Filament Guide with Jam Sensor by anhtien

Last crawled date: 3 years, 1 month ago

There are two annoying situations that can ruin your prints: one is when the filament ran out and the other is when the filament gets jammed up and knotted to the spool. For the first issue, we have the filament out sensor thingy https://www.thingiverse.com/thing:2533511
Introducing a new filament guide that can detect jam and act on it. It resources to the roller type stop switch and wiring pi GPIO 2 off the Raspberry Pi as hardware solution.
The Octoprint uses the “Filament Sensor Reloaded” plugin to graciously pause the print to let you change filament but it only supports one sensor. If you only use the Filament Jam sensor (and not the Filament Out sensor), you can read the instruction from the plugin and done.
If you want to use both the Filament Out sensor (GPIO-0) and Filament Jam Sensor (GPI-2) then the solution (while waiting for the new plugin) is to use Raspberry shell script to detect the Filament Jam condition and turn off the printer when it occurs. The script "checkForFilamentJam.sh" was uploaded, all you need to do is download it to the Raspberry Pi. There is a catch, that is how to make the Raspberry Pi turning the printer off? Well, the solution lies in the "Power Supply, Raspberry Pi, Relay Module, Fan Case" thingy https://www.thingiverse.com/thing:2480530, which uses GPIO-1 to turn off / on the printer via a relay module.
YouTube video (https://youtu.be/eZ3a8W54gvE) recorded over 4 minute showing the Filament Jam Sensor in action (sorry I didn't know exactly when it got jammed). It turned the printer off when filament was deliberately jammed by a paper clip. Just skip to about the last minute to see how the Pi handled it.
The video shows the stop switch being "clicked" few times before it "aligned" with the script's 5 second check to turn the printer off. It means the printer was turned off Only when the check at the 5 second interval detected the switch being pressed in that split second (literally). This is to give the RPi few chances to make sure the filament is really jammed before turning the printer off. You can set the check timer down to sleep 1s (for 1 second) if you want the printer off within the first or second click, but the Pi might suffer some performance hit. This Guide can also be used as an extra On/Off switch if you manually hold it down few seconds, no need to reach to the back to turn it off.
Caution: try the clip approach to make sure your installation works but I am not responsible for any damages to your printer or anything. You can see that the extruder can pull the filament quite hard and dragged the 5 lbs spool holder until it hit the frame. This test was pretty brutal but it reflected the real scenario.
Wiring:
Connect the NO (Normally Open) middle pin of the stop switch to Raspberry Pi pin header 13 (which is GPIO-2 for WiringPi or BCM GPIO-27) if you have the Raspberry Pi Rev B. If you have other version, you can find out which pin header for GPIO-2 or modify the shell script accordingly. Connect the second wire to the C (COM) pin on the stop switch to any ground pin on the Raspberry Pi.
Software:
Download the checkForFilamentJam.sh script to the main /home/pi folder when you login to the Raspberry Pi and enter the following command after it boots:
./checkForFilamentJam.sh &
The script will run in the background and check for the filament jam condition every 5 seconds. If the script does not start, it might be because the copying back and forth make it not executable. If it's the case, just issue the command "chmod +x checkForFilamentJam.sh". When the script detects the jam from GPIO-2, it sends signal to GPIO-1 to turn off printer and exits. You need to resend the command next time around.
Installation:
You can reuse the side M3 screw and change the top screw to M3-21mm to attach the filament guide to the top left or top right of the Anet A8 printer.
Printing:
Rotate X axis 270deg to print it upside down, use 50mms speed and 30% infill with support generation.