Industry Applications
Application
Case Details
01 Preface
02 Market Value of Internal Combustion Engine Fuel Systems 
03 Fuel Injector Product Processes and Equipment
04 Case Study of Grinding Tools for the Middle Hole Seat Surface
4.1 Selection of Process Tools
4.2 Process Measures and Peripheral Products
4.3 Process Effects
05 Conclusion
Keywords: automobile, engine, fuel injection system, grinding process
01 Preface
Internal combustion engines are currently the dominant form of power machinery worldwide and a key determinant of societal efficiency; they have long been the focus of Arrowstone’s research.
02 Market Value of Internal Combustion Engine Fuel Systems
In 2023, China’s internal combustion engine output reached 44.7376 million units, representing a year-on-year increase of 2.85%.
In 2023, sales of diesel internal combustion engines reached 5.1165 million units, a year-on-year increase of 19.36%.
In 2023, sales of gasoline internal combustion engines reached 39.5847 million units, up 1.88% year on year.
If we assume four cylinder blocks per internal combustion engine and one fuel injector per cylinder block, the estimated annual production of fuel injectors in China would be as follows:
1) The new engine market ≈ 45 million units × 4 nozzles per unit = 180 million fuel injectors;
2) Domestic aftermarket ≈ 336 million units × 4 units per vehicle × replacement rate of 5% = 67 million units;
3) Overseas aftermarket ≈ 100,000 ten-thousand units × 4 units per unit × replacement rate of 5% × penetration rate of 40% = 80 million units;
The total number of fuel injectors is approximately 18,000 + 6,700 + 8,000 = 327 million units; this represents a tremendously large market, with annual consumption measured in the hundreds of millions—second only to personal durable consumer goods such as mobile phones (global mobile phone sales in 2023 were approximately 1.17 billion). Therefore, in-depth research is highly necessary.
03 Fuel Injector Product Processes and Equipment
Among the eight major subsystems of an internal combustion engine, the fuel system is the core subsystem. Within the fuel system, the delivery valve, plunger and barrel assembly, and delivery valve are the three critical mating components, which demand extremely high machining accuracy and present significant challenges in grinding. In particular, the injector delivery valve assembly, as the central component of the fuel injection system, has its precision and surface finish directly determining the fuel spray pattern and the engine’s combustion efficiency.
As shown in the table below, this outlines the main process steps (Phases) and typical equipment configurations for needle valve bodies at representative Chinese manufacturers, with the critical processes highlighted in the red box being the focus of our discussion today.
Serial Number
|
Needle Valve Body Machining Steps
|
Definition of Processes and Phases
|
Equipment
|
Brand
|
1
|
Raw-hole drilling
|
Perform rough machining of the needle valve body blank, using four-axis gun drilling with a single clamping setup to form the injector’s central bore in one operation.
|
Four-axis gun drilling machine
|
German TBT
|
2
|
Hole position
|
Machining all hole positions on the needle valve body
|
Vertical Machining Center
|
German SW
|
3
|
Electrochemical Electrolysis Oil-Storage Tank
|
Ensure the oil reservoir dimensions are maintained while also ensuring there are no burrs.
|
Electrochemical Machining (ECM)
|
Germany (EMAG)
|
4
|
Nozzle machining
|
Micro-hole electrical discharge machining with flow rate accuracy of ±1%.
|
Micro-hole electrical discharge machining machine
|
Rui + GF +
|
5
|
Extrusion grinding
|
Online monitoring of the flow rate through the extrusion needle valve body, with compliance to the flow rate standard and error controlled within ±1%.
|
Abrasive Flow Machining (AFM) Equipment
|
Beauty (Yi Qu Hong)
|
6
|
Traffic Detection
|
The valve body of every oil nozzle is 100% tested for flow consistency.
|
Traffic detection equipment
|
Beijing Machine Science
|
7
|
System Traffic Monitoring
|
After installing the original fuel injectors, test the technical parameters under various operating conditions.
|
Common-rail injector test bench
|
meaning
|
8
|
Middle hole, seat surface, large end face
|
CNC high-precision center-hole and seat-surface grinding machine. Used for machining the center hole, seat surface, and large end face of needle valve bodies.
|
Center-hole seat surface grinder
|
Rui UVA, etc.
|
04 Case Study of Grinding Tools for the Middle Hole Seat Surface
In the production of fuel injectors, the grinding process is a critical step for ensuring the nozzle’s dimensional accuracy and surface finish. By selecting appropriate grinding wheels, optimizing grinding parameters and coolant selection, and employing precision grinding equipment and tooling fixtures, high-precision grinding of the fuel nozzle can be achieved.
