3D Printer Extruder Remote Health Monitoring

Description

This is a force monitoring solution for 3d printers with bowden extruders. The force generated by extruding filament while 3d printing can indicate whether the printer extruder is in good health or there is a fault.
With the sensor controller board connected to a Raspberry PI, we can use services such as Twitter to transmit mini force sensor data reports that can be accessed by mobile device. Data collection networks such as Xively can also be used to generate an overall picture of how the 3d printing is doing.

3d printing is mostly reliable, so it's just a case of checking the mini sensor reports on twitter occasionally while you catch up on some sun out in the garden. And you know, if there is a problem, you can still act quickly and avoid those 3 hour plus in air printing because the filament broke in the bowden tube.

Details

System Design Diagram

It is not necessary to complete the whole project in order to get some useful functionality. I currently use an Arduino Uno and Processing on the PC to occasionally check the extruder health on my 3d printer. I would just need to add a loud buzzer to have a short range alert system. I could set the buzzer to trigger when the force sensor measurements get too high, or too low when other conditions are met.

You can checkout this article for the basic circuit and source code: Arduino Load Cell Circuit & Sketch for Calibration Test

STEPS

The steps below are a summary of what needs to be done to get the project to completion. The steps will link to a more detailed explanation or instructions further down the details section of this page.

Step 1

So, if you look at the system design diagram below, we first need to set up the load cell, that means we need to decide how the load cell will be attach to the 3d printer. Files to 3d printed part of the load cell bracket will be provided with this project, however, an additional bracket may need to be designed to complete the load cell fixture to the 3d printer chassis. Setting up the load cell will be detailed below.

Step 2

This where we look at adding some sort of controller to the load cell. Initially, you can go for the simple set up to start with as explained above, or you can get on board with the Teensy 3.1. More details to come on how and why the Teensy 3.1.

Step 3

We now look at setting up a Raspberry Pi, We'll assume that the Raspberry Pi is up and running by this point, but I'll recommend some links here to get the Raspberry Pi up and running to a level needed for this project

Step 4

Get the Raspberry Pi to accept data from the sensor controller. We could have the the Raspberry Pi collect data from more than one printer, so we need to think about an I.D. scheme for the printer.

Step 5

=======taking a short break

Load Cell Set Up

With the updated system design, this project should now be a lot more accessible to more 3d printer owners. The load cell for force sensing is now fitted within the bowden tube instead of being attached directly to the stepper motor. It should be noted though that it is important to have a bend in the extruder bowden tube in order to measure as much of the force as possible that is generated by the stepper motor. Test results of how much force is measured from the total force generated by the stepper motor will be detailed below when ready. So that the readings are consistent from the load cell, the bowden tube will need to be floating in air, electrical wires and such should not be cable tied to the bowden tube.

=====more to follow

Software

Libraries Required

Teensy 3.1:

Adafruit: adafruit/Adafruit_ILI9340

Adafruit-GFX-Library
Software License Agreement (BSD License)

Raspberry Pi:

Twitter: ryanmcgrath/twython
The MIT License

Xively: xively-python
Open Source, under the BSD 3-Clause license

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Other Documentation

I've written a couple of articles that demonstrates how the filament force sensor behaves under different 3d printing conditions, and how it can be used to test extruder components:

3D Printer Extruder Filament Drive Gear Review & Benchmark

http://airtripper.com/1676/3d-printer-extruder-filament-drive-gear-review-benchmark/

Airtripper Extruder Filament Force Sensor – Introduction

http://airtripper.com/1338/airtripper-extruder-filament-force-sensor-introduction/

Nice Project! - Do I need this?

Mostly, for the average 3d printer user, you won't need a filament force sensor. However, if you have a 3d printer with a bowden extruder, you might at least need a little help in setting the right retraction distance.

Is the filament force sensor a worthy 3d printer add-on just for a small set-up issue? Probably not.

However, what is common with most 3d printer users, there are long print jobs, often taking many hours. I'm not going to admit to leaving the printer alone for a moment during those long print jobs, but on the occasion,...

Components

1 × Load Cell Load cells can be obtained from cheap kitchen scales costing around 5.00 GBP.

