Limit switches are important for safety of you and your machine. Besides emergency switch (or E-stop for short) these are meant to immediately stop everything and also signal the controller that state. Limit switches can be position on either positive, negative or both sides of the axis travel on your CNC machine. On some machines, limit switches can also be used for homing the machine, eliminating the need for an additional switch. Different devices have different pins designated for E-stop so read the manual to find out which pin is used in your case. This Mach3 limit switch tutorial will cover all of them as all of the PoKeys devices are configured the same way.

Emergency stop switch is the one that assures the safety for the operator. If this switch is pressed, the machine must not move. Also, if something goes wrong during operation it is crucial that you have at least one in the reach of your hand. It is not uncommon that there is more than 1 E-stop on larger machines. In this case, all switches are wired in series – activating one of them will trigger the emergency stop. The switch should lock when pressed and cut power to the machine without affecting the controller.

For this case either special emergency relay or E-stop with two terminals is required, one NC (normally-closed) through which the machine is powered and one NC (normally-closed) or NO (normally-open) that signals the that an error occurred and the E-stop has been pressed. The E-stop should be properly wired. An example for one E-stop switch is shown below.

This part will cover Mach3 limit switch configuration in positive and negative direction. Homing switches will be covered in the next chapter. Limit switches are not crucial for the operation of your machine but are a good safety feature to have. Although these can be to some extent replaced by soft-limits, the hardware switches can prevent damage to your machine in unpredicted operation. Soft limits are machine borders determined in software and will be discussed later in this Mach3 limit switch tutorial. Even if you do have soft limits setup, limit switches will provide additional protection to your machine.

Limit switches are mounted at the ends of the machine travel, but so, that, when the machine hits the switch, it still has room to stop before crashing. This switches can be wired in many different ways. Most common ones are to have NC switches wired in series, NO switches wired in parallel or if the controller has enough inputs, to wire each switch separately. Another option is to wire all of the switches on one input and the software will, depending on the axis moving and the direction, determine which switch was pressed, but I recommend to use separate input for each axis. An example of two most common connections are on this picture.

For helpful information on how to run the Mach 3 software with your plasma table from Arclight Dynamics check here for education, tricks, tips and more. Included along with Mach3 is a trial version of LazyCam which will (supposedly) convert DXF files into G-code after you input the tool info, offsets etc. There are no instructions with Lcam but there are tutorial videos.

To enable limit switches in Mach3, open PoKeys plugin configuration and go to pulse engine settings. Here you can select on which pin your limit switch is connected. And if Mach3 shows that the limit switch is active, even if it is not, you have the option to invert it (if NO switches are used). When you configure the input pin, if the square is red that means that the switch is active, and if it is not if should be inverted. In this example only X-axis was set.