I am having problems with my tevo tarantula large bed 12Volt power supply, I am getting the thermal protection message when heating my bed with target temperature set to 115 degrees. The process slows down after reaching 90. I changed merlin settings to trigger thermal shutdown after 5minutes/2degrees and added a cover to the printer, so getting now 103 degrees (usually shutdown was at 100/101).

link to a video showing panel: https://photos.app.goo.gl/jiW9NE7wEB4H0mOy1 printer under the polystyrene cover

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    $\begingroup$ I'm unable to parse your question. Where do 115 and 300 affect your ability to heat above 100? $\endgroup$ – Sean Houlihane Feb 26 '18 at 12:57
  • $\begingroup$ question rephrased thanks for comment @SeanHoulihane $\endgroup$ – profesor79 Feb 26 '18 at 13:57

You need to increase the power of the heated bed. With a given amount of power, there is an upper limit to the maximum temperature you can reach because at a given point losses due to conduction, convection and radiation will balance out the heating power and the temperature will not increase any more.

Sometimes, inability of the bed to heat up is due to the supply voltage sagging under load. First, measure the supply voltage with and without the bed turned on. If you find the supply drops significantly when the bed is turned on, you need a new power supply.

Otherwise, you will need to either:

  1. Get a new, higher-power heated bed. Make sure that it is compatible with your electronics, or upgrade them as needed.

  2. Increase the supply voltage so that the bed you already have will give more power. Some power supplies have a small adjustment potentiometer that lets you adjust the output voltage. Be careful when doing this. Even a small change in voltage gives a big increase in power. For a heated bed with resistance R at voltage U, the power dissipation is U2/R. Going from 12V to 13.5V already gives 26% more power.

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  • $\begingroup$ will check above and give a ticket to TEVO as per specification the set shall go to 110 degrees. $\endgroup$ – profesor79 Feb 26 '18 at 14:43
  • $\begingroup$ As the voltage drop with bed heater enabled was low, then decided to raise the voltage on the PSU and that did the job. Thank you. $\endgroup$ – profesor79 Feb 27 '18 at 13:42

Some simple steps that may help to reach higher temperature:

  1. Check if you can use heated bed insulation of any kind - the most common approach is to use cork sheet
  2. Protect heated bed and printer from any possible air movements - arrange a set of walls around printer or just simply put it in the cardboard box large enough
  3. Cover heated bed with cloth or cork sheet until it reaches desired temperature
  4. Replace wires from heated bed to the power supply with thicker ones (2.mm2 / AWG14 should be fine)
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