Cheap and Easy Filament Out Sensor box by anhtien

Last crawled date: 3 years ago

Running out of filament in the middle of a print is annoying, especially when you are not around. This design will detect the filament out condition and pause the print for you to change filament. The whole implementation costs you next to nothing, assume you already use the Raspberry Pi and Octoprint to print your project.
Hardware:
A tact switch KW11-3Z 5A 250V micro switch 3Pin and two wires to the Raspberry Pi.
Wiring:
Solder the first wire to COM pin (marked with letter C) on the switch, this will be the ground wire to the Raspberry Pi.
Solder the second wire to the NO pin in the middle of the switch. This is the Normally Open pin and will connect to one of the GPIO pin on the Raspberry Pi.
I reused the wires off my old earphone that I no longer need. You can probably use 22gauge wires for this project. Make sure it's long enough to get to the Raspberry Pi with wire left to move around.
Assembly:
Pick out the location where you want to place the filament Sensor box and print the correct L2R or R2L box to select the filament moving from left to right or right to left of the box. It has the arrow direction to help you identify its direction too. Next is to choose the adapter (clip or x-carriage) and secure the box to the adapter.
If you choose the x-carriage adapter as shown in the picture, you need the R2L type of box which will eventually make the filament going top down since it will be attached sideway to the x-carriage adapter. You can now go to the testing and installing software steps.
Testing at system level to make sure your wiring is good:
In fact, you can use this step to test out the switch function even before printing anything out, just connect the switch's wire to the Raspberry Pi's ground and GPIO pin you want to use for this project.
The X-carriage installation is used as example but the clip type is similar. First attach the R2L box to the X-carriage adapter using 2 x M3 screws and 2 nuts, then secure the adapter/box assembly to the X-carriage using the existing screws as shown in the picture.
You can now run the stop switch's wires through the sensor box large hole to the Raspberry Pi. The COM wire goes to ground, the NO (Normally Open) goes to GPIO. For the Raspberry PI rev 2, the ground is pin header 9 and this example uses BCM GPIO 17, which is pin header 11. Note that this GPIO-17 is actually GPIO-0 when using wiringpi to test in this step. Next is to place the switch in correct position or else you will run into issue when pushing the filament into the box. For R2L box, the switch is placed with the open tab on the left and the ground wire on the right side (see the first picture). It’s reverse for the L2R box, i.e. the ground wire on the left side. Once done, snap the lid in the correct way to remind you which direction the filament will go (second picture).
Connect to the Raspberry Pi using SSH, username pi. Enter the following two commands to check the GPIO-0 in wiring pi mode (or your own GPIO wiring pi pin number):
gpio mode 0 up
gpio read 0
It should return the value 1 (high) to indicate there is no filament. Now cut a piece of filament and push through the hole and see it come out the other side. Repeat the second command (gpio read 0), this time it will report the value 0 (low). If you get to this point, you are done with the hardware installation. Go on to the software installation.
Software Installation:
Using the browser from another system, connect to the Octopi via http.
Click on the Setting icon (the wrench logo at the top right). Select Plugin Manager.
In the Plugin Manager screen, you should see the “Get More…” long button at the bottom, click that.
One the next screen, use the scroll bar to scroll down until you see “Filament Sensor Reloaded”. Click Install button next to that and let it complete the installation. Click Close when done.
REBOOT the Raspberry Pi to activate the software.
Proceed to the Software Configuration.
Software Configuration:
Once the Raspberry Pi is back, use the Browser to go OctoPrint Settings screen. This time you should see the “Filament Sensor Reloaded” under “PLUGINS”, click that link.
Enter 17 for Pin. Or another GPIO BCM pin you prefer.
Debounce Time should be default to 250ms. If not, type 250.
Switch Type should be default to Normally Open. If not, select it from the list by clicking on the up/down arrows at the end of the list.
Board Pin Mode - select BCM Mode.
Out of filament GCODE,enter the following lines (or copy/paste)
;pause
M600
Make sure the selection box for “Pause print when out of filament” is checked. Click Save button at the bottom right to complete the configuration. Next is the Configuration after clicking Resume steps.
Configuration GCODE scripts:
Go back to the Settings screen, this time click on the “GCODE Scripts” on the left side under “PRINTER”.

In the edit box for "After print job is paused", add the following lines:
G60 S0 ; save current position to S0
G91 ; set to relative positioning
G1 E-1 F300 ;retract the filament a bit before lifting the nozzle, to release some of the pressure
G1 Z+2 F{travel_speed} ;move Z up a bit
G28 X0 ;move X to min endstops, so the head is out of the way
M104 S0 ;extruder heater off
M140 S0 ;heated bed heater off (if you have it)
M84 ; disable motors
;Put printing message on LCD screen
M117 Change Filament


In the edit box for “Before print job is resumed”, enter the following lines:
G90 ; set to absolute positioning
G61 S0 ; restore position

Now you are really done with configuration, click Save
Move to the real test, you can do it as many times as you like to be sure the sensor switch is functioning properly.
The Real Test:
Run the filament through the box and to the extruder. My trick to always get the filament through is to heat the extruder to 200deg, then pull the old filament out. Do not cut the filament like a lot of people suggested, you need the extruder tube to be empty and pulling the filament out is the only way. If you get into the situation of having some filament stuck in the tube, the best way is to use a long thin hex Allen key and push the filament down. If you resource to Allen key to push old filament out and using the X-carriage adapter, you can remove the left screw of the adapter, rotate the sensor box clockwise to have room to work. Before pushing the new filament in you want to cut it diagonally such that its tip is as sharp as a needle, with the sharp tip you can be sure that it will go through the tube easily. The printer should be ready to print by now.
Start to print a test 20mm test cube, when it just started snip the filament above the sensor box (Not under the box) and see it slowly gone down the hole. The second picture actually shows the filament being cut before the print was started. When you hear the clicking sound from the sensor switch, the printer should also detect filament out condition and move the extruder head to the left and display "Change Filament".
At this point the motor is disabled and all heaters are off waiting for you to come to its rescue. I assume that you are normally not there next to the printer when the filament run out, this is a safety feature you might want to keep.
You need to go to the Octoprint's Temperature tab to manually heat the extruder hotend up to 200deg, heat bed to 60 deg (or the heat settings you desire).
Once the extruder temperature is reached, pull the old filament out and push the new filament through the box and into the hotend hole.
Click Resume to see the printer goes back to the old position and continue the print. The good part of this little Filament Sensor design is mostly for peace of mind, you don't want to have a 10 hours left of printing of the air with the hotend & heat bed still fuming at high temperature. Saving the print is also nice too.
I also uploaded my setup for other GCODE scripts from Octoprint in case you are interested.
Note: I provide the clip type of adapter so you can install the filament sensor box at various location but I did not try it out yet. The clip adapter lets you attach the box vertically or horizontally (two flavors), and each clip adapter allows the box to attach in two different directions.
If you choose to design a new type of adapter then make sure to have two holes with 1.75mm radius spaced 14mm apart, the two holes within the R2L or L2R boxes are 3.75mm from the edges.
Update 1: Added the improved top that presses the switch firmly inside. Also add a little side gap on the top to make its removal easier
Update 2: Added note about new pause scripts to resume at the same spot. It did not resume at the same spot earlier, hit & miss. The major change is the pause script section is moved to GCODE Script "After print job is paused". Refer to fun Snap Cubes thingi https://www.thingiverse.com/thing:2560893 to see photos of my Filament Out condition tests.