When scratches show up on a metallographic specimen, it’s rarely “just cosmetic.” They can mask fine microstructural features, distort grain boundary interpretation, and force you into repeat preparation. In many labs, rework adds 20–40 minutes per sample once you include repolishing, cleaning, re-etching, and re-imaging. In production QA, that delay can ripple into batch release decisions.
Below is a practical, 3-step troubleshoot-and-fix workflow you can run immediately—plus parameter-setting tips for the Laizhou Jincheng LMP-4 automatic grinding & polishing machine (LCD touch control, stepless pressure, and speed control) to help you stabilize results across operators.
You’ll solve scratches faster when you classify them by pattern. Use a quick check under your microscope at 50×–200× before changing consumables or machine settings.
Scratches are most often caused by stage carryover, incomplete removal of prior damage, or contamination. Before you tweak speed and pressure, make sure your workflow is mechanically clean and logically staged.
If you move from 320/600 grit grinding to polishing without removing all prior scratches, you lock damage into the surface. A practical rule: don’t advance to the next stage until 100% of the previous stage’s lines are gone under your inspection magnification. Between stages, rinse with running water (or clean coolant), then use fresh ethanol/isopropyl rinse and dry with oil-free air. Replace towels that shed fibers.
For harder alloys (tool steel, Ni-based), a firmer cloth and controlled load reduce pullout and chatter marks. For softer metals (Al, Cu), a softer cloth can help—but only if pressure is reduced to avoid smearing and edge rounding. If you see “micro-tearing,” reduce pressure first; if you see persistent deep lines, step back one grit and re-level.
A single dried diamond agglomerate can create a scratch field that looks like “machine vibration.” Keep slurry nozzles capped, purge lines after shutdown, and dedicate rinse containers per step. If you share equipment across materials, schedule soft metals after hard materials only if you can do a thorough bowl/cloth cleaning in between.
Once your process is staged correctly, you’ll get the biggest consistency gains by standardizing three things: stage time, rotational speed, and contact pressure. The LMP-4’s LCD touch interface and stepless pressure adjustment make it easier to lock in repeatable recipes across shifts—especially when you use single-point loading to keep force stable and reduce edge damage.
Use these as baseline parameters. If scratches persist, step back one stage rather than increasing pressure. In many labs, reducing pressure by 20–30% and extending time by 15–25% lowers scratch density without sacrificing flatness.
Start → Select stage (Pre-grind / Coarse polish / Final polish)
Set platen speed (rpm) → Set time (min:s)
Set stepless pressure to a stable baseline → Enable single-point loading if you need uniform contact
Run stage → Rinse + alcohol clean → Dry with oil-free air
Inspect at 50×–200× → If scratches remain, repeat current stage (not higher pressure) or step back one stage
A materials lab preparing carburized steel samples reported persistent fine scratches after final polish. Operators kept increasing polishing time, but the scratch density barely changed. The root cause wasn’t time—it was pressure spikes during stage transitions and inconsistent loading between specimens.
Result: rework frequency dropped from about 1 in 3 samples to less than 1 in 10 over the next two weeks, and operator-to-operator variability became noticeably smaller.
If you’re not sure what to change first, use this quick self-check. Answering “Yes” suggests your highest-probability fix.
After each run, wipe splash zones, rinse the bowl, and check for embedded abrasive grains. If you use diamond suspension, flush the nozzle with clean liquid and cap it to avoid crystallized particles.
Use saved stage recipes (where available) and document: material, mounting method, abrasive sequence, rpm, load setting, and time. Consistency is what makes your metallography scalable.
If you notice repeat scratches in the same area across multiple samples, inspect platen/holder seating and consumable wear. A slightly uneven cloth or mis-seated holder can mimic “mystery scratches.”
Get the recommended LMP-4 automatic grinding & polishing parameter sheet (by material), plus a practical checklist for stage transitions and cleaning habits—so your team can run the same recipe and get the same surface quality.
Explore the LMP-4 Automatic Metallographic Grinding & Polishing Machine & Download the Process FormTip: If you tell us your material (e.g., carbon steel, stainless, aluminum, copper, titanium) and target finish, we’ll suggest a starting recipe you can apply immediately.
When you comment, include your material, abrasive sequence (grit/μm), cloth type, and your current speed/pressure/time. If you can describe whether scratches are directional or random, you’ll usually pinpoint the fix in one round of adjustments.
