i3-am8.md 12KB
title: i3 AM8 description: Rebuild of my i3 clone with aluminium extrusions, CoreXZ, Klipper x-parent: 3d-printing x-position: 25 x-date: 2022-02-01 x-update: 2022-06-10
x-comments: true
In February 2022 I finally decided to re-build my CTC i3 Pro B with an upgraded frame and better parts. The following are the new integral components:
- “AM8 - Metal Frame for Anet A8” by pheneeny on Thingiverse
- 2040 extrusions and nuts from Dold Mechatronik
- Core XZ AM8 Conversion by 93djen on PrusaPrinters.
- Sherpa Mini Extruder on GitHub
- Sourced from AliExpress
- NF Crazy Hotend
- Clone of Mosquito Hotend
- Contact Mellow Store on AliExpress to source it
- SKR Mini E3 v3.0 Mainboard
- Fysetc Mini 128x64 LCD panel V2.1
- Cloned version by BCZAMD on Amazon
Initially I simply wanted to re-use the mechanical parts from my old printer. But after talking to my friend Tobias about the project, he came up with the idea to convert the AM8 into a CoreXZ machine, and also immediately delivered a complete design! We selected the parts based on what I mostly still had lying around.
Other mechanical / electronical parts, like motors and the heatbed, I re-used from my previous printer.
Custom 3D-Printed Parts
Mounts for PSUs, MOSFET, Mainboard, Pi, Relais.
TODO links, photos
Power Supply Wiring
I added two power supplies to the printer. One is +5V, solely for powering the Raspberry Pi, and it is always on. The other is +24V, for running the printer itself. This is switched by a relais module, connected to the Pi.
I’m not entirely comfortable with the 220V wiring, so I added plan to add an enclosure that should prevent any shock hazards from touching.
As a small quality-of-life improvement I put a piece of shrink wrap tubing over the indicator LED of the +24V supply. I don’t understand why the manufacturer decided to put an unbelievably bright blue LED on there… 🤦
In an attempt to avoid any ground loops and power supplies driving each other, I decided not to connect the Pi and the Mainboard using USB. Instead I ran a cable between them, only connecting GND and the UART Rx and Tx lines. This is the only place where the grounds of the +5V and +24V supply are connected. The mainboard is not fed any external +5V.
As I’ve re-used 12V fans from my old printer, I had to add a small PCB with a 24V -> 12V converter to power them. I simply used a small LM2596 module soldered onto a perf-board with some connectors. The mainboard switches GND for all accessories, so using 12V fans is as simple as connecting the negative lead to the mainboard connector, and the positive lead to +12V instead of the mainboard connector.
LCD Connection
On a whim, I decided to get a Fysetc 12864 clone. Only later I realized that it is not really compatible with my chosen mainboard, as it does not have the standard EXP1/EXP2 connectors. Fortunately this can be fixed easily, you just need to connect the required pins to free IO pins of the mainboard. I decided to ignore the SD card interface, as I won’t be using it and the mainboard has one as well. So only the LCD and rotary encoder pins are required. My LCD board also has some RGB LEDs, so I decided to wire them up as well. The other question concerns the cabling. The standard 2x 10pin ribbon cables are hard to route and prone to interference. Counting the required pins, and looking at my cable stash, I decided to simply use some Cat5 ethernet cabling. With 8 cores per cable I only had to use two pieces in parallel.
Configuring it correctly turned out to be a bit tricky. Initially I thought I had hardware revision 1.2, based on the reviews on Amazon, with plain RGB LEDs on board. But I couldn’t get anything to light up, neither around the encoder nor the LCD backlight. That’s when I took a closer look and saw the WS2811 chips on the LCD PCB (and later also the revision printed on it 😅). Turns out I actually have revision 2.1.
One thing you should check before using a display like this: the RST and KILL pins and their respective resistors. The push button on the front of the LCD panel can be connected to either the RST or KILL pin. If you do a custom cabling, like I did, it doesn’t really matter which one of these you choose. But my display only came with R3 installed, which I didn’t notice at first. Because I wired up the KILL pin instead of using RST, I would have needed R4 instead of R3. I decided to simply switch out the 0Ω-link. The other resistor, R1, is also important. It should not be populated, otherwise the display will feed +5V back to the GPIOs of the MCU, which are only 3.3V tolerant.
To mount the LCD to my frame I used “Mini 12864 LCD Display Housing for 2020 V-Slot” by derebbe. You need to replace the kill button on the panel with a shorter one for this model to work.
TODO problems with encoder, kill button pullups?! TODO display no longer showing anything
TODO photo(s) of cabling
Klipper Firmware
After hearing many good things about Klipper from Tobias and others, I really had to try it out myself. And I have to admit, even though I didn’t believe it at first, it’s much better than Marlin in many areas, even for non-fancy printers like mine.
I’m using MainsailOS on a Raspberry Pi 3B. Installation and Configuration was really straight-forward with the configuration guides of Klipper and Mainsail.
Here is my current printer config file.
