As additive manufacturing is used more frequently to produce short-run production parts and manufacturing tools, like jigs and fixtures, engineers need to consider how well the parts hold their dimensions over time. The main controlling factor in assessing dimensional stability is the production material.
A Stratasys white paper, entitled "The Accuracy Myth: Don't Make the Mistake of Confusing Resolution with Accuracy" addresses the question of long-term stability of parts produced by additive manufacturing along with other important issues such as resolution, accuracy and repeatability. The fourth in a series of excerpts from this white paper is included below, along with a link to the full paper.
Sheku Kamara, director of the rapid prototyping lab at the Milwaukee School of Engineering cites three repeatability considerations:
1. From part to part in a single build on a single machine
2. From part to part in multiple builds on a single machine
3. From part to part in multiple builds on multiple machines
To scrutinize the repeatability of the FDM (Fused Deposition Modeling) process, two exhaustive studies analyzed thousands of dimensions over hundreds of parts manufactured on multiple systems. One study showed that the large-format, production-oriented FDM Production 3D Printer had a standard deviation of just 0.0017 in. (0.043 mm), which means that 99.5% of all dimensions were within +/- 0.005 in. (0.13 mm). The other study showed that the multi-purpose – prototyping and production – systems studied produced 95.4% of all dimensions within +/- 0.005 in. (0.13 mm), for a standard deviation of 0.0027 in. (0.069 mm).
View or download the complete white paper: Don't Make the Mistake of Confusing Resolution with Accuracy.