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Getting an Accurate Hot end Temp?

Posted: Wed Jan 15, 2014 8:26 pm
by analog_banana
Apparently it's really important to have an accurate idea of what temperature your hot end is.
I know how to measure my true hotend temp by putting a thermocuople down into the nozzle.

Once I know the difference between true temp and the temp reported by the thermistor -
how do I recallibrate the machine to include this offset?

Is there an amount I can enter it somewhere in the firmware?
Or is this something to do with "thermistor tables"???

Re: Getting an Accurate Hot end Temp?

Posted: Thu Jan 16, 2014 3:38 am
by analog_banana
Well I found out how to do this after a long time searching...
There is a post - I think by a staff member, buried in this forum:

http://forum.seemecnc.com/viewtopic.php?f=48&t=1650

This shows how to compensate for an inaccurate thermistor reading in firmware.
Maybe seemeCNC should write up a manual for Rostock max calibrating?

GeneB's guide is fantastic, but surely an official manual by the manufacturer,
including stuff like this would be a good move?

There seem to be so many "secrets" I have had to discover to get this machine working.
I would rather just RTFM than Search TF Entire Forum every step of my kit build.

Re: Getting an Accurate Hot end Temp?

Posted: Thu Jan 16, 2014 3:43 am
by analog_banana
Oh.... repetier firmware only
I guess it can't me done until I upgrade..

Re: Getting an Accurate Hot end Temp?

Posted: Thu Jan 16, 2014 8:09 am
by Eaglezsoar
analog_banana wrote:Well I found out how to do this after a long time searching...
There is a post - I think by a staff member, buried in this forum:

http://forum.seemecnc.com/viewtopic.php?f=48&t=1650

This shows how to compensate for an inaccurate thermistor reading in firmware.
Maybe seemeCNC should write up a manual for Rostock max calibrating?

GeneB's guide is fantastic, but surely an official manual by the manufacturer,
including stuff like this would be a good move?

There seem to be so many "secrets" I have had to discover to get this machine working.
I would rather just RTFM than Search TF Entire Forum every step of my kit build.
It would be impossible to write a manual that covers every possible question or scenario that comes up.
Searching the forums is a necessary evil. One thing that makes it easier is to use Google to search the forum
where you would go to Google and type in site:forum.seemecnc.com search term (the words search term can be anything you are searching for)
Google will then search the entire forum search for the words you are looking for. A lot easier than using the forum search functions.

Re: Getting an Accurate Hot end Temp?

Posted: Thu Jan 16, 2014 10:10 am
by analog_banana
Thanks Eaglezsoar,
Of course I agree with you: an infinite manual, containing the answers to all possible questions, is not feasable or desirable.

I'm am surprised that all the great information here - much of it provided by your good self - on top of GeneB's already excellent manual -
has not been gathered into a new PDF for newbies like myself.

I had a look at examples of manuals for some other machines:
If anyone else is looking for a an in-depth guide to print settings, I can heartily recommend the "LulzBot_TAZ-User_Manual-ebook.pdf‎".
I know it's not for delta printers, but it's "slic3r in Depth" chapter is a really good walkthrough of print techniques with slic3r.

Re: Getting an Accurate Hot end Temp?

Posted: Thu Jan 16, 2014 11:33 am
by Eaglezsoar
analog_banana wrote:Thanks Eaglezsoar,
Of course I agree with you: an infinite manual, containing the answers to all possible questions, is not feasable or desirable.

I'm am surprised that all the great information here - much of it provided by your good self - on top of GeneB's already excellent manual -
has not been gathered into a new PDF for newbies like myself.

I had a look at examples of manuals for some other machines:
If anyone else is looking for a an in-depth guide to print settings, I can heartily recommend the "LulzBot_TAZ-User_Manual-ebook.pdf‎".
I know it's not for delta printers, but it's "slic3r in Depth" chapter is a really good walkthrough of print techniques with slic3r.
I downloaded the Taz User Manual and it does have a good chapter for Slic3r. Thanks for the tip!
As a reminder, Geneb has an excellent Slic3r usage guide as part of the assembly manual. If you take a look it has info that is not in the Taz manual.

Re: Getting an Accurate Hot end Temp?

Posted: Thu Jan 16, 2014 12:31 pm
by dpmacri
analog_banana wrote:Thanks Eaglezsoar,
Of course I agree with you: an infinite manual, containing the answers to all possible questions, is not feasable or desirable.

I'm am surprised that all the great information here - much of it provided by your good self - on top of GeneB's already excellent manual -
has not been gathered into a new PDF for newbies like myself.

I had a look at examples of manuals for some other machines:
If anyone else is looking for a an in-depth guide to print settings, I can heartily recommend the "LulzBot_TAZ-User_Manual-ebook.pdf‎".
I know it's not for delta printers, but it's "slic3r in Depth" chapter is a really good walkthrough of print techniques with slic3r.
There's also a wiki for SeeMeCnC (wiki.seemecnc.com) that's been relatively recently created. It's still lacking details but would be a good place to start adding some of these "tips". Feel free to add tips you've found and expand on what's on the wiki.

Re: Getting an Accurate Hot end Temp?

Posted: Tue Jan 21, 2014 11:05 am
by analog_banana
I managed to find some settings that matched my macine's thermistor readings to my real-world thermocouple readings
+/- 1degree for the Hotend
+/- 5 degrees for the bed

Here they are in Marlin:
==============================================================================
// 5 is 100K thermistor - ATC Semitec 104GT-2 (Used in ParCan) (4.7k pullup)
// 6 is 100k EPCOS - Not as accurate as table 1 (created using a fluke thermocouple) (4.7k pullup)

#define TEMP_SENSOR_0 5
#define TEMP_SENSOR_1 0
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 6
==============================================================================

After these firmware changes my PID tuning was much more stable and repeatable.
And.. that's how I calibrated my temperatures.

Re: Getting an Accurate Hot end Temp?

Posted: Wed Jan 22, 2014 12:28 pm
by MSURunner
One thing that I would caution is that, yes, accurate temperatures are helpful, BUT printing temps are a bit of an art form in finding that requires a bit of practice. Filaments differentiate quite wildly as far as the temperatures they print well as even the moisture content. So a filament's temperature may vary even as the roll goes along. Do not get too worked up on needing to print at 5 degrees cooler or hotter than someone else.

Re: Getting an Accurate Hot end Temp?

Posted: Wed Jan 22, 2014 1:33 pm
by analog_banana
Thanks, I agree - if the print looks good, it is good.
I'm really happy to get have a clue that my temperature is accurate now
as I can cross that off my list of what is wrong with my kit.