Motion controller
Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules controller
MELSEC iQ-R motion modules for CC-Link IE TSN servo networks controlling 1 to 256 axes, with minimum operation cycles of 62.5 µs (RD78G) and 31.25 µs (RD78GH).
Need this part, a replacement or a complete package? Our experienced UK engineering team helps you select, source and obtain the right products, with pricing, delivery coordination and after-sales support.
Pricing and availability
Get pricing, sourcing and replacement support
Need Mitsubishi Electric parts, a replacement or a suitable alternative? Send us a part number, or tell us what the machine needs to do. Our UK engineers will come back with the right product, pricing, lead time and delivery, whether that is the original part, a checked alternative or a complete axis.
- Original parts or a checked alternative
- Pricing, lead time and delivery in one reply
- Components, complete axes and ongoing support
No obligation. Add what you know and an engineer will help with the rest. Prefer to configure it? Build a specification.
Spec builder
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Select every part you need and answer the questions an applications engineer would ask. Our engineers use your specification to come back with the right products, pricing and lead times. You see your summary before we ask for any details.
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- 1Products
- 2Performance
- 3Environment
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- 5Your spec
What are you specifying?
Select everything you need. A motor, drive and gearbox can be specified together as one axis.
Key specifications
| Fieldbus | CC-Link IE TSN 1 Gbps |
|---|---|
| Axes | 1–256 |
| Axes max | 256 |
| Operation cycle | 62.5 µs min (RD78G), 31.25 µs (RD78GH); 250 µs min in Simple Motion mode for RD78G4/8/16 |
| Functions | position, speed, torque, synchronous and cam control; linear (4-axis), circular and helical interpolation |
| Programming | GX Works3: ladder, SFC, FBD/LD |
Summarised in our own words from Mitsubishi Electric Corporation's published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1 · Source 2
Specify Motion is not affiliated with Mitsubishi Electric Corporation. Mitsubishi Electric and MELSEC iQ-R RD78G / RD78GH motion modules are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Engineer support
Speak to our engineers about your project
Our experienced engineers are on hand, ready to help with your project. Whether you need the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules itself, help sourcing it, or a modified or custom design built around your load, speed and space, tell us what the machine has to do and we'll come back with the right option.
- Help sourcing MELSEC iQ-R RD78G / RD78GH motion modules and spares for installed machines
- Modified and custom designs when a catalogue part doesn't fit
- Complete axis: motor, drive, gearing and feedback matched together
Typical applications
What a motion controller is
A motion controller plans and coordinates movement for one or more axes, sending position, velocity or torque commands to servo or stepper drives. It generates trajectories with defined acceleration and jerk, synchronises axes for interpolation, electronic gearing and camming, and handles homing, limits and registration inputs. Commands reach drives over pulse, analogue or, most commonly now, EtherCAT and other real-time networks. Many controllers also include PLC functions to IEC 61131-3, combining logic and motion.
When engineers choose a motion controller
Choose a dedicated motion controller when a machine needs coordinated multi-axis motion beyond basic point-to-point moves, such as robots, gantries, packaging and CNC. It gives deterministic timing and motion libraries. The trade-offs are cost, programming effort and ecosystem lock-in. For simple machines with a few independent axes, a PLC with motion function blocks or intelligent drives with stored moves may be enough.
How to specify the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules
Send these with your enquiry and an engineer can confirm the right MELSEC iQ-R RD78G / RD78GH motion modules variant or an equivalent:
- Number of axes and drives
- Network and cycle time (ms)
- Motion functions: interpolation, camming, robotics
- Programming environment and languages
- I/O and expansion
- HMI and connectivity
- Safety integration
Common mistakes to avoid
- Choosing a controller that does not support the drives' network
- Underestimating cycle time needs for many axes
- Ignoring programming tools and skills in the team
- Not planning for future axis count
Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules: frequently asked questions
Can you help replace Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules or source the original?
Send the full model code, quantity and required date. Our engineers can check original-part availability and assess suitable alternatives, including supply-network options where appropriate. We confirm compatibility and any changes needed before recommending a replacement.
What is the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules?
MELSEC iQ-R motion modules for CC-Link IE TSN servo networks controlling 1 to 256 axes, with minimum operation cycles of 62.5 µs (RD78G) and 31.25 µs (RD78GH). It is made by Mitsubishi Electric Corporation; Specify Motion can help source it or propose an equivalent.
Who makes the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules?
The Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules is made by Mitsubishi Electric (Mitsubishi Electric Corporation) and is listed here for engineers comparing options. Specify Motion is not affiliated with Mitsubishi Electric Corporation; brand names are used only to identify the product.
Is there an alternative to the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules?
We can assess suitable replacement options. Our engineers can review the original model and propose options for your load, speed and environment. An engineer confirms the fit against your application before recommending anything.
What is the difference between a motion controller and a PLC?
A PLC handles machine logic, sequencing and I/O. A motion controller specialises in trajectory planning and coordinating axes. Many modern controllers combine both, running PLC logic and motion libraries on one CPU. Choose based on axis count, motion complexity and timing requirements.
Why is EtherCAT common for motion control?
EtherCAT offers short cycle times, precise synchronisation using distributed clocks and simple cabling, which suit coordinated multi-axis motion. Many drives and I/O devices support it. Other real-time networks such as PROFINET IRT and Sercos are also used, so check what the drives and controller support.
Further reading: How to select a motion controller or plc · Controllers and PLCs
Other motion controller series
Engineer support
Our engineers are ready to help with your project
Tell us about your project and how you use the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules: the load, speed, duty and environment. An experienced engineer will review it and reply, normally within one working day.
- Reviewed by an engineer, not an autoresponder
- Like-for-like and better-fit alternatives
- Standard, modified and custom options
Prefer to configure it? Use the spec builder.
How it works
From enquiry to delivery
Send a part number or describe the application. Our engineers take it from there: the right product, a clear quotation, and delivery and support arranged.
- 01Tell us what you needSend a part number, or configure the application, quantities and timing.
- 02An engineer reviews itWe check the specification and find the original part, a checked equivalent or a complete axis.
- 03Receive your quotationProducts, pricing, lead time and compatibility notes in one reply.
- 04Order and deliveryWhen you are happy, the order is placed and delivery and after-sales support are arranged.