**NOTE: This machine has been returned to the original owner. This page is kept for reference only.** ## Introduction The CNC machine is a 6040 CNC, which simply means that the bed is 60 cm long and 40 cm wide. This is a standard architecture that is made by many manufacturers. It is a 3-axis machine, with the axes as shown below. The Y is the longest axis, along the bed, X is across the bed, and Z is the vertical axis. The origin is near the front, left hand corner. There is a stepper motor for each axis and a Pulse Width Modulation (PWM) spindle motor that drives the cutting tool. In addition, there are limit switches at the ends of some of the axes to prevent the motors trying to drive the head past the limits. {width="5.236805555555556in" height="5.236805555555556in"} The second component is the Controller, which contains the driver electronics and the connections through to the 3 stepper motors. The PC is connected to the Controller via a parallel cable. In this configuration the signals that drive the stepper motors are sent via the parallel cable. The PC does most of the synchonisation and timing of these signals to control the speed and direction of all the motors and sense the limit switches. More modern CNCs typically use an intelligent Controller, typically running GRBL on an Arduino. Such a Controller does all of the timing, and the PC just sends commands via a USB or WiFi connection. ## Communicating with the CNC CNCs receive instructions via G-Code, which is a low-level command language, similar in status to an assembly language. Normally you don't need to know much about G-Code, except when things go wrong. Typical G-Code instructions are: ~~~ gcode G00 X3 Y4 Z0 - move the head to the coordinates (3, 4, 0) G01 X0.33 Y54.68 Z0.1 - cut from the current position to coordinates (0.33, 54.68, 0.1) G92 X0 Y0 Z0 - set the current working coordinates to (0, 0, 0) M30 - stop the G-Code program and rewind to the beginning ~~~ There are dozens of G-Code instructions to control every aspect of CNC, 3D printing, robots and laser engraving machines. See [*All3DP G-Code Commands*](https://all3dp.com/2/3d-printer-g-code-commands-list-tutorial/) for a more detailed introduction to G-Code. All coordinates are in millimetres. ## Turning on the CNC 1. Turn on the power switch and check the status of the CNC Controller. - The DRIVE switch should be turned on, and lit. It is turned on in the UP position. - The Emergency button may be depressed. To ensure that it is not depressed, rotate it clockwise until it either clicks out, or can't be turned any further.\ \ **The Emergency button is the Panic button. When something goes wrong, press it to immediately stop the CNC.**\ \ Once pressed, the Emergency button will remain pressed until it is released by turning it. {width="2.1875in" height="2.9167366579177605in"} 2. Start the PC by pressing the On button. The PC will boot into LinuxCNC, which is a version of Linux with a Real Time kernel to ensure that it meets the timing demands of communication with the CNC. Login into the PC using the username/password: `hacker/cnc` 3. Run the CNC interface software, which is confusingly called LinuxCNC, by clicking on the "Launch CNC6040" icon. This will display the LinuxCNC user interface. There are many interfaces to the LinuxCNC system -- this version is the original, called Axis. {width="7.672520778652668in" height="5.625in"} The interface has the following components: - Top row menu for File handling, Machine control and changing the Preview panel. - A list of command buttons, discussed below - A Manual Control panel that allows the user to Home the CNC, jog the head, and set the spindle speed - A Manual Data Interface (MDI) panel (currently hidden) that allows the user to directly enter and execute G-Code commands - A list of G-Code options that are currently enabled on the CNC - Near the bottom, a list of G-Code that is currently being executed. This is scrolled up as G-Code commands are executed. - In the centre, the Preview Panel which graphically shows the tool path of the currently loaded G-Code program. - At the top of the Preview Panel are some positional data, given the current coordinates of the tool head on the CNC. This positional data is also shown in the Digital Read-Out panel, which is currently hidden. - At the bottom, below the Preview Panel, the Position status is shown: as using either Machine or Work Coordinates -- these will be discussed further below. - On the right a panel with: - The current spindle speed. This speed can either be set manually, or by G-Code commands; - A Clear Offsets button that sets the machine coordinates to known values; - A Clear Job Coordinates which resets the current Work Coordinates; - A Touch Off Z button which resets the Z coordinate of the tool head to zero. You may see a dialogue box that complains about not being able to see the Pendant -- ignore this because we are not using the Pendant. {width="2.2916666666666665in" height="1.2065671478565179in"} 4. Before using the CNC interface you need to click on the Emergency Stop (E-Stop) button  {width="0.27774278215223097in" height="0.27774278215223097in"} in the top left corner. This is the software equivalent of the Emergency Stop button on the controller, and will stop any existing activity. 