Thu Jun 28, 2018 12:47 pm
This may not be of much help but, worth the one-minute read…
Five yrs ago I had very similar problems and did quite a bit of work to understand the cause/solution… That was on a DaVinci printer I hacked.
I no longer have that printer and tossed out the stack of paper/notes so I recommend Googling a bit if problems continue after replacing with the correct thermistor and resetting PID to default. Check RepRap website (and Marlin…)
Here’s what I remember…
I tweaked the controller code, thermistor tables, manually set the PID, auto-tuned the PID… I jimmied up a resistor test network… I even added my own design for the thermistor circuit.
If you haven’t yet discovered, the code (for controller) may have look-up tables that are specific to various thermistors thus, if replacing a thermistor, you must use the same one (or tweak the code to use the correct one).
Two of the new (correct) thermistors I tried turned out to be bad. After testing a group of them with homemade circuit and heat gun (and ice-cube), I needed to reset the controller to use the default PID values - custom tuning and Auto-tuning caused nothing but headaches for the temp’s stability such that fluctuations of ‘one’ degree outside the envelope stopped the printer from printing. (There are code settings for ‘how much time to wait’ which can also be commanded via the cmd line input in Simplify)
During discovery, I disabled (in the code) the waiting for temp stability - that did the trick (temporarily). Finally, I had time to re-do all the settings and PID with a new thermistor and all was good.
I built two new printers from kits and after one year, the same problem happened - this time I knew enough to use the correct thermistor (and, again, found the first new one was bad!!! )…
Sorry I can’t be more help but, I recommend resetting the PID to default, disconnect the existing thermistor and use some jumper wires to a new thermistor and heat it (with hair drier, soldering iron…) to test it before installing on the bed…
3D Print Parts
https://www.thingiverse.com/Still_Breathing/designs