Mitsubishi Q Series vs iQ-R Series: Which MELSEC PLC to Choose?

By Abdullah Zahid
23 min read
Mitsubishi Electric MELSEC-Q Series and iQ-R Series modular PLC racks compared side by side for industrial automation platform selection

Mitsubishi Q Series vs iQ-R Series: Which MELSEC PLC Should You Choose?

Controls engineers and system integrators searching for clarity on the MELSEC-Q Series Modular PLC versus the MELSEC iQ-R Series Modular PLC are typically at a fork in the road: either a new system is being specified and a platform standard must be set, or an existing Q-based facility is expanding and someone needs to make a defensible case for staying put or migrating. This comparison draws directly from Mitsubishi Electric manufacturer documentation, distributor knowledge, and community experience to give you the clearest possible framework for that decision. The core trade-off is a proven, widely installed ecosystem with a broad module lineup on the Q side versus higher system bus performance, modern CC-Link IE Field networking, and long-term lifecycle alignment on the iQ-R side.

If you already know which platform fits your project and are ready to source hardware, check current pricing and availability for Mitsubishi MELSEC modules at LeadTime.ca — ships worldwide.

Q Series or iQ-R Series: Which Platform Fits Your Project?

The MELSEC iQ-R Series Modular PLC is the right choice for most new medium-to-large Mitsubishi PLC installations. Choose it when:

  • You are designing a new system and need high-speed system bus performance with modern network options including CC-Link IE Field
  • Long-term lifecycle support and platform standardization are a procurement and maintenance priority
  • Your project requires integrated safety CPUs, advanced diagnostics, or MES connectivity within the Mitsubishi platform
  • Your engineering team is trained on GX Works3 or will be investing in that training anyway
  • You are planning a plant-wide migration roadmap from legacy systems to a single Mitsubishi standard

If your project must match an existing Q-based architecture, depends on Q-only special modules such as the QJ71MB91 Modbus RTU slave card, or cannot absorb the engineering and downtime cost of migration right now, staying with the MELSEC-Q Series Modular PLC or running a hybrid Q plus iQ-R system remains a practical and well-documented option. Specific alternative part paths are covered in the scenarios and variant sections below.

On this page:

What Each Platform Is and Where It Sits in the MELSEC Family

Mitsubishi Electric's MELSEC modular PLC family spans several generations and form factors. The MELSEC-Q Series Modular PLC, often called System Q, is the previous-generation flagship modular platform. It accumulated a large global installed base across automotive, food and beverage, packaging, and general manufacturing applications, and it brought significant performance improvements at the time of its introduction. The module lineup is extensive and mature, covering digital I/O, analog, motion, communication, data logging, and a wide range of special function cards developed over many years.

The MELSEC iQ-R Series Modular PLC is Mitsubishi Electric's current flagship modular platform, positioned as the strategic successor for new medium-to-large system designs. Manufacturer catalogs and technical overviews describe it as a high-speed system bus platform with a wide range of CPUs capable of serving diverse automatic control needs. It is designed around modern Ethernet-based CC-Link IE Field networks, offers dedicated safety CPUs and safety modules within the same rack architecture, and is engineered with newer software tools. Alongside these two, the MELSEC family also includes the iQ-F compact series and FX series for smaller applications, but the Q versus iQ-R comparison is the relevant one for engineers specifying medium-to-large modular systems.

Lifecycle and Long-Term Support: What the Q Status Means for Your Project

Manufacturer positioning describes the MELSEC-Q Series Modular PLC as a mature platform with a long installed base, with the industry direction pointing toward iQ-R as the main platform for new modular PLC projects. Mitsubishi Electric does not publicly announce specific lifecycle end dates in the same way that every vendor handles this, but the strategic direction is clear from catalog language and product roadmap emphasis: iQ-R is the platform where new investment in CPUs, modules, and software tooling is concentrated.

For procurement planners, this has practical implications. Spare parts for large Q-based plants will remain available for the foreseeable future, but engineering effort around Q in terms of new module types, new performance tiers, and new network options is winding down. Plants with extensive Q installations are not facing immediate obsolescence, but starting a new greenfield project on Q today requires a clear justification — most commonly the need for Q-only modules or integration with an existing Q installed base.

For new project engineers, the lifecycle reality is straightforward: iQ-R delivers longer-term confidence in software updates, security patches, new module availability, and manufacturer support. That alone often settles the question for large capital projects with multi-decade operational expectations.

