Stack height and confirmed layer count together reveal the state of an automated core. Reconcile thickness, coating, contact gaps and compression before adjusting a sequence whose height and count disagree.
Define the state in which height is measured
Record the probe location, support arrangement, applied pressure and whether the top layer has settled. For a stepped or locally incomplete geometry, define which region the height represents. A height measured at an exposed tip is not interchangeable with one measured on a fully supported section.
Use an effective layer thickness established under the same relevant contact condition. Bare steel gauge alone may omit coating and contact effects. In a simplified uniform stack, the expected height is N times the effective layer thickness t, and the residual is measured height minus N × t. This is a diagnostic baseline, not a complete compression model.
Compare the residual with count evidence
| Observation | Candidate explanation | Discriminating check |
|---|---|---|
| Height high; count consistent | Gaps, increased effective thickness or changed pressure | Repeat under the defined contact state |
| Height low; count consistent | Compression, thinner material or count overstatement | Matched thickness evidence and placement history |
| Sudden count-height disagreement | Missing/repeated part or local placement error | Last confirmed layer and local profile |
| Gradual residual drift | Accumulated thickness bias or evolving contact state | Residual by layer and pressure-state comparison |
A systematic per-sheet thickness bias accumulates with layer count. A missing physical sheet is instead a discrete event. Use the independent example below to distinguish the two before changing the placement record.
Keep pressure and sequence as separate channels
Repeat height at a consistent pressure state where the process permits. If the residual changes strongly while the physical layer count is unchanged, contact and compression are implicated. If the count record itself lacks physical placement confirmation, it remains a separate unresolved channel.
Use height as a process observation alongside count and sheet identity. Robot/tool measurement uncertainty and position-dependent effects remain separate from the material build; a height residual cannot uniquely identify the missing or doubled layer. [1]
The nominal 0.23 mm catalogue gauge gives a 230 mm steel-thickness sum for 1,000 sheets. [2] Assume the effective compressed thickness estimate is biased by +0.002 mm per sheet: the predicted stack height shifts by 2 mm, equivalent to 8.70 nominal gauges. By contrast, one missing nominal sheet changes steel thickness by 0.23 mm. Investigate systematic gauge/compression bias before translating a 2 mm height residual into nine missing sheets. Retain layer identity and count independently, then compare height only under a defined measurement force and stack state.
Sheet gauge distribution, coating build, burrs, local waviness and compression define measured height. The stack-height controller must not conceal a wrong count by increasing clamp force.
Trend the height residual through the sequence and compare local joint geometry. Accept the assembly when final height, confirmed layer count and the joint condition are reconciled.
References
- G. Qiao and B. A. Weiss, Industrial Robot Accuracy Degradation Monitoring and Quick Health Assessment, Journal of Manufacturing Science and Engineering 141, 2019. DOI: 10.1115/1.4043649.
- Nippon Steel Corporation, Grain-Oriented Electrical Steel Sheets, catalogue D004je, April 2020, specification and typical-property tables.