Appearance
A manufacturer of aquaculture feed extruder ring dies (X155CrVMo12, 56 HRC, 400 mm x 200 mm, 1800 through-holes of 1.5 mm x 200 mm) used a 12-spindle gun drilling machine (carbide TiAlN, Vc = 35 m/min, f = 0.012 mm/rev, oil at 50 bar). 1800 holes in 150 passes over 15 hours. Hole diameter tolerance +/-0.02 mm, Ra 0.4 microns. Pellet size distribution: 85% within +/-0.1 mm of target.
Aquaculture Component Comparison
| Component | Material | Bore Ø (mm) | Bore Length (mm) | Tolerance | Drilling Method | Vc (m/min) | f (mm/rev) | Coolant / Pressure | Key Requirement |
|---|---|---|---|---|---|---|---|---|---|
| Feed extruder ring die | X155CrVMo12, 56 HRC | 0.4–3.0 | 50–300 | Dia +/-0.02 mm; Ra < 0.8 µm | Multi-spindle gun drilling | 30–40 | 0.010–0.015 | Oil, 40–60 bar | Pellet size uniformity |
| RAS pump shaft | 316L/2205 duplex | 20–50 | 3000–8000 | Straightness < 0.1 mm/m | Gun drilling | 50–70 (316L) | 0.03–0.05 | NSF H1 oil, 40–60 bar | Weight reduction; bearing cooling |
| Cage mooring anchor shaft | 4140/4340 Q&T | 30–60 | 2000–5000 | Straightness < 0.2 mm/m | Gun drilling | 60–80 | 0.04–0.08 | Oil, 40–60 bar | Load monitoring access |
| Propeller shaft | 316L/duplex | 40–80 | 2000–5000 | Straightness < 0.1 mm/m; G6.3 balance | Gun drilling | 50–70 | 0.03–0.05 | Oil, 40–60 bar | Dynamic balance |
| Oxygen injector nozzle | 316L/ceramic | 0.2–2.0 | 10–50 | Flow tolerance +/-5% | Micro gun drilling | 20–30 | 0.003–0.008 | Oil mist, 60–80 bar | Bubble size control |
FAQ
How are the ring die holes for aquaculture feed extruders drilled, and what tolerance is required? Ring dies are drilled on multi-spindle gun drilling machines with 6–24 spindles, drilling 0.4–3.0 mm holes through 50–300 mm of hardened tool steel (56–60 HRC). The hole diameter tolerance is +/-0.02 mm to maintain consistent pellet size. The die runs 150–600 passes depending on the total hole count (up to 48 000 holes for large dies). Each spindle drills a hole per pass at Vc = 30–40 m/min, f = 0.010–0.015 mm/rev.
What is the function of the centre bore in RAS vertical turbine pump shafts? The centre bore (20–50 mm, full shaft length) provides a passage for the lubrication/cooling water to reach the pump bearings. The gun-drilled bore also reduces the shaft weight by 10–15%. The bore must be straight within 0.1 mm/m to prevent bearing wear at 1450 rpm operating speed.
How are fish cage mooring anchor shafts drilled for load monitoring? The centre bore houses a load cell rod that measures the mooring tension in real time for storm warning systems. The bore is gun-drilled to 30–60 mm through the full shaft length (2–5 m) in 4140/4340 steel at Vc = 60–80 m/min, f = 0.04–0.08 mm/rev.
What is the surface finish requirement for oxygenation injector nozzle bores? The bore surface finish must be Ra < 0.4 µm (preferably Ra < 0.2 µm after electropolishing) to control the bubble size (target: 50–200 micron bubbles for optimal oxygen mass transfer efficiency). The injector nozzle bores are micro gun-drilled using PCD-tipped drills at Vc = 20–30 m/min, f = 0.003–0.008 mm/rev.
How are water circulation propeller shafts dynamically balanced after gun drilling? Propeller shafts (316L/duplex, 40–80 mm bore, 2–5 m length) are dynamically balanced to G6.3 grade after gun drilling and after the propeller is mounted. The gun-drilled centre bore provides access for balance correction by removing material from the bore wall at angular positions identified by the balancing machine.
The information provided in this article is for general informational purposes only. Data and recommendations are based on published research and industry experience as of 2026.