Hardware Architecture: Base Units, Power Supplies, and CPUs Compared

One of the most important physical facts in this comparison is that the MELSEC-Q and MELSEC iQ-R platforms use different base units with different physical designs. They are not interchangeable. A Q module cannot be inserted into an iQ-R base, and an iQ-R module cannot be inserted into a Q base. This is not a software or firmware limitation — it is a hardware form factor difference. Manufacturer documentation confirms this directly.

On DIN rail mounting, Mitsubishi Electric documentation states that base units from both platforms use DIN rail and that rails can often be used in common where the mechanical specifications of each base unit align. This means a panel that physically accommodates both form factors may be able to use a shared rail, which is relevant for hybrid and migration scenarios. However, each base unit must still be evaluated for its own physical dimensions and mounting requirements.

Power supply modules are also platform-specific. Q-series power supply modules are not interchangeable with iQ-R power supply modules. Critically, manufacturer documentation explicitly states that current consumption differs between MELSEC-Q and MELSEC iQ-R modules, and that designers must pay careful attention to power capacity when selecting models for each platform. This means that if you are migrating from Q to iQ-R or designing a hybrid system, you cannot simply transfer the Q power budget calculation. A full recalculation is required using the current consumption figures for the specific iQ-R modules selected.

CPU ranges on both platforms are broad. The MELSEC-Q offers a wide range of CPU options suited to many application scales, with performance appropriate for its generation and well-proven in large systems. The MELSEC iQ-R offers a wide range of CPUs with the high-speed system bus architecture as a platform-level feature, and higher program capacity options for demanding applications. Exact instruction speeds, program memory sizes, and maximum I/O point counts are variant-specific and must be taken from the current CPU datasheets rather than generalized across the family.

I/O and Special Function Module Lineup: Where Q Still Leads

The MELSEC-Q module lineup is the broadest of the two platforms. Years of development produced digital I/O modules, high-resolution analog modules, multi-axis motion controllers, data logging cards, MES interface modules, and a wide range of communication and special function cards. Some of these modules were developed to serve application niches that have not yet received direct iQ-R equivalents. The QJ71MB91 Modbus RTU slave module is the most frequently cited example in distributor and community discussions: it provides Modbus RTU slave functionality on Q racks and currently has no direct equivalent module for iQ-R as of available documentation.

The MELSEC iQ-R module lineup is growing and focused on modern application requirements. High-performance motion control, advanced data logging, MES connectivity, safety I/O, and CC-Link IE Field communication modules are available, and the range continues to expand. For most standard digital and analog I/O requirements, iQ-R coverage is solid. The gaps that engineers encounter tend to be in specific communication protocols or specialized analog functions where the Q lineup accumulated niche cards over many years.

The practical guidance here is to build a full module list for your application before committing to either platform. Any module that is critical to your system and appears only in the Q catalog is a strong argument for either retaining Q or implementing a hybrid architecture. Exact channel counts, resolution specifications, and features depend entirely on the individual module part number and must be verified in the current module datasheets.

Performance and Scalability for Demanding Applications

At the platform level, Mitsubishi Electric catalogs characterize the MELSEC iQ-R as a high-speed system bus design with a wide CPU range suited to diverse and demanding automatic control applications. The high-speed system bus is a distinguishing architectural feature relative to the Q platform. For applications with fast scan time requirements, complex multi-CPU coordination, high-axis-count servo systems, or large program structures, iQ-R's architecture is positioned as the stronger foundation.

The MELSEC-Q Series delivered strong performance for its generation and was successfully deployed in large and complex systems across automotive assembly, high-speed packaging, and multi-axis machine control. It supports mature motion control options through dedicated modules and has handled large I/O counts in real-world installations for many years. The performance limitation of Q relative to iQ-R is not a question of whether Q can handle industrial loads — it clearly can and does in millions of installed systems — but rather a question of headroom, modern network throughput, and alignment with where the technology is going.

For engineers designing new systems with performance budgets to spare, the practical difference may not be visible in day-to-day operation. For engineers pushing the limits of scan time, multi-CPU shared memory, or high-density motion coordination, the iQ-R architecture provides a better-defined growth path. The exact performance figures — instruction execution speeds, maximum I/O points per system, program capacity — are CPU-model-specific and must be drawn from the relevant CPU datasheets rather than from family-level comparison.

