CYLINDER LINER HONING (PURPOSE, HONING TEXTURE, ANGLE & PROCEDURE)

Honing is a well-adapted and widely used cylinder liner surface finishing process. Honing process produces a precision surface inside surface of a cylinder liner by scrubbing an abrasive stone against it along a definite path. Honing is primarily used to improve the geometric & texture of the surface.

Why honing necessary:

The mechanical power loss in the engine accounts for about 16% of the total energy losses in the engine and half of this loss is caused by friction in the piston-liner. Oil consumption with unwanted of combustion products such as HC-, CO-, CO₂, NOx  gas and particles emission can be controlled by the liner surface topography. It also reduce oil slobber.

Honing Angle & Surface Texture:

The honing angle and texture should me such that it will increase cylinder liner working life. In conventional plateau honing the angle kept straight. Slide honing can generate more ideal plateau on liner surface. Diagonal honing or helical honing is more consistent way. 

Fig: Honing Texture

Helical honing reduce cylinder wear 40% less than conventional plateau honing.

The honing angle should be above 20°, generally 40° to 50°.

Honing tool:

Honing Machine- The selection of honing machine depends on to the honing process (vertical or horizontal honing), honing angle, definite depth of honing, bore diameter, stroke length etc. It should be selected according to the engine manufacturer recommendation.

Honing stones-Normally diamond abrasive stone used but for smoother liner surface SiC ceramic honing stone used.

Honing procedure:

-Select honing machine and stones (oil stone) according to engine manufacturer.

- Install abrasive stones on rotating jaws.

Fig: Honing stone attached with jaw

-Install honing machine and adjust reciprocating motion -stroke length, Stroke per minute, rotating motion- rpm and surface pressure of the rotating jaws.

Fig: Honing stroke length limit switch

Fig: Honing speed setting knobs

- Start honing according to described procedure of the machine.

- Continue the process as long as the desired surface roughness achieved.

Fig: Honing process inside cylinder liner

- After that clean the surface with cleaning brush

Fig: Cylinder liner inner surface cleaning brush

The finishing of the cylinder liner surface results in a criss-cross patterned topography consisting of a series of honing valleys of different density, peak radii, depths and widths related to selected machining parameters (speed, feed and surface pressure) along with selection of honing tool composition of grain size, grain material (diamond or SiC), binding material and grain density.

Cylinder liner honing video: