Filament Force Sensor

thingiverse

This is a Bowden filament force sensor that can be used to explore details of your printer setup. It comprises: Two 10kg load cells ( Size:80x12.7x12.7mm)(M4one end, M5 at the other end) Two M5 Pneumatic couplers One HX711 ADC module One NodeMCU V2. Two 28mm M4 bolts plus screws. The code for the NodeMCU can be found here: https://github.com/dagnall53/dEEbugger_PUBLIC/tree/patch-2 Use 28-30mm screws to connect the two sensors, and 8mm screws to connect the "opposite" housing. To use with the current code, program your NodeMCU with my version of the deeBugger software, and allow it to log into your network- the code uses WIFI Manager, so passwords etc are not stored in the Arduino sketch. Once it is running, you need to log into the deeBugger, and change channel 1 to "HX711". provided you have everything connected right you will see a screen like the example. You may have to change the connections to the load cells if you get negative pressure readings when extruding. you should also check the accuracy of the cell with a known weight. The design tares the load at startup. The scaling /calibration factor is around line 16 and 17 of Scopecommands.cpp: "float CH1scaleset=2.09; float CH2scaleset=2.09;" Change the 2.09 to a value that suits your sensor. I found that this value is "near enough" for the 10kG sensors I used. I made the unit with two load cells as this was easier than designing and making the other arm without the load cell. To assemble, place the two load cells near each other but not touching, and screw them together with the m4 bolts at one end. and drill both the M4 threads to clearance on one sensor. Fit the screw through the case and the (drilled out) sensor to screw into the unmodified sensor. Space the sensors with 4 washers. At the opposite end to the screws, screw in the M5 pneumatic coupling. (Why the load cells have M4 at one end and M5 at the other I do not know, but it is very useful for this application) Make sure that the load cells are not touching. They do not move much but must not be touching. In the picture, the black tape is providing some strain relief to the sensor wires, and holding the spare sensors wires neatly. Wire one load cell to the HX711 ADC. Wire the HX711 to the NodeMCU. (SCK to D6 DT to D5) Connect the HX711 power to 3.3V and ground. If you use my "dEEbugger-" code you can connect a second senor to chB to (slowly) monitor two filaments. Power up the NodeMCU, connect to wifi, switch to "HX711" and log in on your PC/Ipad etc. You can now observe the actual force being used to push the filament. If you switch on the "logger" function, you will need to have the NodeMCU connected to a terminal/monitor, such as that included in the Arduino programming suite. If you have this connected, the program will print its force readings out to the terminal / monitor, where you can save them. To slow down the samples per second sampling rate, Click the "Terminal" in the scope, and type "SCOPE SPS 10" (return) This will set the scope to 10 samples per second. There are lots of other nice features in the deeBugger software and you can read about it at : https://github.com/S-March/dEEbugger_PUBLIC - I have simply added the ability to read the HX711 and modified the scope graticule.