Network and Communication Options: CC-Link IE, MELSECNET, and Modbus

Network strategy is often the deciding factor in the Q versus iQ-R choice, and the differences here are significant and practical.

The MELSEC-Q platform has strong support for MELSEC legacy networks including MELSECNET/H and Melsecnet/10, as well as CC-Link via appropriate communication modules. These networks represent the backbone of many long-running Mitsubishi installations and are well-understood by experienced Mitsubishi engineers. For plants where these networks are already in place and will continue to operate, Q's legacy network support is a real advantage.

The MELSEC iQ-R platform is positioned around CC-Link IE Field and other Ethernet-based networks through dedicated modules and CPU options. CC-Link IE Field is Mitsubishi's current high-speed industrial Ethernet network standard, and iQ-R is the natural controller for new systems built on this network. For projects with plant-wide Ethernet integration requirements, IT/OT convergence goals, or future readiness for CC-Link IE TSN, iQ-R is the platform to specify.

On network coexistence, Mitsubishi Electric documentation explicitly states that MELSEC iQ-R modules can access MELSEC-Q modules via the network, and that both platforms can be used together in the same network. This is the foundation for hybrid and phased migration architectures.

The Modbus situation deserves direct attention. The MELSEC-Q has the QJ71MB91 Modbus RTU slave module, which provides a well-established path for Modbus RTU slave functionality. As of current distributor and community documentation, there is no direct QJ71MB91-equivalent Modbus RTU slave module available for the MELSEC iQ-R. Engineers who require Modbus RTU slave capability in an iQ-R system will need to evaluate alternative architectures, protocol gateways, or continued use of Q for the Modbus-facing portions of the system. This is one of the clearest cases where a specific Q module requirement drives the platform decision.

Aspect MELSEC-Q Series MELSEC iQ-R Series
Primary networks MELSECNET/H, Melsecnet/10, CC-Link via modules CC-Link IE Field and Ethernet-based networks via dedicated modules and CPUs
Legacy MELSEC network support Native and mature Can participate via appropriate modules; iQ-R can access Q modules over the network
Modbus RTU slave QJ71MB91 dedicated module available No direct QJ71MB91-equivalent as of current documentation; alternative architectures required
CC-Link IE Field Available via modules Primary network platform; strong module support
Q and iQ-R coexistence Can share networks with iQ-R when configured appropriately Documented: iQ-R and Q can be used together in the same network

Engineering Tools, Diagnostics, and the GX Works3 Transition

Engineering tool requirements are a practical factor that affects project cost and team readiness in ways that hardware specifications alone do not capture.

Existing Q-based plants are typically programmed and maintained using GX Works2 or GX Developer. These tools are well-understood by engineers who have worked with Q systems and hold large libraries of tested Q programs. Moving to iQ-R means moving to GX Works3, which is a different tool with a different project structure, different configuration concepts, and different diagnostics interfaces. Community and training material feedback describes GX Works3 as an improvement in project organization and diagnostic capability, but also reports a genuine learning curve for engineers transitioning from GX Works2.

The MELSEC iQ-R is engineered for GX Works3, and the improved diagnostics, structured project management, and compare functions available in the newer software are part of what makes iQ-R the more capable platform for complex systems. For new projects where no existing Q code base needs to be carried forward, the tool transition is a one-time investment. For migration projects, the effort includes project conversion, validation, and team training — which must be planned and budgeted, not assumed away.

Teams that are already fully proficient in GX Works3 and iQ-R have a clear efficiency argument for standardizing on iQ-R. Teams still deeply embedded in GX Works2 and Q have a legitimate short-term reason to consider staying with Q for incremental expansions, while planning the toolchain transition as a separate initiative.

Safety, Security, and Compliance Considerations

The MELSEC iQ-R platform offers dedicated safety CPUs and safety I/O modules within the same rack architecture as standard control. This integrated approach to safety is one of the stronger arguments for iQ-R in applications requiring functional safety compliance, as it allows safety and standard control to share the same physical platform and network infrastructure. Safety ratings, SIL levels, and performance level certifications are always variant-specific and depend on the exact safety CPU, safety module, and validated architecture — these must be confirmed against official Mitsubishi safety manuals and relevant standards for each application.

The MELSEC-Q platform supports safety PLC functions through safety PLCs and networks within the broader Mitsubishi family, but the integrated safety architecture within a single iQ-R rack is a more modern approach that simplifies long-term compliance and system support. For new safety-critical system designs, iQ-R is the preferred platform, provided the specific safety architecture is validated as described above.

