Application Notes
Roughness Evaluation of the Side Surface of Piston Rings
Piston ring
Application
Piston rings are attached to pistons to ensure that an engine’s combustion chamber remains airtight. The sides of piston rings need to maintain a certain level of roughness as they slide against the cylinder sleeve (the liner inside the cylinder). This roughness is integral to ensuring the smooth movement of the pistons in the cylinder while minimizing the abrasion caused by friction. Verifying the surface roughness of piston rings is essential during quality management inspections. Because piston rings are thin and ring-shaped, microscopic inspection of the sides involves securing the sample vertically in a customized fixture. When the piston ring is placed on the observation stage of a microscope fixed in this position, it can obstruct the movement of the objective lens.
Piston ring secured in a fixture
Olympus’ solution
The Olympus LEXT OLS5000 3D measuring laser microscope is used to measure surface roughness.
The OLS5000 microscope, when fitted with an optional extension frame, is capable of measuring samples up to 210 mm in height, enabling the observation of piston rings mounted in a fixture.
OLS5000 microscope features
- The microscope’s extension frame enables the observation/measurement of samples up to 210 mm in height.
- Measurement performance is enhanced to 4 times the speed of the previous LEXT model.
- Superior resolution (plane resolution: 0.12 µm) achieves high-precision measurement.
- Smart scan functionality for the acquisition of high-precision data helps eliminate data inconsistencies between operators.
Laser microscopy imagery of the side surface of a piston ring
(50X objective lens; 1x zoom)
Related products
LEXT OLS5500
Hybrid 3D Optical Profilometer
- Traceable surface measurements from the nanometer to micrometer scale
- Laser scanning microscopy (LSM), white light interferometry (WLI), and focus variation microscopy (FVM) in one award-winning platform
- First 3D optical profilometer to offer guaranteed accuracy and repeatability* for both LSM and WLI measurements
- WLI mode delivers up to 40x faster measurement throughput than conventional LSM
- Exceptional precision across surfaces with in-house engineered optics
- Intuitive interface and smart automation streamline operation for users of all levels
- AI-enhanced and high-throughput workflows with PRECiV™ software integration
*Based on Evident’s internal research as of October 2025. The guaranteed accuracy and repeatability apply only if the device has been calibrated according to the manufacturer’s specifications and is in defect free condition. Calibration must be performed by an Evident technician or an Evident-authorized specialist.
LEXT OLS5100
The LEXT™ OLS5100 laser scanning microscope combines exceptional accuracy and optical performance with smart tools that make the system easy to use. The tasks of precisely measuring shape and surface roughness at the submicron level are fast and efficient, simplifying your workflow and delivering high-quality data you can trust.