Designing an incoming acceptance test for a linear stage

Agree what incoming acceptance will establish

An incoming test can establish whether an identified stage and controller configuration meet an agreed requirement under recorded conditions. Begin with the purchase requirement, then choose the measurement and decision rule. A shipping inspection does not establish positioning accuracy, repeated-return behavior or the smallest useful physical motion; each needs its own evidence.

Use the catalogue basis guide and current quotation to separate documented values, derived values and unconfirmed claims. Agree the working range, payload point, responsibilities and unresolved requirements before delivery. The two worksheets below are original planning aids to adapt with the responsible engineer, not a certified test procedure.

Build an acceptance matrix before running the stage

Give each selected characteristic its own requirement identifier, agreed limit and decision rule. Leave an untested characteristic marked not evaluated, even if adjacent checks pass. The matrix specifies what to agree; it supplies no universal limits or repetition count.

Characteristic	Procedure and conditions to agree	Evidence and decision boundary
Received condition and configuration	Compare model, serial numbers, accessories, hardware, firmware and compensation files with the order before changing settings.	Received-condition photographs and configuration snapshot; resolve discrepancies separately from motion performance.
Safe functional travel	Define the permitted motion envelope, approach and stopping allowances, limit behavior and operating settings using the applicable documentation.	Motion and event log for the agreed envelope; successful travel alone is not an accuracy result.
Positioning error	Agree target coordinates, arrival direction, load, measurement line, settling/acquisition method and independent physical reference over the required region.	Preserve command and reference readings with their coordinate transformation; compare the defined error metric using the agreed uncertainty treatment and decision rule.
Repeated-return behavior	Return to the same targets under a declared approach policy; distinguish same-direction arrivals from reversals and keep the homing policy fixed.	Retain every return reading and the agreed summary of their spread; a narrow spread does not establish a small positioning error.
Homing or restart behavior	Define the restart sequence, which reference is re-established and which configuration is retained; evaluate it separately from uninterrupted returns.	Before/after physical-reference readings linked to restart events; conclude only for the restart sequence actually tested.
Resolution and small physical motion	Distinguish the command increment from measured response; agree local position, step sequence, acquisition and reference capability for the intended motion.	Record requested increments and independently observed displacement; a changing display does not establish physical motion. If the setup cannot resolve it, mark that characteristic not evaluated.

Prepare the fixture and reference chain

Record the received condition before commissioning makes a discrepancy indistinguishable from a later change. Select reference instrumentation for the required range, uncertainty and physical measurement location. A full-travel positioning experiment and a local small-motion experiment may need different arrangements.

Name the functional point on the workpiece or payload, the fixed reference base, and the sensing line’s direction and offset from that point. Save a dimensioned setup sketch or annotated photograph. If the fixture permits measurement only at a substitute point, explain the relation to the functional point and what remains unverified. The controller’s encoder readback is useful diagnostic information; it is not an independent physical reference at the workpiece.

Prepare a safe motion envelope with approach and stopping distance. Confirm units and total travel: a ±15 mm coordinate range spans 30 mm total. A nominal travel figure does not authorize motion into hard stops. Check permitted controller settings against the applicable documentation before an automated sequence.

Write a reproducible sequence and raw observation register

Specify warm-up, environmental recording, load, orientation and cable routing. Choose targets that represent the agreed working region and application-critical locations. Define arrival direction, speed, acceleration, dwell and acquisition interval. Agree the repetition count and its rationale for the intended conclusion; there is no single count suitable for every requirement.

Keep homing and compensation policy explicit. A baseline with one initial reference, a test with repeated homing and a restart test answer different questions. Label them separately. Record whether compensation is enabled and retain the file identity rather than comparing undocumented configurations.

Use one observation identifier to join the following fields. These are register fields, not example measurements. Keep native files as well as any analysis export.

Register group	Fields to retain	Why they belong in the report
Run and configuration identity	Run ID, operator, stage/controller serials, firmware, settings snapshot and compensation-file identity.	Connects readings to one reproducible configuration.
Geometry and coordinate basis	Workpiece/payload point, sensing line and offset, reference base, coordinate zero, sign convention and any transformation.	Shows where and in which coordinate frame position was measured.
Commanded position	Target ID, command value, unit and command time.	Records the requested position without presenting it as a measurement.
Controller readback	Raw value, channel/encoder identity, unit and acquisition time; state when unavailable.	Keeps internal feedback distinct from the command and independent reference.
Independent physical reference	Raw reading, unit, acquisition time, instrument identity, calibration reference and uncertainty-budget version.	Preserves the physical evidence used in the stated position or displacement calculation.
Motion and conditions	Cycle/return index, arrival direction, speed, acceleration, dwell, homing/restart event, load and environment record.	Allows comparisons only between compatible conditions.
Validity and disposition	Valid/invalid status, reason, interruption or deviation, original-file link, analysis revision and linked retest ID.	Makes exclusions and later decisions traceable without deleting observations.

Keep invalid runs, failures and retests distinguishable

Define invalid-run conditions before testing, such as lost reference acquisition or an unplanned fixture disturbance. Preserve the affected data and explain the reason and affected interval. An unfavorable reading from an otherwise valid run is not a reason to invalidate it. If a stop or interruption prevents completion, report the missing scope instead of treating it as passed.

Agree who may authorize a retest, the cause to address and which sequence to repeat. Link the retest to the original run and report both. A changed mounting, load, cable route, firmware, settings or compensation file needs a new configuration identity and a decision about which affected characteristics require re-evaluation; do not silently combine readings from before and after the change.

Separate raw observations, calculated summaries and acceptance conclusions. Following NIST’s uncertainty-reporting guidance, state either combined standard uncertainty u_c or expanded uncertainty U with its coverage factor k, and explain the components and evaluation basis. Do not infer a coverage probability from k alone. The uncertainty statement supports interpretation; the contractual decision rule still determines how the result is judged. Use distinct dispositions for pass, fail, inconclusive and not evaluated, with the reason and remaining action stated.

Hypothetical example: a short inspection window

Suppose a machine uses only the central portion of a longer stage for inspection. The buyer proposes local acceptance there plus a basic motion check over the remaining permitted stroke. These are separate objectives: the local measurement does not establish full-travel positioning performance. No measured value or acceptance threshold is implied.

Before delivery, supplier and buyer agree whether that scope is sufficient and identify the camera mounting height and intended cable loop. If the fixture changes before installation, the incoming report describes only its recorded setup; the installed process may need its own verification. The responsible engineer must confirm the actual method and applicable contractual or standards requirements.