Fanuc Parameter Backup

title: Fanuc Parameter Backup and Restore Procedures category: machines tags: [fanuc, 18i, 16i, 21i, 30i, parameter, backup, restore, battery, SRAM, boot, USB, memory-card] compiled: 2026-04-11

Summary

Every Fanuc control from the 16/18/21i generation through the 30/31/32i supports parameter backup and restore via boot menu, memory card, or data server. Most shops never do this until a battery dies and they're down for days. A full SRAM backup takes under two minutes and a $15 memory card. Recovery without one takes 3–10 days and a Fanuc service tech. This article is the step-by-step procedure across the common Fanuc control generations, written so you can walk up to the machine and do it right now.

Why This Matters

  • The SRAM battery backs up all volatile data: parameters, tool offsets, work offsets, macro variables, pitch-error compensation tables, and PMC (ladder) data. When it dies, every bit of that is gone.
  • Battery typical life: 3–5 years. The control will fire a low-battery warning alarm (typically alarm 300 or 301 on most Fanuc generations — verify against your operator manual) well before total loss. Check your alarm history page regularly.
  • Recovery without a backup means re-entering parameters from the machine builder's spec sheet — often hundreds of values covering servo tuning, axis configuration, spindle setup, and PMC ladder constants. Most shops don't have that sheet. Expect 3–10 days of downtime and a $1,000–$5,000+ Fanuc service call just to get the machine functional again, not optimized.
  • One Reddit post showed a new employee accidentally destroying the only backup copy of a machine's data. The mill went down with no path to recovery except a full Fanuc service rebuild of parameters [r/CNC]. Don't be that shop.
  • If you convert a machine between inch and metric, parameters like second home positions must also be updated or the machine will crash into hard stops [r/Machinists]. A backup before any such change is non-negotiable.

What to Back Up

Fanuc controls store data in several distinct regions. Each can be backed up individually (text-based method) or all at once (SRAM image):

Region Contents Typical Filenames
PARAMETERS Nxxxx values — machine config, servo gains, accel/decel times, pitch-error comp, axis limits, spindle config CNCPARAM.TXT or similar
OFFSETS Tool length offsets, tool radius comp, work offsets G54–G59, extended work offsets G54.1 Pxx TOOLOFST.TXT, WORKOFST.TXT
MACRO VARIABLES Custom macro common variables (#500–#599, #100–#199 on some), system variables MACRO_V.TXT
PMC DATA Ladder logic I/O assignments, timers, counters, keep relays, data tables — everything the machine builder programmed into the PLC side PMC_DAT.TXT, PMC_PRM.TXT
PROGRAMS O-number part programs stored in CNC memory Individual Oxxxx files or ALL_PROG.TXT
SRAM IMAGE Full binary snapshot of all SRAM contents — covers every region above in one file SRAM_BAK.001, SRAM1.BIN, etc.

The SRAM image is the gold standard. It restores everything in one shot. The text-based backups are useful for inspecting individual values or transferring specific data between similar machines.

This is the most complete backup. It creates a binary image of the entire SRAM, so restoration recovers everything in one operation.

