3018 CNC Upgrade

Introduction

3018 CNC (without wiring, spindle and board)

I recently purchased a 3018 CNC, so as to perform simple milling, cutting, and engraving operations. The 3018 CNC is simple, cheap and well, quite limited in terms of features. I may point out that although quite essential, its main board allows for quite some modding.

In order to get around those limitations, I modified the CNC and added several of the features which were not included out of the box (mostly to keep low the price tag).

Most of them were inspired by the very useful webpage which is definitely worth reading : https://www.instructables.com/id/Upgrade-Your-CNC/

Mod list

• Z-Probe : z-probe is a very useful addition to the CNC as it allows building an height map, which can cope with (low) build accuracy of the DIY CNC kit. Simply connect two alligators clip to ground pin (any of the one GND), and to the PIN A5.

GRBL Height Map

•  Axis End stops: adding hardwired constraints to the CNC prevent unsafe displacement (in particular as far as X and Y axis is concerned). Moreover the auto homing feature can be turned on.
• More powerful Spindle. By taking advantage of a low cost 3D printer and several parts, I changed the 775 spindle with a more powerful one. The one I installed is a 100V, 500W air cooled spindle. It is way heavier, and its external diameter is bigger, therefore it does not fit in the original housing. It is way less noisy, and more powerful; nevertheless the change is particularly complex, and therefore I would suggest it only if the 775 is limiting your operations too much. The complexity of the change is mainly due to: precision in the 3D print, installation of the lead screw and linear bearings. The spindle motor is heavy and the stepper motor is connected upside down, hence the stepper / axis joint screw is the one which will cope with all the weight. Please find below a brief list of the parts needed for the mod:
  1. Threaded Rod
  2. Lead screw
  3. Red line laser module (2x)
  4. Linear Bearing (2x)
  5. Air cooled 500W Spindle 
  6. DC-DC Buck Converter: this component takes as input the former motor voltage ( 24 V approximately), and converts it to a 10 V signal.
  7. PWM to 1-10V converter board: this component receives the signal from the pin between Zen and Yen (which is a PWM signal of the Motors duty cycle). It then gets as VCC the 10V signal of the DC-DC Buck converter, and then outputs, a 1-10V signal which feeds the Mach 3 port of the 500W Motor power supply. In this way it is possible to control the 500W motor via GCODE, as with the previous motor. Please find below a picture of the schematics to wire the components. The resulting assembly can run either in AUTOMATIC mode (controlled via GCODE), or in MANUAL (controlled by a pot) mode.

• Laser pointers: as I was printing a new spindle housing, I added room to integrate 2 Line laser pointers. they are very handy to understand in a glance where the axis is pointing. Definitely worth.
• Z Axis pitch: as I was changing the spindle housing, due to the extra weight, I was wondering whether the (not so powerful) Stepper motor, mounted vertically, could cope with the load. Therefore I bought a smaller pitch screw. Some extra configuration is needed so to avoid stall and keep dimensional coherence.

Woodpecker Board Pinout

Configuration files

The configuration of the CNC is the one below:

$ < $0=10 (step pulse, usec)
$1=25 (step idle delay, msec)
$2=0 (step port invert mask:00000000)
$3=6 (dir port invert mask:00000110)
$4=0 (step enable invert, bool)
$5=0 (limit pins invert, bool)
$6=0 (probe pin invert, bool)
$10=3 (status report mask:00000011)
$11=0.010 (junction deviation, mm)
$12=0.002 (arc tolerance, mm)
$13=0 (report inches, bool)
$20=0 (soft limits, bool)
$21=1 (hard limits, bool)
$22=1 (homing cycle, bool)
$23=3 (homing dir invert mask:00000011)
$24=15.000 (homing feed, mm/min)
$25=200.000 (homing seek, mm/min)
$26=250 (homing debounce, msec)
$27=2.000 (homing pull-off, mm)
$100=800.000 (x, step/mm)
$101=800.000 (y, step/mm)
$102=3178.600 (z, step/mm)
$110=5000.000 (x max rate, mm/min)
$111=5000.000 (y max rate, mm/min)
$112=200.000 (z max rate, mm/min)
$120=10.000 (x accel, mm/sec^2)
$121=10.000 (y accel, mm/sec^2)
$122=4.000 (z accel, mm/sec^2)
$130=280.000 (x max travel, mm)
$131=168.000 (y max travel, mm)
$132=60.000 (z max travel, mm)

The bold terms refers to the change in pitch of the z axis thread.