On the security side, newer platforms generally offer more options for access control and communications security. Any controls engineer responsible for OT network security should review the specific security features and firmware update paths available for both platforms as part of the platform selection process. Platform choice does not replace a formal risk assessment, and any hardware changes in operating systems require qualified personnel and appropriate lockout/tagout procedures.

Hybrid Architectures and Phased Migration from Q to iQ-R

One of the most practically useful facts in this comparison is the manufacturer-documented ability to run MELSEC-Q and MELSEC iQ-R on the same network. This makes hybrid architectures not just possible but officially supported, and it is the foundation of every realistic phased migration strategy.

In a typical phased migration, new control segments and new machines are built on iQ-R while stable Q racks handling proven I/O and special functions remain in service. The iQ-R controllers access Q modules over the network using documented network and adapter options. As shutdown windows and capital budgets allow, Q subsystems are replaced with iQ-R equivalents. This approach avoids the business risk of a simultaneous plant-wide replacement and allows engineering teams to build iQ-R competence on lower-risk segments before tackling core production systems.

The specific adapter modules and network configurations required for Q and iQ-R coexistence are variant-dependent and must be verified against current Mitsubishi migration documentation. Mitsubishi Electric provides migration tools and technical documents to assist engineers in mapping Q systems to iQ-R equivalents. The level of effort for a full migration should not be underestimated: it involves hardware replacement, project conversion in GX Works3, I/O rewiring confirmation, functional testing, and safety validation where applicable. Piloting on one representative machine before committing to a plant-wide migration is consistently recommended by engineers who have been through this process.

Seven Decision Scenarios: Which Platform to Choose and Why

Scenario Recommended Platform Key Rationale
New high-speed packaging line with CC-Link IE Field and future TSN needs MELSEC iQ-R iQ-R is positioned for high-performance systems and modern CC-Link IE Field-based networking; long-term lifecycle supports new installations
Expansion of existing Q line using QJ71MB91 Modbus RTU slaves MELSEC-Q or hybrid Q handling Modbus Q has an established Modbus RTU slave module; no direct iQ-R equivalent currently documented
Plant-wide standardization with mixed Q and non-Mitsubishi PLCs iQ-R as plant standard with phased hybrid migration iQ-R provides long-term platform stability and modern networks; Q and iQ-R coexistence on same network is manufacturer-documented
Mid-size OEM machine with moderate I/O and standard networks iQ-R preferred for new long-term standard; Q acceptable if existing Q library and customer base justify it Q reuse reduces immediate engineering effort; iQ-R is the stronger long-term choice for OEMs setting a new standard
Safety-critical system upgrade requiring integrated safety PLC functions MELSEC iQ-R iQ-R offers dedicated safety CPUs and safety modules within the platform; simplifies long-term compliance when architecture is validated
Brownfield plant with many Q racks and limited shutdown windows Hybrid: iQ-R for new segments, Q racks remain in place Q and iQ-R coexistence supports phased upgrades; full replacement can follow once shutdown windows and budgets allow
Engineering team fully trained on iQ-R and GX Works3 MELSEC iQ-R Leveraging current team skills reduces engineering risk; iQ-R aligns with Mitsubishi's current training and documentation emphasis

If you are ready to source hardware for any of the scenarios above, check current module availability and pricing at LeadTime.ca — we ship worldwide and can advise on lead times before you commit to a build.

Head-to-Head Platform Comparison

Feature MELSEC-Q Series Modular PLC MELSEC iQ-R Series Modular PLC
Platform generation Previous-generation modular PLC platform Current flagship modular PLC platform
Typical role Large and medium systems, long-running installed base New medium-to-large systems, complex lines, plant-wide control
Base units Q-specific base units; not interchangeable with iQ-R R-specific base units; not interchangeable with Q bases
DIN rail usage DIN rail mounted; rails can often be used in common with iQ-R where mechanical specs align Same general DIN rail compatibility per manufacturer documentation
Power supply modules Q-specific; current consumption based on Q modules R-specific; module current consumption differs from Q — power capacity must be recalculated
CPU range Wide range suited to many applications; strong performance for its generation Wide range with high-speed system bus and higher program capacity options
Module lineup breadth Very broad and mature, including many niche special modules Growing; focused on modern applications; some niche modules still stronger on Q
Lifecycle positioning Mature platform; manufacturer direction points to iQ-R for new projects Strategic successor; main platform for new Mitsubishi modular PLC projects
Engineering tools GX Works2 / GX Developer in existing plants GX Works3 with improved project structure and diagnostics
Safety integration Safety via safety PLCs and networks within Mitsubishi family Dedicated safety CPUs and safety modules within same iQ-R rack architecture

Full technical specifications for specific CPU and module part numbers are available on the product pages at LeadTime.ca.

