How can I troubleshoot my CNC that is not communicating?

There are several steps to verify if a CNC is communicating, or if it is a CNC that is not communicating. You will first want to verify the RS232 cable is connected to each device securely. There maybe two ports on the controller or appear to be a port on the front of the unit, however, this may not be connected inside the machine. CNC communication troubleshooting can be time-consuming and frustrating, so we recommend following these hints below:

Hint 1:
Verify information is coming out of the communication port by placing an RS232 mini tester directly on the back from the computer, sending a file from the CNC control, and viewing the status of the tester. This device should show RD or RX activity when the control is sending to the computer. If you do not have this tester, you can contact SFA and purchase this valuable tool for $20, as it will save time and identify if the CNC controller or PC is failing.

Hint 2:
Make sure you are on the correct port on the back of the computer. Remove any switch boxes, adapters, misc. cables and try connecting directly into the computer serial RS232 port. If there is only one port, verify the COM port number in the device manager and match your software to this port. There maybe be various RS232 communications on your PC and you’re unaware of this port. If there are various ports, try moving the cable to the other ports.

Hint 3:
Verify the voltages on the cable are within the RS232 limits. If you are running an Ethernet cable as a serial cable, you may run into serious reliability issues. Ethernet cable (CAT5/6) cable is designed for networking computers and should not be substituted for RS232 cable to interface to a CNC control. You want to adhere to the machine tool builder’s specifications and not damage the port due to improper grounding or shielding. SFA does not sell or recommend Ethernet cable as RS232 as this normally will void warranties and damage equipment.

Note: SFA’s RS232 cable uses 8 wires, 3 levels of shielding, and has been proven to handle cable runs over 200+ feet. If you need a lengthier connection, consult our Account Executives for wireless or Ethernet solutions.