In the automotive manufacturing sector, what is the specific machining process flow for producing engine cylinder blocks on machining centers?

In the automotive manufacturing sector, what is the specific machining process flow for producing engine cylinder blocks on machining centers?

The machining process flow for automotive engine cylinder blocks follows the principles of “benchmarking first, step-by-step precision finishing, and multi-surface coordination.” It involves three major stages: rough machining, semi-finishing, and finishing, relying entirely on the machining center's high-precision positioning and multi-process integration capabilities.

Core Process Flow

Pre-treatment and Benchmark Machining

Cylinder block blanks (typically aluminum die-cast or cast iron castings) undergo stress-relief aging treatment to eliminate internal stresses, followed by removal of surface gates and flash.

A vertical machining center machines the “one surface and two pins” benchmark (usually the cylinder block bottom surface and two locating pin holes), establishing the positioning reference for all subsequent operations and ensuring consistent machining benchmarks.

Rough Machining Stage (Stock Removal)

Rough-machine the cylinder block top surface, crankshaft bore end faces, and oil pan mating surface using vertical or gantry machining centers to rapidly remove substantial stock.

Rough-bore critical hole systems such as cylinder bores, crankshaft bores, and camshaft bores, leaving a 3-5mm semi-finishing allowance. Simultaneously machine some non-critical threaded holes and oil passages.

Employ high-feed tools and high-pressure cooling systems to minimize thermal deformation from cutting and enhance machining efficiency.

Semi-Finishing Stage (Precision Transition)

Switch to high-precision tools for semi-finishing boring of cylinder bores and crankshaft bores, correcting shape errors from rough machining while leaving 0.1-0.3mm finishing allowance.

Machine mounting surfaces and locating holes on cylinder block sides, along with preliminary shaping of intake/exhaust passages, ensuring positional accuracy between surfaces.

Clear machining chips and verify critical dimensions meet intermediate tolerance requirements.

Finishing Stage (Precision Assurance)

Finish-bore cylinder bores using horizontal machining centers (five-axis machining centers on select high-end production lines). Refine surface roughness via honing to achieve Ra 0.2–0.8 μm.

Finish grind crankshaft and camshaft bores to guarantee coaxiality and roundness error ≤0.005mm, meeting bearing assembly requirements.

Finish machine oil pan and cylinder head mating surfaces to ensure flatness ≤0.01mm/m, while completing tapping and chamfering of all threaded holes.

Inspection and Post-Processing

Critical dimensions (e.g., cylinder bore diameter, hole spacing, flatness) are verified using a coordinate measuring machine. Non-conforming parts are returned for rework.

Surface strengthening treatments (nitriding or laser honing for select models) are applied to cylinder bores to enhance wear resistance.

Internal oil and air passages are cleaned of chips and contaminants, dried, and subjected to leak testing before final storage.

Critical Process Requirements

Maintain consistent locating references to prevent cumulative errors from multiple setups.

Employ “single-setup multi-operation” for critical hole systems, leveraging machining centers' multi-axis interpolation and automatic tool-changing capabilities to minimize clamping frequency.

Control cutting speed and feed rates during machining, combined with cooling lubrication systems, to prevent thermal deformation affecting precision.