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Excerpt 3: The Accuracy Myth: Don’t Make the Mistake of Confusing Resolution with Accuracy

Accuracy Myth WhitepaperResolution has long been one of the qualities used to evaluate the performance of an additive manufacturing system. But today, additive manufacturing systems are most commonly used to build parts that measure several inches across and have tolerances of several thousands of an inch or greater. In this situation, the resolution of the manufacturing system is much less important than its overall accuracy, the deviation between the CAD model and the measured value of the part

A Stratasys white paper, entitled "The Accuracy Myth: Don’t Make the Mistake of Confusing Resolution with Accuracy" explains how accuracy, repeatability and resolution apply to additive manufacturing. Below is an excerpt from the white paper that contrasts a machine that delivers high resolution with one that provides high accuracy along with a link to the full white paper.

Accuracy Myth white paper"High-end Fused Deposition Modeling (FDM) systems can produce parts with layer resolutions down to 0.005 in. (0.127 mm), delivering a part that isn’t as smooth as an injection molded part. However, they have an overall accuracy or tolerance of +/- 0.0035 in. or +/- 0.0015 in./in. (+/- 0.089 mm or +/- 0.0015 mm per mm), whichever is greater. This falls easily within the average tolerance for an injection molding job, which is typically 0.005 in. (0.127 mm"

"If the additive manufacturing machine’s most important requirement is to produce a part with a class-A surface finish or sharp edges, then you may need a system whose forte is high resolution. But smooth surface finish or sharp edges do not mean you have an accurate part. Consider the following image. Part one was built on a 3D printer with a very high layer resolution of 0.0015 in. (0.0381 mm). Part two was built on an FDM 3D printer using a lower-resolution setting of 0.010 in. (0.25 mm)."

High Resolution vs. High Accuracy: Color maps reveal that part one – built on a very high-resolution 3D printer – is not as accurate as part two, built using a lower-resolution setting on an FDM system. Purples and reds reveal that the very high-res printer produced deviations of +/- 0.020 in. (0.51 mm) or more. Greens reveal the FDM-built part is mostly in the +/- 0.005 in. (0.13 mm) range.

View or download the complete white paper.

Joe Hiemenz

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