5. Next click on the Machine Power button {width="0.2916305774278215in" height="0.2916305774278215in"} near the top left corner. This effectively turns the CNC interface on and enables the buttons under Manual Control \> Axis & Spindle. The CNC interface is now ready to use. ## Coordinate Systems CNC machines have several coordinate systems, depending on their mode of use. The **machine coordinates** are the absolute coordinates that the machine uses for the whole machine. They are set at start up, and Homing. The extent of these machine coordinates closely match the extent of movement of the head along each of the axes. The **work coordinates** are normally set for each job. The user needs to decide where the zero origin is for the work job, then move the head to that position and zero the machine by setting the work coordinates to zero for that position. All subsequent work on that job is done relative to these work coordinates. G-Code also has the ability to set and unset multiple **subsets of work coordinates** for sub-parts of a job. This is normally down when the job requires multiple identical sub-parts. The status bar at the bottom of the LinuxCNC interface shows the coordinate system being used: - **Position: Machine Actual** The CNC is using the machine coordinates - **Position: Relative Actual** The CNC is using work coordinates. The respective G-Code commands are: ~~~ gcode G90 - Use absolute machine coordinates for the XYZ axes G91 - Use relative work coordinates for the XYZ axes ~~~ ## Digital Read-Out (DRO) An important part of the LinuxCNC display is the Digital Read-Out, which displays the current coordinates of the tool head in the X, Y, and Z axes. This is essential information to understand the progress of the CNC milling, and to diagnose when problems occur, such as hitting limit switches, or making unwanted cuts. The DRO is constantly updated and displayed as millimetres to 3 decimal places. By switching to the DRO panel the user can see the DRO data, without the underling Preview panel graphics. ## Homing Stepper motors don't have origin -- they just rotate forwards or backwards relative to their previous position. When the CNC is turned on, its machine coordinates are (0, 0, 0). This can be anywhere in the CNC tool space. To standardise the work coordinates the machine needs to be **Homed** to establish a standard position for the origin of the machine coordinates. This is done by moving the tool head to limit switches whose positions are known on each of the axes. At present LinuxCNC has been configured to home to zero on the X axis, the far limit on the Y axis (coordinate 585), and the upper limit on the Z axis. 1. Ensure that the bed of the CNC is free from any obstruction or clutter. 2. Click on the Home All button.\ The head should now start to each of the limit switches in the order Z, X, Y. As it does so, it will update the coordinates in DRO display of LinuxCNC screen. 3. Click on the **Clear Offsets** button. This sets the machine coordinates to known values that correspond to the positions of the limit switches on each of the axes. {width="7.268055555555556in" height="5.9319444444444445in"} Unfortunately, this leaves the head at the positive end of the Y axis. In the DRO panel the machine coordinates are set to the pre-defined positions of the limit switches (0, 595,58). The Distance-To-Go (DTG) coordinates are set for each move, and indicate the distance that the current move needs to make along each axis before completion of the current move. The G54 coordinates are the part being processed. The coordinates are relative to the machine coordinates. The G92 coordinates are the work coordinates, relative to the work origin, defined by the G92 command. The Tool Length Offset (TLO) coordinates are the position of the tool tip, relative to the spindle. ## Jogging Jogging is a manual process by which the user can move the head in either direction along each of the axes. It is normally used to position the head for the next job. Jogging can be done either step-by-step or continuously. The user can only jog along one axes at a time. To jog the head: 1. Select the axis to be jogged: {width="2.7079943132108486in" height="0.26385608048993875in"} 2. Select either **Continuous** or step mode, by selecting one of the options, 5mm, 1mm, 0.5mm, 0.1mm, 0.05mm, 0.01mm or 0.005mm. 3. Click on either the **+** or **--** buttons to jog the head in the required direction. You will notice the coordinates change in the upper right window as the head is moved. > In Step mode the head will move one step at the specified length and > direction on each click of the **+** or **--** button. > > In Continuous mode, the head will move in the specified direction as > long as the **+** or **--** button is held