Why is honing important?
Honing has to do with how – scrubbing with abrasive (as opposed to an operation that produces chips), of which common objectives include getting a specific finish or very finely toleranced geometry. During routine maintenance, besides calibration of cylinder liner diameter and visual inspection of liner surface, honing patterns, liner surface quality, and roughness should be carefully examined and, if needed, restored. The quality of the liner surface is very important for the even distribution of lubrication oil and the proper operation of the piston rings.
When is honing necessary?
To produce state-of-the-art surface finishes without compromising productivity, a multistep honing process, combining rough honing with peak or plateau honing, is used. The honing process’s outcome depends on many parameters, including the machine type, working conditions, tools, process fluid, and, most importantly, the operator experience.
For restoring liner surfaces, honing is the method that is recommended by engine makers. At the honing rigs at our workshops in Piraeus and Tuzla or onboard the vessels, we make sure to perform honing each time using the appropriate honing stones for achieving the suggested roughness values and honing pattern.
Other uses of honing
Besides restoring the surface quality, honing of liners can also be used to repair liners contaminated with cat fines that have suffered scuffing, corrosion damages or scratches and hit marks. In such cases, honing using special cutting diamond stones can remove damaged material and save the liner from scrapping. At Injegov, we perform honing using our Chris marine honing machines onboard and at our dedicated honing rigs.
When Honing (abrasive flow machining), the amount of Material Removal can be controlled to remove as little as 002”.
It will depend on the case and target the customer sets, along with our experts’ guidance. The rougher the starting surface finish is, the more material removal will be needed to achieve the best finish possible.
Common misconceptions regarding cylinder liner honing
Owners should be aware, though, of some common misconceptions regarding cylinder liner honing:
1st Honing method is not the same for all liners of all makers. Different liners require different roughness and honing patterns which in turn require different honing stones and arms.
2nd Honing stones and tools must be kept in good condition as they directly affect the quality of the honing procedure. Damaged grinding stones or improper tool operation will result in substandard results.
3rd Honing is not machining! Although honing can remove material and surface damages (especially using diamond stones) and can marginally improve overall liner geometry, honing cannot completely remove ovality from liners!
Also good to know:
How much does honing remove from the cylinder?
When Honing (abrasive flow machining), the amount of Material Removal can be controlled to remove as little as. 002” and will depend on the case and target set by the customer, along with our experts’ guidance. The rougher the starting surface finish is, the more material removal will be needed to achieve the best finish possible.
Is cylinder honing necessary?
When replacing piston rings with new, it is always preferable to restore the liner surface by honing! Honing creates small pockets on the liner surface, trapping oil and ensuring proper cylinder lubrication.
So, do I need new rings after honing?
Yes, the new rings need a fresh honed surface to bed in, even if the original honing pattern is visible. The honing pattern holds vital oil for the ring; it lubricates, cools, and removes wear particles.