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Hello, Daan! Great question –

Just a quick addition here: I also had a quick check of a few parts we have in stock at the Xometry office: We measured the dimensions of a few identical MJF PA12 parts as printed vs vapor polished ones with a digital caliper, and we didn’t see any substantial differences outside of the regular dimensional accuracy ranges of MJF (±0.2 mm up to 100 mm and 0.2% above that value). Attaching a couple of pics for reference, but we overall compared 8 different samples  

[Daan Bakker]

Hi everyone,

I’m exploring vapor polishing for PA11 SLS parts. Concerned about how it might affect part tolerance and dimensional accuracy. Does anyone have insights or experiences on the dimensional changes to expect for PA11/PA12 (SLS or MJF 3d printing)? Tips on maintaining tight tolerances while improving surface finish would be great too!

Thanks in advance!

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[Attila Szucs]

Hello Daan,

It’s fantastic to see you venturing into vapor polishing for SLS parts. This process can indeed enhance the surface finish of PA11 and PA12 parts, making them smoother and more aesthetically pleasing. Given your concern about maintaining dimensional accuracy, here’s what you need to know:

Understanding Dimensional Changes:

• Vapor polishing works by slightly melting the outer surface of the part, smoothing it in the process.
• PA11 and PA12, being semi-crystalline polymers, are susceptible to minor dimensional changes due to this outer layer alteration.
• Typically, the change is in the range of a few microns but can vary based on the part’s geometry and the exact conditions of the vapor polishing process.

Tips for Maintaining Tight Tolerances:

1. Test and Measure: Before proceeding with production parts, test the vapor polishing process on a few sample parts. Measure these pre- and post-polishing to understand the average dimensional change you can expect.
2. Adjust Part Design: If you consistently see a certain degree of shrinkage or dimensional change, consider adjusting your part designs to compensate.
3. Controlled Environment: Ensure the vapor polishing process is conducted in a controlled environment, with consistent temperature and exposure time to minimize variations.
4. Layer Thickness Consideration: Parts printed with finer layer thickness might show less noticeable changes after vapor polishing due to their already smoother surface.
5. Post-Process Measurement: Always measure your parts after vapor polishing to ensure they still meet the required tolerances. Consider using this data to further refine your process.

Experiences with PA11/PA12:

• Both materials are known for their durability and flexibility, which is retained after vapor polishing.
• Dimensional changes are typically minimal but more noticeable on edges or thin features.
• Anecdotally, some have reported up to a 0.5% change in dimension, though this is highly dependent on part design and polishing conditions.

Conclusion: Vapor polishing can significantly improve the surface quality of PA11 and PA12 parts. By carefully controlling the process and adjusting for any dimensional changes, you can maintain tight tolerances while achieving a superior finish. As always, experimentation and precise measurement are key to refining your approach. Should you have further questions or need more detailed advice, feel free to reach out. Happy to help you navigate these advanced finishing techniques.

Best wishes, Attila

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[Evgeny Misnikov]

Hello, Daan! Great question –

Just a quick addition here: I also had a quick check of a few parts we have in stock at the Xometry office: We measured the dimensions of a few identical MJF PA12 parts as printed vs vapor polished ones with a digital caliper, and we didn’t see any substantial differences outside of the regular dimensional accuracy ranges of MJF (±0.2 mm up to 100 mm and 0.2% above that value). Attaching a couple of pics for reference, but we overall compared 8 different samples  

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[Daan Bakker]

Thank you for the info!

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[Manon Bouriaud]

Hi Daan, to give you a comprehensive overview, I also recommend checking out a video we’ve created on vapor smoothing. It’s quite informative and visually demonstrates the process and its effects on 3D printed parts. You can watch it here: https://youtu.be/1LoPp8gc5yI?si=O8LgbiTRYpdwsAW9

We also ran a few experiments on 3D prints and it turned out that you can achieve a much smoother surface without affecting the parts’ dimensional accuracy with vapor smoothing. We have an in-depth article on this finishing process, you can have a look here: https://xometry.pro/en-eu/articles/3d-printing-vapor-smoothing/

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