down. This is normally for > gross movement of the head over long distances. ## Spindle Speed The spindle speed can be set manually or in G-Code by the G96 or G97 commands. To set the spindle speed, use the buttons under **Spindle: {width="2.1941699475065617in" height="0.666583552055993in"} To start the spindle rotating in the clockwise direction click {width="0.31940398075240595in" height="0.26385608048993875in"}, and then select the speed by clicking on the **+** or **--** buttons. To start the spindle rotating in the anti-clockwise direction (for a left-head threaded bit) click {width="0.3055172790901137in" height="0.2916305774278215in"} and then select the speed. To stop the spindle, click on the **Stop** button. The spindle speed will be determined by: - The type of stock material -- plastics and polymers require must lower speeds than wood or aluminium, otherwise they melt - The type of tools -- some tool bits are designed to operate at higher or lower speeds than others - The type of finish -- depending on the type of stock material, different speeds will give different quality results The current spindle speed is shown in the top right of the interface screen. {width="1.9764238845144357in" height="1.3593121172353455in"} ## Preview Screen The Preview Screen in the centre of the LinuxCNC interface shows a preview of the tool paths when a G-Code program is loaded. Non-cutting moves (G0 commands) are shown as cyan lines. Cutting moves (G1 commands) are shown as solid white lines. The positions of Pauses or Dwells (G4 commands) are shown as small pink X marks. Non-cutting moves (G0 commands) prior to the first cut, and after a tool change, but before he next cut are not shown. The maximum extents or dimensions of the G-Code program in each axis direction are shown as pink lines with the lengths in mm shown near the middle of these lines. If any of these extents exceed a limit of the CNC, they are shown in a red rectangle, and will also cause an error message when the program is run. As the program is run and the tool head moves, it leaves a back-plot trace: ----------------------------------------------------------------------- Manual jogs Non-cutting Moves Straight Cuts Circular Cuts ----------------- ----------------- ----------------- ----------------- Yellow Green Red Magenta ----------------------------------------------------------------------- The tool head is shown as a white, inverted cone. {width="4.406626202974628in" height="3.5324857830271217in"} The Preview display can be manipulated by the following commands: {width="50%"} > {width="0.22916666666666666in" > height="0.22916666666666666in"} Zoom In > >  Zoom Out > > {width="0.25in" height="0.25in"} Top > view, looking down the Z axis, for viewing the XY plane from above. > > {width="0.25in" height="0.25in"} > Rotated Top view, looking down the Z axis, with the X & Y axes rotated > through 90 degrees, for viewing the rotated XY plane from above. > > {width="0.25in" height="0.25in"} Side > view, looking from the positive end of the X axis, for viewing the YZ > plane from above. > > {width="0.25in" height="0.25in"} Front > view, looking from the origin end of the Y axis, for viewing the XZ > plane from below. > > {width="0.28125in" > height="0.25in"} Perspective view (default), adjustable using the > mouse and Drag/Rotate toggle selector > {width="0.3332917760279965in" > height="0.3055172790901137in"} > > {width="0.25in" > height="0.25in"} Clear the back-plot trace \[Ctrl-K\]. ## Setting up a Job When a job has been designed (CAD) and converted to G-Code (CAM), it is ready to be machined. It is assumed that the tool bit has been chosen and loaded into the chuck / collet of the CNC, and that the stock material has been chosen and shaped for the job. 1. **Clamping The stock material needs to be clamped to the bed of the CNC. There are 2 types of clamps normally used: - **Stays**, Clamps or Hold-downs are levers that are bolted to the T-slot channels in CNC bed to securely hold the stock material from moving. During machining there is a lot of lateral force on the stock, and there needs to be sufficient Stays that are securely tightened to hold the stock. - **Stops** are solid pieces, typically cylindrical or square that are bolted to the T-slot channels in the CNC bed, and used for multiple jobs, so that for each job the stock material can be aligned to the same position for machining. > The Stays, Stops and their Bolts must not be in the path of the head > or any part of the head assembly, otherwise a collision will occur, > and the job will be ruined. > > Stays and Stops should not be moved during the job. Trying to move any > clamp while the CNC is operating is destined to fail because the stock > material is likely to move before the clamps can be reapplied, or the > user may come in contact with the head and be injured. > > If Stays or Stops have to be moved then it is best to Pause the job, > and carefully move and reapply the clamps, making sure that the stock > material is not moved, and that the head is not jolted. 