gSender Complete Workflow: Connect, Zero, Run, and Recover
What gSender Is
gSender is a free open-source CNC controller and G-code sender made by Sienci Labs. Works with any GRBL-based CNC machine. Download at sienci.com/gSender.
Connecting
Launch gSender. Select your machine port (COM port on Windows, /dev/tty on Mac/Linux) and baud rate 115200. Click Connect.
If no port appears: verify USB is plugged into the CNC controller board, check Device Manager for driver issues, close any other software using that port.
Homing
If your machine has limit switches, click Home All. The machine moves to the homing switches and sets machine coordinate zero there.
If no limit switches (LongMill MK2 does not by default), skip homing and use manual work zero.
Jogging
Use jog controls to move the spindle. Start large (10-50mm steps) to traverse the bed, switch to 1mm and 0.1mm for precise positioning. Always raise Z before jogging XY to avoid dragging the bit across material.
Setting Work Zero (XYZ Zero)
Work zero is where X=0, Y=0, Z=0 for your job. Set this correctly before every job.
XY Zero: jog the bit to wherever your CAM software placed the origin. Click Zero X and Zero Y. The display resets to 0,0.
Z Zero (paper method): slide a sheet of printer paper under the bit. Lower in 0.1mm steps until the bit grabs the paper with slight resistance. Click Zero Z.
Z Zero (touch plate): place touch plate under the bit, clip the alligator lead to the bit, click Probe Z. The machine contacts the plate and sets Z automatically.
Loading G-Code
Click Open File and select your .nc or .gcode file. The 3D preview shows your toolpaths. Verify paths are positioned correctly, depth looks right, no obvious errors.
Air cut test: raise Z by 5-10mm and run the job without cutting. Watch the machine trace paths in air.
Running the Job
Lower Z back to zero. Click Start Job. Monitor for burning smell (feed too slow), chatter (reduce feed or depth), or workpiece shifting (stop immediately).
The feed rate override slider lets you reduce speed in real time without stopping.
Pausing and E-Stop
Pause: stops movement, router keeps running. Resume with Start.
E-Stop: immediately halts all movement. After an e-stop you must re-zero before restarting.
Recovering Mid-Job
If the machine loses position:
- Re-zero XY and Z carefully to the original position
- Right-click any line in gSender G-code viewer to Start From Line
- Run from slightly before where the problem occurred
For broken bits: e-stop, install new bit of same type, re-zero Z only (XY should not have moved), restart from a line before the break.