WEEK 15: MACHINE DESIGN
Objectives
Group assignment:Have us...?
--> Our group page is available Here
Previously, during week 14...
During last week we build and assembled a passive CoreXY drawing machine. For this weekly assignment we have to automate it.For doing this, following the suggestion of our instructor Matteo, we decided to use an Arduino Uno board with a CNC Shield and some drivers. The software to interpret GCODE we used is GRBL.
Grbl is a no-compromise, high performance, low cost alternative to parallel-port-based motion control for CNC milling. This version of Grbl runs on an Arduino with a 328p processor (Uno, Duemilanove, Nano, Micro, etc). Via
Modifying and flashing GRBL
During this week I was in charge of preparing the software to move the motors and automate our machine. Basically I had to solve two problems:So I could solve the first problem modifying config.h file. I basically uncommented the line 189, defining #define COREXY;. Easy peasy.
For the second problem I modified the file named spindle_control.c with the instruction found Here.
--> Modified files are available at our Group Page
.Than I moved the downloaded GRBL folder inside Arduino app/Contents/Java/libraries, I opened Arduino IDE and I flashed on our board the grblUpload sketch.
After that I connected all motors to the CNC Shield. For helping me, I created a simple image that explains how to connect a stepper and a servo motors.
For testing X and Y axis, we used Universal GCODE Sender, a Java software made for controlling CNC machines with a GUI via serial commands. Basically, to test our machine, I tried with these simple commands:
G0 X10 - moving only on X axisG0 Y10 - moving only on Y axisG0 X10 Y10 - moving on X and Y axis at the same timeM5 S200 - moving servo upM3 S200 - moving servo downAfter that, I modified again the spindle_control.c file in order to change as well the servo motor's angle movement. At line 48 and 49, infact, I found:
#define PEN_SERVO_DOWN
and
#define PEN_SERVO_UP
These two parameters regulate what I want. Basically I reduced the delta between the first and the second one (bringing at 16 and 18). In this way I could have a minimum rotation angle that allowed me to lift the pencil from the sheet without straining the servo motor.
To make the changes effective, I opened Arduino IDE and I flashed again grblUpload.
Creating a simple GCODE
To the final test of our machine, I created a simple GCODE file for drawing three 10 mm square in three different positions. As I said before, I used M3 and M5 commands to simulate Z axis. Here's the code.
(3 10 mm SQUARES GCODE - DARIO BERNABINI, TOMMASO LOMBARDI, GIADA ALLOCCA - FAB ACADEMY 2018)
(M3 S200=Z DOWN)
(M5 S200=Z UP)
(Angle width in spindle_control.c, line 48 and 49)
M5 S200
M3 S200
G91 G0 X10
G91 G0 Y-10
G91 G0 X -10
G91 G0 Y 10
M5 S200
G91 G0 X30
M3 S200
G91 G0 X10
G91 G0 Y-10
G91 G0 X -10
G91 G0 Y 10
M5 S200
G91 G0 Y30
M3 S200
G91 G0 X10
G91 G0 Y-10
G91 G0 X -10
G91 G0 Y 10
M5 S200
Final Result and future improvements
In this page I only embedded the final video I made for our project. You can find all contribution, future improvements and in general the entire work in our Group Page. The assignment of the last two weeks has been among the most difficult but fun and satisfying of those done so far and I was very happy to have contributed to the creation of as simple but fully working machine.For the future, we think the needed improvements could be the following ones: