If you have successfully mastered the challenges associated with printing from ABS, which we discussed in the previous part, a world of advanced surface finishes opens up for you. It is precisely in this area that ABS absolutely excels and offers possibilities that PLA users can only dream of.
The best known of these is undoubtedly chemical smoothing with acetone, which can transform a layered print into a perfectly smooth and glossy object. Let’s look at how to do this, and also explore other techniques that will turn your ABS print into a masterpiece.
Chemical Smoothing: From Layers to Perfection
A unique property of ABS is its solubility in acetone. This can be used for a technique called acetone vapor smoothing, which effectively “melts” the surface layer of the plastic and thus smooths out all traces of individual layers.
Principle and Safety First
STRONG WARNING: Working with acetone and its vapors is dangerous. Acetone is highly flammable and its vapors are irritating and harmful to health. Always work in a well-ventilated area, away from sources of open flame, and use protective equipment (gloves, goggles, respirator).
The principle is simple: an ABS print is placed in a closed container, at the bottom of which is a small amount of liquid acetone. Acetone vapors gradually condense on the surface of the model and begin to etch it. This causes surface irregularities to merge together, creating a perfectly smooth and glossy surface that resembles an injection-molded product.
Step-by-step procedure
- Preparation: Find a suitable, well-sealing container (ideally glass or PP plastic) and create a small platform inside it (e.g., from aluminum foil) on which the model will stand, so that it does not come into direct contact with liquid acetone.
- Acetone Application: Place paper towels soaked in acetone at the bottom of the container to increase the evaporation surface area.
- Exposure: Place the model on the platform, carefully close the container, and allow the vapors to act. The exposure time varies depending on the size of the model and the concentration of vapors, typically ranging from 10 to 30 minutes. Visually monitor the process constantly.
- Removal and Curing: Once the surface is sufficiently smooth, carefully remove the model and let it cure completely in a well-ventilated area for several hours to days. During this time, the surface is soft and susceptible to damage.
Advantages:
- Perfectly smooth and glossy surface.
- Fast process (compared to sanding).
Disadvantages:
- Loss of sharp edges and fine details.
- Slight change in model dimensions.
- Safety risks.
Traditional Methods: Sanding, Filling, and Painting
If you need to maintain sharp edges or prefer mechanical finishing, ABS is an excellent material for this.
Sanding and Filling
Unlike PLA, which easily heats up and “pills” when sanded, ABS sands much better. Both dry and wet sanding can be used. For filling larger irregularities or joints between glued parts, it is ideal to use two-component body filler, which is easily sanded smooth after curing.
Gluing and “Welding”
ABS parts can be joined very strongly. In addition to standard super glues or epoxy adhesives, so-called chemical welding can also be used. By applying a small amount of acetone to the surfaces to be joined, the plastic is slightly etched, and when pressed together, the parts literally weld into a single monolithic piece. This joint is extremely strong. This technique is ideal for printing large models that need to be divided into multiple parts.
Painting
ABS accepts paint very well. After thorough sanding and degreasing of the surface, it is crucial to apply a layer of primer. This unifies the surface and ensures perfect adhesion of the final paint. Subsequently, acrylic spray paints or modeling paints applied with a brush or airbrush can be used.
Mastering ABS post-processing will take your prints to a whole new level of quality. Despite the more demanding printing process, it is this versatility in finishing work that keeps ABS at the forefront of technical materials.
In the final part, we will look at modern alternatives to ABS, such as ASA, and explore composite variants that push the boundaries of strength even further.
