How to set up and control the idraw v2 A3 plotter under Linux

I recently (June 2022) bought the idraw v2 A3 plotter. It's an excellent piece of kit and I'm very happy with it. However, it's not supported under linux - the Inkscape extension does not check for the linux port name, so you just get connection errors. I prefer to work from the command line anyway, so here's how I set it up. I think this will also work well for other GRBL plotters. Hopefully somebody will find this useful.

HARDWARE

I bought the idraw v2 plotter version without a base. This needs to be setup carefully. The kit comes with four metal bars. Two of them are short (I'm calling these the 'X-bars') and two are long (the 'Y-bar' and the 'arm', the latter being the part that moves). The Y-bar is connected to the X-bars with two smallish screws that allow some movement (perhaps deliberately). This means that the arm is not guaranteed to be level. If it's pointing upward the pen is lifted from the paper on the right hand side, if it's pointing downwards the pen starts to dig into the paper - neither is good. I loosened the screws and supported the arm with a small piece of wood while positioning it using a small spirit level. A bit fiddly but in the end I got it level.

The circuit board does not remember the position of the head when the power goes off, so you need to move the arm and head manually to the (0,0) position before starting (to the other end of the Y-bar opposite the circuit board). WARNING: do this slowly and gently because moving the arm this way creates induction currents in the circuit board. When the power goes off the firmware always performs the pen-up action.

SOFTWARE

Briefly, you start with an SVG file. This is first optimized, then the optimized version is converted into GCODE, and finally the GCODE is sent to the plotter.

The serial port on my system (Tumbleweed) is called /dev/ttyUSB0. I understand that on Raspberry Pi's it's called /dev/ttyACM0, and it may be different on other systems still. I'm sticking here to the first version.

TIO

First of all, it's useful to check out the firmware with a terminal serial port comms program such as tio (available through most package managers). Start with

     tio -e /dev/ttyUSB0

You should see the GRBL firmware 'chatter' string, after which you can type in some commands. The device needs to be initialized, for which I use

 G21 G17 G90 F100 G00 Z0 G92 X0 Y0 Z0

This means:

G21 use millimeters
G17 use the XY plane (this is not a 3D device)
G90 use absolute positioning
F100 use speed 2500 for drawing (max 25000, used for moving with pen up), you may want to increase this
G00 Z0 pen up
G92 X0Y0Z0 save the current location of the head as (0,0,0)

Please note that Z increases in the downward direction. The pen-down command is

     G00 Z5

Please note that the 5mm may not be the right one for your device, you may have to experiment a bit to get it right.

After this you can send move commands such as

     G00 X50 Y50

and you should see the arm move to position (50,50,0).

vpype

I use the vpype command to optimise the SVG. Install with

 pip3 install vpype

The command I use is (remember, this is for A3 paper)

vpype read inputfile.svg scaleto 26.7cm 39cm linemerge -t 0.1mmlinesort write --page-size a3 --format svg --center output.svg

vpype requires a configuration file called .vpype.toml (note the dot at the start) which is placed in your home directory. It looks like this:

[gwrite.idraw]
default_profile = "gcode"
unit = "mm"
invert_y = true
document_start = "G21\nG17\nG90\nF2500\nG00 Z0\nG92 X0 Y0 Z0\n"
layer_start = ""
line_start = ""
line_end = ""
segment_first = """G00 X{x:.4f} Y{y:.4f}\nG00 Z5\n"""
segment_last = """G00 Z0\n"""
segment = "G01 X{x:.4f} Y{y:.4f}\n"
document_end = """G00 X0 Y0 Z0"""

juicy-gcode

I use the juicy-gcode command to convert the SVG to GCODE link here.

The command is (using output.svg from the previous step)

    juicy-gcode output.svg -f flavor.txt -o output.gcode

This requires a configuration file called flavor.txt that looks like this:

gcode
{
begin = "G21\nG17\nG90\nF2500\nG00 Z0\nG92 X0 Y0 Z0\n"
end = "G00 X0 Y0 Z0"
tooloff ="G0Z0"
toolon = "G0Z5"
}

gcode-cli

Finally, I use the gcode-cli command to send output.gcode to the plotter link here. There are alternatives as well, but I like this one. This program needs to be compiled from source by the command

   make

Before doing that, it's worthwhile to edit the file main.cc and make a couple of changes. First find the line that says

int initial_squash_chatter_ms = 300;

Change the 300 to 2000 to allow plenty of time for the firmware chatter to finish (otherwise the program will hang). Then find all occurrences of ttyACM0 and replace them with ttyUSB0 (or whatever on your system).

To use the program simply type

    gcode-cli output.gcode

and enjoy the result.

Cheers

monperrus / idraw2linux