2. **Safe Height The CAM process should establish a **Safe Height** which is the distance above the maximum height of the stock that the tool head can move without colliding with any clamps, bolts or other parts of the stock material. Typically a Safe Height of 5 or 10 mm is used, with the requirement that all non-cutting moves of the head are done at the Safe Height. > This especially applies to the movement of the tool head at the end of > a job. It is very easy to complete a job, leave the tool head in the > final cutting position, press the **Home** button, and then helplessly > watch while the tool head makes a bee-line for the zero Home position, > by cutting straight through the finished product! 3. **Zeroing the Job Once the stock material has been clamped to the CNC bed, the tool head needs to be moved to the zero or origin position to start the job. This position is normally marked on the stock material. a. Ensure that the tool head is at a Safe height before proceeding. b. If the spindle is on, turn it off so that it doesn't scar the stock material. c. Jog the tool head along the X and Y axes to the marked zero point. d. Slowly jog the tool head down along the Z axis using 0.1mm steps or less, until the tool head is just above the height of the stock material. This can be done by placing a piece of 80 gsm paper on top of the stock material, and jogging the head down until the tool just touches the paper, so that the paper can only be moved with some resistance. If the paper cannot be moved, the tool is too low. 80 gsm paper is about 0.1 mm thick, so this gives a good consistent positioning of the tool in the Z axis. e. Set the origin of the work coordinates by using the G-Code command: > G92 X0 Y0 Z0 {width="6.59375in" height="5.38159886264217in"} Go to the Manual Data Input (MDI) tab and enter the command: G92 X0 Y0 Z0 Click the **Go** button. 4. **Spindle Speed Set the spindle speed. ## Running a Job A G-Code job can be run using the following buttons: > {width="0.25in" height="0.25in"} > Open a G-Code file \[O\]. The G-Code path will be displayed in the > Preview panel, and the G-Code will be displayed in the lower panel. > > {width="0.25in" > height="0.25in"} Reload current file \[Ctrl-R\]. Useful if the G-Code > file is being edited concurrently. > > {width="0.22916666666666666in" > height="0.22916666666666666in"} Begin executing the current file > \[R\]. A back-plot trace will be created on the Preview panel, and the > code will scroll through the lower panel. > > {width="0.22916666666666666in" > height="0.22916666666666666in"} Execute next line \[T\] after a pause. > Useful for debugging. > > {width="0.21875in" height="0.21875in"} > Pause Execution \[P\] Resume Execution \[S\]. Useful for ad hoc > changes of clamps or tools. > > {width="0.21875in" > height="0.21875in"} Stop Program Execution \[ESC\]. While the job is running: - Keep a close watch on the job. Errors in design can frequently occur, and you may need to hit the Emergency Stop to avoid further damage to the stock material and the CNC. - Watch for overheating. If the bit is stationary in wood it can start smouldering and ultimately catch alight. When cutting metal, such as aluminium, it is important to have a mist spray of water on the cutting tool to avoid overheating. - Watch for melting when cutting plastics or other synthetics. These materials have low melting points and require low spindle speeds to be cut accurately, without the cut surface melting. - Watch for movement of the stock material, typically caused by insufficient or weak clamping. This usually means discarding the ruined stock material. - Remove cut waste with a vacuum cleaner. This keeps the cut space tidy, allows you to see what is happening, reduces dust, and reduces the chances of cut shards falling into the cut area and marking the cut surface. This is particularly the case with plastics and aluminium. - Ensure that the cut path and cut order are efficient to achieve the best result in a reasonable time. - Watch for the tool bit becoming blunt. The best option is usually to start again with a new tool. - Watch for the spindle overheating. This spindle is air cooled, and may overheat on long, hard jobs. - Watch for the final cut of a loose object. When cutting a complete object out of the stock material, then final cut will sever the object from the surrounding material. At this point it is easy for the object to fall back against the rotating tool bit and be ruined. You need to plan to capture the final object before it is damaged. - Make sure that when the job is finished you raise the tool bit to a Safe Height before returning to Home, so that the tool bit doesn't cut through your finished object. Often the return to Home is programming in the G-Code as a penultimate instruction. This also applies to moving the tool bit between different objects in the one job. - In the event of a power failure, give and start again. - The job may be paused and resumed at any time to allow adjustments or a break.