Arduino

Programming A CNC


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CNC G-Code Programming

INTRODUCTION:

A CNC can be programmed a few different ways, one way is to learn G-Code and write files for the machine, this will also require some more advanced understanding of the Machine you're programming, all machines are different (Read on for more details); the other way is to use a few computer programs, starting with a drawing software and ending with Machine Software, or a Machine can be programmed by having it mimic and remember your moves.

How to program a CNC Machine:
The easy way to program a CNC is to use Computer Software, this method at times may still require some tweaking but if this is the case machine code references can be found by doing a search online, Wikipedia.org has an article about G-Code and M-code and most manufacturers post machine information online.

Programming a machine by manually generating a file will require a whole bunch of G-Code, M-Code, and Post Processor command memorisation or reference, this method may also result in errors. Editing a Computer Generated file (if required) will eliminate the requirement to know the post script for the machine, for example the programmer will need to know the file extension for saving the file, the programmer will need to be aware of any special commands required by the Machine Software later used for compiling the file if programming by hand.

Programming using Computer Software:
Starting with CAD (Computer Aided Design) a drawing needs to be rendered, there are many different formats however when starting out the only thing we need to know is if the drawing is a "Vector Image" or a "Bitmap Image".

Knowing the difference is important because a Bitmap image format won't work unless converted to a Vector format and doing so isn't an easy task, Bitmaps are Pixel based Vectors are Math based. Have you ever noticed how a Jpeg Image will distort when being resized? This distortion is called pixilation and is caused from the Pixel (drop of Ink) being stretched too much; Vectors on the other hand are built using compilers (programs like Adobe) that position the Drawing based on math like "linear interpolation" used for round corners or circles, and Geometry is used to position lines precisely on your monitor no matter how much you stretch or shrink the image.

CAD Software can be either Proprietary or Opensource, some Proprietary versions can cost thousands per year per seat, others can be found free online, CAD/ CAM can also be found together, for example Gibbs CAM, MasterCAM, or Vectric-Aspire, are Proprietary CAD/CAM packages.

Vector format images can be found online if you don't have, or can't find software that works, common formats will have the extension .STL, .DXF, .DWG, .EPS, even .PDF, however PDF files more times than others contain Bitmaps that won't allow the Image File to be loaded into the CAM (Computer Aided Manufacturing) Software.

CAM (Computer Aided Manufacturing); this software allows you to load the CAD drawing (Vector Image) and generate cut paths for your machine, as noted before all machines are different, control maybe different, some have different Motors, some have different Axis movement and may even have more plains of motion, some have ATC (Automatic Tool Change) mechanisms, some deposit material, some use tangential cutting tools, this making a generic G-Code file for all CNC machines impossible, bringing us to a Post Processor A.K.A Post Script file, this file contains Meta Data (Information about information) telling the software how to export the G-code.

Machine Software; this software is used to compile the file generated by the CAM software and export it to a Serial Bus (RS232/ RS485/ USB) or Parallel Port (DB25).
Serial Control: packets of information are sent to a Micro-Controller or PLC, this Controller/ PLC is pre-programmed to process commands sent from the PC, or, programmed to process and send information back to the PC for the Machine Software to process.

Interfacing:

Parallel Control: Electrical Pulses in the range of 3.3V to 5V are sent to an external buffer, in most cases a Breakout Board or Driver Card containing Electrical Components and Driver IC's (Buffers) that are wired to Motors, in most cases being Stepper Motors (Often found in old Dot Matrix Printers).
Add Functions: MODBUS:

MODBUS is a way to add external Microcontrollers for sensing or control, e.g. Torch Height Control, Cameras, and Encoders for distance and speed sensing, PWM Spindle speed control, among many other things.

Accredited Software Training in your area:
**More Information soon**

Some Great Links Related to CNC Programming:

Modbus:
https://code.google.com/p/simple-modbus/ 
www.buildlog.net/blog/2011/02/modbus-arduino-mach3-and-brains-oh-my/ 
www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf 
Plotting, data acquisition:
http://john.crouchley.com/blog/archives/454 
http://koolplot.codecutter.org 
www.makerplot.com 
www.arduinoos.com/2010/05/serial-comm-ports-for-ever-and-ever/ 
http://playground.arduino.cc/Main/StreamingOutput 
http://www.instructables.com/id/Wireless-outdoor-Arduino-weather-station-with-PC-l/ 
Python:
www.akeric.com/blog/?p=1140 
www.instructables.com/id/Arduino-and-Python/step2/Python-Code/ 
https://www.python.org/downloads/ 
http://www.instructables.com/id/Interface-Python-and-Arduino-with-pySerial/ 
http://playground.arduino.cc/interfacing/python 
http://playground.arduino.cc/Main/InterfacingWithSoftware 
http://petrimaki.com/2013/04/28/reading-arduino-serial-ports-in-windows-7/ 
Serial Communication:
https://sites.google.com/site/adifferentlemming/Home/projects/arduino#TOC-Multiple-Serial-devices-with-Arduino 
http://playground.arduino.cc/Main/InterfacingWithHardware#ui 
http://shallowsky.com/blog/hardware/ardmonitor.html 
Arduino:
http://playground.arduino.cc/Main/SketchList 
http://playground.arduino.cc/Main/GeneralCodeLibrary 
http://playground.arduino.cc/Main/SketchList#Storage_code 
http://playground.arduino.cc/Main/SketchList#IO_code 
Arduino Time-Speed:
http://playground.arduino.cc/Code/ReadReceiver 
http://electromechhobby.blogspot.ca/2012/12/rpm-counting-with-hall-effect-sensor.html 
www.r-site.net/site/struct.asp?lang=en&at=//op%5B@id=%273038%27%5D 
http://playground.arduino.cc/Main/ReadingRPM 
https://code.google.com/p/arduino-rotary-encoder-with-velocity/ 
http://www.r-site.net/site/struct.asp?lang=en&at=//op[@id=%273038%27
https://sites.google.com/site/measuringstuff/more-sensor-examples 
Testing Microcontroller:
http://playground.arduino.cc/Main/ShowInfo 
Transmitter/ receiver/ HAM:
http://www.instructables.com/id/Wireless-indoor-outdoor-thermometer/ 
Arduino C++ Game(s)!!
http://playground.arduino.cc/Main/SimpleSimonSays 
http://playground.arduino.cc/Main/RockPaperScissors 
http://www.instructables.com/id/Arduino-LED-Water-Jumping-With-Music/ 
Raspberry-PI
www.raspberrypi-spy.co.uk/2012/06/simple-guide-to-the-rpi-gpio-header-and-pins/ 
https://www.raspberrypi.org/documentation/installation/installing-images/ 
EMC-Machine software:
www.linuxcnc.org 
www.linuxcnc.org/docs/html/code/Contributing-to-LinuxCNC.html 
http://git.linuxcnc.org/gitweb 
GOOD FINDS! Noteworthy!
http://playground.arduino.cc/Main/ArduinoSpeedGate 
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