Coordinate Measuring Machine Baseline Calibration Steps before Equipment Relocation
Pre-move CMM baseline calibration extracts ISO 10360 error maps and thermal vibration logs to lock down machine accuracy and transfer transport liability.
Scale Linearity
Meaning
Consistency of the scaling factor across the entire measurement range of a linear encoder defines the spatial uniformity of a positioning system. Achieving high scale linearity ensures that a measured displacement of one millimetre at the start of travel is identical to one millimetre at the end. This parameter is fundamental to the accuracy of coordinate measuring machines.
Distortion Source
Manufacturing defects during the etching of the graduation lines or non-uniform thermal expansion of the scale substrate introduce spatial distortion. As the readhead moves along the axis, these variations cause the indicated position to drift from the actual position. When the environment experiences temperature changes, uneven heat distribution further degrades scale linearity across long axes.
Measurement Metric
Quantifying the deviation involves measuring the error at regular increments across the full travel length. These errors are plotted as a curve, and the peak-to-peak value represents the total linearity error of the scale. Metrologists use ultra-stable laser interferometers in controlled environments to compile this data.
The resulting curve is expressed in micrometres per metre of travel, providing a standard metric for comparing different encoder models.
Compensation Protocol
Modern motion controllers store these error curves in non-volatile memory to apply real-time mathematical corrections. This calibration corrects for static errors, ensuring that the scale linearity meets the required specifications under working conditions.