Filament Holder Scale A1mini / Generic

Overview

This Filament Scale is designed for precise filament weighing by automatically deducting the spool's weight to show the true net filament amount.

It features a simple web interface optimized for ease of use on devices like PCs and mobile phones.

Through this interface, you can easily enter the spool weight for any filament type and manufacturer. Measured weights of spools, along with a simple description, can be saved to the scale for future use.

Calibration of the scale is performed with just a few clicks within the web interface.This model is designed for the Bambu Lab A1 mini, but can be easily adapted for other printers. Source files (STEP, FreeCAD) are included for adaptation.

Description below is related to Bambulab A1mini, but can be easily adapted for other printer.

Power supply is provided by AMS interface of A1mini, but can be easily adapted for other printer.

Designed in FreeCAD, source files included.

Print Settings

The 3MF file created in OrcaSlicer is included.

Material: PLA
Layer Height: 0.2 mm
Perimeters: 4
Top/Bottom Layers: 4
Infill: Gyroid 40%
Supports: Yes

Bill of Materials (BOM)

• 1pc ... Raspberry Pi Pico 2W

• 1pc ... LM2596 module

• 1pc ... HX711 digital load cell weighing module

• 1pc ... YZC-131 load sensor 3kg

• 1pc ... 1N5819 40V 1A DO41 Shottky diode

• 1pc ... Microfit 4 pins, 2 rows (2 pin is also usable, see photos)

• 1pc ... Dupont 4 pin (load sensor connection)

• 2pcs ... 1,4x4 BN 13577 screw for thermoplastic

• 5pcs ... 2,2x5 BN 82428 screw for thermoplastic

• 4pcs ... M4x16 PH2

Assembly Instructions

Mechanical assembly

NOTE: Electronics should be disassembled during wiring/soldering. Plastic part could be damaged due to the soldering temperature.

1. Push load cell wiring through the holder hole into the bay for electronic equipment. Pull the load cell inside the holder and mount with M4x16 screws.
   
   

   

   
   

2. Mount Rpi Pico 2W to the electronic bay cover with 1,4x4 screws. Pull power supply cable through the cover hole.
   
   
   

   

   
   

3. Mount HX711 and LM2596 to the electronic bay cover with 2.2x5 screws .
   IMPORTANT: USE WASHER FOR RIGHT SCREW !!!
   
   

   

   
   

4. Connect the electronic wiring according to Electronic/Electrical assembly below.
   

5. Download the software, see chapter Software below.
   

6. Insert gently cover with electonic equipment into the electronic bay. Mount with 2.2x5 screws.
   
   

   

7. Connect power supply, connect the scale via web browser. Continue with scale calibration described in chapter Software below.
   
   

   

Electronic/Electrical assembly

Circuit diagram (the power cable is for Bambulab A1 mini. Please adapt power supply cable / connector according to your printer):

IMPORTANT: Adapt the LM2596 output voltage setting, as shown in the photo. The LM2596 comes in variants with different potentiometer sizes. Some of these do not fit the design. Changing the potentiometer to a fixed resistor 1k will also prevent catastrophic failure after an unintentional change of output voltage. Check 330R rezistor, there can be diferent value on your version. 

IMPORTANT: Check the LM2596 module output voltage before connecting to other devices !!!!

IMPORTANT: Shorten pinheader as close as possible to PCB.

ADVICE: The load sensor wiring should be ended by a Dupont connector to make assembly/disassembly with the HX711 module possible.

Software

For SW equipment see https://github.com/vmalat/UltimateFilamentScale

Scale calibration:

1. Go to the settings
   
   

   

   
   
   

2. Calibrate scale, see instuctions on the website, return back when succesfully finished.
   
   

   

Related projects

Update of the axle is available:

Updates

2025-12-15 Infill value fixed in description
2025-12-05 Description updated.

Disclaimer

The creator is not liable for any damage to your hardware or any unintended results caused by the use of this project, its code, or its documentation. Use at your own risk.