Printing with PLA, temperature?

Hi,

First of all, you guys rock! Thanks!

I just got my hands on an hand held infrared thermometer to check my temperatures.

My bed temperature are off by only 5 degrees. Software: 60 Thermometer: 55

But the hotend temp is off by quite a bit: software: 180 Thermometer: 100.

Is this due to the surface of the hotend beeing cooled extremly fast, is it the hardware that has flaws or is it a mix of both?

It's more likely due to what is called 'emissivity' -the ability of the metal surface to emit the correct value for it's temperature, IR thermometers can be adjusted but each metal is different.

The best way is to stick a thermocouple down into the hot-end when the filament is removed.

---

Another RS Ormerod Mk1 meets the world

Retired now but I used to make....
CNC Machined Mk1 aluminium bed support plates for the Ormerod
CNC machined X-plates and ribs for Mk1 & Mk2 Ormerods
CNC machined bed support arms for the Mk2 Ormerod.
Dual Hot-End heatsink blocks.

I tried with a cheap IR thermometer, and got the same value as you for the heat bed. Would not surprise me if 60°C measured at the thermistor means 55°C actual surface temperature. I got readings of about 140°C for the outside surface of the heater block.

With a thermocouple, I actually got readings only a degree or two less when holding it against the outside surface of the hotend (in the corner between the tapered brass nut and the heater block) compared to measuring down the inside of the nozzle.

I read up a fair bit on IR technology after thinking I would buy an IR thermometer to do the same as you have done. As Davek0974 says, an IR thermometer is not quite as good as it may sound. It's accuracy depends entirely on the nature of the material you are measuring, with silver objects (such as the aluminium hotend) being very inaccurate unless you compensate, and glass cannot be measured with an IR thermometer. In addition you will find that the target area (the size of the spot it is measuring) is almost certainly bigger than the size of the hotend, so the temperature you are reading will be the average of the hotend and background. They are good for fast comparative measurements - looking for hot-spots and bad cable joins etc., but are not that good for taking accurate measurements unless you first calibrate them for the material you are measuring. I eventually bought a thermocouple thermometer which is not only far cheaper but also much more accurate and better suited for this particular purpose.

Dave

Allright. I guess I'll have to buy a thermocouple thermometer. And repeat the investigation. Ebay here I come!

Thanks for your thoughts!

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Aagaard
Allright. I guess I'll have to buy a thermocouple thermometer. And repeat the investigation. Ebay here I come!

Thanks for your thoughts!

Get one that comes with a long wire thermocouple probe that ends in two joined wires rather than a stiff rod. That way you can feed it down the Bowden tube right to the nozzle and get an extremely accurate reading of the temperature of the molten plastic inside the nozzle. If you have the wrong type of probe, wire thermocouples are pretty cheap even from RS. Many multimeters have a thermocouple input and thermometer mode, so if you are buying new kit perhaps get such a multimeter plus a thermocouple probe so that you have a more versatile instrument for your toolbox.

Dave

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dmould
..Get one that comes with a long wire thermocouple probe that..

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dmould March 10, 2014
I used a thermocouple thermometer (RS part number 206-3722) The K type thermocouple that comes with the instrument has a lead that is long enough and thin enough to fit down the bowden tube. I removed the filament, took the bowden tube out of the extruder and fed the thermocouple down the tube till it bottomed in the molten plastic left in the nozzle, so the reading is about as accurate as you could get. IR thermometers are not going to be reliable because (1) the target area is a lot smaller than the spot size for most instruments and (2) the aluminium has poor IR emissivity, which is going to give extremely unreliable readings unless you know exactly what correction factor to apply.

Obviously any thermocouple thermometer should work - some multimeters have a thermocouple input. Perhaps your digital stake thermometer will take other types of thermocouple in which case just get a thermocouple that will fit down the tube (such as RS 787-7709).

Dave
(#106)

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Erik