Universal Gcode Sender is the software interface that connects your computer to your CNC.

The UGS screen allows you to monitor and control the operation of your CNC, including the most common functions of homing and setting the zero point of the work piece.

When operating your CNC UGS will display an ALARM for issues that require your immediate attention.  UGS will also let you know if it encounters any problems with your Gcode file, these are labeled with Error Codes.

Alarm 1 

Alarm 1 indicates that “Hard Limits have been triggered.”  Hard Limits are switches used by some CNCs to designate the travel limits on any given axis. If triggered the CNC immediately stops to keep the spindle from exceeding the travel limit.

BobsCNC Evolution Series and KL7 Series CNC Routers use soft limits which are programmed into the GRBL firmware on the microprocessor of the Control Board.

Every time the CNC is successfully homed the Spindle is driven to a known location determined by the position of the home switches. Soft limits are set to keep the Spindle from travelling beyond the cutting area.

When an Alarm 1 appears, it means that “Hard Limits” has been turned on in your firmware.  If this feature is turned “on” electrical noise and voltage spikes can trigger a false alarm and stop the machine.

An “ok” will show that it command has been changed.


Type $$ and hit Enter, this will refresh and display the updated firmware settings as shown.

November 17, 2020 — Keith Havens