RP part surface quality versus build orientation: when the layers are getting thinner

Abstract

Surface quality is a very important factor to be considered in determining part build orientation in rapid prototyping (RP) processes. Previous research has shown that parts built with inclined planes or curved surfaces along the build orientation have large staircase effect, thus have higher surface roughness compared to parts built with only vertical surfaces. However, as layers are getting thinner in rapid prototyping processes, the opposite might be true. In this study, a number of experiments and measurements are conducted first. In a single machine setup, two cylinders are built, one along axial direction and the other along transverse direction using an Objet® machine. Measurements have shown that surface roughness of RP parts built along the transverse direction is better than those from the axial direction. Through analysis and observation, the authors can conclude that when layers are small enough, surface curvature or slope along the build orientation may no longer be a major concern for RP part surface quality. Instead, the authors have observed that on-the-layer contour layout may cause even more serious surface quality problem. In other words, surface quality is not only dependent on build orientation, but more on scanning orientation on layers.

Evaluating the Quality Surface Performance of Additive Manufacturing Systems: Methodology and a Material Jetting Case Study

“…Chen et al [10] analyzed the surface quality of the cylindrical parts printed on the Objet EDEN 350 and observed some errors (rough surface areas) on a layer perpendicular to the scanning direction. These were caused by the lower resolution of 600 dots per inch (DPI) (0.042 mm) in the X -direction and Y -direction compared to 1600 DPI (0.016 mm) in the Z -direction.…”

“…However, Polyjet technology used on the EDEN 350 machine allows only deposition of thinner layers of 0.016 mm. In addition, Chen [10] concluded that, for very low thickness, the effect of change in layer thickness has a very low contribution toward change in surface roughness.…”

“…Based on the ISO/ASTM 52900-15 standard, the AM processes are classified as follows [4]: vat photo-polymerization (VP), binder jetting (BJ), material extrusion (ME), material jetting (MJ), sheet lamination (SL), powder bed fusion (PBF), and directed energy deposition (DED). Some examples of the technologies that fall within these processes types include stereolithography (SLA) as a VP process [5], fused deposition modeling (FDM) as an ME process [6], laminated object manufacturing (LOM) as an SL process [7], selective laser sintering/melting (SLS/SLM) as a PBF processes [8,9], 3D inkjet printing (3DP) as a BJ process [7], polymer jetting (PolyJet) and multi-jet printing (MJM) as MJ processes [10,11,12], wire and arc additive manufacturing (WAAM) and laser-engineered net shaping (LENS) as DED processes [13].…”

“…The surface quality of the parts built by the AM technologies is an important parameter, which can influence the product accuracy, minimize the post-processing operations, and enhance the functionality of the product. Within the literature, many studies focused on the surface roughness [5,6,8,10,11,12,17,18,19] of the parts made through additive manufacturing. Some studies investigated the influence of part orientation on surface roughness [7,20], for different layer manufacturing technologies such as FDM, SLS, LOM, and SLA.…”

System Performance and Process Capability in Additive Manufacturing: Quality Control for Polymer Jetting

“…It is advantageous to print a circular model that has holes standing up on the build platform, so support material does not fill the holes [38]. Additionally, if a circular model is lying down on the build platform and printed in glossy printing mode, then the surface quality is affected by some errors [41]. The experimental roughness (Ra) values for the PolyJet material jetting process are specified according to the finish type as follows: for matte finish in the range of 0.5-15 μm, and for the glossy finish in the range of 0.5-4 μm [42].…”