Procedure

  1. Power off the machine at the main disconnect or CNC power button.
  2. While powering ON, hold the designated soft keys to enter the boot/IPL screen. The exact keys vary by generation: - 16i/18i/21i (standard MDI panel): Hold the two rightmost soft keys simultaneously while turning power on. Keep holding until the System Monitor / Boot screen appears. On some machines this is the SELECT and CAN keys — verify against your specific operator manual. - 30i/31i/32i: Typically hold the two rightmost soft keys on the horizontal soft key row, or on some configurations hold SELECT + right arrow. The boot screen is similar but has more menu options. - 0i-D/0i-F: Same general approach — two rightmost soft keys during power-on.
  3. In the boot menu, navigate to "SRAM DATA UTILITY" or "SRAM BACKUP" (exact wording varies by firmware version).
  4. Select "SRAM DATA BACKUP".
  5. Select the destination device: - 16i/18i/21i: PCMCIA memory card inserted in the card slot on the control front panel. Use a standard PCMCIA Type II ATA flash card (typical sizes 64 MB–512 MB are more than sufficient; SRAM images are usually 1–8 MB depending on SRAM size option). - 30i/31i/32i and newer 0i-F: USB memory stick inserted in the USB port on the control. Use a basic USB 2.0 stick, FAT16 or FAT32 formatted. Some older firmware has trouble with sticks larger than 2 GB — use a small dedicated stick.
  6. Confirm the backup and wait. Typical time: 30–90 seconds depending on SRAM size.
  7. Verify the file was written. Check the file listing on the card/stick from the boot menu. Typical filename: SRAM_BAK.001 or SRAM1.BIN — the control names it automatically.
  8. Reboot normally by selecting the appropriate menu option or cycling power.

Critical Notes

  • This backup is only restorable on the same model and series control with the same SRAM configuration. A backup from a 18i-MB will not restore to a 18i-TB or a different 18i-MB with a different SRAM size option. Do not assume cross-compatibility.
  • PCMCIA cards are getting scarce. Buy several now and dedicate them to backup duty. Industrial-grade CompactFlash cards with a CF-to-PCMCIA adapter also work on most 16i/18i/21i controls.
  • Label every card/stick with: machine name, control model, date of backup, and SRAM size. A shoebox of unlabeled cards is worthless in an emergency.
  • On some 16i/18i systems, a PCMCIA-to-CompactFlash adapter is needed. USB is generally not available in the boot menu on original 16i/18i firmware without hardware retrofit.

Method 2: Parameter I/O via PARAM Screen (Text-Based, Per-Region)

Use this for partial backups, for inspecting/editing parameter values, or when the boot menu is inaccessible (e.g., you can't power-cycle the machine right now).

Procedure

  1. At the main CNC screen, press the SYSTEM hard key.
  2. Use soft keys to navigate to PARAM (for parameters), OFFSET/SETTING (for offsets), MACRO (for macro variables), or PMC → PMCPRM (for PMC data).
  3. Press [OPRT] (Operation) soft key.
  4. Select PUNCH or F OUTPUT (terminology varies — on 30i-series it's often OUTPUT).
  5. Set the output channel: memory card, USB device, RS-232 port, or data server depending on your I/O channel parameter setup (parameter 0020 selects the I/O device number — typical range 0–9, verify against your operator manual).
  6. Press EXEC or the execute soft key. The control writes a human-readable text file.
  7. Repeat for each data region you want to back up.

Output File Format

Text-based parameter files look like this:

N00000  #7        00000000
N00001  #7        01100000
N00014  #7        00000000
...

These can be opened in any text editor, inspected, and even hand-edited if you know exactly what you're doing. They're restorable on any Fanuc control of the same generation and type via the READ or F INPUT function on the same screen.

When to Use Text-Based Backup

  • Transferring specific parameters between two similar machines (same builder, same model)
  • Documenting parameter changes for audit/traceability
  • Backing up just offsets or macros without a full power-cycle
  • Sending parameter files to a Fanuc service engineer for remote troubleshooting

Method 3: Data Server / Ethernet (Newer Fanucs)

If your control has the Ethernet Data Server option (standard on most 30i/31i/32i, optional on late-model 0i-D/F), you can push backups over the network to a shared folder via FTP.

Setup (One-Time)

  1. Configure the control's IP address, subnet mask, and gateway via the ETHPRM (Ethernet Parameter) screen under SYSTEM.
  2. Set up an FTP server on a shop PC or NAS. Any basic FTP server works (FileZilla Server, Windows IIS FTP, etc.).
  3. Configure the Data Server's host address, FTP username, password, and target directory in the Ethernet parameters on the control.
  4. Test connectivity — the control typically has a PING function in the Ethernet diagnostics.

Backup

Once configured, the I/O procedure is the same as Method 2 — just select the Data Server/Ethernet as the output device (I/O channel). Files land on the network share.

