Crankshaft Cleaning Machine: 50MPa High-Pressure Oil Gallery Cleaning and Oblique Oil Hole Cleanliness Control

Abstract

The entire cleaning challenge for crankshafts is concentrated in the deep-hole cleaning of oblique oil holes. This article starts from the contamination deposition mechanism in oblique oil holes, analyzes the process principle and pressure selection logic of high-pressure insertion cleaning, and compares three crankshaft cleaning solutions: high-pressure for commercial vehicle main journals, targeted high-pressure for passenger vehicle crankshafts, and flexible ultrasonic cleaning.

Keywords

Crankshaft cleaning machine, crankshaft high-pressure cleaning machine, oblique oil hole cleaning, oil gallery cleaning, camshaft cleaning, crankshaft cleanliness, particle size

I. Oblique Oil Holes: The Entire Challenge of Crankshaft Cleaning

The external structure of a crankshaft is relatively simple. The main journals and connecting rod journals are surfaces of revolution, and cleaning them is not difficult. The real challenge lies in the oblique oil holes: to deliver lubricating oil from the main journals to the connecting rod journals, inclined through-passages are drilled into the crankshaft. These holes have small diameters, long paths, and corners.

Metal chips and burrs generated during machining tend to deposit on the walls and corners of oblique oil holes, and conventional spray cleaning cannot reach them at all. If chips remain in the oil galleries, they will circulate in the lubrication system after assembly, scoring bearings and journals, with serious consequences. Therefore, the core of crankshaft cleaning is the cleaning of oblique oil holes.

II. Principle of High-Pressure Insertion Cleaning

High-pressure insertion cleaning involves inserting a slender nozzle into the oil passage and continuously jetting high-pressure water as the nozzle moves along the hole axis. The impact force and carrying action of the water flow remove deposits from the hole.

This process is effective only when three conditions are met: the nozzle outer diameter matches the hole diameter, ensuring smooth insertion while maintaining an annular return flow during jetting; the pressure is sufficient to peel off deposits from the hole wall but does not exceed the bearing capacity of the hole opening and wall; and the stroke covers the entire oil passage, including corners and outlet sections.

III. Comparison of Solutions for Different Crankshafts

• Commercial vehicle six-cylinder diesel engine crankshaft: Gantry robot loading, overall spray pre-cleaning, robot-held workpiece targeted cleaning, 50MPa high-pressure oil gallery cleaning, rinsing, robot-held workpiece compressed air blow-drying plus vacuum drying, air-conditioning cooling to ≤ room temperature ±5°C. Cycle time 180 seconds, overall cleanliness ≤30mg, particle size ≤600μm, dryness: no residue on journal surfaces.

• Passenger vehicle crankshaft: Lift-and-step high-pressure cleaning machine, gantry robot loading, lift-and-step conveying, overall cleaning plus targeted high-pressure cleaning, compressed air rotary scanning blow-drying, manipulator horizontal transfer, air-conditioning cooling. Dimensions 8m×5m×4m, cycle time 60 seconds/piece, cleanliness ≤8mg, particle size ≤500μm, dryness: no residue on journal surfaces, workpiece temperature ≤ room temperature ±5°C.

• Flexible crankshaft cleaning: Overall ultrasonic cleaning plus targeted high-pressure water cleaning plus rinsing, drying plus vacuum drying, air-conditioning cooling to workpiece unloading temperature ≤ room temperature ±5°C. Compatible with four-cylinder and six-cylinder crankshafts, main journal high-pressure cleaning, automatic nozzle change, multi-variety compatibility. Dimensions 11m×9m×4.5m, cycle time 180 seconds/piece, overall cleanliness ≤30mg, dryness: no water marks on journal surfaces and in passages, particle size ≤600μm.

The three solutions reflect different priorities: the commercial vehicle solution emphasizes pressure and deep oil gallery cleaning; the passenger vehicle solution emphasizes cycle time and conveying efficiency; the flexible solution emphasizes variety compatibility and automatic nozzle change.

IV. Camshaft Cleaning and Deburring

Camshafts and crankshafts are both shaft-type parts, but in addition to oil holes, camshafts also have cam lobes that need to be processed. Taking the camshaft robot flexible deburring and cleaning machine as an example, it removes burrs from oil holes and cam lobes. Cleaning uses high-pressure insertion cleaning for oil holes, overall cleaning, and high-pressure cleaning of external surfaces. Drying uses blow-drying plus vacuum drying. Cycle time: Model A 66 seconds/2 pieces, Models BCDE 78 seconds/2 pieces. Gantry robot loading and unloading, overall cleanliness <3mg, particle size <300μm, dryness: completely dry.

The camshaft solution has significantly stricter specifications than the crankshaft: cleanliness <3mg, particle size <300μm. The reason is that camshaft oil holes are smaller and more sensitive to particle size, and the mating surface precision between cam lobes and tappets is high.

V. Key Points for Crankshaft Cleaning Equipment Selection

• Crankshaft type: Four-cylinder or six-cylinder, passenger vehicle or commercial vehicle, determines equipment specifications and cycle time.

• Oil gallery parameters: Hole diameter, length, and number of corners determine the insertion nozzle type and cleaning pressure.

• Specification targets: Cleanliness ranges from ≤3mg to ≤30mg, particle size from 300μm to 600μm, directly determining the length of the process chain.

• Variety compatibility: For mixed-model production, consider automatic nozzle change and program switching capability.

• Temperature control: Shaft-type parts are temperature-sensitive and usually require cooling to within room temperature ±5°C.

FAQ

Q: Why does crankshaft oil gallery cleaning require such a high pressure as 50MPa?

A: Oblique oil holes have small diameters, long paths, and corners, and deposits adhere firmly. Lower pressure cannot generate sufficient impact force inside the hole to peel off and push out deposits. 50MPa is a common configuration for commercial vehicle six-cylinder diesel engine crankshafts. The actual pressure must match the hole diameter, depth, and material; excessive pressure may damage the hole opening.

Q: What is the difference between crankshaft cleanliness ≤8mg and ≤30mg?

A: ≤8mg is used for passenger vehicle crankshafts, and ≤30mg for commercial vehicle crankshafts. The difference mainly comes from part structure and OEM requirements. Passenger vehicle crankshafts are smaller with shorter oil galleries and a lower residual base, allowing stricter targets. Commercial vehicle crankshafts are larger with greater oil gallery volume, so absolute values are relatively looser. Both must simultaneously meet their respective particle size specifications.

Q: Why is workpiece temperature controlled after crankshaft cleaning?

A: Crankshafts are precision shaft-type parts. Temperature deviation from room temperature affects subsequent dimensional measurement results and assembly fit. Also, high temperature accelerates uneven evaporation of residual moisture on the surface, possibly forming water marks. Therefore, crankshaft cleaning equipment generally includes an air-conditioning cooling process to bring workpiece temperature back to within room temperature ±5°C.

Q: Can camshafts and crankshafts be cleaned on the same machine?

A: They are both shaft-type parts with similar principles, but camshafts have cam lobes and deburring requirements, while crankshafts emphasize deep-hole cleaning of oblique oil holes. The process configurations are not completely identical. In actual projects, they are mostly designed separately for each part, or a flexible model is used to achieve compatibility through program switching and automatic nozzle change.