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Rep .092 Heating issues
#1
I have an mk9 12v 40w heating cartridge and when heating up extruder it heats up fast to 90C and then it very slowly heats up to a max of 140C before it starts to fail.

Here are a few things about my build:

I am not using the small circuit board, I hard wired the connections.
I am using the davinci heating wire to a lever nut, to the mk9 heating wire/cartridge.
I ended up cutting some extra slack to the mk9 heating wire that was extra and my temps increased (maxed out at 120C originally now 140C)
When I lift up on the wires to the extruder the temp increases to a max of 145C.
Thermistor is NTC 100k.

Anyone have an ideas of what it could be?
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#2
what is the temperature when extruder is cold ? may be the davinci thermistor table do not fit well your thermistor
are you sure the thermistor has good contact with nozzle ? need to touch the extruder and must not move - using some thermal conductive element - this was mentioned by Keith in the past : https://forum.voltivo.com/showthread.php?tid=8263
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#3
Thanks Luc. Your very helpful. By the way another guy on another forum bought the same thermistor as me and his extruder heats to 200C and then burns out with false reading. So it seems like this thermistor has a common issue.

Room temp readings seem normal at ~26C. It is a tad bit lower than what I normally would expect something around 30C.
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#4
so it means the thermistor table is not correct for this thermistor, may be it says it is 140 but actually it is 250 or higher so cannot go up.

you may verify by requesting a temperature of 110, and see if filament melt at nozzle contact, if yes it means real temperature is higher than calculated using table.

you may need to change minimal extrusion temperature if you want to extrude at 110 or lower depending of your tests

you may use you extruder by changing you reference temperature or find another thermistor

I remember someone provided an excel sheet to calculate a new table for new thermistor on this forum
Edit: found it https://forum.voltivo.com/showthread.php?tid=8308
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#5
I thought about that. last night I pushed some filament in at around 100C and it didn't melt fully but about 1-3mm came out. Does Repetier have a required temperature to use the stepper motor? I tried using the stepper motor in rep host manually and nothing happened. Stepper motor is 12v 1.8 nema 17.
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#6
in configuration.h for extrusion:

/* \brief Minimum temperature for extruder operation

This is a saftey value. If your extruder temperature is below this temperature, no
extruder steps are executed. This is to prevent your extruder to move unless the fiament
is at least molten. After havong some complains that the extruder does not work, I leave
it 0 as default.
*/
#define MIN_EXTRUDER_TEMP 170


and for changing temperature in printer menu

#define UI_SET_MIN_EXTRUDER_TEMP 170
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#7
Sweet thanks. I'll check out the table for my thermistor. I think the seller had a table too.

*Edit* Here is description of thermistor

"Item:NTC Thermistor Model:B2-100-3950-1 R @ 25: K 100K-1% B25/50:K 3950-1% Element:Thermistor,type MJB2 Characteristics (1) Electrical characteristics A: Resistance value: R(25°C)=100K±1% B: B Value: B=3950±1% (calculated from resistance value at 25°C and 50C) C: Insulation resistance 50MΩ or over by DC500V megger (between glass and lead wire) (2) Thermal time constant (τ): τ≤10~17s (in still air) (3) Thermal dissipation constant (δ): δ=1.1~1.6mW/°C (in still air) (4) Operating temperature range:-50~+260°C Outgoing Inspection The product shall be inspected at every delivery lot inspection items,sampling quantities and sampling acceptable standard are as follows. Inspection Item Sampling acceptable standard Remarks Resistance value n=20, Ac=0, Re=1 2.3(1)(a) B-value n=10, Ac=0, Re=1 2.3(1)(b) Insulation Resistance n=5, Ac=0, Re=1 2.3(1)© Shape & Dimension n=5, Ac=0, Re=1 2.2 Appearance n=5, Ac=0, Re=1 2.2"

One guy said he is using EPCOS table and its working fine. I might try that first before looking for custom table.
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#8
I think this is the table I need:

https://cae2100.wordpress.com/2014/03/08...or-marlin/

Does that table look right?
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#9
Hey Luc,

There are two tables used with R1 & R0. Is R0 the heated bed and R1 the extruder?
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#10
extruder table is USER_THERMISTORTABLE0 but supplier table won't work as davinci circuit is specific https://forum.voltivo.com/showthread.php?tid=8308

that is why I Tom tried to build an excel calculator, (in the previous post I gave you)
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#11
Okay I'm understanding now. I'm using my motherboard resistors, instead of circuit board. Since 1.0a uses MB resistors instead of circuit board. I need to find out what resistors are being used on my MB before I plug in the data for a table. I'm assuming they are the same value as the circuit board.
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#12
Hey luc! Last question I promise! Since I'm not using the small pcb circuit board and I have a 1.0a wouldn't my resistors be different from the R0 R1 and R2 resitors? Attached is pics of the resistors near my thermistor wires (Orange and black) I don't see the R0, R1, and R2 resistors.


I think I found my r2 resistor here


Does it matter that the r2 resistor is not near the thermistor connection? Sorry I'm a noob[Image: image-5.jpg][Image: image-6.jpg]
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#13
I think you mixe board r naming and thermistor table r naming
on old boards
R1 = 4700 (R27 on board, reads 472)
R2 = 10000 (R29 on board, reads 103)

For the bed NTC it is
R1 = not populated (R28 on board)
R2 = 47000 (R30 on board, reads 473)

I am not sure what are the ones for new generation and I am not electronician sorry, but I see your r27/r29 seems different than mine
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#14
My board looks new. But R27 is 1k ohms (1111) So wouldn't that have to change in the REP code from R1 to R27?
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#15
As I wrote, your board resistor values looks differents than mine which make sense as 1.0 and 1.0a use different tables. but that said, i cannot confirm r27 on 1.0 is same usage as 1.0a, you can see jumper to reset are different , so others codes may also be different.
as I do not own an 1.0a to test, and as I am far from being an electronician neither a thermistor expert, sorry honestly I cannot comment more on this.
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#16
It's okay. I got it working. It was my cable and my thermistor was in a bad location. But I still think I need to modify my table. Or I could technically use a lower temp when printing. I just need to change direction of stepper motor and I'm good to go. Thanks for your help.
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#17
The 3950 100k resistor has low resistance for high temps and high resistance for low temps. So using the table with the R0 R1 R2 values I can't get a correct table created for my thermistor.

I honestly think this is my best bet:

https://cae2100.wordpress.com/2014/03/08...or-marlin/
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