For example, precision grinding of fuel injectors using CBN grinding wheels can ensure the accuracy of critical dimensions such as orifice diameter, orifice geometry, and taper, while also improving surface finish and wear resistance. This grinding approach not only enhances injector performance and reliability but also effectively reduces manufacturing and maintenance costs.
Two Case Analyses
Case 1
Machine tool: UVA
Grinding wheel specifications: center hole 1A1W, 4×6×2×16.5×M2 CBN
Seat: 1A1W–Z/60°3.3×11.5×1.5×21.6×M2 CBN 
Grinding wheel speed:
Medium hole: 90,000 RPM
Seat surface: 60,000 RPM
Grinding allowance:
Middle hole: Φ0.1mm
Seat surface: Φ0.1 mm
Grinding method: Sintered diamond roller
Maintenance cycle:
Seat surface: 10 pieces/repair
Middle holes: 12 pieces/repair
Workpiece material: 18CrNi8, HRC ≥ 55
Contrast Test Report, Table 1
Brand
|
Type
|
Roundness (μm)
|
Roughness (Ra)
|
Machining Accuracy and Other Factors
|
An arrow piercing stone
|
Seat surface
|
0.64~0.84
|
0.101~0.126
|
The angle, dimensions, and roundness meet the requirements, and the durability and service life are comparable to those of imported grinding wheels.
|
|
Middle hole
|
0.36~0.42
|
0.072~0.096
|
The dimensions and taper meet the requirements, and the durability and service life are comparable to those of imported grinding wheels.
|
Master
|
Seat surface
|
0.85~0.89
|
0.127~0.187
|
\
|
|
Middle hole
|
0.35~0.47
|
0.075~0.097
|
\
|
Case 2
Machine tool: BAHMÜLLER ULTRA
Grinding wheel specifications:
Center hole: 1A1W 4×6×2×14.5×M2 CBN
Seat: 1A1W–Z/60°3.3×9×1.5×23.5×M2 CBN
Grinding wheel speed:
Medium hole: 95,000 RPM
Seat surface: 85,000 RPM
Grinding allowance:
Middle hole: Ф0.02~0.03mm
Seat surface: Φ0.1–0.15 mm
Grinding method: Sintered diamond roller
Maintenance cycle:
Middle hole: 10 pieces/repair
Seat surfaces: 8 pieces/repair
Workpiece material: 38CrMoAlA, hardness ≥ HRC 55
Contrast Test Report, Table 2
Brand
|
Type
|
Roundness (μm)
|
Straightness (μm)
|
Taper (μm)
|
Roughness
|
An arrow piercing stone |
Seat surface
|
0.38
|
\
|
\
|
Ra0.06/Rz0.55
|
|
Middle hole
|
0.26
|
0.3~0.8
|
0.4~1.0
|
Ra0.08/Rz0.66
|
A-Schmeier
|
Seat surface
|
0.36
|
\
|
\
|
Ra0.06/Rz0.55
|
|
Middle hole
|
0.45
|
0.4~0.8
|
0.6~1.2
|
Ra0.12/Rz1.32
|
By carefully selecting grinding processes and parameters, it is possible to achieve high-precision, high-quality, and highly efficient machining. For example, in the aerospace industry, the grinding of engine blades demands extremely high precision and surface quality; the adoption of similar grinding techniques can significantly enhance blade performance and service life. Furthermore, in medical device manufacturing, grinding technology is extensively used in the machining of surgical instruments to ensure sharpness and durability of the cutting edges.
These success stories further demonstrate the critical role of grinding technology in enhancing product quality and reducing production costs. By continuously optimizing grinding processes and equipment, the manufacturing sector will be better positioned to meet increasingly stringent market demands, thereby driving technological advancement and industrial upgrading.
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