Chemical Smoothing / Vapor Smoothing
Vapor Smoothing at 3Faktur
Illustration: AMT SF 50 at 3Faktur / Source.
3Faktur works with the PostPro SF 50 vapor fusion system from the British manufacturer AMT. You can order this service at 3Faktur for all ordered PA 12 components ordered.
Functionality of the Chemical Smoothing
Illustration: Functionality of Vapor Smoothing / Source: AMT / Youtube
In chemical smoothing, the components to be processed are exposed to a vaporized solvent in a closed chamber. The solvent condenses on the surface leading to a partial loosening (“melting”) of the surface, which is often rough on 3D printed components. The liquefaction of the surface closes pores and smoothes out small irregularities. The result is a smooth, virtually pore-free surface.
We currently offer Vapor Smoothing only for the material polyamide 12 (PA 12). There are four main fields of application for this finishing process: Visible parts, gas- or liquid-carrying components, simplified cleaning and improvement of mechanical load-bearing capacity.
Gas- or Liquid-Carrying Components
Figure: Example of liquid-bearing component processed with Vapor Smoothing / Source: AMT.
The Multi Jet Fusion process can be used to produce components with a high density, which are often already ‘tight’ when unmachined with the appropriate wall thickness. However, the relatively high porosity of the surface can be problematic. Gases can escape through these pores or liquids can ‘migrate’ along the surface due to capillary effects, resulting in leaks.
Chemical smoothing completely closes surfaces. The machined components are thus particularly suitable for applications in which leak tightness is functionally necessary.
Simplified Cleaning or Reduced Microbial Adhesion
Figure: Water-repellent properties contribute to easy cleaning / Source: AMT
The typically rough surfaces created in powder-based 3D printing are difficult to clean. Due to the porosity of the surface, liquids are literally absorbed. However, in applications such as clean rooms or medical and laboratory diagnostics, cleaning or disinfection is mandatory.
Chemical smoothing reduces the roughness. At the same time, all pores are closed, which leads to a hydrophobic effect on the surface (see figure). As a result, the components are much easier to clean and can be used in sensitive areas. The lower surface roughness thus also leads to reduced microbial adhesion.
Due to the gloss and pleasant feel achieved, small to medium-sized additively manufactured components in particular can hardly be distinguished from injection-molded parts after vapor smoothing.
For larger surfaces or components, technically induced surface effects, such as print head lines, can be enhanced. However, excellent results can be achieved with a targeted digitally incorporated surface structure (e.g. pyramids, organic structures such as wood or leather structures).
Improvement of Mechanical Properties
The porosity of the surface is only a few tenths of a millimeter thick (approx. 0.1 -0.2 mm). For wall thicknesses of >3 mm, the influence of the surface on mechanical stability is negligible. For thin wall thicknesses, however, the situation is different; especially for very thin wall thicknesses (< 1 mm), the surface essentially determines the mechanical properties. Microcracks caused by the porosity reduce the stability considerably.
Vapor smoothing significantly reduces the roughness and largely closes microcracks, resulting in improved load-bearing capacity, which is expressed, for example, in an approx. 25% improvement in elongation at break. This effect decreases with increasing wall thickness.
This is relevant for film hinges, grid structures, printed threads, protruding or other filigree elements.
Special Features of Chemical Smoothing
The components are suspended from a fixture and pushed into the processing chamber. There they are exposed to the vaporized solvent for only a few seconds, which condenses on the component surface and acts there for a few minutes. This is followed by a drying process of approx. 30 – 45 minutes, during which the solvent evaporates completely from the surface. The chamber is completely hermetically sealed during processing and drying. Following drying, the fixture is removed from the chamber and the machined components are removed from the fixture.
Most components can be easily hung from existing structures. However, some geometries require an additional structure to allow or facilitate hanging.
FAQ Chemical Smoothing
What are the processing costs per component?
The unit costs are calculated primarily according to the size and surface of the component. In general, the costs are in the low to mid single-digit EUR range per component, but with a minimum charge of EUR 25 plus VAT for one component geometry. Based on your CAD data you can calculate the costs in our online calculator calculator.
Do I have to add structures to the component so that it can be suspended in the machining chamber?
If the geometry of your component is not suitable for optimal suspension in the chamber, we will contact you. If it is necessary to attach a structure, you can do it or we can do it. In the latter case, of course, in consultation with you.
Do the dimensions or accuracy of the component change?
The changes are minimal and typically less than 0.4%. In the case of large, flat objects, which are already susceptible to warpage in printing, warpage or intensification of warpage effects may occur.
Does edge rounding take place?
Processing takes place in the µm range and has no noticeable effect on edges. Only very filigree elements, especially lettering, may become somewhat ‘blurred’ as a result of processing.
Do the mechanical properties of the material change?
In the Multi jet Fusion process, the 3D printed material is dense on the inside (approx. 98 – 100% dense), but the surface is porous. The smaller the wall thickness, the more the property of the surface affects the overall behavior and reduces the mechanical load capacity accordingly.
By reducing the porosity during chemical smoothing, the mechanical load capacity of thin wall thicknesses is increased. The process thus has a positive effect on the load-bearing capacity.
However, the thicker the wall thickness, the smaller this effect.
Does solvent remain on the material?
The manufacturer of the process assures that no significant amounts of solvent remain on the material. Our own analyses of this have so far confirmed this statement.
Does chemical smoothing extend the production time of the ordered components?
In the case of a combination with black coloring, the production time can be extended by up to 1 working day. This is due to the drying phases required for both processes, which usually cannot be carried out on the same working day.