Vapour Smoothing Markforged CFR Parts with AMT PostPro3D Technology


One of the beautiful characteristics of Markforged CFR (carbon-fibre reinforced) parts is they are smooth right off the print bed, so no post-processing is needed to make them good enough for consumer-facing applications.

But what if you want them even smoother?

In that case, you want to use AMT PostPro automated technology. AMT uses a patented chemical vapour smoothing process that effectively post-processes additively manufactured thermoplastics, including composite parts.

All things considered, automated smoothing is best, and no machine does it better than the AMT PostPro. Here’s what you need to know:

Why AMT?

Prior to AMT vapour smoothing, if you wanted to make Markforged CFR parts smoother, you had two options:

  1. Mechanical post-processing e.g. sanding, polishing
  2. Chemical post-processing e.g. acid baths, acetone vaporised nitric acid or acetic acid

The problems are obvious: manual post-processing is inconsistent and takes too much time, and chemical post-processing can degrade parts.

AMT PostPro technology gives us reproducible, smooth parts, without compromising the part’s geometry or mechanical properties. It does this with a new vapour smoothing process that has been tested and verified by Markforged.

How it works

Vapour smoothing is a finishing technique for additively manufactured parts that improves surface finish by removing a very thin layer of surface plastic.

The first vapour smoothing machines were effective but would often compromise the mechanical properties of parts, creating issues with stiffness, strength and flexibility due to chemicals eating into the plastic.

In the case of Markforged CFR parts, the opposite problem exists, because Onyx filament has strong resistance to solvents and petrochemicals, rendering acetone-based vapour smoothing ineffective. To smooth Onyx, you need to use dangerous acids and solvents that most people do not have access to or the means to use safely.

AMT PostPro

With AMT PostPro, parts are suspended in a chamber and exposed to solvent vapour. The vapour condenses on the parts, smoothing the polymers at the surface. After processing, the machine heats back up, causing the solvent to re-vaporise. It is extracted from the parts and the processing chamber. Parts are then thoroughly dried in the processing chamber, leaving behind just a newly smoothed surface.

Testing and results

Markforged tested the efficacy of AMT PostPro technology and found it to be an effective and efficient way to smooth CFR parts.


Their tests found that AMT post-processing actually enhances the mechanical characteristics of many parts, with no degradation found.

Here’s a snapshot of their results:

  • +24% – Onyx XY Tensile Stress at Yield
  • +74% – Onyx XY Young’s Modulus
  • +19% – Onyx XZ Young’s Modulus
  • 80% – Average reduction in surface roughness across tested surfaces

The last point – an 80% average reduction in surface roughness across tested surfaces – shows just how effective the smoothing process is.

Find out more

AMT PostPro systems is now available at Additive-X. Contact our award-winning team on 01765 694 007 or email to find out more.