This will vary slightly depending on your particular brand of MMU but the steps are essentially the same with some being dependent on hardware configuration.
The Klipper configuration files for Happy Hare are modular and can be found in this layout in the Klipper config directory:
mmu/
base/
mmu.cfg
mmu_cut_tip.cfg
mmu_form_tip.cfg
mmu_hardware.cfg
mmu_software.cfg
mmu_sequence.cfg
mmu_parameters.cfg
optional/
mmu_menu.cfg
mmu_ercf_compat.cfg
client_macros.cfg
mmu_vars.cfgThis makes the minimal include into your printer.cfg easy: [include mmu/base/*.cfg]. That will also ensure the correct load order!
The mmu.cfg file is part of the hardware configuration but defines aliases for all of the pins used in mmu_hardware.cfg. The benefit of this is that configuration frameworks like Klippain can more easily incorporate. It is also in keeping with an organized modular layout.
This can be daunting but the interactive installer will make the process easier for common mcu's designed for a MMU (e.g. ERCF EASY-BRD, Burrows ERB, etc) and perform most of the setup for you. A few tweaks remain and include the setting of endstop options, optional extruder "touch" homing as the usual pin invert checking, etc.
Endstop setup and options can be found here
Note that all sensors can be setup with a simple section in mmu_hardware.cfg. This ensures things are setup correctly and only requires you to supply the pins. There is no need to comment out if not used, you can leave the pin empty or reference an empty alias. In those cases the sensor will be ignored
# FILAMENT SENSORS ---------------------------------------------------------------------------------------------------------
# Define the pins for optional sensors in the filament path. All but the pre-gate sensors will be automatically setup as
# both endstops (for homing) and sensors for visibility purposes.
#
# 'pre_gate_switch_pin_X' .. 'mmu_pre_gate_X` sensor detects filament at entry to MMU. X=gate number (0..N)
# 'gate_switch_pin' .. 'mmu_gate' sensor detects filament at the gate of the MMU
# 'toolhead_switch_pin' .. 'toolhead' sensor detects filament after extruder entry
# 'extruder_switch_pin' .. 'extruder' sensor detects filament just before the extruder entry
#
# Sync motor feedback will typically have a tension switch (more important) or both tension and compression
# 'sync_feedback_tension_pin' .. pin for switch activated when filament is under tension
# 'sync_feedback_compression_pin' .. pin for switch activated when filament is under compression
#
# Simply define pins for any sensor you want to enable, if pin is not set (or the alias is empty) it will be ignored (can also comment out)
#
[mmu_sensors]
pre_gate_switch_pin_0: ^mmu:MMU_PRE_GATE_0
pre_gate_switch_pin_1: ^mmu:MMU_PRE_GATE_1
pre_gate_switch_pin_2: ^mmu:MMU_PRE_GATE_2
pre_gate_switch_pin_3: ^mmu:MMU_PRE_GATE_3
gate_switch_pin: ^mmu:MMU_GATE_SENSOR
extruder_switch_pin:
toolhead_switch_pin:
sync_feedback_tension_pin:
sync_feedback_compression_pin:This is the file where Happy Hare stores all calibration settings and state. It is pointed to by this section at the top of mmu_software.cfg:
[save_variables]
filename: /home/pi/printer_data/config/mmu/mmu_vars.cfg
Klipper can only have one save_variables file and so if you are already using one you can simply comment out the lines above and Happy Hare will append into your existing "variables" file.
If all other pin's and setup look correct RESTART KLIPPER and proceed to step 2.
Verify that the necessary endstops are working and the polarity is correct. The recommended procedure is:
MMU_MOTORS_OFF
# remove filament from ERCF and extruder, move selector to center of travel
QUERY_ENDSTOPS
# or use the visual query in Mainsail or FluuidValidate that you can see:
mmu_sel_home:open (Essential)
toolhead:open (Optional if you have a toolhead sensor)Then manually press and hold the selector microswitch and rerun QUERY_ENDSTOPS.
