Filament Watch Octoprint Plugin

Initial work based on the Filament Watch plugin by RLLynch.

Are you sure you want to do this? ;)

Features

• Pause, cancel, or just send GCODE when filament stops
• Automatic search for attached Arduino/rotary encoder
• Adjustable alarm boundaries
• USB connection to Octoprint/Octopi
• Helper functions for other plugins that might want access to extrusion data. Docs

Required sensor

Using this plugin requires a rotary encoder sensor, and an Arduino micro controller to manage the encoder. The enclosure STL files are designed for a rotary encoder with a 38mm (dia) x 35.5mm body, 6mm shaft and capable of running on 5v. The pulses/revolution of the encoder is not very critical; the encoder is run in quadrature mode, so the rated P/R will be multiplied by four. So even with a 100 P/R encoder and a 23mm encoder wheel, the resolution would be under .2mm - more than enough for accurate monitoring.

• Note if you do use an encoder with other than 600P/R, the DPM value in the Arduino code needs to be modified. Future versions will make this configurable through Octoprint.

Purchased Parts:

1. Quadrature encoder:

• Verified: Signswise 600p/r Incremental Rotary Encoder Dc5-24v Wide Voltage Power Supply 6mm Shaft [Amazon link]
• Pending verification:
• Other encoders may work, providing you come up with a suitable enclosure.

2. Arduino controller supporting 5V and Serial over USB:

• Verified: Adafruit Metro Mini 328 - 5V 16MHz [Adafruit link] [Pinouts]

3. USB A to Micro-B cable for Arduino [Adafuit link]

4. Optional: 2 x 0.1" pitch header blocks [Adafruit link]

5. Optional: (depending on case you use) 608 ball bearing [Amazon link]. These are the same bearings used in skates and skateboard wheels. You don't need anything fancy here - don't spend money on ceramic or high abec bearings. Old dead ones will work as long as they roll smoothly.

6. Optional: 30mm Rotary Encoder wheel [Ali Express Link]. The enclosure stl files below include a wheel stl that is designed for the enclosure, and is usually printed in a soft material like TPU/Ninjaflex. Manufactured wheels are higher quality, but generally not so much as to affect Filament Watch. If you do use a manufactured wheel, choose a case that is designed for it.

Printed parts - Enclosures and wheels:

There are several options for the encoder housing, depending on what will work with your setup.

1. RLLynch's base and wheel and optional mini metro enclosure

2. My housing for the D6

Wiring

Wiring instructions for the Metro Mini 328

Optionally solder the header blocks first. (Note check your enclosure to see if it's compatible with the header blocks)

1. Encoder red (power) - 5V
2. Encoder black (ground) - GND
3. Encoder green (output 1) - digital pin 3
4. Encoder white (output 2) - digital pin 2

Installation

1. Install the plugin in Octoprint Settings->Plugin Manager:

• Manually using this URL: https://github.com/gmatocha/Filament-Watch-Octoprint-Plugin
• From the Octoprint Plugin repositry (pending)

2. Compile and flash Arduino/filament_watch/filament_watch.ino into the Metro Mini using either the Arduino IDE, or the command line scripts shown below:

3. Connect the Metro Mini by USB to the computer running OctoPrint. Attach the wheel to the encoder and place it in the base. Feed the filament through the base.

Configuration

After installation, configure the plugin via OctoPrint Settings interface.

• Allowed Deviation (mm): If monitored length is more or less than the forecast gcode,

Pause and Resume Scripts

In addition to preventing wasted filament after a feed problem, in many cases Filament Watch allows problems to be corrected without destroying the print in progress. To do this, you'll need to use OctoPrints GCODE Scripting feature to move the print head out of the way on pause, then return it to the exact same location when the print resumes.

Copy the scripts below into the After print job is paused, and Before print job is resumed fields in Octoprint->Settings->GCODE Scripts

Scripts below built from here, here, and the official scripting docs.. Thanks Gina and OutsoucedGuru for the excellent write-ups!

After print job is paused

; From 
{% if pause_position.x is not none %}
; relative XYZE
G91
M83

; retract filament, move Z slightly upwards
G1 Z+5 E-1.5 F4500

; absolute XYZE
M82
G90
; move to a safe rest position, adjust as necessary
G1 X0 Y0

; Home X and Y only
;G28 X Y

;disable heater, but not bed because we want to keep adhesion
{% snippet 'disable_hotends' %}

{% endif %}

; play a jaunty tune (if your printer speaks)
M300 S440 P1000
M300 S660 P1000
M300 S440 P1000
M300 S660 P1000
M300 S440 P1000

Before print job is resumed

{% if pause_position.x is not none %}

; turn filament heaters back on
{% for tool in range(printer_profile.extruder.count) %}
    {% if pause_temperature[tool] and pause_temperature[tool]['target'] is not none %}
        {% if tool == 0 and printer_profile.extruder.count == 1 %}
            M109 T{{ tool }} S{{ pause_temperature[tool]['target'] }}
        {% else %}
            M109 S{{ pause_temperature[tool]['target'] }}
        {% endif %}
    {% else %}
        {% if tool == 0 and printer_profile.extruder.count == 1 %}
            M104 T{{ tool }} S0
        {% else %}
            M104 S0
        {% endif %}
    {% endif %}
{% endfor %}

; relative extruder
M83

; prime nozzle
G1 E-5 F4500
G1 E5 F4500
G1 E5 F4500

; absolute E
M82
; absolute XYZ
;G90

; reset E
G92 E{{ pause_position.e }}

; move back to pause position XY
G1 X{{ pause_position.x }} Y{{ pause_position.y }} F1500
; then move back to pause position Z to minimize risk of bumping part off bed
G1 Z{{ pause_position.z }} F1500

