A suspected drill-smear problem needs samples that show where and when the condition appeared. An unidentified finished-board cross-section may reveal an issue but provide little information about its origin. Plan sample selection before the remaining panels pass through additional processing.
Define the suspected observation
Union Tool’s evaluation categories include resin smearing, hole-wall roughness, nail heading and other drilling outcomes. Keep these categories distinct in the investigation. A dark region or irregular wall should not receive a mechanism label solely from a low-magnification image.
Ask the examining laboratory or qualified process team what sample preparation and views are needed to assess the suspected feature. Record the construction and hole type they are being asked to evaluate.
Preserve the manufacturing coordinates
| Coordinate | Why it matters |
|---|---|
| Panel location | Shows whether observations cluster spatially |
| Stack position | Retains top-to-bottom drilling history |
| Hole family | Links geometry to the observation |
| Tool history | Connects the sample with accumulated tool use |
| Process stage | Separates as-drilled and subsequently treated evidence |
Mark sample orientation before cutting. Once a small section is removed, its original location and entry direction can become impossible to recover from appearance alone.
Compare appropriate process stages
Where the approved investigation allows it, retain representative material before and after the relevant cleaning or preparation step. Use comparable constructions and hole families. Comparing unrelated holes from different lots can produce a persuasive-looking picture with little diagnostic value.
Do not interrupt production or remove required treatment without authorization from the process owner. Investigation samples need a controlled status so they cannot accidentally return to normal product flow.
Build a causal test, not a gallery
- Write the current hypothesis and competing explanations.
- Choose samples that can distinguish them.
- Record examination method and exact locations.
- Compare observations with the process history.
- Use a controlled follow-up trial to evaluate the proposed cause.
Keep an image’s scale and preparation details with its caption. A visually dramatic image should not be compared with another taken under different conditions as though their appearance directly measures severity.
The outcome may be that the available evidence is insufficient. State which sample or measurement would resolve that uncertainty instead of turning the original suspicion into a confirmed root cause.
For example, if only completed boards remain, document that the as-drilled condition was not observed. A later trial can deliberately retain comparable samples at earlier stages. This is more informative than assuming the final image reveals exactly what was present before every subsequent treatment.
See drill-use records for tool history and inspection planning for connecting the examination to agreed product acceptance.
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