Using gSender



Here’s a great video that goes over much of how a g-code sender works in the context of gSender. See Kelly explain many of its uses and features:

Starting Up

When you double click the gSender icon to open up the program, it can take several extra seconds to load if you have Microsoft real time virus protection on your computer. This scan delay should only happen the first time you turn on your computer.


Connect to your CNC machine by hovering over ‘Connect to Machine’ at the top left corner, and pressing the COM port you wish to connect to. Sometimes there’s more than one COM port available, so you may need to try both to see which one your machine is connected to.

Once you have selected the COM port, your machine should be connected. This is confirmed when you see the plug icon turn green with a check mark. You should also see the status on the top right corner of the visualizer change to ‘Idle’, and the controls activate, allowing you to press them.

If you are not seeing those changes when you connect, please check the following:

  1. Arduino is securely attached to the LongBoard.
  2. Any other programs that can talk to the Arduino are closed (ex. Arduino IDE, Easel, UGS).
  3. See if you have other COM ports available, and try to connect to them.

Jogging and Presets

You can move the machine by using the Jog Control, through the arrow buttons. Change the ‘XY move’ and ‘Z move’ to adjust the distance you travel per click. You can also change ‘Speed’, which determines how fast the machine will move when jogging.

The ‘Rapid’, ‘Normal’, and ‘Precise’ buttons will allow you to toggle to different distance and speed values quickly. You can change these values by going to the settings and editing the ‘Jogging Presets’ in the ‘General’ section.

Set Zero and Gotos

Each g-code file or project will have a starting position that all other movements are referenced off of. This is the zero or origin. There are two ways to manually set your zero on gSender.

  1. Set the zero for each axis one at a time using ‘Zero X’, ‘Zero Y’, and ‘Zero Z’
  2. Set the zeros all at once using ‘Zero All’

The large blue numbers tell you the current position of your machine. If you want to return to your zero position, you can press the ‘Go to’ for each individual axis or ‘Go to XY0’ to return to the starting position in X and Y in one movement. You should see all three large blue numbers read “0.00” once you have returned to your zero for all axes. Note that ‘Go XY0’ will not move the z-axis to its zero.

You can reset your zeros anytime when the machine is not actively running a job. The machine will remember your zero in most cases. If you turn the lead screw with your fingers or push the gantry, the machine does not know you moved it, therefore it will lose the zero position. You can jog on the Jog Control without losing your zero position because gSender knows you are moving the machine.

You can also enter coordinates directly. By clicking on the location, a field will appear, allowing you to enter your coordinates manually. This is helpful when you are using the paper method to find your Z axis on the Vortex for example.

Endstop buttons

If you have endstops on your machine, whether limit switches or homing switches, gSender provides added features. As long as homing cycle ($22) is enabled on your machine you’ll notice additional buttons appear in the ‘Location’ area of gSender.

This ‘Home’ button and the 4 corner buttons are there to initiate a homing cycle to find machine limits and to quick-travel to them after homing is complete.

If you’d like more information on how to set up and use limit switches, read here:


The probe allows us to automatically set a zero position, usually at the bottom left corner of the stock material, using a touch plate. Usually you’d have to enter a tool diameter each time you probe, but gSender also gives the option to save tool sizes for re-use. You can see this in the ‘Tools’ section of the probe settings. Add different end mills by entering the diameter in millimeters or inches, and then pressing ‘Add Tool’.

Once you have set up the touch plate, banana plug and magnet on the machine, you can choose which axis to probe for, and the diameter of the bit you are using if applicable. The bit size can be selected from the drop-down of saved bits, or can be typed in manually. Jog the machine so that the bit is hovering over the Sienci Labs logo on the touch plate. Then press ‘Probe’.

Before the process begins, there is a conductivity test to ensure that the touch plate components can conduct electricity, which allows a signal to be sent to the LongBoard when there is contact. You can either bring the touch plate to the end mill or touch the banana plug and magnet together. Make contact a few times just to confirm there is conductivity, as the red circle should flicker to green.

A blue button called ‘Start Probe’ will appear if you have successfully confirmed conductivity. Ensure that the touch plate components are set up for probing, then press ‘Start Probe’. The machine will move to probe three sides of the touch plate, twice on each side. There should not be any crashing or abrupt movement. Once the process is over, remove the touch plate components from the machine and then press ‘Go to XY0’. The bit should be overtop the bottom left corner of the stock material, and pressing ‘Go to’ next to the ‘Zero Z’ should bring it to touch the surface. More information can be found on our touch-plate resource page.

Loading Job Files

If you have already prepared a project file, ensure the following:

  1. The file is an *.nc, *.gcode, *.tap, *.gc, or *.cnc file.
  2. The file is exported to the correct post processor for the LongMill. Please see this page for the correct post processor for your CAM software:

To run your project on gSender, press the ‘Load File’ button. A dialog box should pop up, where you can navigate to where your file is. If you want to reload a previous file you can also click the ‘>’ button which will allow you to select from recently opened files.

Double click on the file, and the project should load in and be shown on the Visualizer. Once loaded, you’ll be able to see information about your project such as: its estimated cut time and cutting dimensions, and if the file is too big and slowing down your computer you can always click the ‘X’ on the ‘Load File’ button to unload it.

