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I have an ender 5, and I'm not certain that the bed is getting up to temperature. Or maybe I'm not understanding what it should be like when it gets up to temperature.

If I use an infrared thermometer, where should I aim it, and what should it be saying in comparison to what the screen on the printer says?

For example, if the screen says 50 degrees should the thermometer read 50 degrees, or should it read something different because that's an internal temperature or something not a surface temperature?

At the moment the bed seems "nicely warm" when the temperature on the display says that I should burn my hand if I touch it.

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  • $\begingroup$ The least expensive is probably using a multimeter that comes with a thermocouple, and taping the thermocouple junction to the bed with kapton tape. $\endgroup$
    – Perry Webb
    Jan 24 at 17:38

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Sensor mounting

An Infrared Thermometer prefers a non-reflective surface to accurately read the temperature reliably - glass is reflective for Infrared light under many angles and can in the worst case result in measuring anything but what you want to measure. To that degree, a piece of paper tape (Painter's tape or Washi-tape works fine) can act as a mounted measuring point.

A contact temperature sensor can be mounted touching the plate in a location easily by putting it in contact using some tape.

Sensor positioning

However, do note that the temperature sensor of the printer is not mounted on the top of the build platform but at the heater element under it. This means two things:

There is a temperature differential between the heater (which would be quite hot but not scorching in an instant of touching it) under the aluminium bed, the top of the aluminium bed, and even more if correlated against the surface of your build platform.

On the other hand, to verify your sensor setting, you need to measure under the bed at the heating element or at the interface between the heater and the aluminium bed. For example, you could use a spot right next to the heater as your probing point. This is incidentally quite close to where the temperature sensor should be mounted anyway.

Bed temperature control

Depending on your setup, the temperature difference between heater and the build surface could be up to about 15 °C and I would deem that an acceptable number. In accounting for the wanted build surface temperature, one can adjust the set heater temperature accordingly, as shown in this experience I had:

On particularly a cold day in late 2021 the heating in the room was not gaining enough heating water from the central unit set to a lower setting than it ought to. As a result, the room was down from the usual temperature to a rather cold ca. 12 °C. On that day I had to increase the bed temperature by a couple of degrees to gain proper bed adhesion, but it fixed itself once I figured out to fix the setting on the central unit.

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  • $\begingroup$ I've also noticed needing to vary temperatures when the temperature of the room isn't constant. Also, printing on glass with a glue stick coating needs significantly different settings than printing on a 1 mm thick build surface on the glass. $\endgroup$
    – Perry Webb
    Jan 24 at 17:23
  • $\begingroup$ Are you sure that "An Infrared Thermometer needs a non-reflective non-glass surface"? the point is that glass reflects IR, in addition to emitting their own. However, if you have a glass surface which is at about 60 °C and the environment at 20 °C, the reflection will be weaker than the self-emission (emissivity coefficient 0.85-0.95, so not bad). I found that keeping the IR thermometer at 10 cm from the glass and perpendicular to it produces a very good reading. Like, 60 °C thermistor below silicone heater, and 59-61 °C for the top surface of the glass. Maybe you can improve the answer. $\endgroup$
    – FarO
    Jan 25 at 9:43
  • $\begingroup$ @FarO reworded, but head-on avoids the problem by choosing the very best angle. going off-kilter can result in measuring the ceiling though, where a non-glass measuring point helps. $\endgroup$
    – Trish
    Jan 25 at 9:57
  • $\begingroup$ "in the worst case result in measuring anything but what you want to measure" I'm not an expert so I can't be sure, but I would expect the worst case to be the plate PLUS the reflection. The emission from the glass itself (given the high em. coefficient) cannot disappear based on the angle. I will ask in physics.SE sometime. $\endgroup$
    – FarO
    Jan 25 at 10:05
  • $\begingroup$ if you try to measure an item that is 60°C and the surface emits 60°C, but also reflects 20°C, the thermometer, depending on how much of the background bleeds into the measurement, will measure something in between 20 and 60, but what it actually measures is dependant on the angle - it is not the surface or the reflected temperature, but a smeared temperature somewhere in between. $\endgroup$
    – Trish
    Jan 25 at 10:28
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The actual numerical reading doesn't really matter - as long as the first layer goes down, and stays down through the entire print.

I've noticed that the center of the bed is ~2 degrees C under the set temp, and the edges could be 15 degrees low.

So "verify by effect" - if the bed seems too cold and you're getting lifting, then raise the temp and use that new value. Write it on the side of the filament spool too.


If you're looking for a hardware solution, some of the IR cameras or camera add-ons for cellphones may be suitable.

FLIR is one such device - be aware they're not cheap! Some photos at https://toms3d.org/2019/05/02/testing-5-different-heated-beds/

enter image description here

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  • $\begingroup$ is the photo from the heater sde or from the top side? I suspect the heater because of the differentials. $\endgroup$
    – Trish
    Jan 23 at 22:44
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    $\begingroup$ ok, I found it in the accompanying video - that is a lullzbot mini, and you actually see the heater element through the glass - which means you are technically seeing the temperature of the heating element directly, as Tom found the right angle to look through it. That also explains the distortion of the thermal image on the right. $\endgroup$
    – Trish
    Jan 23 at 23:44
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    $\begingroup$ Side note: you might be able to rent or borrow a FLIR camera for testing the insulation of your home or searching for heat leaks. $\endgroup$
    – Trish
    Jan 23 at 23:55
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    $\begingroup$ The least expensive FLIRs I've see are cellphone addons. At least one OEM making rugged phones for construction has a model with a FLIR. The temperature is probably accuracy with a metal bed plate, but with a glass plate you could be looking through the class to the heating element. A FLIR works the same as an infrared thermometer. If your measuremt is much hotter than the actuall surface temperature of the bed, your thermometer is probably seeing the heating element. $\endgroup$
    – Perry Webb
    Jan 24 at 16:46
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    $\begingroup$ I looked at the glass heated bed on a German Reprap x400 3D printer. It measures between 100-110 °C with the bed set at 110 °C. It appears the pigment giving the glass an opaque white color blocks infrared. My guess is it probably increases the thermal conductivity of the glass. I don't see an image of the heating element as in the image in the above answer. $\endgroup$
    – Perry Webb
    Jan 24 at 17:13

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