A few months ago I retrofitted an old foam cutter based on a MM2001 hardware.

This system works quite well, but the unipolar stepper motors are very weak and prevent any fast motion... which is "annoying" when the hot wire is at one end of the machine and you want to go to the opposite side...

So why not building a brand new controller with the following requirements :

• able to drive a hot wire
• equiped with 4 bipolar steppers
• driven by standard polulu shields
• and with an ESP32 MCU
• FluidNC driven
• able to "eat" gcode produced by any "foam cutter" software

Let's go it's an easy project which shouldn't cost more than 20$ (without motors) !

Electronics

Schematics

This schematics is extremly simple as it implements 4 times the basic way to use a polulu driver

Apart from the steppers, the only useful part is the hotwire. It's a 1m long 0.3mm nichrome wire which is fine tuned powered by a PWM under 40V (same PSU for the steppers).

• PWM is produced by a two stages mosfets setup
• the big BUZ11 takes care of the power line
• the small 2N7000 is powered at 5V and its gate is triggered by GPIO32 of the ESP32
• 5V supply is delivered by the USB cord plugged into the ESP32 and by an external supply for polulus and hotwire

Finally I have added  two home switches inputs (homeX and homeY) although they are useless for a foam cutter!

And exposed a few more pins of the ESP32 to be used (or not) for future projects!

PCB

I have designed a nice and compact PCB allowing to "shield" the drivers and the ESP32 modules.

The PCB was kindly sponsored by PCBWay and is as usual of excellent quality.

You can order it here: PCBWay shared project. It's cheap, delivered very fast and so professional looking!

and if you are new to PCBWay please use this affiliated link : https://pcbway.com/g/o35z4O

Soldering this board is fairly simple. 

Here is the result:

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Software

This board is directly compatible with FluidNC firmware. So we will only focus on FluidNC configuration.

If you don't know how to install FluidNC, please refer to this log : https://hackaday.io/project/193659-lets-convert-a-dc-motor-into-a-stepper-one/log/225300-installing-fluidnc

Configuring FluidNC is not totally simple but if you follow the documentation it is feasible without too much difficulties.

Here is the config.yaml file for my machine.

name: 4 axis hot wire cutter
start:
  must_home: false
axes:
  x:
    steps_per_mm: 200
    max_rate_mm_per_min: 1000
    acceleration_mm_per_sec2: 10
    max_travel_mm: 1000
    motor0:
      limit_all_pin: NO_PIN
      limit_neg_pin: NO_PIN
      limit_pos_pin: NO_PIN
      hard_limits: false
      pulloff_mm: 1
      standard_stepper:
        step_pin: gpio.13
        direction_pin: gpio.15:low
        disable_pin: NO_PIN
  y:
    steps_per_mm: 200
    max_rate_mm_per_min: 1000
    acceleration_mm_per_sec2: 10
    max_travel_mm: 1000
    motor0:
      limit_all_pin: NO_PIN
      limit_neg_pin: NO_PIN
      limit_pos_pin: NO_PIN
      hard_limits: false
      pulloff_mm: 1
      standard_stepper:
        step_pin: gpio.12
        direction_pin: gpio.14:low
        disable_pin: NO_PIN
  z:
    steps_per_mm: 200
    max_rate_mm_per_min: 1000
    acceleration_mm_per_sec2: 10
    max_travel_mm: 1000
    motor0:
      limit_all_pin: NO_PIN
      limit_neg_pin: NO_PIN
      limit_pos_pin: NO_PIN
      hard_limits: false
      pulloff_mm: 1
      standard_stepper:
        step_pin: gpio.27
        direction_pin: gpio.26:low
        disable_pin: NO_PIN
  a:
    steps_per_mm: 200
    max_rate_mm_per_min: 1000
    acceleration_mm_per_sec2: 10
    max_travel_mm: 1000
    motor0:
      limit_all_pin: NO_PIN
      limit_neg_pin: NO_PIN
      limit_pos_pin: NO_PIN
      hard_limits: false
      pulloff_mm: 1
      standard_stepper:
        step_pin: gpio.25
        direction_pin: gpio.33:low
        disable_pin: NO_PIN
stepping:
  engine: RMT
  idle_ms: 250
  pulse_us: 20
  dir_delay_us: 0
  disable_delay_us: 0
user_outputs:
  digital0_pin: NO_PIN
  digital1_pin: NO_PIN
  digital2_pin: NO_PIN
  digital3_pin: NO_PIN
PWM:
  output_pin: gpio.32:low
  enable_pin: NO_PIN
  direction_pin: NO_PIN
  disable_with_s0: false
 s0_with_disable:...