Polishing Concave Aluminum Parts: Symptom, Cause, Check and Adjustment
This page reproduces the published troubleshooting table for concave aluminum parts: the symptoms with their likely causes, what to check first and the adjustment to test. On a concave part the rim and the recess do not receive media equally, so the same adjustment can behave very differently on the two. No media size, cycle time, speed, compound concentration or finish value is stated, implied or supplied here.
Browse the published rows
Choose a section or search the published rows, then read the article text.
Symptom, likely cause, what to check and recommended adjustment
| symptom | likely cause | what to check | recommended adjustment |
|---|---|---|---|
| Concave area is cloudy, rim is bright | Media contact is concentrated on the edge | Media size, part orientation, recess depth | Try smaller or better-shaped media that can enter the curve more evenly |
| Edges are rounded before the inner surface improves | Cycle time or cutting strength is too high | Edge radius, processing time, media aggressiveness | Reduce cutting stage time and separate smoothing from polishing |
| Surface has gray film after finishing | Aluminum fines, unsuitable compound, dirty water | Water clarity, compound type, media cleanliness | Improve rinsing and use aluminum-safe finishing compound |
| Bright finish is uneven from part to part | Parts are shielding each other or loading is too dense | Part-to-media ratio, batch size, part nesting | Reduce loading density and prevent parts from stacking in the bowl |
| Small scratches remain inside the curve | Media is too coarse or previous machining marks are deep | Initial surface roughness, media grade, polishing sequence | Add a finer finishing stage before final bright polishing |
Why concave parts behave differently
On a concave part the rim and the recess do not receive media equally. The rows below are the published article own symptoms and adjustments for that situation. They do not supply a media size, a cycle time or a finish value for your part.
Source and its limits
Published reference page; captured 5 October 2026. SHA256: 634897de21717c3ac5ffd79ff55cf72231c760e6149ada377997351d1ae3ab84.
- Symptoms, checks and adjustments are the published article own, reproduced verbatim. They are directions to test on a sample, not a validated recipe.
- No media size, cycle time, speed, compound concentration or finish value is stated, implied or supplied.
- A symptom lists a likely cause and a first check, not a diagnosis.
Table headers as published
- Symptom / Likely Cause / What to Check / Recommended Adjustment
Frequently asked questions
What media size or cycle time should I use on a concave part?
This page states none. The rows describe what the source says to check and what to test; the media size and cycle time come from your own trial and the supplier.
Why does the rim finish before the recess?
Because media contact concentrates on the outer edge, and whether media can enter the curve depends on its size and shape. That is the geometry effect the published table describes.
Does it diagnose my part?
No. A symptom lists a likely cause and a first check. The same visible mark can have more than one cause, and confirming it needs a controlled test on a sample.
Does it state cycle time, speed or temperature?
No. No cycle time, speed, amplitude, load ratio, concentration, temperature or removal result is stated or implied anywhere on this page or in its download.
Are the tables quoted exactly?
Yes. Every cell is taken from a single source table cell and verified against the captured page, including wording and punctuation.
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