Mitsubishi QD70D4 4-Axis Positioning Module

The QD70D4 is a dedicated positioning module within the MELSEC Q Series, capable of controlling up to four axes independently or synchronously. It generates high-speed differential pulses for driving servo amplifiers or stepping drivers, achieving precise speed and position control. Typical applications include CNC machines, pick-and-place systems, and multi-axis assembly stations.

Technical Specifications

• Number of Axes: 4 (independent or interpolated)

• Output Pulse Type: Differential line driver (maximum 1 Mpps)

• Positioning Data: 600 data points per axis

• Interpolation Functions: Linear, circular, and helical

• Control Methods: PTP (Point-to-Point), speed control, and path following

• Acceleration/Deceleration: Trapezoidal and S-curve profiles

Advanced Motion Features

The QD70D4 supports electronic gear and backlash compensation, reducing mechanical errors. Its built-in positioning logic allows the CPU to offload real-time trajectory calculations, ensuring deterministic motion even in complex sequences. The module also includes an external I/O interface with 6 inputs and 4 outputs for limit switches, ready signals, and alarm monitoring.

Programming and Configuration

Using Mitsubishi's GX Works2 or MT Developer2, engineers can configure positioning parameters, create motion profiles, and simulate axis movement. The module's memory stores positions, speeds, and acceleration values in battery-backed SRAM, eliminating re-download after power cycles. Data link with the main CPU occurs through high-speed bus communication, achieving update rates under 1 ms.

Diagnostics and Reliability

LED status indicators on the front panel show power, communication, and axis error conditions. Self-diagnostic routines detect encoder disconnection, over-travel, and driver faults, triggering immediate protection actions. The QD70D4 operates in temperatures from 0 to 55°C and withstands vibration up to 5G, making it suitable for demanding industrial environments.

Integration Example

In a four-axis labeling machine, the QD70D4 coordinates servo-driven conveyors and rotary actuators, achieving synchronized glue application at 200 cycles per minute. Combined with MELSEC Q CPU, the module enables closed-loop performance without external motion controllers.