Micro Molded Part Metrology Standards for Receiving Acceptance Inspections
Establishing rigorous non-contact metrology standards and ISO 14253-1 guardbanding protocols prevents defective micro-molded parts from entering production.
Micro Molded Part Metrology
Meaning
Dimensional inspection practices for miniature plastic components demand specialized high-resolution instrumentation. This field is known as micro molded part metrology, which governs the measurement of features measured in micrometers. The discipline does not apply to standard-sized injection-molded products with millimeter tolerances.
Measurement Challenge
Standard mechanical contact probes are often too large to touch the tiny features of microscopic components. In micro molded part metrology, the metrologist must use optical or non-contact methods to measure the dimensions of the part without deforming the plastic. The force of a physical probe can easily bend or crush a micro-scale rib or pin.
This limitation makes optical sensors and computed tomography scanners the preferred tools for these inspections.
Environmental Influence
Very small parts are highly sensitive to temperature and humidity variations in the laboratory. Because of this sensitivity, micro molded part metrology must be conducted in cleanrooms with strict temperature controls. A shift of only two degrees Celsius can cause a plastic part to expand beyond its micro-scale tolerance limits.
This environmental constraint means that the measurement room must be as tightly controlled as the molding room itself.
Instrument Calibration
Traceable calibration standards are essential to ensure the accuracy of high-magnification measuring systems. Applying micro molded part metrology requires the use of specialized glass grids or certified ruby spheres to verify the resolution of the optical system. This calibration must be performed regularly to maintain the validity of the measurements.
It provides the customer with proof that the micro-scale features are within specification.