; reset to feed rate before pause if available
{% if pause_position.f is not none %}G1 F{{ pause_position.f }}{% endif %}
{% endif %}

Using Filament Watch

The Graph:

The graph on the Filament Watch tab shows four values:

• GCODE Commanded (black): This is the extruded length sent to the printer. Note it deviates from reality because of queuing and the time the printer takes to execute the moves. On large slow prints this deviation can be quite large.
• Measured Len (blue): This is the measurement from the rotary encoder, plus a drift correction that is applied on a regular interval (controlled by Drift Correction Interval in settings). You can see a drift correction here at -95 seconds. Drift Correction prevents false alarm triggers from accumulated small errors on large prints.
• GCODE Forecast (yellow): This is Filament Watch's best guess of how much filament has been extruded in real-time. This is the line that Filament Watch uses when determining whether an alarm condition has occurred.
• Alarm Boundary (green area): GCode Forecast +/- Allowed Deviation from settings plus an additional deviation allowance calculated from the difference between the GCODE Forecast and CGODE Commanded. If Measured Length goes outside this value, an alarm is triggered. Note this value is dynamic; after a wide deviation allowance is set, it will slowly (defaults to .1 mm/sec) return to the Allow Deviation value.

Values Table

• Summary, Printing, Armed, and Alarm show the current state of Filament Watch.
• GCODE Forecast, Commanded, and Measured length show the current values plotted on the graph. The value after the slash is the instantaneous extrusion rate calculated over the last second. This can be useful when diagnosing under extrusion issues.
• Allowed Deviation is the width of the Alarm Boundary. The value in parentheses is the current difference between Measured Length and the GCODE Forecast (ie, the current error).
• Current Feedrate - the latest sent feedrate for the head (movement, not extrusion). Note this is the commanded rate, not the forecast rate, so it may not reflect reality at that moment in time. This can be useful when diagnosing under extrusion issues.

Manual Buttons

• Arm/Disarm - use this if you want to manually override the arm state while the print is running.
• Correct Drift Now - causes drift correction (set Measured Length to GCODE Forecast value) to be applied immediately. Useful if you're getting close to alarming, but you know there are no print problems.

Log

The section at the bottom shows the last 10 Filament Watch log lines, including drift corrections. See below.

Tuning

As the print runs, Filament Watch will monitor accumulated errors and make suggestions for dialing in the exact rotary encoder diameter. Look for this value in the Filament Watch logs (circled below):

• At the beginning of the print, this suggested diameter will be way off, but will close in on the correct value the longer the print runs.
• Ironically, prints with many short moderately paced moves will produce a more accurate suggested diameter than prints with long slow extrusions. This is because forecasting must be used on the long slow prints, while short fast prints mean sent and measured lengths stay closer.

Using Filament Watch - Reliably

I'll be honest with you...get ready.

You probably don't want to use Filament Watch. Boom.

Filament monitoring seems like a no-brainier right? Throw in a rotary encoder....measure what moves and compare to what's supposed to move...simple right?

Here's what they're not telling you. If the monitor is not significantly more reliable than your prints, it's worse than useless. Let's say 1 in 20 - 5% - of our prints fail because of a condition Filament Watch might detect (and since we're being honest - there are many it won't). Ok great, we can perhaps save half of those 1 in 20 prints. But if Filament Watch has the same error rate - false positive errors on 1 in 20 prints - then you will actually have MORE failed prints using Filament Watch even when it accurately detects true failures. For this reason Filament Watch has to be significantly more reliable than the printer itself to at least not be a hindrance. Throw in the fact that there are so many printers, so many different firmwares and motherboards with different caching buffer sizes and planning schemes, and so many physical configurations, and you start to get a sense of scale of this problem. But wait it gets worse - then there's the slicer, the print settings, and the model itself.

All this means what Octoprint sends is almost never synchronized with the real world (which is what Filament Watch sees). Sometimes it's not. even. close.

So is all lost? No, not at all. But expectations must be set.

Here are my suggestion for success with Filament Watch:

• Until you have Filament Watch dialed in, set Alarm Action in settings to GCODE only. Then set the GCODE script to nothing or just beep (if your printer speaks) to notify you of an alarm. Here're some beeps for Marlin based printers:

; Beeps
M300 S600 P700
M300 S400 P700
M300 S600 P700

• Don't rely on Filament Watch until you've verified it with the same or similar models. What does "similar" mean?

  • Same printer and slicer? Obviously
  • Similar speed? Yes
  • Same layer height? Yes
  • Similar model? Yes. Huh? Why the model itself? Because a Benchy with its small intricate moves will look very different to Filament Watch than a full volume cube, even with identical print settings.

• Wide alarm tolerances are OK. The difference between a 25mm alarm boundary and a 50mm boundary might only delay an alarm by 30 seconds...which won't make a difference between a salvageable and failed print. But it might prevent a false alarm that does fail the print.

• The same goes for the drift correction interval - a fast (say 120 second) drift correction might delay some alarms, but will make false alarms less likely.

Wow, that was all doom and gloom. Is there any reason TO use Filament Watch?

Yes. Obviously Filament Watch can and does detect out of filament, tangles, and clogged nozzles. But it can also be an important diagnostic tool. I've found some models (the Big Slow Perimeter file in the Parts\Test Parts directory, for example) that produce under-extrusion at some points in the model. On my D6, it will reliably under-extrude (extruder will skip steps) between 52% and 55% complete, and again on the last few percent. At this point it's printing slow (12.5mm/s moves) exterior walls at below 1mm/s extrusion rates. These defects are barely noticeable in the final print (until you know what to look for)...so they're not "failures", but I did learn something new about what my printer is actually doing. Now just to find a solution... ;)

Enjoy