Thor GRBL

Thor GRBL is a modification made from GRBL to allow the control of 8 stepper motors simultaneously.

Getting Thor GRBL

GRBL modification for Thor can be cloned/downloaded in Thor's GRBL repository.

Compiling & Flashing GRBL

In this wiki page from the GRBL wiki is explained how to compile GRBl. They also have this other page explaining how to flash GRBL to an Arduino.

Communication using Thor GRBL

To communicate with the control board, connect the Arduino Mega via USB to the PC. There are tools like Universal Gcode Sender which facilitate the connection and communication between the board and the PC. Anyway, you can communicate with the board via Serial using your favorite method.

Thor is moved using a custom Gcode. This is the structure: G0 A## B## C## D## X## Y## Z## where A corresponds to the motor of the first articulation, B & C corresponds to the motors of the second articulation, D corresponds to the motor of the third articulation, X corresponds to the motor of the forth articulation and Y & Z corresponds to the motors of the fifth and sixth articulations. ## represent the absolute value of rotation (measured in degrees) of each articulation except the last two.

To control the tool there is the Gcode M3 S## where ## is a value between 0 (0V) and 4000 (5V).

Initial configuration

Before moving Thor, there are some adjustments that have to be made.

• First of all, usefull codes. Send $X to kill the alarm lock, probably caused by a homing fail. $H will run a homing cycle. $$ will show you the GRBL settings.

• By default, GRBL disable the steppers if they are not being used. This feature, that can be very cool for CNC machines, is a huge problem for Thor. Thor can end a movement in a position where it needs to be holded by the motors, and disabling them will make Thor falls. To disable it just send the code $1=0