Bead blasting drives fine media at high speed to strip scale, blend machining marks, or create a satin surface on metal, plastic, or glass. Because the beads round over sharp peaks without cutting deep valleys, the process leaves parts uniformly matte and ready for anodizing, painting, or assembly. This guide explains every step—media choice, air pressure, masking, and inspection—so you can set up a repeatable bead-blast line in your shop.
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- Why understand bead-blast basics first
- Bead media types and core properties
- Air pressure, nozzle size, and coverage
- Surface finish grades and roughness
- Masking and fixturing best practices
- Safety, dust control, and PPE
- Equipment setup & maintenance checklist
- Cost, speed, and cycle-time comparison
- One-Stop Machining Solution
- Quick recap before hitting the trigger
Why Understand Bead-Blast Basics First
Bead blasting looks simple—hold a nozzle, pull a trigger, watch parts turn matte. In practice, finish uniformity depends on media hardness, flow rate, stand-off distance, and even part temperature. By learning the fundamentals, you can:
- Reduce scrap from over-blasted edges and warped thin walls.
- Cut cycle time with optimal nozzle overlap.
- Predict surface roughness before shipping prototype parts.
Bead Media Types And Core Properties
Start with the right bead. Glass beads dominate decorative work, but ceramic or stainless beads resist wear in high-volume cells. The table lists mainstream choices.
| Media | Mohs hardness | Density g/cc | Typical size µm | Best use |
|---|---|---|---|---|
| Soda-lime glass | 5.5 | 2.5 | 50–300 | Light deburr, aluminum |
| Ceramic bead | 7.2 | 3.9 | 70–250 | Extended life, steels |
| Stainless shot | 6.5 | 7.6 | 150–400 | Peen & clean in one pass |
| Plastic polycarbonate | 3.5 | 1.2 | 200–600 | Paint removal on composites |
| Walnut shell | 2.5 | 1.1 | 300–800 | Soft metals, antique parts |
Glass beads shatter after 6–10 cycles. Ceramic beads survive 30–40 cycles, cutting media cost when throughput is high.
Air Pressure, Nozzle Size, And Coverage
Uniform finish comes from stable velocity and bead flow. The chart below links common nozzle bores and pressures to exit speed (measured with a Pitot tube).
Nozzle Ø mm | Air bar | Exit speed m/s | Flow kg/h -------------------------------------------------- 4 | 4 | 120 | 20 6 | 5 | 130 | 38 8 | 6 | 140 | 60
For thin aluminum, keep speed under 130 m/s to avoid peening dimples. Use a 30° traverse pattern with 50 % overlap. With these numbers, a 150 mm square plate reaches full coverage in about 45 seconds.
Surface Finish Grades And Roughness
Customers often request “matte” or “satin” but every shop interprets words differently. Use profilometer Ra to lock spec clarity.
| Media & size | Pressure bar | Overlap % | Result Ra µm (Al 6061) | Visual |
|---|---|---|---|---|
| Glass 100-150 µm | 4 | 60 | 1.2 | Dull satin, soft glow |
| Glass 200-250 µm | 5 | 50 | 2.8 | Coarse matte |
| Ceramic 150-180 µm | 6 | 50 | 1.6 | Semi-gloss, harder bite |
| Plastic 300-500 µm | 3 | 70 | 0.8 | Silky, paint-ready |
Document the exact bead spec, pressure, and Ra on drawings to stop re-match hassle across vendors.
Masking And Fixturing Best Practices
Blast media enters threaded holes and bearing seats easily. Mask them before the cabinet door closes.
- Plug holes with silicone pull-tabs rated to your pressure.
- Use laser-cut stainless masks for large gasket faces; magnets hold them.
- Clamp parts on a rotating spindle to cut shadow lines on cylinders.
For small batches, a cardboard shield with duct tape works in a pinch—just watch edge leaks.
Safety, Dust Control, And PPE
Micro-glass dust irritates lungs. Always run a cartridge filter rated <1 µm. Operators wear:
- N95 or P100 respirator.
- Cut-resistant gloves; bead bounce can fray skin.
- Ear plugs when pressure exceeds 6 bar.
Check filter manometer daily; replace cartridges when ΔP exceeds 600 Pa to keep airflow stable.
Equipment Setup & Maintenance Checklist
Downtime hurts. Use this weekly list:
- Sift media; remove fines under 50 µm.
- Inspect nozzle for oval wear; replace when bore grows 1 mm.
- Drain moisture trap; wet beads clump.
- Confirm regulator gauge matches PLC set-point.
Cost, Speed, And Cycle-Time Comparison
The quick table ranks common media for speed and cost per blasted square meter.
| Media | Coverage rate cm²/min | Media life cycles | Cost $/kg | Cost per m²* $ |
|---|---|---|---|---|
| Glass 150 µm | 450 | 8 | 0.9 | 0.28 |
| Ceramic 170 µm | 500 | 35 | 3.8 | 0.24 |
| Stainless 200 µm | 300 | 50 | 7.2 | 0.48 |
| Plastic 400 µm | 380 | 20 | 4.0 | 0.32 |
*Assumes 10 kg/h flow and full recovery.
One-Stop Machining Solution
From material selection, precision CNC machining to surface finish, we provide with professional one-stop machining solutions. Upload your 3D file for a consolidated quote.
Quick Recap Before Hitting The Trigger
- Select media hardness by part material—glass for Al, ceramic for steel.
- Keep pressure under 5 bar when wall thickness is ≤2 mm.
- Overlap passes by 50 % for even matte with no tiger stripes.
- Record Ra and bead spec on drawing to avoid finish debates.
- Sift media weekly and change filters when pressure drop spikes.
Follow these steps and bead blasting will turn rough machined parts into clean, uniform surfaces that impress customers and cut post-processing time.