Expert Verdict: The Right Call for Your Application

The MELSEC iQ-R Series Modular PLC is the correct platform for most new medium- and large-scale Mitsubishi modular PLC projects. The high-speed system bus architecture, modern CC-Link IE Field networking, integrated safety CPU options, and alignment with GX Works3 make it the stronger long-term foundation for any new system that does not have a specific, documented reason to stay on Q. The lifecycle positioning is clear: iQ-R is where Mitsubishi is investing in new modules, new features, and new software capabilities. Engineers specifying new installations who choose Q without a concrete justification are building in a lifecycle liability from day one.

That said, the MELSEC-Q Series Modular PLC is not a bad platform — it is a proven and widely deployed one with real strengths. If your application depends on the QJ71MB91 Modbus RTU slave module or other Q-only special function cards, if you are expanding an existing Q-based line with minimal architecture change, or if your shutdown windows and capital budget do not yet support a full migration, Q is a practical and defensible choice. The hybrid approach — iQ-R for new control segments, Q racks remaining for stable I/O and special functions on the same network — is the most common real-world answer for brownfield facilities and is fully supported by manufacturer documentation. Forcing an all-or-nothing decision when your plant is 60% Q and your next project needs Modbus RTU serves no one well.

From a procurement standpoint, iQ-R is the primary focus for new Mitsubishi modular PLC stocking, and that reality affects both lead times and the depth of distributor expertise available. Q hardware remains available but sourcing some of the more specialized Q modules can involve longer lead times as the lifecycle matures. The key procurement decision is not just which box you are ordering today, but what the availability picture looks like over the next five to ten years of your system's life. If you want to map your Q-installed base to iQ-R equivalents, verify communication module options, or get a realistic lead time before committing to either platform, contact the LeadTime.ca team directly — or check current availability on the product page at LeadTime.ca. We ship worldwide and work with engineers at every stage of the selection process.

For volume pricing or to confirm lead time before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

What Engineers Are Reporting About Q and iQ-R in the Field

Community sentiment across PLC forums, automation discussion groups, and distributor knowledge-base content is broadly consistent: iQ-R is seen as the natural successor to Q and is recommended for new projects, while Q retains genuine respect and active use in existing installations. Engineers who have worked with both platforms frequently describe iQ-R as a measurable step forward in system bus performance and network capability, and positive feedback on CC-Link IE Field integration in demanding applications comes up consistently. GX Works3 receives credit for better project organization and improved diagnostic visibility compared to GX Works2, though the transition from one to the other is described as a real learning investment rather than a minor update.

On the Q side, the most common community concern is lifecycle trajectory for new projects — engineers who have been through the process of specifying Q on a new line and then dealing with the migration conversation two or three years later tend to be the most direct about recommending iQ-R from the start. Q's module depth is consistently cited as its strongest ongoing argument, and the QJ71MB91 Modbus RTU gap on iQ-R comes up repeatedly in forum threads where engineers are trying to replicate Q communication architectures on the newer platform. Several engineers in these discussions report resolving the Modbus requirement through protocol gateways or by keeping a Q rack in service specifically for Modbus-facing devices, which underscores how practical and common the hybrid approach already is in the field.

Migration experiences reported in the community range from straightforward single-machine conversions to multi-year phased projects at large facilities. The recurring lesson from successful migrations is the value of piloting on one machine first, investing in GX Works3 training before the project clock starts, and using Mitsubishi's documented migration tools rather than attempting manual project conversion. Engineers who approached migration as a structured project with clear phases report good outcomes; those who underestimated the tool conversion and validation effort consistently report scope and schedule surprises.

