MITSUBISHI ELECTRIC MELSEC iQ-R/Q/L Complete Guide

MITSUBISHI ELECTRIC MELSEC iQ-R/System Q/L Series Selection and Safety Redundancy Application Guide

Introduction: Mitsubishi Electric's modular PLC three carriage

Mitsubishi Electric's MELSEC series holds a pivotal position in the global PLC market, with the iQ-R series serving as the new flagship platform, the System Q series as the proven modular mainstay, and the L series meeting small and medium-sized applications with a compact baseless design. The three series share a unified programming environment (GX Works2/3) and network architecture (CC Link IE), but each has its own focus on performance, scalability, and security levels.

For engineers planning new systems or facing upgrades to old A-series/nS series, understanding the core differences, redundancy implementation methods, security certification levels, and communication troubleshooting methods of these three product lines is the key to ensuring project success. This article is based on the latest product catalog and provides a practical guide covering selection, redundant configuration, security integration, network troubleshooting, and upgrade paths.

IQ-R Series: The Next Generation Automation Core Platform

2.1 CPU Product Line and Selection Points

The iQ-R series offers eight general-purpose PLC CPUs with program capacities ranging from 10k to 1200k steps, as well as RENCPU models with embedded CC Link IE Control/Field ports (such as R04ENCPU, R120ENCPU). Core performance parameters:

Model Program Capacity Basic Instruction Processing Time Built in Ethernet/CC Link IE

R00CPU 10k step 31.36 ns None

R04CPU 40k steps 0.98 ns None

R04ENCPU 40k steps 0.98 ns available

R120CPU 1200k step 0.98 ns None

R120ENCPU 1200k step 0.98 ns available

Selection trap: If you need to directly connect to the CC Link IE Field network (such as remote I/O or motion control), you must choose the RENCPU model, otherwise additional network modules need to be added. In addition, R00CPU does not support multi CPU systems and cannot use SD cards.

2.2 Redundant Systems and SIL2 Process Control

The iQ-R series supports high availability redundant systems and connects the primary and backup CPUs through the redundant function module R6RFM. The redundant system complies with the IEC 61508 SIL2 standard and can maintain data tracking (up to 1M words) during switching. The specific configuration is as follows:

Standard redundancy: Two R-series process CPUs (R08PCPU~R120PCPU) are each equipped with an R6RFM module, synchronized through multimode fiber (up to 550m).

SIL2 redundancy: Using the R08PFCPU-SET~R120PSFCPU-SET kit (including SIL2 process CPU and SIL2 functional module R6PSFM), combined with diagnostic digital I/O (RX40NC6B, RY40PT5B) or analog I/O (R60AD8-G, R60DA8-G), a SIL2 compliant safety circuit can be constructed.

Engineering experience: In SIL2 redundant configuration, each safety input signal requires two input modules (RX40NC6B) for dual channel reading, and each safety output requires two output modules (RY40PT5B) to achieve 1oo2 switching. Analog safety input requires two analog input modules and one analog output module for read back verification. Do not mix standard I/O modules, as it may compromise safety integrity.

2.3 Secure CPU and General Security Control

The iQ-R safety CPU (R08SFCPU-SET to R120SFCPU-SET) can execute the standard program and safety program in the same module at the same time, and connect the safety equipment (grating, emergency stop switch, door lock) through the CC Link IE Field network. This CPU has obtained T Ü V Rheinland certification and meets ISO 13849-1 PL e and IEC 61508 SIL3.

Common malfunction: The safety CPU reports "Safety communication timeout". Troubleshooting steps:

Check the power and fiber connections of secure remote stations (such as NZ2GFSS2 series) in the CC Link IE Field network.

Use the security monitoring function of GX Works3 to view the specific slave status.

Confirm that the F-H parameters of the secure slave station are consistent with the configuration of the master station (especially the watchdog time).

If the security slave is replaced, a new security verification must be performed and a new security signature must be applied.

2.4 Motion CPU and Simple Motion Module

The iQ-R motion CPU (R16MTPU/R32MTPU/R64MTPU) can control 16/32/64 axes, supporting 4-axis linear interpolation, 2-axis arc interpolation, and 3-axis spiral interpolation. It is connected to the MR-J4-B servo amplifier through the SSCNET III/H network, with a communication cycle as fast as 0.222ms.

For applications that do not require a complete motion CPU, simple motion modules RD77GF (CC Link IE Field connection) or RD77MS (SSCNET III/H connection) can be used to control up to 16 axes, supporting functions such as electronic cam, speed torque control, and marker detection.

Troubleshooting: When there is an alarm of "excessive tracking error" on the motion axis, first use the oscilloscope function (MT Works2) to check the deviation curve between the commanded position and the actual position. Common reasons include: SSCNET III/H fiber bending radius is too small, joint contamination, or low position loop gain setting in amplifier parameters. Clean the fiber end face (using a dedicated cleaning pen) and check if the network cycle setting matches the actual capability of the amplifier.