A drilled hole that appears off-center to an internal land can reflect more than one underlying difference. The hole position, internal pattern position and inspection reference must be evaluated separately. Correcting the drill program before identifying the source can shift other layers or features in the wrong direction.
Define the comparison coordinates
Identify the hole, internal layer and land being examined. Record the panel orientation and the viewing convention used by the measurement method. Keep nominal design coordinates separate from measured offsets.
Union Tool’s drilling evaluation treats hole registration accuracy as a specific quality characteristic. That supports checking the drilled feature directly rather than inferring its accuracy solely from its relationship to an internal pattern that may also have moved.
Build a location-by-layer comparison
| Comparison | Question |
|---|---|
| Hole to reference | Where is the drilled feature in the agreed coordinate system? |
| Internal land to reference | Where is the relevant layer feature? |
| Layer to layer | Do the internal features move together? |
| Across the panel | Is the observed difference spatially consistent? |
Use signed directional measurements when possible. Reporting only the magnitude of an offset can conceal whether several layers share a direction or differ from one another.
Check the earlier evidence
Review available patterned-core, layup and post-lamination records alongside the drilling setup. Include material and panel orientation. The investigation should preserve the possibility of more than one contributing stage until the evidence distinguishes them.
For example, if several internal layers show different offsets relative to the same hole, a single global drill shift may not resolve the entire relationship. Confirm the layer-specific evidence before proposing a correction.
Test a correction against all affected features
- State the suspected source and supporting measurements.
- Identify the process variable being changed.
- Use representative panel locations and layers.
- Check critical clearances and connections after the trial.
- Record the resulting approved process scope.
A local improvement should not be accepted without checking relevant locations elsewhere. A correction optimized for one corner can leave another area or layer with a different result.
If measurement preparation or resolution limits the conclusion, document that limitation. More precise language cannot recover information that the examination method did not provide.
Keep the final record connected to the actual coordinates and source revision. This makes a later recurrence comparable without reconstructing a reference system from photographs.
Check whether the inspection result reports the center of the hole, the visible opening or another fitted boundary. Those definitions can differ at an irregular feature, so the comparison should use an agreed method rather than an undocumented cursor placement.
The layup map preserves upstream alignment evidence, and hole-position reference control supports a consistent measurement definition.
Move from reading to a build-ready project
Use the fabrication and assembly checklists to prepare drawings, production files and test requirements.
Open the DFM checklist