Installation and Wiring Considerations for Q and iQ-R Systems

  • Q and iQ-R base units are physically different and require separate panel space; they cannot share a rack or accept each other's modules, but DIN rails can often be used in common where mechanical specifications of both base units align
  • Power supply modules must be selected per platform, and current consumption figures differ between Q and iQ-R modules — always recalculate power capacity from scratch using the iQ-R module specifications rather than carrying over Q power budget assumptions
  • Network cabling and topology requirements depend on the specific communication modules selected; CC-Link IE Field on iQ-R uses Ethernet-standard cabling, while MELSECNET/H and legacy CC-Link on Q use platform-specific media and topology rules
  • In hybrid Q plus iQ-R installations, confirm network segment configuration and module access paths against current Mitsubishi migration and coexistence documentation before finalizing panel layouts
  • Any wiring modifications to operating systems require qualified personnel and appropriate lockout/tagout procedures; platform selection does not replace a formal risk assessment or safety architecture review

Common Selection Mistakes and How to Avoid Them

These are the six mistakes that come up most frequently when engineers and buyers are choosing between the MELSEC-Q Series Modular PLC and the MELSEC iQ-R Series Modular PLC. All six are avoidable with the right verification steps.

Choosing Q for a brand-new large system without reviewing lifecycle direction. Familiarity with an installed base is not the same as a justified platform choice. Review manufacturer lifecycle information and strategic direction before specifying Q on a new system. Use Q for new projects only when compatibility with existing Q hardware or Q-only modules is essential and documented.

Assuming Q modules can be physically reused in an iQ-R rack. Q and iQ-R have different base units and different module form factors. Q modules cannot be inserted into iQ-R bases. Network-level access through adapter or coexistence configurations is a separate question from physical module interchangeability — confirm both dimensions in official compatibility documentation.

Carrying Q power supply sizing into an iQ-R design without recalculation. Manufacturer documentation explicitly states that current consumption differs between Q and iQ-R modules. Power capacity must be recalculated using iQ-R-specific figures for every module in the rack.

Expecting QJ71MB91-equivalent Modbus RTU slave functionality on iQ-R. There is no direct equivalent module for iQ-R as of current documentation. If Modbus RTU slave capability is mandatory, verify available iQ-R communication modules, evaluate gateway or alternative architecture options, and consider whether Q-based solutions need to remain in the Modbus-facing segment.

Underestimating the GX Works3 migration effort. Existing Q projects do not transfer to iQ-R without conversion, validation, and team training. Plan this as a separate work package, pilot on one representative machine, and budget the training time before the project schedule starts.

Treating Q and iQ-R as equivalent for safety without verifying specific ratings. Safety PLC capability on iQ-R requires specific safety CPUs and safety modules with verified certifications. Confirm safety ratings, required architectures, and SIL/PL applicability against official Mitsubishi safety manuals and involve qualified safety specialists in the design.

Wrong-Part Prevention Checklist Before You Specify Either Platform

Before finalizing your platform selection, verify every item on this checklist. Each point represents a documented source of specification errors and change orders.

  1. Confirm lifecycle status and long-term support expectations for Q in your region.
  2. Check whether any required special modules exist only on Q (Modbus RTU, specific analog or logging cards).
  3. Verify network strategy (CC-Link IE Field / TSN, Ethernet, legacy MELSEC networks) and module support per platform.
  4. Confirm CPU performance and memory requirements for the application; do not assume all Q and iQ-R CPUs are equivalent.
  5. Review compatibility options (adapter modules, mixed networks) before planning a partial migration.
  6. Verify engineering tool requirements and training effort for GX Works3 and any project conversion steps.
  7. Validate power supply and base unit capacity; current consumption differs between platforms and modules.

If any item on this checklist raises an unanswered question, contact LeadTime.ca before placing your order. Getting the platform right at specification stage costs nothing; getting it wrong after procurement costs significantly more.

Frequently Asked Questions

Is the MELSEC-Q Series being discontinued, and should I still start new designs on it?

Mitsubishi Electric positions the MELSEC-Q Series Modular PLC as a mature previous-generation platform, with the MELSEC iQ-R Series Modular PLC as the strategic successor for new modular PLC projects. No specific end-of-sale dates are publicly enumerated here, and Q hardware remains available through distributors. However, for new medium-to-large system designs where long-term lifecycle support, modern network capabilities, and new module availability matter, iQ-R is the better-founded choice. Continuing with Q on new projects is reasonable only where existing Q architecture compatibility or Q-only module requirements make it the right technical fit.

Can iQ-R CPUs directly reuse existing Q I/O modules and racks?

