As labor costs continue to rise, more and more 3-axis CNC machines on the market require the addition of a 4th axis to reduce the number of setups and lower labor costs. The following is a brief introduction to the process of adding a 4th axis.

First, we must determine whether our existing CNC machine can support the addition of a 4th axis. Currently, commonly seen Fanuc systems on the market include the 0 series, 0i-A series, 0i-B series, 0i-C series, 0i-D series, and 0i-F series. Due to their age, machines with 0, 0i-A, and 0i-B systems generally have little value for retrofitting and will not be discussed here.

So let’s take a look at the table below to see if your machine can support the addition of a 4th axis:

From the table above, you can determine whether your machine supports adding a 4th axis. (Some machines may already use the 4th axis for functions like a servo tool magazine—such cases are outside the scope of this discussion.)

Once the system requirements are met, we look at the motor and drive. Currently, the common types are the ai series and bi series. Motors from the ai and bi series are generally interchangeable and require little attention. However, drives must be selected carefully.

Our basic principle is to match the 4th axis drive to the same batch as the existing three axes. For example, if the first three axes use A06B-6114-HXXX, then the 4th axis should preferably also use A06B-6114-HXXX. Fanuc does offer some compatibility; for instance, the standard drive for the 0i-MD is A06B-6117-HXXX, but A06B-6240-HXXX can also be used. However, for the newer 0i-MF, only A06B-6240-HXXX is supported. So, as a general rule, stick with the same batch when possible.

Once the hardware is selected, we’ll talk about parameters and PLC. The Fanuc 0i series parameters are largely consistent with only minor differences. Refer to the table below for guidance:

Finally, regarding the PLC — since all CNC machine PLC programs on the market are custom-designed by their manufacturers, there is no unified standard. We can only provide a general overview.

As we are retrofitting a finished CNC machine, many signals don’t need to be handled manually. Just pay attention to the following internal PLC signals:

In addition, you will need to handle:

• 4th axis unclamp detection signal

• 4th axis clamp detection signal

• 4th axis solenoid valve control signal

These three signals are not standardized and must be configured based on the actual situation by the installer.

Given the wide variety of CNC machines on the market and the differing design philosophies across manufacturers, installation personnel must continually summarize and accumulate experience to handle different scenarios effectively.