You can think of the Semi-Closed Loop System as an “electronic insurance policy”. The system uses a special sensor that is installed on each of the 4 CNC motors. This sensor monitors the movement of each motor and compares that movement against what UCCNC is telling it to move.

As an example, if UCCNC wants to move X 35mm to the right and something is interfering with that movement and it only moves 31mm, then the Semi Closed Loop System will immediately stop the system.

The beauty of this system is that you can simply rehome the machine and then continue the job right where you left off. This is especially handy when you are using expensive materials that you do not want to waste.

It is comprised of 4 sensors, one mounted on each of the Y-axis motors, one on X and one on Z. The sensors monitor the motors’ movements and compare that movement against what UCCNC (your project’s G-Code file) is telling the motor to move. In the event that one of the motors does not match the intended movement, then the system will immediately go into E-Stop.

As your machine is cutting a project, if it runs into an obstruction, or if there is any other situation that causes the machine to stall in one of the axes, it will stop the system.

To reset, you can simply rehome the machine and then continue running the job from where you left off. You can use the RUN FROM HERE button on UCCNC and the job will continue as if the error never happened. You can watch the following video to learn how to use this feature on UCCNC:

When you buy an Automatic Tool Changer (ATC), the system might come with an orange switch box. That switch box is intended for use with the ATC on the D.Series line of CNC machines as well as the M.Series machines that DO NOT have a Tool Magazine on the back of the machine. If you did not purchase the optional Tool Magazine then you would need to use the Switch Box. If you have the Tool Magazine, then you DO NOT need to use the switch box.