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Nov 11, 2025
The blown film extrusion air ring is the last piece of metal the melt touches before it becomes film. In that 60 mm of travel, it decides whether you ship ±2.2 % gauge or spend the week explaining scrap to the plant manager. At Bojing we’ve built 4,800 rings since 2006; the selection process below is the same checklist we run on every order before the first chip is cut.
| Spec | Precision Target | How to Measure |
|---|---|---|
| Thickness | 12–35 μm | 10 m beta average |
| 2σ Gauge | ≤ ±2.8 % | 36-point scan |
| Layflat | 1,200–3,200 mm | Nip caliper |
| Resin | 0.7–2.0 MI LLDPE | 190 °C melt index |
| Output | 280–550 kg/h | 30 min scale |
Fill these in before you open any brochure. Blank cells mean you’re guessing.
Die OD at 210 °C = room temp + 0.50 mm (700 mm example).Blown film extrusion air ring lower lip ID must fall between 700.20–700.80 mm. We machine the ring bore after measuring your die at operating temperature. No catalog guesswork.
Target velocity 33–37 m/s Volume (m³/h) = velocity × 2π × radius × gap × 3,600
650 mm die, 1.05 mm gap, 35 m/s → 1,480 m³/h Every ring ships with a laminated curve for 30 / 34 / 38 m/s at your exact gap.
| Lips | Frost Line (DD) | Velocity | Best For |
|---|---|---|---|
| Single | 1.0–2.2 | 24–28 m/s | ≥ 40 μm |
| Dual | 2.3–5.0 | 31–38 m/s | 20–35 μm |
| Triple | 4.5–7.5 | 34–42 m/s | ≤ 18 μm |
Triple adds 14 kW and $4,800. Use only for sub-15 μm medical grades.
| Output | Minimum Segments | Reaction |
|---|---|---|
| ≤ 320 kg/h | 24 manual | 3–5 s |
| 320–450 | 36 piezo | 0.3 s |
| ≥ 450 | 48 servo | 0.2 s |
At 380 kg/h the melt pump pulses every 1.8 s. Fingers lose; piezo wins.
Lip: 6061-T6, 50 μm hard anodize
Air exit: Ra 0.4, 12-point check
Concentricity: ≤ 0.10 mm hot
Gap uniformity: ±0.015 mm full circle
48-point laser scan on every ring. Fail one point, back to the mill.
| Future Need | Cost Now | Cost Later |
|---|---|---|
| ≤ 380 kg/h | $0 | – |
| 400–500 | $1,300 | $12,500 + 4 days |
Pre-drill the ports. Bolt on IBC when the PO lands.
| Die Ø | Output | Gauge | Model | Gap | Segments | Blower |
|---|---|---|---|---|---|---|
| 450–600 | 220–340 | ±3.0 % | BJ-600Pro | 0.98 mm | 24 | 1,180 m³/h |
| 650–800 | 320–480 | ±2.5 % | BJ-750Pro | 1.08 mm | 36 | 1,520 m³/h |
| 850–1,100 | 450–620 | ±2.0 % | BJ-1000Pro | 1.18 mm | 48 | 1,920 m³/h |
Die OD (hot) + target frost line in DD. Reply in one hour with model, gap, and blower curve.
We build rings that lock the frost line and stay locked.
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