Sample Size Calculator

Evaluation Scope and Metrological Standards

Reliable batch inspection in additive manufacturing hinges on measuring enough specimens without wasting operational time or raw filament. When running small batches of 20 to 200 components, inspecting every single unit proves cost-prohibitive, whereas testing only two or three parts leaves major blind spots regarding bed-level shifts, nozzle wear, and thermal gradient drift.

This calculator establishes standard sampling sufficiency thresholds following ISO 2859-1 attribute sampling and ISO 22514 statistical process capability guidelines. By calculating sample sizing based on target confidence intervals (typically 95% or 99%) and acceptable deviation bands (±0.05 mm to ±0.20 mm), production engineers can definitively verify whether a print run complies with drawing tolerances before downstream assembly.

Process Variation Breakdown

Metrological variability in fused filament fabrication and selective laser sintering arises from multiple interacting factors. The physical location of parts across the build plate creates distinct cooling dynamics, while continuous extrusion introduces micro-fluctuations in layer adhesion. Sampling protocols must capture both positional variance across the build plate and chronological variance between sequential print jobs.

• High-precision features (bearing press-fits, alignment pins) demand a minimum sample of 12 parts or 20% of the batch size to achieve a Cpk threshold of 1.33.
• Non-critical exterior housings can be verified with reduced sample quantities (5 to 8 specimens per print plate) under relaxed 90% confidence boundaries.
• Outlier specimens exceeding 3σ from the batch mean trigger mandatory multi-point inspection of adjacent build plate quadrants.