Pietro Elettrico

Update: This project is now done. If you want to see any improvements, write them down so we can plan V2 together.

Warning:

• This is not a simple project, so I would not recommend committing unless you are experienced in 3D printing and electromechanics.

• Many components are only available from Taobao. They were chosen because they offer the best performance for the lowest price. Feel free to substitute any components if you understand their purposes and that the substitution can perform the same tasks.

• Minor disassembly of the grinder will be required. I take no responsibility if your Pietro explodes.

Features:

• Field-oriented control (FOC) of the stepper motor for efficient power delivery with low vibration. The motor maintains constant RPM independent of load.

• 10:1 geared Nema23, resulting in enough torque to grind even the hardest beans. Espresso grind is also possible with slow feeding.

• Only requires disassembly of the handle part; anything that could affect grind performance and reliability is unmodified.

• Every 3D printed piece can be printed on a 180x180mm bed (A1 mini).

• Internal AC-DC converter, removable power cable.

• Single toggle button to turn on the grinder.

• Very low power consumption, ~60W during full load.

Printing Instructions:

I print every piece with high flow PETG for its good layer adhesion and strength, but PLA should also work, as nothing gets warm even under extended usage.

Important: Brim is highly recommended as all the interfaces between printed pieces must be flat. Let each print cool completely before removing from the build plate. Using hotter build plate temperature, glue stick, and negative Z-offset value all help to increase part adhesion to the build plate.

Important 2: As everything is designed for low-tolerance fitment, make sure your printer is very well calibrated. I recommend printing Front first to check if it fits your grinder snugly. It should have zero wobble, but not require too much force to put on and take off.

Main, Front, Interstage

• Print without support

• 5 walls, 2 mm top and bottom layers

• 20% infill

• Make sure the threads on Interstage is well resolved

Motor Cover

• Print without support

• 3 walls

• 10% infill

• Make sure the threads on Motor Cover is well resolved

Base

• Print with minimal support

• 3 walls

• 10% infill

• This part must be filled with concrete for strength and weight.

Connector

• PETG works fine, but upon further testing, TPU offers a significant reduction in grinding noise and corrects for minor misalignments in the system. (update 11.05.2025)

• Print with minimal support

• 5 walls

• 20% infill

Assembly Instructions:

Wiring Diagram:

Connector:

Install 3x M5 heat set inserts into the connector.

Remove the single screw on the handle cover, and remove the handle, pin, two detent pins and springs.

These can all be set aside, they will not be used in this build.

Temporarily use the handle pin to align the position of the connector to the spinner piece. 

Install the connector with the single screw previously used to hold the handle cover. The connector must be sized so that it presses onto the spinning part all the way. After it is tightened, remove the handle pin.

Install the aluminium coupling with 3x M5x16 screws.

Base:

First, pour concrete into the base for rigidity and weight. As designed, the base will not be strong enough to be used straight from the printer.

Install 4x M5 heat set inserts into the base. Then, install the aluminium plate along with the aluminium extrusion onto the base.

The aluminium plate needs to have a hole drilled through the center for the wires to pass through.

Wire the button, power converter, C6 socket together, and run 1 wire (EARTH) through the aluminium extrusion.

Main:

Install 4x M5 and 4x M3 heat set inserts into the flat side of main.

Install 4x M4 heat set inserts and 2x 4x100 mm pins into the front of main.

Slot main into the aluminium profile, and secure with an M5 flat head screw. Run the wires up from the aluminium profile into main and out of the hole in the back.

Install interstage with 4x M3 screws. Run the wire through the interstage. Tighten the screws in diagonal pattern for proper centering.

Take the X57 ribbon cable, on the driver board side, keep only V+ and GND, de-pin and remove all other wires. On the other side, remove the JST connector and run the two wires down the aluminium profile into the base, and connect to the power converter.

Motor:

Install the motor with 4x M5 socket head screws. Now the base will be very back-heavy, so support it so it does not fall back.

Glue the small cylindrical neodymium magnet onto the motor shaft at the back. This will be used as the encoder for the motor. Install the X57 board onto the motor. Plug in the power.

The motor leads can be cut and peeled. Then connect as shown. The default rotation direction of the motor depends on how the phases are wired.

The EARTH wire must be connected to a grounding point on the exposed pad of the X57 board. This is to prevent a ground fault of the power converter from sending AC into DC components.

Front:

The grinder can now be installed. Push it in all the way, and clamp with front with 4x M4 socket head screws.

Programming the X57 Motor Driver:

Update (26.06.2025): From the experiences of others, it is now recommended to program the driver with protocols other than TTL, as it is quite finicky to get to communicate properly.

Important: Before the driver can be programmed, it must first be powered on and connected to the motor with at least 12V at V+ pin for self-calibration. After the calibration is finished, it can then be programmed with as low as 5V at the V+ pin (however below 12V the motor will not spin).

The driver can be connected via TTL, RS232, RS485, CAN with their respective USB adapter. It can be powered directly by 5V at the V+ pin from the adapters.

Once the board is connected to the PC and powered on, open the ZDT control software attached (https://drive.proton.me/urls/CXVYH87DER#82YSTBqXCl59)

In the top left sub-section, connect the board. If successful, it will show the following texts in green. If not, try a different USB port on your PC.

To configure the parameters of the board, set everything as follows. Then make sure the dropdown (1) is changed to what's in the picture, and click (2) to program the board.

Finally, program the automatic start function by setting this sub-section as follows. Then make sure the dropdown (1) is changed to what's in the picture, and click (2) to program the board.

Note that if you choose to control the stepper driver board with external signalling, this part should be left alone.

Now the board has been successfully programmed and will spin the motor automatically when given power.

Non-Printed Part Lists: