SoliForum - 3D Printing Community — Hotend Doesn't Hold Temperature

Re: Hotend Doesn't Hold Temperature

2014-04-29T23:36:17Z

Happens more often than you'd think. Glad it all worked out.

Re: Hotend Doesn't Hold Temperature

2014-04-29T18:23:14Z

Solved! You all were correct, just needed troubleshooting with a multimeter.

The board was putting out a constant 12.3V to the hot end even when the hot end lost heat. When I checked the voltage at the hot end, it was intermittent. I found out that at a very specific point in the wire going to the hot end, the wire must have had a break. When I wiggled just that part of the wire, connectivity went to zero. So I cut out the bad section, soldered a piece of wire in, taped it up and closed everything off, and now it is working perfectly!

Thanks again everyone for helping. It would have taken me a long time to arrive at this conclusion on my own. Who would have thought a wire could break on the inside when it looks perfectly normal on the outside!

Re: Hotend Doesn't Hold Temperature

2014-04-29T14:32:12Z

ronsii wrote:

The best thing I would think to do is start eliminating possibilities, like Ward says test the thermistor... insert a cold extrusion gcode in a file to print then let it go... I would think the thermistor is good though otherwise you peek would have melted and other problems would have shown up. If you have a multi meter connect some extra wires to the hotend heater(at the board) and monitor the voltage on it while printing this will tell you a lot.

+1 just have to do some troubleshooting.

Re: Hotend Doesn't Hold Temperature

2014-04-29T05:16:24Z

Thank you everyone for chiming in. I played around with the print speed and bed on/off a little and I could definitely see a correlation between nozzle temp. and bed on/off as well as extrusion speed. If I slowed down the print, the nozzle temp. went back up. But then it would start falling again 5 minutes later despite the slower speed.

I will get my multimeter and try all of the suggestions tomorrow. Need some sleep for now. Thanks again.

Re: Hotend Doesn't Hold Temperature

2014-04-29T04:52:08Z

It doesn't look like there's any correlation between your problem and the bed heater on/off, which means the power supply is probably not to blame (if it was drooping, this would make a big difference).

I'd be checking the heater resistance at the board connector, and wobbling the connectors and cables all the way along to check that the heater and it's wiring wasn't faulty. If it's failing open circuit intermittently, or the resistor itself had baked and increased a bit in resistance, then you'd see this kind of problem (output on full-tilt but no heat).

Re: Hotend Doesn't Hold Temperature

2014-04-29T04:41:49Z

The best thing I would think to do is start eliminating possibilities, like Ward says test the thermistor... insert a cold extrusion gcode in a file to print then let it go... I would think the thermistor is good though otherwise you peek would have melted and other problems would have shown up. If you have a multi meter connect some extra wires to the hotend heater(at the board) and monitor the voltage on it while printing this will tell you a lot.

Re: Hotend Doesn't Hold Temperature

2014-04-29T04:31:25Z

If you open up the PSU where the AC wires connect to the board. If it's a problem you will be able to see it. I am not convinced that is your problem though. Maybe a bad thermistor? Some one with more expertise should chime in on that.
In the mean time you could test it by letting it go through it's process of cooling by itself. then without stopping the print try pushing the filament though by hand to see if it is indeed cooling or just a funny reading. Of course you would have to try this with the tension arm loose or quickly loosen it when you pause it. Or can you feel that it is actually cooling down. Even 160 is really hot to the touch.

Re: Hotend Doesn't Hold Temperature

2014-04-29T04:21:37Z

I tried turning the bed temp. off during the print to see if that would allow more power to flow to the extruder. It seemed to help initially but then the extruder temp. kept dropping anyway (see attached graph). If I do need to replace my PSU, what would you recommend I buy? Also, which leeds tend to get hot, is it something I could solder myself?

Thanks for all the great advice!

Re: Hotend Doesn't Hold Temperature

2014-04-29T03:45:48Z

The main wires going into the PSU get hot and the solder melts off the connection. If your having issues with power the E3D will certainly aggravate them. Good news is for about $30 bucks you can upgrade your PSU.

Re: Hotend Doesn't Hold Temperature

2014-04-29T03:39:10Z

No LED flicker. The wires going into the heater look solid. I just started a PID tune and I'll test it again after I enter the new values.

I've been thinking of upgrading to an E3D and this is a good excuse to do it. But I wanted to make sure that the problem isn't something else. What are "PSU" issues?

Re: Hotend Doesn't Hold Temperature

2014-04-29T03:25:45Z

And your not getting any error? My guess is PSU issues but like I said earlier it could be many things. Check all the connections especially where the heater wires enter the plugs those are a common source of problems. Do your LED's flicker?

Re: Hotend Doesn't Hold Temperature

2014-04-29T03:20:20Z

Attached is a graph of my most recent attempt. I stopped it when it got down to 185C, which was already 15 degrees below target.

Re: Hotend Doesn't Hold Temperature

2014-04-29T03:06:11Z

This could be caused by many things could you post a screen shot of your temp graph as it happens?

Hotend Doesn't Hold Temperature

2014-04-29T03:02:59Z

Everything worked great for 6 months. Now, at the beginning of the print, the hot end gets up to 200 C but as soon as the print starts, it steadily loses temp until I have to stop it because it goes below 160 C. If I pause, it will go back up to 200 C. It seems like the resistor is just not powerful enough anymore. Does this mean the resistor is dying? Or does it have to do with the transistor on the board? Oh, and it's an SD3 with original heater and thermistor. Thanks.