LinuxCNC User Introduction

This document is focused on the use of LinuxCNC, it is intended for readers who have already installed and configured it. Some information on installation is given in the following chapters. The complete documentation on installation and configuration can be found in the integrator’s manual.

LinuxCNC is a suite of highly-customisable applications for the control of a Computer Numerically Controlled (CNC) mills and lathes, 3D printers, robots, laser cutters, plasma cutters and other automated devices. It is capable of providing coordinated control of up to 9 axes of movement.

At its heart, LinuxCNC consists of several key components that are integrated together to form one complete system:

The below illustration is a simple block diagram showing what a typical 3-axis CNC mill with stepper motors might look like:

A computer running LinuxCNC sends a sequence of pulses via the parallel port to the stepper drives, each of which has one stepper motor connected to it. Each drive receives two independent signals; one signal to command the drive to move its associated stepper motor in a clockwise or anti-clockwise direction, and a second signal that defines the speed at which that stepper motor rotates.

While a stepper motor system under parallel port control is illustrated, a LinuxCNC system can also take advantage of a wide variety of dedicated hardware motion control interfaces for increased speed and I/O capabilities. A full list of interfaces supported by LinuxCNC can be found on the Supported Hardware page of the Wiki.

In most circumstances, users will create a configuration specific to their mill setup using either the Stepper Configuration Wizard (for CNC systems operating using the computers' parallel port) or the Mesa Hardware Wizard (for more advanced systems utilising a Mesa Anything I/O PCI card). Running either wizard will create several folders on the computers' hard drive containing a number of configuration files specific to that CNC machine, and an icon placed on the desktop to allow easy launching of LinuxCNC.

For example, if the Stepper Configuration Wizard was used to create a setup for the 3-axis CNC mill illustrated above entitled My_CNC, the folders created by the wizard would typically contain the following files:

A graphical user interface is the part of the LinuxCNC that the machine tool operator interacts with. LinuxCNC comes with several types of user interfaces which may be chosen from by editing certain fields contained in the INI file:

These User interfaces are a way to interact with LinuxCNC outside of the graphical user interfaces.

As mentioned above, many of LinuxCNC’s GUIs may be customized by the user. This may be done to add indicators, readouts, switches or sliders to the basic appearance of one of the GUIs for increased flexibility or functionality. Two styles of Virtual Control Panel are offered in LinuxCNC:

LinuxCNC uses translation files to translate LinuxCNC User Interfaces into many languages including French, German, Italian, Finnish, Russian, Romanian, Portuguese and Chinese. Assuming a translation has been created, LinuxCNC will automatically use whatever native language you log in with when starting the Linux operating system. If your language has not been translated, contact a developer on IRC, the mailing list or the User Forum for assistance.

This manual does not pretend to teach you how to use a lathe or a milling machine. Becoming an experienced operator takes a lot of time and requires a lot of work. An author once said, We learn by experience, if one possesses it all. Broken tools, vices attacked and the scars are evidence of the lessons learned. A beautiful finish, tight tolerances and caution during the work are evidence of lessons learned. No machine nor program can replace human experience.

Now that you start working with the LinuxCNC software, you have to put yourself in the shoes of an operator. You must be in the role of someone in charge of a machine. It’s a machine that will wait for your commands and then execute the orders that you will give it. In these pages, we will give the explanations which will help you to become a good CNC operator with LinuxCNC.

When LinuxCNC is running, there are three different major modes used for inputting commands. These are Manual, Auto, and Manual Data Input (MDI). Changing from one mode to another makes a big difference in the way that the LinuxCNC control behaves. There are specific things that can be done in one mode that cannot be done in another. An operator can home an axis in manual mode but not in auto or MDI modes. An operator can cause the machine to execute a whole file full of G-codes in the auto mode but not in manual or MDI.

In manual mode, each command is entered separately. In human terms a manual command might be "turn on coolant" or "jog X at 25 inches per minute". These are roughly equivalent to flipping a switch or turning the hand wheel for an axis. These commands are normally handled on one of the graphical interfaces by pressing a button with the mouse or holding down a key on the keyboard. In auto mode, a similar button or key press might be used to load or start the running of a whole program of G-code that is stored in a file. In the MDI mode the operator might type in a block of code and tell the machine to execute it by pressing the <return> or <enter> key on the keyboard.

Some motion control commands are available concurrently and will cause the same changes in motion in all modes. These include Abort, Emergency Stop, and Feed Rate Override. Commands like these should be self explanatory.

The AXIS user interface hides some of the distinctions between Auto and the other modes by making auto-commands available at most times. It also blurs the distinction between Manual and MDI, because some Manual commands like Touch Off are actually implemented by sending MDI commands. It does this by automatically changing to the mode that is needed for the action the user has requested.