to 500mA.

Simplest thing to do is to get a LED strip designed for 12V. They can be cut at every third LED. They have 3 LEDs + resistor in each set. Cut to length and wire from PSU 12V output.

Peter

Re: Heated bed failure

A bit more information on my issue. The wire break was in fact just outside the RAMBo housing, within the sheathing just past the cable tie. I guess this is where most of the flexing occurs.

At the point of hte break, the plastic had melted and some strands of wire were poking through:

Peter

Re: Heated bed failure

I thought might be having this problem, my display was showing that my heated bed was only getting up to 24 degrees(compared to about 18 when everything is off)when i was trying to warm up my printer to 50 for PLA. But checking closer the bed actually seems to be getting considerably hotter than that. I don't have a thermometer to measure it, but it feels much closer to the 100 degrees for ABS, and I would guess closer to 120.
Do you have any ideas on what could cause this? After visual inspection the cables look ok. Could the the thermocouple have worn out? Thanks for any ideas.

Re: Heated bed failure

re: OctoPrint

I just power my Raspberry PI separately and keep it running all the time. Don't have to worry about doing clean shutdowns this way.

Re: Heated bed failure

Kenny

Thermistor, not thermocouple. Completely different things (but they do a similar job).

I don't think that thermistors "wear out". they either tend to work or they don't.

Check the position of the thermistor; it is obviously getted a few degrees warmer than ambient. I presume you haven't replaced it at any time? If you have then you may well need to make a firmware change.

Measure the resistance of the thermistor at ambient. Hold it between two fingers for a few seconds and measure again. Post the values here and I may be able to see if it's OK or not.

Peter

Re: Heated bed failure

I haven't replaced it ever. I measured 1.34 kilohms at ambient and 1.20 after I held it for around 20 seconds. The initial position looked good, with the bead right under the hole in the center of the build plate. I did notice a small black spot inside the bead, is this normal or is that a sign of some burning?

Re: Heated bed failure

Kenny

The thermistor should measure 100K Ohms at 25 degrees C, decreasing as the temperature increases (NTC). Looks like yours is not working as it should. Either contact support via live chat on the shop pages or you can get a replacement here: http://e3d-online.com/Electrical/Components/100k-Ohm-NTC-Thermistor-Semitec

Note that you have to replace it with the exact same type, otherwise you will have to make some changes in the firmware.

Peter