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The build is complete and your component lies cooling in the print bed. But when it comes to additive manufacturing – or any other manufacturing discipline, for that matter – the finishing touches cannot be overlooked. 

You’ll often hear AM advocates talk about 3D printing post processing. Virtually all 3D-printed parts require some level of aftercare, and it’s worth putting a little thought to this, as the 3D printed surface finish you choose can transform both the part’s appearance and performance under real-world conditions.     

Here’s an introduction to 3D print surface options and the benefits they can bring to your AM build.

What is the best surface for 3D printing?

3D printing post processing shouldn’t be an afterthought, but a consideration built into the design stage of every component. After all, the finish you apply can make or break the functionality of your product in its end-use environment.

Here are some of the most common 3D print surface finishing techniques.

 

Painting

The most familiar and self-explanatory post processing method of all, painting can be used for anything from improving an object’s aesthetics to sealing the surface and boosting resistance to heat and chemicals. As with any painting job, an initial layer of primer (and often a putty filler) should also be applied. 

 

Plating

Applying a thin layer of metal is a popular 3D printing post processing option, often used to make plastic parts more hard-wearing. This method can also increase resistance to corrosion and oxidation, improve heat transfer or electrical conductivity – or simply give a component more visual appeal.

Plating is achieved by exposing the part to an electrical current or chemical solution, and you’ll commonly see a first layer of nickel or copper applied, followed by additional layers of chrome, tin, platinum, palladium or rhodium.

 

Sanding

You’ll notice that AM parts often show the microscopic lines where each new layer has been printed. Depending on the application, that might not matter: nobody is going to notice the tiny visual imperfections of a component used in heavy industry. But AM is used in countless sectors – from fashion to film sets – where aesthetics definitely do matter, and that’s where sanding comes in. 

As the most fundamental of the 3D printing post processing techniques, sanding is really no different from the age-old method of rubbing down a jagged length of wood with sandpaper. It’s well worth taking this step, as it will not only improve the part’s appearance but also make it easier to coat and/or paint. 

 

Bead Blasting

The downside of sanding is that you can’t reach every hidden nook and cranny of an intricate part. In these instances, bead blasting is ideal. The process sees a spray of finely reground thermoplastics fired at the component to optimise a less-than-perfect 3D print surface. Just be wary of concentrating too hard on a given area and creating divots or dents.

 

Shot Peening

At first glance, there are similarities between bead blasting and shot peening, which sees microscopic beads fired at the surface of a component. However, there’s quite a different end goal in mind with shot peening, which creates compressive stress in the part and ultimately makes it more resilient.

 

Heat Treatments & HIP

The risk of a 3D-printed part failing can be dramatically reduced by using one of the various vacuum furnace heat treatments available, which balance out stress areas and increase density. To further boost the performance of a given component in a harsh environment, Hot Isostatic Pressing (HIP), eliminates pores and offers unrivalled strength. 

 

Vibratory units

Metal parts, in particular, will often be placed in a vibrating unit containing ground-up plastics or ceramics (the critical point is that whatever you use must be softer than the component itself). The pulsating of the unit causes the granules to strike the component and polish it in the process. It’s highly efficient, allowing you to process several parts at once.

 

Tumbling

Similar to the vibration process with one important difference: tumbling sees parts rotated in a drum, rather than vigorously shaken, and as such is often a better option for more fragile components.  

 

Vapour Smoothing

When the goal is a shiny 3D print surface – rather than a matte finish – vapour smoothing is well worth investigating. The process sees the part placed in a vapour chamber, where its surface is melted with a solvent – before liquefaction is stopped by rapidly reducing its temperature in a cooling chamber. Not only does the part retain its shape but any pores are filled and the surface sealed.

If a component is too large to fit in a vapour chamber, dipping it directly into a solvent is a common alternative. Yet another option for sealing the surface is to apply an epoxy coating, either by hand or by immersing the part in a resin.

 

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