NAME

README - Scripts and instructions for running EMC2 based RepStrap

DESCRIPTION

This package helps you to build a Linux EMC2 based RepStrap machine (Non standard RepRap machine, useful for bootstrapping a RepRap).

If you have a desktop milling machine controlled by EMC2 or Mach3 already, with some hardware modification, specifically adding the plastic extruder print head, it would be mechanical capable in printing 3D plastic model. This package serves as a guide to your integration.

The package comes with two big components:

An Amtel AVR firmware, to be compiled with Arduino (http://www.arduino.cc), which is designed for the following hardware combinations:
- the RepRap's Extruder Controller 2.2 (http://reprap.org/bin/view/MainExtruder_Controller_2_2)
- DC Motor and Magnetic Rotary Encoder (http://reprap.org/bin/view/Main/Magnetic_Rotary_Encoder_1_0) as extrusion driver, with software PID loop implemented.
- Thermocouple or Thermistor for temperature reading
- Resistive heating element driven by MOSFET
The program architecture is also flexible enough to extend the support to stepper motor (Patch is welcome!), as well as a different motherboard design.
EMC2 Integration. A set of scripts allows communication to happen between the EMC2 and the firmware mentioned above. As long as the communication protcol is compatible, this set of scripts are still useful even if it's not the same firmware. The protocol is developed based on the RepRap 3rd Gen Electronics internal communication protocol.

A few more scripts included for adopting Skeinforge GCode output. Skeinforge is one of the primary tool to generate RepRap usable GCode from STL and other 3D format.

File Layout

/ExtruderController

An AVR firmware for the Extruder Controller 2.2 (http://reprap.org/bin/view/MainExtruder_Controller_2_2).

/hal

EMC2 integration scripts

mcode-inject.py: A script being invoked by EMC2 when M1xx User M-Code is being executed. It notifies the driver through HAL.
RepRapSerialComm.py: A module to enable serial port communication with the RepRap/RepStrap extruder controller.
repstrap-commtest.py: A test script to verify the communication and hardware correctness.
repstrap-extruder.hal: A HAL script to be included in the EMC2 setup.
repstrap-extruder.py: A user space driver to control and communicate with the RepStrap extruder controller.
repstrap-extruder.pyvcp: A PYVCP gadget for EMC2's AXIS UI allowing control of the extruder and reporting its status.
skeinforge2emc.pl: A filter program to convert Skeinforge GCode output to a more EMC2 friendly input.
softlink-mcode-inject.sh: simple shell script to create necessary soft-link to accept M1xx M-Code.

/README

The documents of the scripts and everything.

SETUP GUIDE

Firmware

A firmware should comes with the package. Now config your hardware in the Hardware.h, then compile and burn the firmware with Arduino (http://www.arduino.cc/).

    TODO: Documentation for this section is to be completed

EMC2 Setup

Put all these scripts and files in one folder, say, your home folder. The location is assume to be /script/folder in the following document.

Make sure all the scripts are excutable:
```
    chmod a+x *.pl *.py *.sh
```

Edit your EMC2's machine ini (usually in ~/emc2/config/your-machine/your-machine.ini) to include the following lines:

    [AXIS]
    ...    
    PROGRAM_PREFIX = /script/folder
    PYVCP = /script/folder/repstrap-extruder.pyvcp
    
    [FILTER]
    PROGRAM_EXTENSION = .skf Skeinforge Output
    skf = /script/folder/skeinforge2emc.pl

There should also be a POSTGUI_HALFILE in the [HAL] section. If not, create one:

    [HAL]
    ...
    POSTGUI_HALFILE = custom_postgui.hal

Now include the HAL file by editing custom_postgui.hal, or create one if it does not exist, and put the following lines into it:
```
    source /script/folder/repstrap-extruder.hal
```
Edit the repstrap-extruder.hal file.

Modify the path that points to repstrap-extruder.pyvcp as you see fit. We will come back and modify steps_per_mm_cube later.
Edit the repstrap-commtest.py and repstrap-extruder.py. Make any correction to the COMM_PORT and COMM_BAUDRATE so to reflect your machine setup. Specifically, the device of your serial port which is hooked to the Extruder Controller.

Usually, the COMM_BAUDRATE value needs not to be modified.

Then invoke the repstrap-commtest.py in your consle to see if the communication works. It should print something like this:
```
    Sleeping for 5 seconds for the serial port and firmware to settle...
    Flushing communicaton channel...
    Querying for Heater 1 temperature (Command 91)...
    Reading back the response...
    Readback result code (1 for success, anything else - failure): 1
    The current temperature is: 19
```
Execute softlink-mcode-inject.sh to have the softlinks needed created.
Fire up the EMC. Now hopefully you can see a green icon for the Connection LED.

Play around with the Heater and Motor setup. The motor >> button should push the filament into the extruder. If the direction is wrong, you have to correct it in the firmware.

For PID controlled DC Motor, you might also experiement with the PID settings and put it back to the firmware when you are done.
Now calibrate the steps_per_mm_cube settings. The value is used for commanding the motor speed in response to the flowrate needed.

You need to know how many steps there are when spinning your extruder motor axis for one cycle. This should be a number related to the encoder count, or stepper number of steps and gear ratio. You should also know how many teeth are there on your axis. Last but not least, please have the thickness of your filament ready. (Measure it! it usually have variation of ~0.1mm)

Now feed a filament into the gear, use position control mode to feed the filament for a cycle or two. Please note that you should either heat up the extruder and be ready to melt the plastic, or don't push too far into it or you might break your setup.

Reverse feed the filament and pull that out, and by measuring the teeth mark on the filament, figure out the length of filament fed for spinning the motor for one cycle.

Open repstrap-extruder.hal and feed all these parameters into the equation and you will get the steps_per_mm_cube value you needed.
To have the new configuration loaded, you must restart the EMC2 Axis.

Skienforge Configuration

Besides the normal configuration that you must go through, like Carve and Speed, you must also configure the following

In the Export Preferences, turn off Delete Comments. Set File Extension to be skf.

In the Speed Preferences, turn on Add Flow Rate. The Flow Rate Setting is calculated as:

    Flow Rate Setting = Math.PI * (Extrusion Diameter over Thickness * Carve's Layer Thickness)^2 / 4 * Feedrate

Try that out!

Now you should be able to print something.

Carve a STL file by Skienforge.
Fire up EMC2's AXIS, open the SKF result file.
Set zero for your print head. And Hit Run!

REFERENCES

http://github.com/sam0737/hrepstrap
This package!
http://reprap.org
RepRap
http://linuxcnc.org
Linux EMC2
http://www.arduino.cc
Arduino Atmel AVR IDE
http://objects.reprap.org/wiki/Builders/EMCRepStrap
EMC2 Based RepStrap Wiki
http://bitsfrombytes.com/wiki/index.php
Skeinforge Wiki
http://objects.reprap.org/wiki/Minimug
Traditionally the first thing to be printed, and you will need this to celebrate your successful print.

TODO

Leverage EMC2 ability to control the motor. Maybe we need a faster communication channel first. AVR USB?
Coordinate the extrusion speed with axis acceleration and speed.

LICENSE

GPL 3.0

AUTHOR

Sam Wong (sam@hellosam.net)