The susceptibility of a CNC machine to different sources of noise and stray currents depends on its design, but grounding, bonding, and shielding play a vital role. As the use of CNC machines becomes more prevalent, minimizing production downtime, product loss, and expensive repair bills becomes increasingly important. Good practices for installation, powering and grounding, and maintenance procedures are all required to prevent malfunction, degradation, and damage to electronics. Today's electronically controlled CNC machine requires a common signal reference ground for its logical circuits to operate reliably. Upsets related to grounding and ground reference are usually attributed to noise or stray currents that find their way into logic circuits. A common wiring-related source is the inductive coupling of noise currents into wires of control and power circuits run in the same raceway or placed in close proximity to each other inside a CNC machine. Additional sources include contactors, relays, solenoids, and motor drives that are internal to the CNC machine. (For more sources, see sidebar "Noise Sources and Coupling Modes" on page 28.)
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