The CNC Retrofit Strategy.
How to evaluate mechanical iron and migrate to an open IPC architecture.
1. Mechanical Evaluation
Before touching a wire, evaluate the cast iron. Measure ball screw backlash with an indicator. Check spindle runout and drawbar pull force. If the mechanicals require a $40,000 rebuild, a retrofit may not make financial sense. If the iron is tight but the control is dead, you have the perfect candidate.
2. I/O Mapping
The most time-consuming part of a retrofit is mapping the existing I/O. Trace every proximity switch, solenoid, and limit switch. Create a spreadsheet mapping the legacy physical address to the new EtherCAT I/O slice address. Do not assume the OEM schematic is accurate; verify every wire.
3. Drive Sizing & Inertia Matching
When replacing proprietary DC servos with modern AC EtherCAT servos, you must match the torque curve, not just the wattage. More importantly, calculate the inertia ratio between the motor rotor and the load (ball screw + table). A mismatch greater than 5:1 will result in a machine that is impossible to tune for high-speed surfacing.
Pro Tip: Safety Circuits
Never run E-stops through standard software logic. Hardwire your safety relays to drop contactor power to the drives, or use certified Fail-Safe over EtherCAT (FSoE) hardware modules.