Tools for 3D Printing

Sanding blocks, file, sanding sticks, and a red-handled tool on a white surface.

As seen in the January 2024 issue of Model Aviation.

BECAUSE OF THE WAY that 3D printing technology works, printed parts generally need some post-printing work done to them before they are assembled. 3D-printed parts can have random bumps on them or imperfections on the surface that need to be removed.

One of the tools that I have found useful for this is a Scotty Peeler label scraper. It is great for removing surface artifacts that might appear on printed parts, such as stringing remnants, or on excess filament from a layer change. The edges of the scraper are sharp like a razor blade, and a quick swipe will slice off any imperfection. This is probably my favorite "new tool" that I’ve added to my modeling room.

Metal blade with text "www.scottypeeler.com" against light background. — The Scotty Peeler label remover is an excellent tool for the removal of surface imperfections and artifacts.

Another tool that I use often is a cabinet scraper. Originally intended for woodworking, this flat piece of metal has a sharp edge that can also be used to remove surface artifacts and imperfections. I like to print parts with a wide brim to prevent them from lifting off of the build plate. When I remove the brim from the part, there is often a small lip of extra plastic that needs to be removed. The cabinet scraper works very well for removing this small lip quickly. Sanding can be done, but the scraper gives a nice, clean edge. Cabinet scrapers are sold in different shapes; you will want a mix of straight and curved scrapers.

Metal French curves on a white background. — Cabinet scrapers are used to remove any flash left on part edges.

Sanding sticks are another useful item. The sanding sticks I use are just emery boards for fingernails. You want the ones that are rigid, not the ones with a foam core in the middle because the foam bends easily when sanding. I use these sticks mainly on the joints where parts are glued together.

Red electric file with two orange nail buffers. — A battery-powered rotary tool and sanding sticks are great for getting good fits on overlap joints.

Many designs have a small overlap where parts are glued together. Typically, there is a small radius where the parts overlap (because of how the plastic flows from the nozzle). This radius can lead to a bumpy seam line if it’s left "as is." The sanding stick is used to remove some of the radius on one side of the joint and to add a slight chamfer to the mating side of the joint. I recently started using a battery-powered rotary tool to add chamfers to mating parts. A low-rpm rotary tool that runs on a single-cell lithium battery works great for this because it does not melt the plastic like a high-rpm tool.

Sanding blocks can be used over large surfaces like wings and fuselage sections to help smooth out the finish of printed surfaces. A 3D-printed part is made up of many small layers, and sanding is required to smooth out the finish for those layers. I tend to use foam-style drywall sanding blocks because they can conform to curved surfaces easily when sanding.

Stacked sanding blocks labeled 60, 80, 120, 220 on a light wood surface. — n assortment of foam sanding blocks of various grits and shapes are needed for the general sanding of printed surfaces.

Brown strip with "180" on a textured light gray background. — A rounded-edge sanding block is great for getting into fuselage contours.

Sanding is not mandatory on a 3D-printed airplane. I have flown many with no finishing done to the surfaces, but if you intend to paint the model or add decals or vinyl lettering, sanding is recommended so that there is a flatter surface to which the decals and vinyl can adhere.

Painting

When painting a 3D-printed airplane, take care in selecting the paint because it must be compatible with plastic. I have been using Krylon Fusion on my polyactic acid (PLA) and lightweight LW-PLA-printed airplanes with no issues. The solvents that they use do not harm the plastic.

A lacquer-based spray paint will cause the plastic to sag when it’s applied and will ruin your model, so stick with paints that are plastic friendly. With Krylon Fusion, I do a light sanding before applying the paint. As with any spray painting, it is better to spray many thin layers instead of fewer thicker ones. I also like to spray on a coat of Krylon Clear after the paint is applied.

Waterslide Decals and Vinyl

I have experimented with both waterslide decals and vinyl decals on 3D-printed models. Waterslide decals that are printed on an inkjet printer will work, but the area to where the decal is applied must be smoothed out either by sanding or by building up layers of paint or clearcoat. A decal applied directly to an "as-printed" surface will fall off after it has dried.

It’s been reported that applying a few coats of clearcoat to the area where the decals will be applied will help them to adhere, as well as applying a clearcoat after they have dried. So far, I have had mixed results with waterslide decals because sometimes they do come loose over time, even if I prep the surface. A thin mixture of white glue and water has worked to get any loose spots reattached.

Vinyl decals have worked the best for me in the long run compared with the waterslide decals. After several attempts with vinyl, I have found that it needs to be of good quality but also not too thick to conform easily. I tested some vinyl trim and registration numbers for a J-3 Cub with a budget vinyl and it fell off of the airplane overnight. It just curled up and would not stick. After some research, I tried a brand called ORACAL 651, and it made a huge difference. So far, it has stayed on long term with no curling or lifting edges.