Validate that you can see mmu_sel_home:TRIGGERED in the list.
If you have toolhead sensor, feed filament into the extruder past the switch and rerun QUERY_ENDSTOPS.
Validate that you can see toolhead:TRIGGERED in the list.
If either of these don't change state then the pin assigned to the endstop is incorrect. If the state is inverted (i.e. enstop transitions to open when pressed) the add/remove the ! on the respective endstop pin either in the [stepper_mmu_selector] block for selector endstop or in [filament_switch_sensor toolhead_sensor] block for toolhead sensor.
Other endstops like "touch" operation are advanced and are not cover by this inital setup.
Once pins are correct it is important to verify direction. It is not possible for the installer to ensure this because it depends on the actual stepper wiring. The recommended procedure is:
MMU_MOTORS_OFF
# move selector to the center of travel
MMU_HOME
# verify that the selector moves to the left towards the home positionIf the selector doesn't move or moves the wrong way open up mmu_hardware.cfg, find the section [stepper_mmu_selector]:
If selector doesn't move it is likley that the pin configuration for step_pin and/or enable_pin are incorrect. Verify the pin names and prefix the pin with ! to invert the signal. E.g.
enable_pin: !mmu:MMU_SEL_ENABLE
# or
enable_pin: mmu:MMU_SEL_ENABLEIf the selector moves the wrong way the dir_pin is inverted. Either add or remove the ! prefix:
dir_pin: !mmu:MMU_SEL_DIR
# or
dir_pin: mmu:MMU_SEL_DIRNow repeat the exercise with the gear stepper:
MMU_MOTORS_OFF
# remove any filament from your MMU
MMU_TEST_MOVE MOVE=100 SPEED=50
# verify that the gear stepper would pull filament towards the extruder
MMU_TEST_MOVE MOVE=-100 SPEED=50
# verify that the gear stepper is push filament away from the extruderIf the gear stepper doesn't move or moves the wrong way open up mmu_hardware.cfg, find the section [stepper_mmu_gear]:
If gear doesn't move it is likley that the pin configuration for step_pin and/or enable_pin are incorrect. Verify the pin names and prefix the pin with ! to invert the signal. E.g.
enable_pin: !mmu:MMU_GEAR_ENABLE
# or
enable_pin: mmu:MMU_GEAR_ENABLEIf the gear moves the wrong way the dir_pin is inverted. Either add or remove the ! prefix:
dir_pin: !mmu:MMU_GEAR_DIR
# or
dir_pin: mmu:MMU_GEAR_DIRIf you have an encoder based design like the ERCF, need to check that it is wired correctly. Run the command MMU_ENCODER and note the position displayed.
MMU_ENCODER
Encoder position: 23.4Insert some filament (from either side) and pull backwards and forwards. You should see the LED flashing. Rerun MMU_ENCODER and validate the position displayed has increased (note that the encoder is not direction aware so it will always increase in reading)
If the encoder postion does not change, validate the encoder_pin is correct. It shouldn't matter if it has a ! (inverted) or not, but it might require a ^ (pull up resister) to function.
[mmu_encoder mmu_encoder]
encoder_pin: ^mmu:MMU_ENCODER Other sensors are generally filament sensors and act on a switch. The easiest way to check these is to run something similar to the following for each sensor/switch.
QUERY_FILAMENT_SENSOR SENSOR=mmu_gate_sensor
Filament Sensor mmu_gate_sensor: filament not detectedActivate the sensor with a piece of filament and run again:
QUERY_FILAMENT_SENSOR SENSOR=mmu_gate_sensor
Filament Sensor mmu_gate_sensor: filament detectedNote thatFrequently enstops / filament sensors that are wired normally open (NO) require ^ (pull up resister) to correctly function.
Ok, last sanity check. Check that the servo you have fitted is operational. Run this simple commmand. The servo should waggle somewhere short of the configured 'up' and 'down' positions. Don't worry yet about calibration. That comes next.
