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:


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.

gsender jogging preset highlighted

Manual Zero and Gotos

Each g-code file will have a starting position in which the coordinates of the toolpaths reference off of. This is the zero or origin. There are two ways to manually set your zero on gSender.

  1. To set the zero for each individual axis one at a time, you can use ‘Zero X’, ‘Zero Y’, and ‘Zero Z’
  2. To set the zeros all at once, use ‘Zero All’

The large blue numbers at the readout indicate the current position of your machine. If you wish to return to your zero position, you can press the ‘Go to’ for each axis or ‘Go to XY0’. You should see the large blue numbers read ‘0.00’ once you have returned to your 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.

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 millimetres or inches, and then pressing ‘Add Tool’.

gsender probing dialogue box highlighting the add tool button

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 over-top the bottom left corner of the stock material, and pressing ‘Go to’ next to the ‘Zero Z’ should bring it to touch the surface.

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.

Double click on the file, and the project should be shown on the Visualizer, along with information such as the dimensions and estimated time.

Once a file is loaded, you might notice that the ‘Load File’ button now has an ‘x’ on it which will allow you to unload the file if you realize it’s slowing down your machine and aren’t ready to run it, as well as if you click the ‘>’ button your file now shows up in the recent files dialog.

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 pressing the ‘+’ and ‘-’ buttons or 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.


Now you’re off and cutting, what a thrill! While you 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.

Start from Line

This feature is handy in cases where:

  1. You only want to cut part of a project, not the entire thing
  2. Your job has been interrupted, so you need to resume from a specific point of the project

With this feature, you can start your job from any line in your g-code, by specifying the line number. To access it, load up your g-code file. You should see the green ‘Start Job’ button, with a small icon on the top right of the button.

From here, you will see a popup, where you can specify what line of the g-code file you wish to begin the job at. Additionally, gSender remembers the last line number executed from the previous job, and the maximum line number of this current job.