3d Printer Temperatures

[Robert Longbottom]

Hi all,

I was playing with the 3D Printer last week to see how happy it is at
the minute. I've upgraded Raspbian and Octoprint so we are now on the
latest versions of those. It still drives ok, and everything looks to
home quite nicely, which is good.

However there looks (to me) to be something wrong with the thermistors
(bed and hot end) because the temperature fluctuates by what seems like
quite a lot (~5oC) when it's just sat on the bench doing nothing. So
last week it was jumping around from (I think) ~18oC to ~23oC between
one reading and the next. In comparison my printer at home deviates by
less that 1degree in the same situation.

I suspect this is why we were seeing "issues" with the hot end. I'll
look to check the wiring as best I can without doing anything
destructive and maybe try a test print this week to see how it's
actually printing these days, since it hasn't been run for a while.

If anyone has any thoughts speak up!

Cheesr,
Rob.

[Gyrobot]

I think we need to look at the Thermistor tables in the firmware. Last night it seems like the PLA was boiling, despite the temperature only being about 160deg.

We also printed quite successfully with Filaflex on the very first try at 35mm/s, but the temperature was 180deg, normally FFX needs 230-240 so it's definitely reading low.

[Robert Longbottom]

Yes, I was going to have a look at what we are using and what might be more appropriate.  Do you have any info in the thermistor

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[jmeosbn .]

Sounds like you may solve our issues then. :)

If you need anything pulling off the SD card (firmware etc.) then let me know and I'll stop off and pick it up.

I'd like to have another go at the sled next week; if we have time before Damian's workshop, It'd be good to finish up the run through of setting up the printer up etc. (I expect one or two others may be interested too!)

Jamie Osborne

[Robert Longbottom]

I did have a look in the thermistor tables to see if I could find a set that looked like it would offset all the temperatures by 40-50 degrees, but didn't have much success and it's a tedious exercise trying to randomly try out the various types.

We are currently configured to use  type=3 - mendel-parts thermistor - other types available seem to be mainly 100k and 200k thermistors made by various manufacturers - different ones have differing resistance curves as the temperature changes, hence you need to pick the right one from the table to get the resistance correctly converted into a temperature.  

I have no idea how we arrived at the type=3 setting, and I'm not sure how you identify the exactly model of these things without having just bought it and knowing.  - @Steve, any idea what it might be?

What I did work out (which now  seems to be blindly obvious, but I didn't know beforehand) is that if you measure the resistance of the thing at room temperature (25oC I think) then that points to whether it is a 100k or a 200k.  So thats something to try if nothing else because it will at least get us in the right ball park.

On Sunday, 19 October 2014 18:18:08 UTC+1, Robert Longbottom wrote:

[jmeosbn .]

Ah... I will try to get the basement closer to room temperature for this evening then! ;)

Jamie Osborne

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