MMU_TEST_BUZZ_MOTOR MOTOR=servoYou can also try:
MMU_SERVO POS=down
MMU_SERVO POS=upHappy Hare implements the MMU control as a "second toolhead" known as the MMU toolhead. The X-axis represents the selector movement and the Y-axis the filament movement until Klipper takes over the control of the extruder as normal. It offers some sophisticated stepper synching and homing options which add additional parameters to the regular klipper stepper definition.
In a nutshell, all steppers (MMU selector, MMU gear) defined in Happy Hare can have muliple endstops defined. Firstly the default endstop can be defined in the normal way by setting endstop_pin. This would then become the default endstop and can be referenced in gcode as "default". However it is better to give the endstop a vanity name by adding a new endstop_name parameter. This is the name that will appear when listing endstops (e.g. in the Mainsail interface or with QUERY_ENDSTOPS). Happy Hare uses a naming convention of mmu_ so anticipated names are: mmu_gear_touch, mmu_ext_touch, mmu_sel_home, mmu_sel_touch, toolhead, mmu_gate, extruder
These would represent touch endstop on gear, touch on extruder, physical selector home, selector touch endstop, toolhead sensor, sensor at the gate and sensor just prior to extruder entrance. In Happy Hare, "touch" refers to stallguard based sensing feedback from the TMC driver (if avaialable).
In addition the default endstop which is only set on the selector in the out-of-the-box configuration you can specify a list of "extra" endstops each with a customized name. These extra endstops can be switched in and out as needed. E.g.
extra_endstop_pins: tmc2209_extruder:virtual_endstop, TEST_PIN
extra_endstop_names: mmu_ext_touch, my_test_endstopDefines two (non-default) endstops, the first is a virtual "touch" one leveraging stallguard and the second an example of a test switch.
Important
If equipped with a toolhead sensor, gate sensor or extruder sensor, endstops will automatically be created with the name toolhead, mmu_gate, extruder respectively.
Happy Hare will automatically enhance Klipper to provide endstop(s) on the extruder stepper. While this might not seem it has value, it can be used to sense pressure on the filament (like hitting the nozzle when loading). Unless you have a sophisticated load cell attached to your nozzle the most likely configuration would be to define a TMC stallguard endstop. You can do this by adding endstop_pin to the extruder definition -- don't worry it won't confuse Klipper!
Ok, so you can define lots of endstops. Why? and what next... Let's discuss syncing and homing moves first and then bring it all together with an example.
The extra endstop mmu_selector_touch described in the mmu_hardware.cfg file is designed for "touch" movement where the selector can feel for filament blocking a gate and autmatically take recovery action. However, you might be wondering if it is possible to perform true stallguard homing on the selector? It certainly is but you need to adjust part of the config for the selector stepper: instead of making mmu_sel_touch an extra endstop, make it the default like so (note it is very important to add the homing_retract_dist: 0):
[stepper_mmu_selector]
...
endstop_pin: tmc2209_stepper_mmu_selector:virtual_endstop
endstop_name: mmu_sel_touch
homing_retract_dist: 0This will not only define mmu_sel_touch as a named endstop for "touch" movement but will also make it the default endstop for homing operation. With this configuration there is no need to have an microswitch or mmu_sel_home endstop defined. Personally I like the reliability of a mechanical homing enstop because it requires no tuning.
The MMU gear stepper(s) defined by Happy Hare not only enables multiple endstops but also can act as both a filament driver (gear) stepper an extruder stepper. This dual personality allows its motion queue to be synced with other extruder steppers or, but also manipulated manually as a separately controlled stepper. The gear stepper can be synchronized to the extruder when in a print and when in this mode it follow all extruder kinematics including pressure advance. It is also possible for the extruder to be synchronised with the gear stepper for loading and unloading operations. In this mode the extruder will follow the kinematics of the gear stepper and can participate in homing moves.
