Sudden temperature drop 230C to 225C

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satoer
Posts: 436
Joined: Mon Oct 01, 2012 8:00 pm
Location: Netherlands

Sudden temperature drop 230C to 225C

Post by satoer »

Lately I'm trying to experiment with ABS. But every time I print at 230 degrees C (or higher) the temperature drops after a couple of minutes printing (See 51:30 in curve).
temprature curve.jpg
I can't find any explanation of this temperature curve online. I Guess the bottom part is the power consumption. The big brown line the average hot end temperature the red line the current hot end temperature and the purple the wanted temperature. So Suddenly the temperature drops 5 degrees. (This is during printing, and not at printing start. So its not because new fillament is cooling it down.) And the control electronics give full power without success. Room temperature is about 22- 23 degrees.

Has anybody an idea why I can't get the extruder hotter?
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rad
Posts: 36
Joined: Thu Apr 18, 2013 7:33 pm

Post by rad »

I had this behaviour once when one of my extruder thermistor gave in.
-> it rises it's resistance leading to a colder temperatur reading then the actual causing the heater to go at it's limit. The real extrution temperatur then is very high much higher than your settings.

Also possible your temperature sensor lost mechanical contatct to the hot end or the heater element itself.

You should check what your plastic does. If it looks like it's 225 degree or if it more looks like thats it's say 260 degree or more.

Also once when it's cold compare the thermistor reading if the bed and the extruder temperatur still show the same room temperature. (Or disconnect and measure the thermistor should have 100kOhm at 25deg.)

satoer
Posts: 436
Joined: Mon Oct 01, 2012 8:00 pm
Location: Netherlands

Post by satoer »

I'ts not the thermistor I think. When its cold the heat bed thermistor and the hot-end thermistor give the exact room temperature. I don't have experience with ABS, but it extrudes and "glues" fine without smoking or decoloring at 218-225 degrees C.
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dognotdog
Posts: 181
Joined: Tue Sep 04, 2012 9:22 pm

Post by dognotdog »

I think that temperature drop is an artifact of temperature regulation. You can notice how the heater was practically off for some time just before the drop. I am seeing similar behavior on fast prints a lot, where it seems that the default PID settings are incapable of keeping the temperature up, and temperature always falls about 5°C below the set value.

satoer
Posts: 436
Joined: Mon Oct 01, 2012 8:00 pm
Location: Netherlands

Post by satoer »

I've found the problem why the temperature suddenly dropped. It's the fan that cools the printed object after a few layers kicking in. It cools down the extruder too much. Haven't found a solution yet besides turning of the fan while printing ABS.
My Felix 1.5 printed designs on Thingiverse
E3D V6 Hot end upgrade for your Felix
Tweezer bracket for your Felix
Led bar upgrade for your Felix

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