Attention:
I recommend anyone to use the newer version of this model here: https://www.thingiverse.com/thing:2615842 !

This is practically a remix of kmsd's "Customizable Better Temperature Tower" ("https://www.thingiverse.com/thing:2491884). The main difference is that you can change the direction of where the highest and the lowest temperature will print: on top or on the bottom of the tower.

I also have made a second version of this remix with an overhang on the right side with a pointy cone on top of it. This is supposed to show how exact your printer prints (and cools) small pointy details. See https://www.thingiverse.com/thing:2615842 for version 2.

Usage example in Slic3r:

1. Generate the tower with openscad:

$ openscad tempTower.scad 

Set the following variables in the openscad window to your liking:

// temperature of the first lowest block
start_temp = 220;
// temperature of the last highest block
end_temp = 185;
// change in temperature between successively printed blocks
temp_step = 5;

Render and export the model to .stl and close openscad.

2. Generate gcode with Slic3r:

1. Open the .stl file in Slic3r.
2. Set layer height to 0.2mm. If not, multiply the skip and block parameters by (0.2mm/new_layer_height).
3. Add the following to:
   "Printer Settings" -> "Custom G-code" -> "Before layer change G-code":

   ; Layer [layer_num]

   This makes it possible for the 'setLayerTemperatur.py' script to recognize the single layers.

4. Set the initial temperature in the filament settings. The pedestal on which the temperature tower stands will be printed with this temperature.
5. Save the .gcode file of the model.

3. Write temperature settings to gcode file with setLayerTemperatur.py:

1. On the commandline:

   $ ./setLayerTemperatur.py -h
   usage: setLayerTemperatur.py [-h] -s STARTTEMP -e ENDTEMP -t TEMPSTEP -f GCODEFILE
   
   Sets the proper temperatures to the corresponding layers of a gcode file
   exported from Slic3r. This allows the temperature tower to have different
   temperatures per block.
   
   optional arguments:
     -h, --help            show this help message and exit
   
   required arguments:
     -s STARTTEMP, --startTemp STARTTEMP
                           Temperature of the first (lowest) block.
     -e ENDTEMP, --endTemp ENDTEMP
                           Temperature of the last (highest) block.
     -t TEMPSTEP, --tempStep TEMPSTEP
                           Temperature change between successively printed
                           blocks.
     -f GCODEFILE, --gcodeFile GCODEFILE
                           The .gcode file to process.
   

   
   $ ./setLayerTemperatur.py -s 240 -e 215 -t 5 -f tempTower_PETG_Black.gcode 
   startTemp: 240
   endTemp:   215
   tempStep:  5
   gcodeFile: "tempTower_PETG_Black.gcode"
   outFile: "OUT_tempTower_PETG_Black.gcode"
   step: -5
   -> M104 S240
   -> M104 S235
   -> M104 S230
   -> M104 S225
   -> M104 S220
   -> M104 S215
   

   By now the different temperatures should have been written to a new .gcode file that starts with "OUT_" and ends with the name of your old .gcode file. This file you can send to your printer and the tower should be printed out with the different temperature settings.