Obsolescence & Migration · 10 min read · Updated November 2026
Mitsubishi FX3U/FX3G and MELSEC-Q End of Life: Migrating to FX5U and iQ-R
Mitsubishi Electric has set production end dates for FX3G/FX3GC (December 2026), the MELSEC-Q Universal CPUs (October 2026), MELSEC-L (October 2027) and FX3U (2028). Japanese-invested factories across Asia run thousands of these. The migration path is well defined, but the devil is in the special modules, the GOT and the GX Works conversion.
Mitsubishi Electric announces discontinuation with long notice and keeps to the dates. The current schedule that matters to buyers: MELSEC-F FX3G and FX3GC — global last order June 2026, production ends December 2026; MELSEC-Q Universal model QCPUs (Q03UDE, Q06UDEH, Q13UDEH and the rest) — last order 30 September 2026, production ends 30 October 2026; MELSEC-L listed models — last order 30 September 2027; FX3U and FX3UC — production end 2028. Repairs usually continue seven years after production end. The successors are the FX5 (iQ-F) for FX3 and the MELSEC iQ-R for Q and L series. We have migrated enough of these to know where the time goes.
FX3U/FX3G to FX5U: nearly painless, with three traps
The FX5U is a better controller in every respect — built-in Ethernet, 4-axis positioning, 200 kHz counters, more memory, SD card — and GX Works3 converts FX3 projects written in GX Works2 (and even GX Developer) with a few clicks. Addresses (X, Y, M, D, T, C) carry over. The three traps:
- Terminal layout. FX5U main units have the same width class but a different terminal arrangement; the removable terminal blocks are not the same as FX3U screw terminals. Plan a re-termination or use the FX5U-...-ES/UL versions with the layout closest to your old unit. The DIN-rail footprint is close enough that the panel usually does not change.
- Special function modules. FX3U-4AD, FX3U-4DA, FX3U-485ADP and the positioning modules have FX5 equivalents (FX5-4AD, FX5-4DA, FX5-485ADP, FX5-40SSC-S) but the buffer-memory maps and the FROM/TO instructions differ. GX Works3 converts FROM/TO to the new module access syntax where it can; every special module call must be reviewed and tested.
- Serial communication and GOT. Protocols such as computer link (MC protocol) and Modbus RTU exist on FX5U but parameters live in a different place; GOT1000 projects need GT Designer3 conversion to GOT2000 when the panel is replaced, and the connection type changes from FX direct to iQ-F direct. Old GOT1000 panels can stay on the FX5U for a while over the same serial link, which lets you stage the HMI replacement.
MELSEC-Q to iQ-R: a real project
The Q series was a modular rack system and so is iQ-R, but the base units, power supplies and most modules are not interchangeable. Q-series modules can be used on an iQ-R base only via the RQ extension base (RQ65B/RQ68B), which is the recommended staging tool: replace the CPU and main base with an R-series CPU, keep the Q I/O on an RQ extension base, then migrate modules at your own pace. GX Works3 converts Q projects, with these points of attention:
| Area | Converts automatically? | Our notes |
|---|---|---|
| Ladder, ST, FBD in GX Works2 | Yes | Label-based programs convert cleanly; device-based with intelligent-module buffer access needs review |
| Intelligent modules (Q64AD, Q62DA, QJ71E71, QJ71C24) | Partially | R60AD4, R60DA4, RJ71EN71, RJ71C24 — different buffer memory; use module labels instead of fixed addresses |
| CC-Link networks | Yes (RJ61BT11) | Field stations keep working; CC-Link IE TSN is the new standard if you add stations |
| Motion CPUs (Q172D/Q173D) | No automatic path | Motion programs are rewritten for R16MT/R32MT or simple motion modules; budget separately |
| Redundant Q (Q12PRH) | No | iQ-R redundancy (R08PCPU) is a different architecture — treat as new design |
What to stock while you plan
The parts we are asked for most: FX3U-32MR/ES, FX3U-48MR/ES, FX3G-24MR, FX3U-4AD/4DA, FX3U-485ADP-MB, Q06UDEHCPU, Q03UDECPU, Q61P power supplies, QX42/QY42P I/O and QJ71E71-100 Ethernet modules. Mitsubishi units from Japanese production are rarely counterfeited, but relabelled units from the Chinese grey market are, so we verify the serial and manufacturing date and photograph labels in our quotations. Hold spares by the last-time-buy formula rather than by "one of each".
Servo and drives are not affected the same way
MR-J4 servo amplifiers (MR-J4-20A) remain in production alongside MR-J5; FR-A800/FR-E800 inverters are current. If the project includes positioning modules (QD75, FX3U-20SSC-H) the motion side migrates to FX5-40SSC-S or RD77MS with SSCNET III/H, which MR-J4 supports — another reason the FX5 path is friendly.
Economics for a typical machine
An FX3U-64MR machine with a 4AD module, a 485 adapter and a GOT1000 7-inch panel migrates to FX5U-64MR, FX5-4AD and a GOT2000 GT2107 for roughly 60–70 % of the original hardware cost, with one to two days of engineering for conversion and test. Compare that with the surplus price of an FX3U-64MR in 2027 and the migration pays for itself at the first failure. For machine builders who still ship FX3 designs, switch the standard now: the FX5U costs about the same and your customers will stop asking when you plan to.
Instruction-level differences that bite
GX Works3 flags every FX3 instruction without a direct FX5 equivalent, and the list is short, but a few patterns are common in machine programs. The FX3 FROM/TO buffer-memory access to special modules becomes module-label access (U0G10 style addressing or the labels generated from the module configuration); converting it is mechanical but every offset must be checked against the new module's buffer map, because the FX5-4AD, for example, scales differently and has more channels. The communication instructions RS and RS2 survive but the parameter location moves from special registers (D8120) to the module parameter dialog; programs that wrote D8120 at run time need the parameters set in the project instead. Pulse-output instructions PLSY, DRVI and DRVA exist on FX5U with the same semantics, but the axis parameters (base speed, acceleration time, limits) are set in the positioning parameter dialog rather than in special registers — a simplification once understood. High-speed counter assignment changes: FX3U's fixed X0–X7 counter allocation becomes configurable, so HSCS/HSCR interrupts must be re-mapped. Finally, the FX5 uses 32-bit D devices and label programming by default; mixed programs that index registers with Z modifiers across 16/32-bit boundaries should be tested with the actual data.
Keeping the old GOT during transition
A GOT1000 connected to an FX3U by the direct CPU connection cable will connect to an FX5U over the same cable type (RS-422 adapter FX5-422-BD or the built-in RS-485) with the connection type changed to "iQ-F direct" — but GT Designer2/3 must be used to update the project, and GOT1000 projects older than GT Designer3 version 1.1xx may need an intermediate conversion. This keeps the HMI cost out of the first phase; plan the GOT2000 replacement when the backlight or touch panel fails, and keep one GOT1000 of each size as a spare for the fleet until then.
Need engineering help with this?
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Quick answers
Does GX Works3 open my old GX Developer FX3U project?
Yes, via GX Works2 format if needed. GX Works3 reads GX Works2 projects directly and converts FX3 to FX5 with a wizard that reports every instruction needing review.
Can I keep my Q-series I/O modules when I move to iQ-R?
Yes, on an RQ extension base (RQ65B, RQ68B) connected to the R-series main base. It is intended as a transition tool and lets you migrate the CPU first and I/O later.
Are FX3U units still available in 2026?
Yes, production continues until 2028 and stock is still normal. FX3G/FX3GC end in December 2026 and MELSEC-Q Universal CPUs in October 2026, so those are the urgent last-time buys.