Deburring Aluminium Parts, What Actually Works
Aluminium is easy to damage and easy to stain. The wrong media peens the burrs flat instead of removing them; the wrong compound leaves water marks that ruin a pre-anodise finish. This guide covers what works in production on 6000-series, 5000-series and cast aluminium.
Choose gentler media
Plastic pyramids or plastic tetra shapes are the default choice for aluminium deburring. They cut burrs without impingement.
Fine ceramic cones (fine-cut grade, 6 to 10 mm) work well where the burr is heavier and the surface will be anodised or painted, small anodise-hidden pitting is acceptable.
Avoid coarse ceramic triangles on visible-cosmetic aluminium. Even one hour of coarse ceramic can leave an 'orange peel' that no downstream polish will remove economically.
For polish or mirror finish on aluminium, run a two-stage process ending in ultra-fine plastic or porcelain with a maize carrier.
Compound: keep it non-ferrous and clean
A general-purpose liquid compound suitable for non-ferrous metals keeps the surface bright, prevents oxide build-up, and lubricates the media action. Concentration is usually 1 to 3% by volume of the water flow.
Never use ferrous inhibitor compound on aluminium, those inhibitors leave residues that interfere with anodising and can cause blotchy chromate conversion.
If parts are heavily oiled from machining, an alkaline degreasant boost at the start of the cycle helps the compound work. Do not run degreasant for more than the first 10 to 15 minutes.
Water flow keeps the surface bright
Standard flow-through is 0.5 to 1.5 L/min on a 300 L bowl. Less water increases abrasive action but risks streaking and oxide build-up. More water lubricates and polishes.
Aluminium going for anodising or paint prep needs generous flow to keep the sludge moving out of the machine, trapped sludge causes localised staining.
Drying is critical
Aluminium water stains within minutes if left wet. Dry immediately after unloading.
Compressed air blow-off works for small batches. For production, use a maize (corncob) dryer, parts come out clean, dry and static-free within 10 to 20 minutes.
For higher-cosmetic requirements, a heated maize dryer at 60 to 70°C leaves parts spot-free. Avoid hot-water dips on aluminium unless the parts are then immediately dried.
Common failure modes
Peened-over burrs: media too heavy or too coarse. Switch to plastic or fine ceramic.
Grey or dull surface pre-anodise: ceramic contamination in the media or ferrous cross-contamination. Segregate aluminium machines from steel work.
Water spots: parts sat wet after unloading. Dry within 5 minutes of unload.
Rolled edges: cycle time too long. Reduce time; the burr is off well before the edge is heavily rolled.
Frequently asked questions
Can I use the same machine for aluminium and steel?
Only if you thoroughly clean it out and change media between materials. Steel particles embedded in the media will stain aluminium.
What Ra should I expect after vibratory deburring on aluminium?
Starting from a machined 1.6 μm Ra, expect 0.8 to 1.2 μm after a plastic-media deburr. Polish stage can take this to 0.4 μm or better.
Do I need a chromate rinse after finishing?
Only if the parts will not be anodised or plated immediately. Otherwise the downstream chemistry handles surface conditioning.