Extruder Temperature Measurements

[bertho 6]

I have seen many questions & comments about temperature errors so I very carefully measured the head temperature of my UM using two different K type thermocouples of good quality and two different meters. All readings were taken at the set temperature of 210C with a stable settled down temperature. Both TCs were properly bolted on to the heater aluminum block and wrapped around the block to reduce conduction errors.

Meter #1: Fluke 52 TC #1 209.4C TC #2 209.1C

Meter #2: Extech 42525 TC #1 210 C TC #2 209 C

The Fluke max error @ 210C is +/-0.4C and the TC max error is +/- 1.1C so the measurement accuracy is typically +/-1C.

So it appears that I am lucky with my UM and all four measurements are within 1 degree C of the set value. I have no idea how other UM performs since this is a single sample measurement. As I have mentioned before, a properly designed TC measurement setup should be very good.

I suspect that many of the reported temperature errors often are measurement errors. It is difficult to accurately measure the temperature since IR is not accurate and temperature probes often do not make proper contact and there is conduction of heat through the measurement leads that will affect the reading.

Bertho

[Daid 306]

Nice :-) I agree with your suspicion:

 

I suspect that many of the reported temperature errors often are measurement errors.

I could not find anything that could explain a huge temperature offset, except for bad chips or bad connections. But one of the common "tests" is to see where it extrudes right. For RepRaps they use a lower temperature with PLA then we do. I think this is not because we have bad temperature accuracy, I think this is because or hot-zone is smaller and our print speeds are higher. We need more temperature to get the PLA to meld quick enough.

(You should have seen the shock on the face of some Prusa mendel users when I told them I was extruding PLA at 230C)

[alaris2 1]

I've stopped using 230 and gone down to 200.

I found 230 causes what people are calling 'plugs'

I wouldn't recommend such a high temperature to anyone now.

we started with 'how low can you go?' and got to 180 and lower, but found structural integrity was a problem, then we seemed to go to 'how high can you go?' and have reached a different set of problems.

200-210 is the safe place I think.

[Daid 306]

Plugs at 230? I've printed at 250C at the beginning, without plugging problems. (the wiki recommended that back then). However, you might get plugs in combination with retraction...

I usually print at 220C, when I need a lot of retraction and small things I print at 210C, when I want to speed up, I print at 230C.

[alaris2 1]

yes, retraction is the main reason. especially since people are now using this feature from the word go.