Okuma 1911-2836 PLC Circuit Board Slot Card Module for CNC Machinery

The Okuma 1911-2836 is a printed circuit board module designed as a PLC I/O or communication slot card for Okuma CNC machine tools. Used in Okuma’s OSP (Okuma Sampling Path) control systems, this board interfaces between the main CPU and field devices such as sensors, actuators, relays, and operator panels. It is a critical component for the operation of Okuma lathes, machining centers, and grinders.

Functional Description

The 1911-2836 PCB typically serves as a digital I/O board or a high-speed counter module within the OSP controller rack. It connects to the backplane via a 96-pin DIN 41612 connector and receives power from the rack’s 5V and 24V supplies. The board processes input signals from limit switches, proximity sensors, pushbuttons, and encoder inputs, and provides output signals to contactors, solenoids, and indicator lights. It is compatible with OSP U10, U100, and P200 control generations.

Signal Specifications

Number of I/O points: Typically 16 inputs and 16 outputs (depending on firmware configuration). Inputs: 24V DC, 5mA, optically isolated with 2ms filter. Outputs: Transistor sinking, 24V DC, 0.5A per point, with overcurrent protection. Some variants of the 1911-2836 include 2 channels of high-speed counter inputs (500kHz max) for spindle or axis feedback. The board has internal diagnostic LEDs for each I/O point, visible through a cutout in the card faceplate. It also includes status LEDs for board power and communication with the CPU.

Communication and Addressing

The board communicates with the main CNC CPU via a high-speed proprietary bus (OSP link). I/O addresses are assigned automatically by the system based on slot position. The PLC (sequence program) within the OSP reads inputs from specific address ranges (e.g., X100-X11F) and writes outputs to Y addresses. The board supports interrupt inputs for time-critical signals. No user configuration is required; the board is plug-and-play when installed in a correctly configured rack.

Physical Dimensions and Construction

Dimensions: 220mm (H) x 30mm (W) x 200mm (D). Form factor: Single-slot Eurocard (3U height). Weight: 0.4 kg. The board is constructed with a 4-layer FR4 PCB, coated with conformal coating for protection against moisture and dust. Edge connectors are gold-plated for reliability. The faceplate includes a plastic label with Okuma part number and I/O designation. A handle is incorporated for safe extraction. Operating temperature: 0-60°C. Humidity: 20-80% non-condensing.

Okuma System Compatibility

The 1911-2836 is compatible with OSP 5000, OSP 7000, OSP U10L, U100L, and P200M control units. It can be installed in any slot of the main rack or an expansion rack. The board is often used in pairs for systems requiring more than 16 I/O points. It is also compatible with Okuma’s Macro PLC function, allowing ladder logic to directly access the I/O. For troubleshooting, the board’s I/O status can be monitored on the CNC screen’s I/O monitor page.

Troubleshooting and Diagnostics

Common failure symptoms: One or more I/O points stuck on/off, intermittent operation under vibration, or complete loss of communication with the CPU. The board’s self-test runs at power-up; error codes are displayed on the CNC screen. If the board fails, the machine may alarm out (e.g., “I/O module fault”). Visual inspection may reveal burned components, cracked solder joints, or swollen capacitors. Replacement involves powering down the machine, removing the card, and inserting a new one. No reprogramming is needed as configuration is stored in the CPU.

Field Wiring

The board has a 50-pin header connector (IDC type) on the top edge (facing up when inserted) for field wiring. A mating cable (typically Okuma 1911-XXXX) leads to a terminal strip or junction box. Alternatively, an interface adapter (1911-2837) can be used for screw terminals. The wiring uses shielded cables for noise-sensitive signals. The board’s ground (GND) must be connected to the machine frame ground for proper EMI performance.

Applications

The 1911-2836 is used in Okuma CNC machines to interface with tool change sensors, coolant valves, spindle load monitors, part catchers, automatic doors, conveyor systems, and safety interlocks. It is also used in retrofit applications where an older machine’s I/O board is replaced. Many machine rebuilders stock this board as a spare part for Okuma equipment.

Storage and Care

Store in anti-static bag in a dry environment between 15-35°C. Avoid exposure to magnetic fields, cleaning solvents, or physical shock. When handling, hold by edges and avoid contact with gold contacts. Use a wrist strap to prevent electrostatic discharge damage. The board has no user-serviceable parts; component-level repair requires specialized tools and schematics.

Conclusion

The Okuma 1911-2836 PLC circuit board is a reliable interface module for OSP-controlled CNC machines. Its robust design and plug-in form factor make it a straightforward part for maintaining legacy Okuma equipment.