Not physically. MELSEC-Q and MELSEC iQ-R use different base units and different module form factors — Q modules cannot be plugged into iQ-R bases. However, Mitsubishi Electric documentation states that iQ-R modules can access Q modules via the network, and both platforms can coexist on the same network when configured appropriately. This network-level coexistence is what enables hybrid and phased migration architectures, but it is not the same as direct physical module reuse.

Is there a Modbus RTU slave module for iQ-R equivalent to the QJ71MB91?

As of current distributor and community documentation, there is no direct QJ71MB91-equivalent Modbus RTU slave module available for the MELSEC iQ-R platform. Engineers with mandatory Modbus RTU slave requirements on iQ-R systems typically address this through protocol gateways, alternative communication architectures, or by retaining a Q rack specifically for Modbus-facing devices in a hybrid system. Verify the latest available iQ-R communication modules with Mitsubishi or a specialist distributor before finalizing your communication architecture.

How difficult is it to convert a Q Series project to iQ-R and GX Works3?

The effort is real and should not be underestimated. Moving from Q to iQ-R involves not only hardware replacement but also project conversion to GX Works3, which has a different project structure and configuration model compared to GX Works2 or GX Developer. Mitsubishi provides migration tools and technical documents to assist with this process. Community experience consistently recommends piloting the conversion on one representative machine before committing to a plant-wide migration, and budgeting explicit time for team training on GX Works3.

Can Q and iQ-R systems share the same CC-Link IE Field network?

Mitsubishi Electric documentation states that iQ-R modules can access Q modules over the network and that both platforms can be used together in the same network when configured appropriately. This coexistence capability is the technical basis for hybrid Q plus iQ-R architectures and phased migration projects. The specific network configuration and any required adapter modules are variant-dependent and must be confirmed against current Mitsubishi coexistence and migration documentation.

Which platform is better for automotive versus food and beverage applications?

Both platforms have been deployed successfully in automotive, food and beverage, packaging, and general manufacturing. The choice is driven less by industry sector and more by the specific requirements of the system: required networks, performance demands, safety integration needs, and whether existing Q infrastructure is already in place. For new automotive and high-speed packaging lines requiring CC-Link IE Field integration and high-performance multi-axis coordination, iQ-R is the stronger foundation. For food and beverage plants with extensive existing Q installations and Modbus-connected devices, a hybrid approach or continued Q use may be the most pragmatic path.

Why Source Mitsubishi MELSEC Hardware Through LeadTime.ca

  • LeadTime.ca ships Mitsubishi MELSEC modules worldwide — not limited to any single country or region
  • We help engineers map existing Q-installed bases to iQ-R equivalents and identify communication module options before ordering
  • Realistic lead time estimates are provided before you commit to a build, reducing procurement surprises on capital projects
  • Volume pricing and project-level sourcing inquiries are handled directly — contact the team for multi-line BOM support
  • Hard-to-source Q modules and iQ-R special function cards are part of our sourcing focus for industrial automation buyers globally

At-a-Glance Comparison Summary

  • MELSEC-Q Series Modular PLC: previous-generation modular platform; broad and mature module lineup; Q-specific base units and power modules not interchangeable with iQ-R hardware
  • MELSEC iQ-R Series Modular PLC: current flagship modular platform; high-speed system bus architecture; wide CPU range; dedicated safety CPUs and safety modules within the rack
  • Manufacturer documentation confirms Q and iQ-R use different base units, though DIN rails can often be used in common where mechanical specifications align
  • Current consumption differs between Q and iQ-R modules — power capacity must be recalculated per platform, not carried over from Q designs
  • iQ-R modules can access Q modules via the network; both platforms can coexist on the same network per manufacturer documentation — this enables phased migration and hybrid architectures
  • QJ71MB91 Modbus RTU slave module exists on Q; no direct equivalent is currently documented for iQ-R — a critical check for Modbus-dependent systems
  • iQ-R is engineered for GX Works3; existing Q plants typically use GX Works2 or GX Developer — project conversion and team training are required for migration
  • For new medium-to-large systems, modern networks, and long-term lifecycle confidence: choose iQ-R
  • For existing Q installations, Q-only module dependencies, or phased brownfield migration: Q or hybrid Q plus iQ-R is the practical answer
  • Pricing for both platforms is available on the product pages at LeadTime.ca; contact LeadTime.ca for volume pricing and lead time confirmation before committing to a build

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