With your file loaded, feel free to also check how it looks. In the bottom right corner of the visualizer use the ‘view cube’ to quickly switch between top, right, left, front, and 3D views by clicking on its different faces. You can also use your mouse scroll wheel to zoom in and out and left-click and drag or right-click and drag on the visualizer to rotate or slide around the work area.

Before running your job there are a few other handy features you can check. The ‘Outline’ button will physically move your machine around the rough perimeter of your cutting job so you can get an idea of the cutting dimensions and if you’ve positioned the job correctly. As well, the ‘Test Job‘ button enables gSender to go through your g-code to look for potential errors or unknown commands, without running it on the machine yet. This will give you an idea of what running your job will look like before running it for real.

Running Jobs

Once your machine is ready with your router and vacuum on, press ‘Start Job’ to begin your cut. You can pause and stop your job at any time with the respective buttons. If you press ‘Pause Job’, you can resume the job from where you left off. Otherwise, ‘Stop Job’ will cancel your job completely.

At the bottom of the screen, a progress bar shows how many lines of g-code have been processed and how many are left. Additionally, you can override the feed rate and spindle speed of the program while the job is running by moving then letting go of the slider, pressing the ‘+’ and ‘-’ buttons for smaller adjustment, or clicking the rotated arrow to reset back to the default value. This is handy for fine-tuning the program cutting speed in order to tune in your material removal rate and ensure you don’t burn or melt material.

If you already know you’ll need to tweak the feed rate or spindle speed for your file before you run it, you can now click the ‘Overrides’ toggle to access overrides before you start the job. This allows the overrides to apply before starting cutting or if the job is already running toggle it back to double-check the job attributes.

Now you’re off and cutting, what a thrill! While your job is running keep an eye and ear out for anything you don’t expect. You can always use the job control buttons during operation to change speeds, pause, resume, or stop cutting altogether.

Job Loss Recovery

Also referred to as “Start from Line” this feature is built right into gSender for the purpose of recovering a carve you were working on that was disrupted by a power loss, USB disconnect, mechanical malfunction, or other failures.

When a job is lost from a disconnect, clicking ‘Stop Job’, or anything similar, your first step should be to ensure that the job you were running is currently loaded, otherwise you need to load it back onto gSender. This is an alternate way of starting / resuming a job so you’ll find this feature as a part of the ‘Start Job’ button on the main visualizer shown as three lines.

In this popup, you’ll get some important information. Remember that every job you run on your CNC is a series of line-by-line instructions as a ‘g-code’ file:

  • Line last recorded: shows where gSender remembers the file failed
  • Maximum line number: shows the total instruction lines in your file
  • Start at line: for you to enter manually where you want to resume cutting from. If your machine was running for a long while after the failure then you’ll want to subtract more from the last line recorded, or if the failure was quick you might only need to subtract 10 or 20 lines. For example: if the last recorded line was 1040 but I hadn’t been paying attention for several minutes and the job had already been running for an hour, then I could assume that maybe 100 lines had passed since the failure so I could restart on line 940.

Now you should be ready to get back into cutting by clicking ‘Start from Line’. This feature took us a long time to create since it:

  • Runs the Start/Stop g-code as you’d expect
  • Accounts for all the typical ‘setup’ g-code that is at the start of the file like units, zeros, spindle speed or laser power
  • Looks at every past machine movement to locate exactly where it needs to resume from

This way you can be confident in returning to your projects even when something goes awry.

In the unlikely event that there is a USB port disconnect from your CNC while running a cutting job, in specific instances gSender will be able to recognize the problem and alert you about it. In these cases, check your USB cable then ensure you write down the “Suggested line to start from” before you confirm the window. From here you can use the ‘Start from Line’ feature as normal, entering in the suggested line number and hopefully resuming cutting where you left off. In the image below, we would be restarting at line 18.


gSender is set up to do many things by default to help keep you aware about things going on with your machine. Though we can’t guarantee it can handle everything, we’ve recently introduced a new Settings menu for Safety where you can access many safety items in one place. This includes:

  1. Safe height movement: this number is used when using the ‘goto’ buttons in gSender to manually move your machine around (it’s independent from a safe height you might set in your CAM software). For machines without homing, entering ‘5mm’ will make it move 5mm upwards from the current position, make the goto movement, then move 5mm back down. If your machine has homing, it’ll move to 5mm from the max Z-axis travel, make the goto movement, and then return back to where the bit started. This behaviour helps homing-capable machines to reach a more ideal safe height to avoid collisions during movements.
  2. G-code warnings: reports back when it sees g-code lines that don’t look correct when the file is loaded or once it’s being sent to the machine. G-code has to follow specific ‘grammatical rules’ similar to other languages for the ‘sentences’ to be correct, so if the lines don’t look correct then your machine might run into problems understanding what it’s supposed to do.
  3. Soft limits warning: enables gSender to tell you when a loaded file might exceed the cutting area of your machine. This requires that your machine has limit switches and soft limits enabled.
  4. History of Errors and Alarms: great for tracking problems you might’ve recently run into to help troubleshooting or getting support. All entries are listed in-order and stamped with a date and time.