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Thermistor tables for bed and extruders
#1
Hi after some discussion with David about bed and extruders beeing in temperature defect - we agreed preheat is a workaround but not the best solution.
After checking the root cause, it looks like to be the thermistor tables which are not good enough- working for some of us but not for all.
Also having this not accurate, table bring issue at start for some printers but also may bring issue when using high temperatures and damage the printers as the sensitive parts are the high and low temperatures.
David is trying to rebuilt the thermistor table using the reprap calculator http://nathan7.eu/stuff/RepRapCalculator...TempLookup

Anyone knows Where did these tables come from and what is the beta value of the thermistors? (in current FW)

Every help is welcome Smile
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#2
I have been trying to improve my print quality and decided to check my extruder and bed temps. The extruder is reading 170 when the printer thinks it at 200.
Has anybody come up with better thermistor tables?
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#3
David is working on this https://github.com/luc-github/Repetier-F.../issues/83
right now he is working on bed - every help is welcome :cheer:
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#4
I'm late to the party as usual, but here is my empirically derived extruder thermistor table.
Hopefully it can save somebody some work.
My platform and extuder now agree exactly with room temp when cold, and are within about 1/2 degree of set point when at operating temp.
I drilled a 3/32 hole in the extruder right above the thermistor hole to stick my thermocouple into for accurate readings.
Worked a treat!

Cheers! https://forum.voltivo.com/images/extrude...ation3.pdf
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#5
Thanks a lot :cheer: - I will check that
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#6
Guys, there is a crucial error IMO on the hot end from the factory. If you pull the factory silicone off the leads to the thermistor you will find no mechanical bond between the hotend and thermistor. What i have done is use some ultra high temp copper form-a-gasket....just put a small dab into the thermistor hole then pass the thermistor back into place. Another small dab to secure the wires, let it cure, and thats it. This fixed my random hot end temp fluctuations.

Kieth
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#7
really ? no mecanical bond ?
I will try your suggestion, thanks a a lot
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#8
Do you thing thermal compound used for CPU heatsinks would work?
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#9
It does.
I used some Ceramique CPU compound and it worked great for the thermocouple test.
I don't see why it wouldn't work fine for the thermistor. If it's silicone based like most it would be good to 500F.
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