Positioning module for multi-axis stepper and servo control
The Siemens 6ES7357-4AH01-0AE0 is an FM 357-4 LE positioning module for the S7-300 rack. It drives up to 8 axes for any purpose, supporting stepper motors via pulse-direction outputs and servo drives via analog setpoints or SSI absolute encoder feedback. Pulse frequency tops out at 750 kHz, which translates to a maximum motor speed of 3000 RPM with a 1000-line encoder — adequate for most pick-and-place, indexing, and linear-motion axes in packaging and assembly machinery. The 750 kbyte NC program memory stores multi-segment motion profiles without external storage.
Encoder interface and I/O complement
The module accepts 5 V differential RS 422 encoder signals with a maximum cable length of 50 m shielded, dropping to 35 m in hybrid mode with servo axes. This covers most machine-mounted encoder runs without a repeater. Input frequency ceiling is 1 MHz; the SSI telegram length is parameterizable to 13, 21, or 25 bit. Digital I/O: 18 inputs and 8 outputs. Inputs accept 24 V signals with thresholds of -3 to +5 V for signal '0' and +11 to +30 V for signal '1'. Outputs switch up to 300 mA each at 24 V, suitable for driving small contactors, indicators, or solenoid valves directly. A 40-pin front connector is required. Power draw: 100 mA from the 5 V backplane bus plus 15 W typical total loss. The 24 V field supply powers the I/O and encoder interface; the 5 V rail only serves the backplane logic.
The 40-pin front connector carries all field wiring — encoder signals, digital I/O, and 24 V supply. Cable entries are through the front face; allow 50 mm clearance above and below the module for connector insertion and cable bend radius.