Four-Spindle Micro Gun Drilling Scales Fuel Injector Nozzle Production

Customer Background

The customer is a fuel injection system manufacturer producing high-pressure fuel injector nozzles and related small round components. Each nozzle carries small-diameter, high-accuracy holes drilled along its axis — orifices that control spray pattern, atomization, and fuel metering. On a modern injector, the orifice geometry (diameter, roundness, and position relative to the seat) is fixed at manufacture and cannot drift: it is the single largest influence on combustion, emissions, and noise, and it must hold across millions of parts.

The Challenge

Injector nozzle micro-drilling is a precision-at-volume problem:

Orifice-to-seat concentricity. The drilled axis must stay concentric with the nozzle seat and guide. An off-center orifice skews the spray cone and produces cylinder-to-cylinder variation that fails emissions calibration — the defect surfaces on the test bench, not at the drill.

Sub-millimetre orifices. Nozzle orifices run Ø1–6mm, with the finest end below 1.5mm. At these diameters the gun drill is fragile, chip evacuation is severely constrained, and any feed interruption snaps the tool — a break mid-batch costs the machine time, not just the part.

Hard, wear-resistant nozzle steel. Injector bodies are hardened steel or stainless selected for seat wear life. Their low machinability accelerates tool wear and demands stable, high-pressure cutting conditions.

Flow consistency across the batch. Spray geometry is verified by flow rate. With hundreds of thousands of nozzles per year, orifice diameter and roundness must hold within a narrow band part after part — the process has to be stable, not just accurate once.

High-pressure chip removal. At Ø1mm, through-tool coolant must carry chips out of a hole barely wider than the drill. Reliable chip evacuation requires coolant pressures far beyond conventional systems.

The Solution

RuidCNC supplied an RD-S Round Job Multi-Spindles Gun Drilling Machine configured for injector orifice production:

• 4 electric spindles at 6,000 rpm — four nozzles drilled in parallel, with automatic load/unload, multiplying daily output per machine
• Ø1–6mm micro-drilling range to 500mm — covers the fine orifice diameters and the longer spill and lubrication bores in one machine
• 200 kg/cm² high-pressure coolant — reliable chip evacuation from sub-millimetre holes protects the fragile drill and leaves a clean bore ready for flow testing
• Chuck + cone clamp with counter-rotation — secure round-part holding that maintains orifice-to-seat concentricity across the whole batch
• Automatic loading/unloading — chuck and cone system supports automated part feed, keeping spindles cutting rather than waiting

Key Machine Specifications

Parameter	Specification
Spindle quantity	4 (electric)
Gun drilling range	Ø1 – Ø6 mm
Max drilling depth	500 mm
Workpiece outer diameter	Ø6 – Ø40 mm (cone)
Spindle max RPM	6,000 rpm
Max coolant pressure	200 kg/cm²
Feeding speed	0 – 2,000 mm/min

Results

Metric	Single-Spindle Process	RD-S (4-Spindle)	Improvement
Parts per shift	900	2,700	3× throughput
Orifice roundness	±0.025 mm	±0.010 mm	60% better
Orifice-to-seat concentricity	±0.030 mm	±0.012 mm	60% better
Flow-rate deviation across batch	±1.8%	±0.6%	67% tighter
Tool life (parts per drill)	180	320	78% improvement
Scrap rate	2.5%	0.5%	80% reduction

Process Validation

The process was validated through:

• Orifice diameter and roundness measurement across a full production batch
• Flow-rate testing of representative nozzles to confirm spray characteristics
• Tool-life tracking over 20,000 drilled parts
• Dimensional inspection per the nozzle drawing’s critical characteristics

Conclusion

The RD-S four-spindle configuration turns injector orifice production from a per-part bottleneck into a process that is both fast and consistent. By drilling four nozzles in parallel with 200 kg/cm² coolant and automatic loading, the customer tripled parts per shift while tightening orifice roundness and holding flow-rate deviation across the batch. For fuel injection suppliers whose combustion and emissions performance is set by orifice geometry, the RD-S delivers stable micro-orifices at automotive volume.

Figures are representative of typical applications.