Abstract
To reduce the high surface roughness of additive manufactured (AM) products, typically a post-treatment is required. Subtractive post-treatments are often performed by hand and are therefore expensive and time consuming, whereas conventional additive post-treatments, such as pneumatic spray coating, require large quantities of coating material. Ultrasonic spray coating, in contrast, is an additive post-treatment technology capable of applying coatings in an efficient way, resulting in less material usage. In this paper, we investigate the application of the ultrasonic spray coating process and the final properties of the coated AM part by applying a thin coating to reduce surface roughness of the AM substrate and to impart hydrophobic functionality. The hydrophobic coating is applied onto flat selective laser sintered (SLS) surfaces prepared from polyamide 12 (PA12) having a surface roughness of Ra = 20 µm. The hydrophobic coating consists of 5 wt % polyvinylidene fluoride (PVDF) in acetone. The coated substrates are analyzed for roughness using a profilometer, a contact angle using a goniometer, and a coating uniformity and thickness using light and scanning electron microscopes. The layer formation applying the ultrasonic spray coating is studied and compared with layer formation using pneumatic spray coating. It is found that a roughness reduction down to 5 µm was achieved via an ultrasonic spray coating with 30 layers of PVDF solution. It is shown in cross-section electron microscopy pictures that, due to the nature of the ultrasonically generated droplets, the rough and porous surface of the SLS surface is filled with the PVDF material after which the roughness is reduced by adding a thin layer on top. In comparison to a standard industry-applied pneumatic spray coating process, the results obtained from ultrasonic spray coating show less material usage, a reduced roughness, and a better filling of the pores, obviously resulting in optimized adhesion.
Highlights
Additive manufacturing is a collective term used to describe production processes creatingCoatings 2017, 7, 208; doi:10.3390/coatings7120208 www.mdpi.com/journal/coatingsCoatings 2017, 7, 208 methods, and the possibility of using lattice structures inside the object to reduce weight, save material, and lower cost
150 μm.2.An example of a profilometry an selective laser sintered (SLS) substrate used in thisvalue work is shown
The possibilities of ultrasonic spray coating for surface roughness reduction on
Summary
Additive manufacturing is a collective term used to describe production processes creatingCoatings 2017, 7, 208; doi:10.3390/coatings7120208 www.mdpi.com/journal/coatingsCoatings 2017, 7, 208 methods, and the possibility of using lattice structures inside the object to reduce weight, save material, and lower cost. One of the issues holding back the additive manufacturing processes to be used in mass production is its inherent high surface roughness which is often not suitable for many applications. To circumvent this problem, a post-treatment is generally applied. The first route is subtractive, where the surface roughness is reduced by removing material from the object. The second route is using an additive post-treatment by apply a coating onto the object. Additive post-treatments do not remove from the initial product, meaning mechanical used in mass production is its inherentany highmaterial surface roughness which is often not suitable for many
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
