1 Topic by ne14pez

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Topic: Extrusion Temp Very High - 223 C, Calibration Problems?

My stock hotend clogged on day 1 and I broke it trying to fix it so I machined a new barrel from steel.  I've gotten very good at taking it out, unclogging (using heat, acetone, etc.).  Now I can only get it to extrude at very high temps like 220-225.  I believe my thermistor is not reading correct values.  When it shows 223, it is really around 195.  My IR thermometer shows a 30-40C difference in temp (Repetier says 220, IR thermometer says 175).

I've gotten parts to print at these temps, but the problem is 1) I am worried that I am running it too hot, 2) I often hit the 230C mark and my printer shuts down.

I've done PID tuning a couple times as well.  Is there a way to calibrate the thermistor readings?

2 Reply by elmoret

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Re: Extrusion Temp Very High - 223 C, Calibration Problems?

IR thermometer is a box of lies for this sort of thing. Emissivity, spot ratio, etc.

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3 Reply by IanJohnson

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Re: Extrusion Temp Very High - 223 C, Calibration Problems?

It's better to use a K type  thermocouple with a multimeter and sticking under the kapton next to the thermistor.

http://solidoodletips.wordpress.com/201 … mperature/

4 Reply by ne14pez

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Re: Extrusion Temp Very High - 223 C, Calibration Problems?

Since I don't have that setup, is there another way I can estimate if my temps are way off, and is there a way to correct for it in the software?  For example, After I do a thorough cleaning of the nozzle and barrel and try to extrude for the first time, I can't get it to even melt the ABS at any temp lower than like 200, and even there, it's just barely melting it.  Is this a clear indication that the temps are off?

5 Reply by ne14pez

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Re: Extrusion Temp Very High - 223 C, Calibration Problems?

at this point, I just want to be able to lower the thermistor temp read by 5 degrees.  I'm just sick of my print stopping because it reached 230.  I don't care if I toast my hotend, it doesn't work at any other temps anyway (and I'm in the process of machining an all metal hotend without a plastic PEEK).  How do I do that?

6 Reply by 2n2r5

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Re: Extrusion Temp Very High - 223 C, Calibration Problems?

Hey ne14pez, a couple things.

If you perform the PID Tune then you won't have crazy temperature swings that shutdown the system.
http://www.soliwiki.com/PID_tuning

Also, to see what temps you should be extruding at, try manually extruding 100mm of filament at 10-20mm/s into the air. Start with your temps at 205-210 and look for teeth marks in the extruded filament (you might have to tighten the tentioner arm a little. Keep bumping up the temps by 2-3C until the teeth marks go away.

If all else fails then you can change the max_temp in the firmware.

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7 Reply by ne14pez

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Re: Extrusion Temp Very High - 223 C, Calibration Problems?

Problem Solved.  It turns out my thermistor was probably measuring just fine.  I ended up building my own all metal hot end and since I put it in, I can extrude easily at 185 C.  I haven't had a problem at all.  The hotend I built was actually pretty cheap using common materials from the hardware store.  I am going to post it in the "hacks and mods" section when I get a chance to compile the info.  Thanks for all of your help!