[include mainsail.cfg]
##########################################
################# System #################
##########################################
[printer]
kinematics: corexz
max_velocity: 200
max_accel: 2000
max_z_velocity: 200
max_z_accel: 500
[board_pins]
aliases:
# EXP1 header
EXP1_1=PB5, EXP1_3=PA9, EXP1_5=PA10, EXP1_7=PB8, EXP1_9=,
EXP1_2=PA15, EXP1_4=, EXP1_6=PB9, EXP1_8=PD6, EXP1_10=<5V>,
# I/O header
IO_1=PD0, IO_2=PD2, IO_3=PD3, IO_4=PD4, IO_5=PD5,
# PWR-DET header
PWR_DET=PC12,
# Unused pin
UNUSED=PA6
[mcu]
#serial: /dev/ttyAMA0
serial: /dev/serial/by-id/usb-FTDI_FT232R_USB_UART_A100OZQ1-if00-port0
restart_method: command
##########################################
################# Motors #################
##########################################
# The stepper_x section is used to describe the X axis as well as the
# stepper controlling the X+Z movement.
[stepper_x]
step_pin: PB13
dir_pin: PB12
enable_pin: !PB14
microsteps: 16 # set by driver
full_steps_per_rotation: 200 # motor specific
gear_ratio: 36:20 # CoreXZ gearbox
rotation_distance: 40 # 20 teeth * 2mm belt
endstop_pin: ^!PC0
position_endstop: 0.0
position_max: 235
homing_speed: 30
# The stepper_y section is used to describe the stepper controlling
# the Y axis.
[stepper_y]
step_pin: PB10
dir_pin: !PB2
enable_pin: !PB11
microsteps: 16 # set by driver
full_steps_per_rotation: 200 # motor specific
gear_ratio: 1:1 # driven directly
rotation_distance: 40 # 20 teeth * 2mm belt
endstop_pin: ^!PC1
position_endstop: 0.0
position_max: 235
homing_speed: 30
# The stepper_z section is used to describe the Z axis as well as the
# stepper controlling the X-Z movement.
[stepper_z]
step_pin: PB0
dir_pin: !PC5
enable_pin: !PB1
microsteps: 16 # set by driver
full_steps_per_rotation: 200 # motor specific
gear_ratio: 36:20 # CoreXZ gearbox
rotation_distance: 40 # 20 teeth * 2mm belt
endstop_pin: ^!PC2
position_endstop: 0.0
position_max: 250
homing_speed: 20
[extruder]
step_pin: PB3
dir_pin: !PB4
enable_pin: !PD1
rotation_distance: 22.67895
gear_ratio: 50:8
microsteps: 16
full_steps_per_rotation: 200
nozzle_diameter: 0.400
filament_diameter: 1.750
heater_pin: PC8
sensor_type: ATC Semitec 104GT-2
sensor_pin: PA0
control: pid
pid_Kp: 21.527
pid_Ki: 1.063
pid_Kd: 108.982
min_temp: 0
max_temp: 250
max_extrude_only_distance: 1400.0
max_extrude_only_velocity: 75.0
max_extrude_only_accel: 1500
###########################################
################# TMC2209 #################
###########################################
[tmc2209 stepper_x]
uart_pin: PC11
tx_pin: PC10
uart_address: 0
#stealthchop_threshold: 999999
run_current: 0.5
[tmc2209 stepper_y]
uart_pin: PC11
tx_pin: PC10
uart_address: 2
#stealthchop_threshold: 999999
run_current: 0.3
[tmc2209 stepper_z]
uart_pin: PC11
tx_pin: PC10
uart_address: 1
#stealthchop_threshold: 999999
run_current: 0.5
[tmc2209 extruder]
uart_pin: PC11
tx_pin: PC10
uart_address: 3
stealthchop_threshold: 999999
#interpolate: True
run_current: 0.3
###########################################
############### Accessories ###############
###########################################
[fan]
pin: PC6 # fan 0
[heater_fan nozzle_cooling_fan]
pin: PC7 # fan 1
[heater_fan controller_fan]
pin: PB15 # fan 2
###########################################
########### LCD / Encoder / LED ###########
###########################################
[display]
lcd_type: uc1701
cs_pin: EXP1_2
a0_pin: EXP1_3
rst_pin: EXP1_5
contrast: 63
encoder_pins: ^IO_2, ^IO_3
click_pin: ^!EXP1_1
kill_pin: ^IO_1
spi_software_miso_pin: UNUSED
spi_software_mosi_pin: IO_5
spi_software_sclk_pin: IO_4
# index 1 is lcd backlight
# index 2 is left encoder led
# index 3 is right encoder led
[neopixel lcd]
pin: EXP1_6
chain_count: 3
color_order: RGB
initial_RED: 0.3
initial_GREEN: 0.3
initial_BLUE: 0.3
##########################################
################# Beeper #################
##########################################
# M300 : Play tone. Usage:
# M300 [P] [S]
# P is the tone duration, S the tone frequency.
[output_pin beeper]
pin: PWR_DET
pwm: True
value: 0 # Silent at power on, set to 1 if active low.
shutdown_value: 0 # Disable at emergency shutdown (no PWM would be available anyway).
cycle_time: 0.001
[gcode_macro M300]
gcode:
# Use a default 1kHz tone if S is omitted.
{% set S = params.S|default(1000)|int %}
# Use a 10ms duration is P is omitted.
{% set P = params.P|default(100)|int %}
SET_PIN PIN=beeper VALUE=0.5 CYCLE_TIME={ 1.0/S if S > 0 else 1 }
G4 P{P}
SET_PIN PIN=beeper VALUE=0