Happy have provides two test moves commands MMU_TEST_MOVE, MMU_TEST_HOMING_MOVE (and two similar commands designed for embedded gcode use). For example:
MMU_TEST_MOVE MOVE=100 SPEED=10 MOTOR="gear+extruder"
This will advance both the MMU gear and extruder steppers in sync but +100mm at 10mm/s. If only only gear was specified the move would only involve the gear stepper and obviously not be synchronized. Several MOTOR combinations can be sepcified with this move and are summerised here:
- gear - the default to move just the gear stepper (technically this is the Y-axis of the MMU toolhead)
- gear+extruder - move the gear but synchronize the extruder to it (the extruder is added to the rail supporting the Y-axis of the MMU toolhead)
- extruder - move the extruder only but with the mmu toolhead kinematics meaning klipper will know nothing about this movement (the extruder is the sole stepper on the Y-axis of the MMU toolhead)
- synced - move the extruder but synchonize the gear stepper to it (same as would occur in print if synchronized printing is enabled)
- both - (legacy) moves move the gear stepper and the extruder together but subject to their own kinematics and move queues
Similarly it is possible to specify a homing move:
MMU_TEST_HOMING_MOVE MOVE=100 SPEED=10 MOTOR="gear+extruder" ENDSTOP=mmu_ext_touch STOP_ON_ENDSTOP=1
This would home the filament using synchronized motors to the nozzle using stallguard! Cool hey?!?
Note
Homing moves can also be done in the reverse direction (and by therefore reversing the endstop switch) by specifying STOP_ON_ENDSTOP=-1. This should be familiar if you have ever used the Klipper MANUAL_STEPPER command.
If you are at all curious (and I know you will be after reading this) you can "dump" out the Happy Hare MMU toolhead with the command _MMU_DUMP_TOOLHEAD. I'll leave it to you to figure out the results.
For quick reference here are the two test MMU move commands:
| Command | Description | Parameters |
|---|---|---|
MMU_TEST_MOVE |
Simple test move the MMU gear stepper | MOVE=..[100] Length of gear move in mm SPEED=.. (defaults to speed defined to type of motor/homing combination) Stepper move speed ACCEL=.. (defaults to min accel defined on steppers employed in move) Motor acceleration MOTOR=[gear|extruder|gear+extruder|synced|both] (default: gear) The motor or motor combination to employ. gear+extruder commands the gear stepper and links extruder to movement, extruder+gear commands the extruder stepper and links gear to movement |
MMU_TEST_HOMING_MOVE |
Testing homing move of filament using multiple stepper combinations specifying endstop and driection of homing move | MOVE=..[100] Length of gear move in mm SPEED=.. (defaults to speed defined to type of motor/homing combination) Stepper move speed ACCEL=.. Motor accelaration (defaults to min accel defined on steppers employed in homing move) MOTOR=[gear|extruder|gear+extruder|synced|both] (default: gear) The motor or motor combination to employ. gear+extruder commands the gear stepper and links extruder to movement, extruder+gear commands the extruder stepper and links gear to movement. This is important for homing because the endstop must be on the commanded stepper ENDSTOP=.. Symbolic name of endstop to home to as defined in mmu_hardware.cfg. Must be defined on the primary stepper STOP_ON_ENDSTOP=[1|-1] (default 1) The direction of homing move. 1 is in the normal direction with endstop firing, -1 is in the reverse direction waiting for endstop to release. Note that virtual (touch) endstops can only be homed in a forward direction |
Hopefully you can see some of the coordinated movements that are possible that are highly useful for an MMU setup. For example, I'm current loading filament with an incredibly fast bowden load using the gear stepper followed by a synchronized homing move of the extruder and gear, homing to the nozzle using mmu_ext_touch (stallguard) endstop. It requires zero knowledge of extruder dimensions and no physical switches! It also has lots of uses for custom setups with filmament cutters or other purging mechanisms.
Altough this advanced functionality is already being used internally in Happy Hare. You will need to use the manual gcode commands or customize the loading and unloading gcode sequences with the provided _MMU_STEP_MOVE and _MMU_STEP_HOMING_MOVE to do highly imaginatively things - let me know how you get on.