1 × INA125 Amplifier and Linear ICs / Instrumentation Amplifiers. 4.50 GBP

1 × Teensy 3.1 USB-based microcontroller development system, 20.00 GBP

1 × Raspberry Pi Model B The Raspberry Pi is a credit-card sized computer. 25.00 GBP

Project Logs

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Tweeting from the Pi
Mark Heywood • 09/06/2014 at 23:10 • 0 comments

Got a new Raspberry Pi up and running, installed Twython for sending twitter feeds, and run the first test.
Awesome! It worked.
So, now I'll be looking at connecting the Raspberry Pi to the load cell test circuit. The test circuit is currently with Arduino Uno, and at this point it is about getting the concept working, and then finalize the controller hardware later.
We've got sensor readings, Skipper
Mark Heywood • 08/25/2014 at 20:27 • 0 comments

3D Printer Extruder Filament Force Sensor Design Comparison
First test shows sensor readings that are surprisingly similar from both sensor designs. Both Processing graphs were running side by side while printing an airtripper extruder part. More testing will be done later, however, current test results provide enough confidence to continue with the light weight indirect force sensor design set-up.
The reduced noise in the indirect force sensor graph is due to the light weight design of the load cell bracket.
The load cell calibration process used is covered in this guide, however, I used a revised circuit for lower voltage in this test. I'll publish the revised circuit used for this test later.
Looking Good
Mark Heywood • 08/24/2014 at 22:37 • 0 comments

Indirect Force Sensor Test Set-Up
So, the new indirect filament force sensor now piggybacks on the direct filament force sensor. The new sensor turned out to be light enough to be supported entirely by the PTFE bowden tube, so no extra bracket needed. The sensor will move as the Y axis moves but this should not effect the force readings too much.
The next step is to calibrate a new circuit, and then the readings can be taken to compare the two different load cell set-ups. Once I get some readings, I'll be first checking if the indirect force sensor is providing linear readings as with the direct force sensor or kitchen scales.
You can see with the design of load cell that it should fit many extruder designs that use similar tube fittings like in the above picture.
Step 1, and so it begins.
Mark Heywood • 08/23/2014 at 22:16 • 0 comments

Indirect Sensor Load Cell Bracket
Got delivery of two more scales today which have this load cell installed, probably the smallest 5 kg load cell you can get hold of for less than 5 GBP. I did an Electronic Kitchen Scales Teardown Versus Load Cells article which includes the scale that contains the load cell above, it is the WH-B05 scale, these are very popular on Ebay, best to search 5kg scale and then match the casing style in the listings to be sure to get all the sellers selling these.
If you are using the straight push fit tube fitting with M6 screw thread, you can make use of one of the 5mm fixing holes in the load cell by tapping an M6 thread, the other hole then can be used to attach the 3d printed bracket which holds another push fit fitting.
I'm hoping to complete the sensor bracket tomorrow if time permits. I'll attach the completed load cell bracket above the existing filament force sensor bracket, and then I can begin comparing indirect force sensing to direct force sensing.
What Title Change?
Mark Heywood • 08/20/2014 at 22:09 • 0 comments

Well , today I got the concept video done and uploaded, also the system design diagram for indirect force sensing is now up in the details.
I've also changed the project title to reflect the goal of this project, and updated other text to better reflect what this project is about. The project detail section needs a bit of work but should start taking shape as I get the resources together.
I now know which libraries I'm using on the Raspberry Pi for Twitter and Xively:
https://github.com/ryanmcgrath/twython
https://github.com/xively/xively-python
I'll perhaps log high resolution data, taken from the force sensor, on the Raspberry Pi , and then compile the data I need from the log to transmit to Twitter and xively.
And I've been for eye test today and now have to wear glasses so I can see what I'm doing close up. Soldering and breadboarding should be a lot easier now.
Direct Force Sensing
Mark Heywood • 08/19/2014 at 20:28 • 0 comments

Here is the system design diagram for the current Airtripper Extruder Filament Force Sensor set-up. The diagram shows direct force sensing where all the forces generated by the stepper motor is transferred to the load cell.
An amended system design diagram is coming up that shows indirect force sensing. This diagram will show how the force sensor can be applied to existing extruder systems. Should be a lot easier to set up than the current extruder force sensor design.
The direct force sensing set up is ideal for testing and benchmarking existing and new hot end designs, stepper motors and drive gear filament pulleys.
Do I have to use your extruder?
Mark Heywood • 08/17/2014 at 01:07 • 0 comments

Just added two updates to the project details:
Nice Project! - Do I need this? - How will this project benefit the average 3d printer user?
I Love My Extruder! Do I have to use yours? - Explains that a compact design is an option that will fit in an existing bowden extruder system.

Processing sketch for graphing the force sensor outputs on a computer is ready to publish, just got to set-up Github for it. Should be useful for projects other than this.
Left it till late!
Mark Heywood • 08/16/2014 at 01:05 • 0 comments

With only five days to go, I've decided to get my entry in for the hackaday prize. I should make the entry requirements before closing, with the 2 minute video taking the most effort to produce.
Much of this project is very well documented on my blog, but what is lacking, is a detailed summary of the build process from start to finish, hopefully, this project page will provide that summary, and the hackaday prize will be the boot up the backside to get it done.