temperature readings

hi all... this is my first post here. please be gentle..

so i have an issue with temperature readings. i purchased an E3D All-metal v6 HotEnd Full Kit - 1.75mm Universal (http://amzn.to/1bj5Oyk). i tried using it with ABS-T filament from hatchbox. using pronterface as interface and marlin on a reprap 1.4.

i noticed that even thought the software reads 230C - or higher, tried up to 255C - the filament is not really melting and oozing off the nozzle. even if i manually push it in. it's rather coming out real slow in a semi melted state. also i used a infrared thermometer (http://amzn.to/1Eaj8jN) to check the hot end temperature and according to that thing the temperature is nowhere near 230C. more like 100C. i have read pretty much all there is to read about that hot end on the forums and the e3d-online site about marlin settings:
TEMP_SENSOR_0 5
HEATER_0_MINTEMP 5

i tried contacting the e3d-online staff for help but so far i just got "bonnie" to tell me to change the TEMP_SENSOR_0 setting to 5. after i actually included in the email that i already did.

also i asked about PID numbers. after i did an autotune on the pronterface console i got 3 different sets of values and not sure shich one to put in the header file.

not really sure how to troubleshoot this. i'd appreciate any help with that.

thanks...

Edited 2 time(s). Last edit at 04/22/2015 11:43PM by malemodel.

The infra-red thermometer will be pretty much useless at reading the temperature of your hot end. Try heating your bed to 60 degrees and see if the thermometer gives you what you expect. Chances are you'll get a lower temp.

If any plastic is coming out at all, then it's being melted. Your extruder will chew through the plastic rather than push it out, if it's not hot enough. Try send a command to the printer to extrude some - G1 E20 F100 - and see if it extrudes OK.

Regarding PID tuning, all three values get put in the config file. You'll get Kp, Ki and Kd from PID tuning, which you record on the following lines in Configuration.h:

#define DEFAULT_Kp 22.2
#define DEFAULT_Ki 1.08
#define DEFAULT_Kd 114

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

hey there 3dkarma... just got a multimeter with a thermocouple. i don't have a hot bed...
when the thermistor - via the pronterface - reports stable 230C the multimeter stayed around 190C.

i guess i could 'lie' to marlin and put something like 275 - 280 as HEATER_0_MAXTEMP but then what's the point of the thermistor and it's "accuracy". is there a way to calibrate within the software so the readings match the reality?

thanks...

There's a thread here [forum.e3d-online.com] that discusses why there would be a discrepancy between a thermocouple and thermistor reading. In short, the thermistor is embedded within the block so will give a higher reading than a thermocouple touched to the outside.

I understand that Hatchbox is pretty good filament, but have you tried a different roll to see if you've got a bad batch?

The only other thing I can think of is a bad thermistor wiring connection - it might be worth checking out.

Regarding software, the only thing I can think of to prove whether or not the thermistor is reading accurately is to take a temperature reading while it's in boiling water (water that's on the hob and actually boiling, not water that's been boiled). You'd have to waterproof the connections. It's a bit much to have to take things apart to do it, though. You could try using different 100K thermistor settings if they give you a different readings, but if you suspect a bad thermistor I would be tempted to replace it instead (they are very cheap).

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

To get a more accurate reading from the thermocouple, feed it into the hot end in place of the filament.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

ok... i'll try both suggestions. although i did stick the thermocouple right next to the heating cartridge. this hot end (http://e3d-online.com/) has crack in the hotend block where the cartridge fits and the thermocouple i got has tiny end point i was able to stick right next to the cartridge - touching it - and it still never got above 192C.
how do i test for bad thermistor wiring - i mean it apparently works. what would a bad wring in this case mean?

thanks...

Edited 1 time(s). Last edit at 04/30/2015 01:15PM by malemodel.

Quote
malemodel
how do i test for bad thermistor wiring - i mean it apparently works. what would a bad wring in this case mean?

Thermistors work by varying its resistance based on temperature. Typically a NTC resistor is used, which means as temps go up, resistance goes down. If you have a loose connection, corroded connector, anything that would add resistance your temp readings can be skewed. Check the resistance at room temp (25 degrees C) and compare that to the data sheet from the manufacturer. For instance, the commonly used Epcos B57540G0502F000 thermistor should be 5k ohm at 25 deg. C.

Also are you sure you have the correct thermistor selected in your configuration?

Quote
cdru
For instance, the commonly used Epcos B57540G0502F000 thermistor should be 5k ohm at 25 deg. C.

Also are you sure you have the correct thermistor selected in your configuration?

The thermistor provided with the E3D v6 is an ATC Semitec 104GT-2 (option 5 in Marlin's Configuration.h, which @malemodel has correctly configured). It should read 100 kOhms at 25 C. They're both in the family of 100K thermistors, all of which should read 100k at room temperature. The Semitec should read 5.556 kOhms at 100C - check the temp table at [www.atcsemitec.co.uk].

I've used the resistance-temp table from the datasheet and compared the values to the temp table for the thermistor in pins.h. It correlates exactly, so I seriously doubt the problem is in the Marlin firmware.

The only other thing I can think of is to re-check your configuration.h to make sure you don't have the thermistor declared twice: the second setting will take precedence.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Have you got anything bridging the two wires that come out of the thermistor? They are very close to each other. If you have heat paste (though, most heat paste is meant to be non-conductive), or some tape or something that could be providing a parallel high-resistance path between the legs, this could slightly reduce the overall resistance seen by the controller. It would indicate a slightly higher temperature.

i can't put the probe all the way into the nozzle it doesn't fit. but if i put it right next to the cartridge i get about 10 - 15 C lower then the thermistor. so the thermistor is not terribly off it's just the truth is probably somewhere between those 2 numbers.
so i tried printing pla instead of abs and that kinda works at 230 -235 C setting in the gcode/slicer. kinda works cause it does print the desired dimensions correctly but the layers are moved "to the left" by the x axis all the time... here is my new post on that - [forums.reprap.org]....
if any of you has any advice on how to fix this i'd be very appreciative...

thanks...