This is a MMU2 IR sensor mod for the BEAR Extruder. It is a derivative of the MMU2 IR sensor on the Delta-P Extruder.
Bear Extruder:
https://github.com/gregsaun/bear_extruder_and_x_axis/releases
Delta-P Extruder:
https://www.prusaprinters.org/prints/3091-delta-p-extruder
UPDATE September 2 2020:
*Door modified again to hopefully fix interference with motor bolt for good.
UPDATE April 14 2020:
Door modified to remove interference with motor bolt.Added an optional extruder body with a pocket for a 1050ZZ bearing. Useful if you run a pulley box and want extra support for the pulley shaft. The bearing pocket requires supports to print!
NOTE!!!!
This sensor mod requires:
Custom IR Sensor PCB
or
Custom Firmware
If you don't enjoy tinkering with and modding your printer, this might not be the best option for you.
Much easier to calibrate
Can open idler door without loosing calibration
No cumbersome chimney
PETG
4 perimeters
.2mm layers
Lever MUST be printed in IR opaque material!
In addition to hardware needed to build a standard BEAR extruder, you will need:
1x spring from a ballpoint pen
1x 3mm x 8mm steel shaft
1x 3mm locknut
1x 4mm OD 2mm ID 16mm long PTFE tube
You also need the melt-in threaded insert and PTFE connector included with the stock Prusa MMU2 kit.
Assemble per the BEAR extruder assembly instructions, substituting the parts included here for the standard BEAR parts.
Install the IR sensor on the side of the extruder body as shown in the pictures.
Install the Lever onto the Door as shown in the cross section picture.
Install the melt-in threaded insert and PTFE holder into the top cover.
Chamfer the ID of both ends of the 16mm long PTFE and insert into top of extruder before screwing down the top cover.
PLEASE READ CAREFULLY
The sensor signal is inverted, therefore custom firmware OR a custom IR sensor is required.
Click here for custom firmware:
https://github.com/teookie/MK3_3.8.1_INVERTED_IR/releases
OR
Click here for custom IR sensor:
https://easyeda.com/teookie/inverted-ir-sensor
One or the other (custom firmware or custom sensor) is required; NOT BOTH. Pick the method that seems easiest to you. Both methods work. I recommend using the custom firmware first to see if you like this mod, and then switching to custom sensor later.
If you choose to use the stock sensor (along with the custom firmware), you will need to remove the 90 degree header and either replace it with a straight header, or directly solder the wires onto the board.
Custom Firmware note:
The provided custom firmware also changes the default uSteps and eSteps for your printer. This will ONLY come into play if you do a HARD RESET of your printer (hold down the button while the printer boots, and select "All data"). In that case, you will need to use gcode to set the correct uSteps and eSteps after the hard reset.
For 1:1 drive extruder (standard for BEAR):
M350 E32
M92 E280
M500
For 3.5:1 drive extruder (vertigo pulley box):
M350 E16
M92 E490
M500
Send M503 to verify settings are correct.
Sensor Calibration Procedure:
-Ensure bontech gears are clear of filament
-Back out the lever screw so that the flag is completely outside of the IR sensor gate
-Use the sensor status menu on LCD to verify IR sensor is reading "1"
-Slowly turn in the lever screw just until the sensor state changes to "0"
-Preheat hotend to 215° C
-Use octoprint or a terminal to rotate the extruder motor
-Verify that the sensor state remains at "0" for a full revolution of the bontech gears; if state fluctuates between 0 and 1, turn in the screw a small amount at a time until it is solidly "0" for a full revolution.
-Turn the lever screw in an additional 1/16 turn
-Calibration complete
The author remixed this model.