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:

If an error has occurred or your system has an obstruction causing the Semi-Closed Loop System to trigger, it will activate the E-Stop mode on the machine. When this happens the first thing you need to do is take note of the line number that you are at in the G-Code window on the lower left part of the UCCNC screen. Write it down or take a photo with your cell phone.

To reset this, you press the Red reset button on the UCCNC screen and then press HOME ALL. This will reset each axis so that everything is back in sync with UCCNC. From that point, you can use the START FROM HERE button and restart the job from right where you left off.

You can view this video on how to use the START FROM HERE button:

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.