Customised Post-Processing: Services NOT Offered at 3DPRINTUK

In the final article in this series on post-processing, 3DPRINTUK want to take the time to round up some post-processing options available for 3D-printed parts that they do NOT offer. In the previous article (Part 2), they focused on automated post-processing solutions that support higher volumes of 3D printed parts and reduce the cost per part with quality finishes. That said, sometimes high volumes are not the prerequisite, and a more customised approach is required.

Bespoke finishing options for single or tiny volumes of parts do not fit within our remit. Still, for clients that want our price/quality for their parts’ production, specialised and bespoke post-processing solutions are available to them. The following is not an exhaustive list, but I think it covers the most famous bespoke post processes: painting, hydrographics, texturing, CNC milling/machining, and electroplating.

PAINTING

As bespoke finishes go, painting a 3D-printed part can provide a very accurate, almost “photo-realistic” finish. This is particularly important for marketing prototypes and small-volume — or singular — artistic models.

There is no getting away from the fact that the results can be astonishing. Still, the trade-off here is that finishing this level requires a great deal of time and effort per part (not to mention the mess and technical skill), whereby the outcome is more relevant than the cost-per-part economics of mid- to high-volume production.

The 3D printing process you select to produce parts for painting will require post-processing to achieve the smoothest possible surface finish. This can include filling, sanding, and priming the part. This is generally to remove support materials, refine the surface finish to smooth it and eliminate defects on the part’s surface.

Some fillers are not set entirely and can affect the paint if you use filler material.

Another thing to remember is that the sandin3D-printednted part by hand removes material unequally from the region part, which means that the part’s dimensional accuracy can be affected.  Wearing a mask is also highly recommended for sanding.

Then there is the question of DIY or contracting out the paint finish. The application and the required outcome will be the determining factor here, for example, for an art installation versus an architectural model.

For DIY painting finishes, paint selection is essential, explicitly choosing high-quality acrylic paint, which can be used with a choice of brush, airbrush, or sprays paint. There are lots of Youtube videos out there for beginners.

Alternatively, a range of professional services utilise highly skilled model makers, of which a good number are familiar with the specific finishing requirements for 3D printed parts. For this, you generally need to build in extra time for delivery.

HYDROGRAPHICS

Also called hydro dipping or immersion printing is a water-based surface printing technique for 3D objects that have been developed over centuries. It can be applied to 3D-printed parts to produce stunning customised finishes on pieces and models. It’s messy and challenging to achieve standardized finishes on multiple models, but hydrographic is not about standardisation.

Any 3D printed part must go through the same post-processing stages as the painting outlined above to achieve the smoothest surface finish possible, plus primer. As with the image, the quality of the surface finish will determine the quality of the hydrographic, so a great deal of sanding and smoothing by other means is required to eliminate any supports, layer lines, or rough surface. Subsequently, the part is dipped in a tank of water that contains the hydrographic design using speciality inks, controlled water temperature, and the application of an “activator” chemical.

The results can be stunning, but there is a time and mess trade-off.

TEXTURING

This is a bit of a weird one — whereby textures *can* be added to 3D printed parts as a post process. But the question must be asked does it need to be done this way, or can you design the required texture into the part and print it? One of the most significant advantages of 3D printing is that you can create this sort of complex detail in a position with little to no economic difference in the cost of the part.

This is particularly relevant for functional textures of parts required for added strength, grip, traction, etc. Again, if the rationale is the aesthetic, is it possible to include it in the design? For fine details and tolerances, however, the best outcome can be to apply it post-build via etching, routing, or grinding methods, but these processes add time and cost.

CNC MILLING / MACHINING 

This is generally a post-process used for metal parts (note it can also be an alternative production method for metal parts). However, it is also possible to utilise it as a post-process for polymer parts to achieve specific goals. It is not a particularly cost-effective method for finishing high volumes of features, but it can be helpful for critical applications that require precise accuracy.

Combining 3D printing and CNC machining can provide a reliable and repeatable method for achieving tight tolerances for critical specifications, such as aerospace or medical components. For example, if a completely flat, surface-to-surface connection is required.

Services are available for both 3- and 5-axis machining of 3D printed parts. Part complexity and the finish requirements generally dictate which process is required.

One important note for this approach is to build in excess material on the 3D printed part to accommodate machining down to the exact tolerances, particularly if fine features or thin walls are involved. The downside is additional waste material, but it is not that much different from sanding.

ELECTROPLATING / METAL PLATING

This is a beneficial finish for 3D-printed polymer parts. It is a relatively complex process and requires specialist equipment and skills. However, several service providers now have dedicated facilities to provide this solution. Most polymer materials can now be electroplated, but you should discuss material selection directly with the solution provider.

Electroplating offers a realistic metal finish that can provide the benefits of both plastic and metal, including added strength and reduced weight. In addition, electroplating protects polymer parts against corrosion, improves electrical conductivity, and reduces friction. The aesthetic finish is generally excellent.  An alternative solution to full electroplating to achieve the look of metal is metallic spraying. Again, this can be achieved by specialist companies, with an example below.

ROUND UP

To round up this series of articles on post-processing, it seemed fitting to provide insight into alternative solutions that are available for a more customised approach to 3D printed parts — even though that’s not our thing. The over-arching aim of the series has been to provide 3D printing users, whether in-house or contracted out, with a comprehensive resource regarding post-processing, the pros and cons, and the options available.

The choice will come down to the application and the dominant requirements to fulfill it in the most time- and cost-effectively.

If you want to discuss post-processing requirements for medium and higher volumes of parts, reach out to our technical customer service team today.

Written by Nick Allen, Managing Director, 3DPRINTUK

Read more from 3DPRINTUK here.

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