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Heated bed too slow to heat? check some possible fixes

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Heated bed too slow to heat? check some possible fixes
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Your bed is taking too long to get to the desired temperature? check some tips to decrease the heating time and make your printer more efficient!

Check the PCB side (the side with lines must be on top)

  1. This is a common mistake, the PCB is mounted upside down, and the material that the board is made of has a pretty good thermal insulation, so the heat produced by the resistance is lost on the other side of the board.  This is pretty easy to fix and you will only need to rotate the board upside-down and replace the thermistor position.
    heated bed
    Heating board example, the side with visible “wires” must be on the top side, touching the glass.

    Voltage of the power supply

    This is more a “workaround” then a fix itself.  most of the switched power supply used in printers have a small trimpot that can increase the output voltage, sometimes up to 20v. do not worry! the ramps can handle such voltage without any problem, so, we will increase it to 16v and use some math and ohm law’s.

    power supply
    On the arrow is the trimpot that you need to turn RIGHT to increase the voltage

    POWER = VOLTAGE * CURRENT   and   CURRENT = VOLTAGE / RESISTANCE

    Stock bed with 12v setup has about 1 to 1.2 ohm.  so  CURRENT = 12v/1r = 12Amps.
    Final power output: 12*12 = 144W of dissipated power

    Stock bed with 12v setup, but 16v input instead:   CURRENT = 16v/1r = 16Amps
    Final power output: 16*16 = 256W of dissipated power

    This is a 112W increase,  112 watts more to heat the bed.  it will not make any magic, but it WILL decrease the heating time.

    Check if the wires powering the bed is getting too hot!

    This is an important step. power will be lost if you use a wrong cable.   But what is the “wrong cable”.
    Let me explain.  Remember on the last tip, when we talked about the power output (200w),  so, something must allow it going from the power supply to its final destination, and a perfect wire would to deliver it all.  well, nothing is perfect.  wires also have resistance, and the resistance will not let all the current flow freely, so, how do we stop this from happening (or at least reduce?).  simple!   there are wires with a thicker core, this will have less resistance and allow more current to flow without losing power on the way.

    705_1SBIG
    Example of the cable used commonly as speaker cable

    First check if the cable is getting hot. if not you are ok and should skip this tip. but, if it’s getting you need to replace the cables with one with a bigger gauge. you can buy them on every store, but here is the tip!, you need a flexible yet with high current. there is a perfect cable for this, and they are used on sound systems,  check on any place that sells sound equipment. they probably have it.  1 meter is okay for most cases.  (also, ask them for one with at least 20A. we are not talking about the cable sizes because every country use a different measure, at least current is universal).

    There is too much wind on the bed

    This is a big problem, for the bed. The wind will dissipate the heat produced by the bed, and if the heating element is not strong enough it will get cooler over time. both slowing down the heating process, reducing the max temperature, and maybe even making the printer stop (after some time, if the temperature don’t raise the printer will shutdown to prevent fire).

Thermal insulation under the bed

Most of the heat produced by the bed will be transferred to the glass, because the board material itself is a thermal insulator, but there will still be heat going down and being lost under the heated bed, there are ways to reduce this. but this is step is the least efficient one, and a bit expensive.
heat insulation


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Written by 

My name is Italo C J Soares, i have 20 years and live on São Paulo - Brazil. Im currently studying Eletrical engineering, and i'm already graduated in Control and automation, Industrial Eletrical Maintenance and also Mechatronics. Currently i'm setting up a machine developing business. i know how to program in: C++ | C# | Arduino | PHP/HTML (newbie) | Java (newbie) Hope to help you guys!

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