Applying vapor polishing to your next 3D printed model

When it comes to finishing 3D printed parts, there are more options available than ever before. In today’s tutorial, we’ll be looking at a highly effective, hands-free method of achieving a smooth finish for your plastic parts: vapor polishing.

What is vapor polishing?

Vapor polishing is a technique for polishing plastics that utilises vapor from solvents to gently melt the surface of a part, causing it to subtly ‘flow’. The printed part is suspended above a chemical bath in an enclosed space, so every area is exposed to the fumes for just long enough to smooth it out without causing any deformation.

This results in a uniform, glossy finish, without any need for sanding or polishing by hand. Similar techniques involve actually dipping the part in a solvent bath, or applying the chemicals via an aerosol, although neither of these can deliver the consistency vapor polishing does. Furthermore, acetone is an effective way of finishing a part without risking the loss of surface details or damaging fine structures — something that can be extremely challenging when polishing parts manually.

For 3D printing applications, gaseous acetone is the most commonly used solvent, although acrylic cement may be used for acrylic parts. As acetone evaporates naturally at room temperature, it is not necessary to heat it, although you may find that a little gentle heating can help speed up the finishing process. A ‘hot plate’ can be useful in this regard, allowing you to heat the chemical bath in a controlled manner.

Vapor polishing is a highly effective choice for finishing medical parts, as it will work on a part’s interior dimensions, as well as the surface. This helps guarantee that the interior of the part is completely free of debris, ensuring that it will be suitable for medical applications and meet all the relevant regulations.

How to achieve a first-class result

• Check your material specifications. Certain 3D printable plastics — nylon materials, for instance — are designed to be resistant to solvents, so vapor polishing is unlikely to prove effective. ABS, on the other hand, responds extremely well to this treatment, so it’s very much a question of choosing the right tool for the job.
• Parts with very rough surfaces are more difficult to vapor polish. In such cases, a little light sanding beforehand will likely produce a higher quality result.
• Do not overexpose your part! Timing is essential here, as too much exposure to acetone fumes will result in part deformation. 15 minutes is the absolute maximum length of time a part should be exposed to acetone fumes. Check your part every five minutes during finishing and remove it at the first sign of warping.
• Give your part time to solidify after treatment. This is important, as the plastic will have a ‘sticky’ feel when it’s removed from the acetone. Do not touch it during this time, as you will leave finger marks and risk damaging it. Leave the part in a well-ventilated area for at least 30 minutes to give it time to properly solidify.
• Certain materials, such as polycarbonate, may require an annealing cycle after vapor polishing to avoid stress cracks. Again, consult your material specifications if you are in any doubt.

Health & safety first!

Bear in mind that the fumes used in vapor polishing can be toxic, so always work in a well-ventilated area, and wear proper hand and eye protection throughout. If you will be using vapor polishing techniques on a regular basis, we would recommend creating in a dedicated polishing station within your workspace. Otherwise, you might consider outsourcing this part of the post-processing stage to a company with specialist facilities for it.

One very important point: if you are using different solvents for different 3D printed materials, always make sure your chemical bath is cleaned thoroughly after each treatment. Certain solvents are highly dangerous when mixed, so do not leave anything to chance.

An effective finishing tool for AM professionals

While vapor polishing is certainly not suitable for every application, it is definitely another useful finishing tool in the AM professional’s arsenal, and can make the post-processing stage for plastic parts for more efficient and effective. We would strongly encourage you to explore it if you are not already!