Automation

Some shops write a simple custom macro program that triggers a parameter output at each power-on or at a scheduled interval. This is machine-builder dependent and requires the [[fanuc-macro-programming]] option. Not available on 16i/18i/21i without Ethernet retrofit.

Restore Procedure (Critical — Read First)

Stop. Read this entire section before restoring anything.

  • NEVER restore an SRAM backup from a different machine. Even two "identical" machines from the same builder may have different servo tuning, pitch comp, or PMC configurations. Restoring the wrong image can cause axis runaways, spindle faults, or bricked controls.
  • SRAM restore is done from the boot menu only. Navigate to SRAM DATA UTILITY → SRAM DATA RESTORE. Select the file and confirm. The control will overwrite all SRAM contents.
  • Text-based restore is done from the normal operating screens via SYSTEM → PARAM → [OPRT] → READ / F INPUT. This is safer for partial restores.
  • After any restore: 1. Power-cycle the control. 2. Clear any alarms. 3. Re-home all axes (manual reference return, typically G28-related). Do not assume the machine knows where it is. 4. Verify work offsets by indicating a known reference surface. 5. Verify tool offsets — spot-check at least 3–5 tools with a tool probe or indicator. 6. Do NOT run a production cycle. Run a dry run (single block, feedrate override at 0%, optional stop on) on a known program first. 7. Check spindle orientation if your machine uses it (tool change, tapping). 8. Verify PMC functions: tool changer sequence, coolant, door interlock, M-codes.

Backup Schedule

Event Action
Acquire a used machine Full SRAM backup + text-based parameter backup before you touch anything
After any parameter change Text-based backup of PARAMETERS at minimum; SRAM backup preferred
Monthly Full SRAM backup as standing maintenance procedure. Put it on the PM calendar.
Before any service work Full SRAM backup before battery swap, drive replacement, board swap, or any Fanuc tech visit
Before firmware update Full SRAM backup — firmware updates can reset SRAM on some controls
Before unit conversion Full SRAM backup before changing inch/metric system parameters

Store backups in at least two locations: one physical card/stick kept with the machine, one copy on a network drive or shop server. Label everything.

Battery Replacement

The SRAM battery is a 3V lithium cell. Common Fanuc part numbers include A98L-0031-0012 (1/2 AA size, CR14250-equivalent) and A02B-0200-K102 (for some 30i-series). Do not guess — check your specific operator manual or the battery compartment label for the correct part.

Procedure

  1. Leave the machine powered ON. This is critical. SRAM is maintained by both the battery and the power supply. Replacing the battery with power off while the old battery is dead will erase SRAM instantly.
  2. Open the battery compartment (usually on the control unit front or side, behind a small cover secured with a screw or clip).
  3. Note the polarity orientation of the old battery.
  4. Remove the old battery and immediately insert the new one. Do this quickly — you have seconds, not minutes, if the old battery is marginal.
  5. Close the compartment. The low-battery alarm should clear on the next power cycle.
  6. After replacement, do a fresh SRAM backup to verify everything is intact.

Warning Signs

  • Alarm 300/301 (low battery): Act immediately. You may have days or weeks, but you might have hours. Back up first, then replace.
  • If the machine has been sitting unpowered for months (e.g., a used machine purchase), assume the battery is dead or dying. Back up before your first power-off.
  • Keep spare batteries in the crib. They cost under $20. The downtime they prevent costs thousands.

Quick Reference Card

Tape this to the machine cabinet:

SRAM BACKUP — DO MONTHLY

1. Power OFF
2. Hold two rightmost soft keys, power ON
3. SRAM DATA UTILITY → SRAM DATA BACKUP
4. Select memory card / USB → Confirm
5. Verify file written → Reboot
Label card: Machine / Date / Control model

See also: [[fanuc-alarm-codes]], [[fanuc-macro-programming]], [[cnc-maintenance-schedule]], [[tool-offset-setup]]