What the MOTN-018 alarm means

The target position cannot be reached with the current robot configuration - outside the workspace or an impossible wrist orientation. This fault ranks high in our FANUC R-30iA / R-30iB / R-30iB Plus service records, and the first site inspection usually finds the source.

Most common causes

  • Point taught in a different user/tool frame than active
  • Robot mounted position changed
  • Target genuinely outside reach
Field note: The first cause shows up most on real machines, so verify it before you go further.

Step-by-step field fix

  1. Verify UF and UT numbers on the instruction
  2. Jog to the vicinity in joint mode and re-teach
  3. Check the robot base calibration if the cell was modified
Safety first: For FANUC motn-018, this alarm family points at arm motion control: after a reset the arm can move unexpectedly, and anyone inside the working envelope is at strike and pinch risk. On site you may look at after confirming power-off the first step yourself: Verify UF and UT numbers on the instruction. Beyond that it is the arm working envelope work - leave it to a professional.

How we diagnose motion alarms on site

FANUC motn-018 belongs to the motion & path family. On FANUC motn-018 the failing stage is alpha-i / beta-i servo amplifiers with PSM supply modules and SVM servo modules (SPM where spindles fit) on the R-30iB Plus / R-30iB Mate Plus / R-30iA - the gap between command and execution: trajectory planning, joint limits, singularities, following error and mechanical resistance. We start reading FANUC motn-018 at the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code.

The chain involved in FANUC motn-018 runs: program command -> trajectory planner -> joint targets -> servo execution -> actual position feedback -> deviation compare.

First check whether FANUC motn-018 only appears at one pose - A six-axis arm near wrist extension or near axis-5 zero has a Jacobian approaching singularity: tiny tool moves demand huge joint rates, and the controller either reports following error or the arm snaps through. When the report is alarms at one position and clean on another path, suspect the singular region first. The fix is not raising speed limits but routing around it: move the part, add an intermediate point, or pass the region in joint interpolation.

Field notes on this page cover FANUC motn-018 (Position Not Reachable); written by the Henghuan repair team, updated 2026-10-01.

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Related Motion & Path alarms

MOTN-017 — Limit Error (Group / Axis) MOTN-023 — In Singularity MOTN-056 — Speed Limits Used
Same family: this code belongs to the Motion & path alarms family - the page collects all Motion & path-family codes we have handled, with the common inspection order and spares.
Other brands: see our KUKA, ABB, Yaskawa and Universal Robots field-fix libraries — or the full 10-brand hub.

Frequently asked questions

QWhat does the FANUC motn-018 alarm mean?

The target position cannot be reached with the current robot configuration - outside the workspace or an impossible wrist orientation. This fault ranks high in our FANUC R-30iA / R-30iB / R-30iB Plus service records, and the first site inspection usually finds the source. FANUC motn-018 sits in the motion & path family; on our work orders the highest-frequency trigger for this code is "Point taught in a different user/tool frame than active".

QCan I clear a FANUC motn-018 alarm myself?

Whether FANUC motn-018 clears on its own depends on the outcome of "Verify UF and UT numbers on the instruction". Finish the flow with "Check the robot base calibration if the cell was modified" to confirm FANUC motn-018 - do not skip it. If that step is clean, the second most frequent cause on FANUC motn-018 is "Robot mounted position changed". Two attempts and still there means stop: FANUC motn-018 involves the arm working envelope, and running FANUC motn-018 on can turn a repairable fault into a replacement.

QFor motion alarms like FANUC motn-018, can you triage remotely first?

The commonest causes we see on FANUC motn-018 are "Point taught in a different user/tool frame than active, Robot mounted position changed, Target genuinely outside reach", so we stock the van against those. For FANUC motn-018 specifically, we carry mechanical and configuration items: grease, limit switches, drag-chain segments, encoder cables and the parameter sheets for common reducers. For FANUC motn-018, motion alarms can often be narrowed remotely first, so an on-site visit is not always immediate. Before we roll, tell us what FANUC motn-018 shows on the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code and what the machine was doing - phone or video triage is free.

This page on FANUC motn-018 was compiled from actual repair records of the Henghuan Robotics repair team. Alarm notes are our own summary for troubleshooting reference only and may vary with controller and software version — please consult FANUC documentation or contact us if in doubt. Henghuan is an independent service provider, not affiliated with or endorsed by FANUC.