FDM: Printing too hot, too cold, and about right

TL;DR: The perfect temperature for FDM printers depends on multiple factors

Introduction

When I started 3D printing, I wondered what the perfect temperature was? The answer varies from 180°C to 280°C depending on who you ask. So I took some detail photos of calibration cubes.

Sensors

If you do not know your exact sensor type, then you are printing with a generic Chinese 100 kΩ resistance sensor. These have a resistance value of about 100 kΩ at 25 °C and are also called thermistors. Their beta value describes how much their resistance decreases when the temperature drops.

But #1: This value is usually defined for the temperature range 0 °C – 80 °C. The temperature range of the thermistor is 0 °C – 80 °C. The resistance of the thermistor is defined by the temperature range 0 °C – 80 °C. At 200 °C you’ll have an offset of 10 °C.

But #2: Your sensor is probably not accurate because it only costs a few cents. In addition, you have heat resistance in your heat block, so you’re off a few degrees again. And you’ll measure that with the built-in ADC and the reference of the cheapest counterfeit Atmega clone your supplier could find.

But #3: The necessary temperature also varies with speed. PLA doesn’t conduct heat well and you need to raise the temperature slightly to liquefy the core of your filament.

Translated with www.DeepL.com/Translator

The calibration cubes

I printed these 150 mm/s in Cura, acceleration 3500 mm/s² with my cheap delta printer. The nozzle is 0.4 mm, the layer height = 0.1 mm.

Too Hot

Printed at 290°C.

You can see the fuzzy skin. This is because my filament is wet (and your’s probably as well). The small gas bubbles expand and make a microscopic styrofoam-like surface.

I think the bottom layers are okay because the filament had enough time to dry in the first few centimeters of the bowden tube.

Too Cold

Printed at 190 °C. At 180°C, my extruder stops and makes clicking noises.

 

 

This print is just at the limit of underextrusion. At the upper left part of the X is some stringing. This is because the extruder is still pushing at the end of the path, but not all the plastic has been squeezed through the nozzle.

 

About Right

Printed at 210°C.

 

Remember that the temperature also depends on the speed.

The slightly glassy surface is important. This is what freshly printed black PLA should look like.

You can see something like a “shadow” right next to the X. This is called ringing. It’s play in the mechanical system. You can fight this by lowering acceleration.

Conclusion

You should play with the temperatures. It is not enough to just print a temperature calibration tower, as the temperature required depends too much on the speed and geometry of the print.

Update

I’ve managed to print at 180 °C.

A cube at 180 °C, but with completely different settings. Only a single wall of 0.4 mm, so the cubic infill can be seen. Also 0.2 mm layer height

Here you can see the results more clearly:

  • in the bottom triangle you can see the wavy lines. This is underextrusion.
  • in the top few mm you can also see severe underextrusion. There is even a hole at the top. That’s because as soon as there is an tiny gap the next layer has nothing to adhere to. The hole “grows” upward.
  • Also take a look at the right side. You can see that the surface has a rough surface. As if it had been stretched and contracted again.

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