Selected Errors in Spatial Measurements of Surface Asperities

Area of Science:

• Metrology
• Mechanical Engineering

Background:

• Contact profilometry is widely used for surface roughness measurement.
• Internal heat sources in measurement devices can cause thermal expansion, leading to errors.
• Understanding these errors is vital for accurate spatial measurements.

Purpose of the Study:

• To investigate the impact of internal heat sources on the thermal expansion of a contact profilometer's X-axis drive.
• To quantify the synchronization error caused by thermal instability.
• To assess the effect of probe movement on structural rigidity and surface leveling.

Main Methods:

• Thermographic studies were employed to analyze thermal stabilization.
• Laser interferometry was used to measure structural rigidity and leveling changes.
• Contact profilometry was utilized to evaluate surface roughness measurement errors.

Main Results:

• Initial synchronization errors reached 16.1 µm on a thermally unstable device.
• Full thermal stabilization of the drive requires 6-12 hours.
• Thermal stabilization significantly reduced X-axis probe positioning errors.
• Profilometer structure vulnerability was measured at 0.8 µm over a 25 mm section due to center of gravity shifts.

Conclusions:

• Adequate thermal stabilization is essential to minimize errors in contact profilometry.
• Individual thermal stabilization times should be determined for specific device variants.
• Accounting for thermal effects and structural rigidity improves the accuracy of surface geometry evaluation.