Citation: Jiang, S.; Hu, K.; Zhan, Y.;
Zhao, C.; Li, X. Theoretical and
Experimental Investigation on the 3D
Surface Roughness of Material
Extrusion Additive Manufacturing
Products. Polymers 2022, 14, 293.
https://doi.org/10.3390/
polym14020293
Academic Editors: Ludwig Cardon
and Clemens Holzer
Received: 19 November 2021
Accepted: 5 January 2022
Published: 11 January 2022
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Article
Theoretical and Experimental Investigation on the 3D
Surface Roughness of Material Extrusion Additive
Manufacturing Products
Shijie Jiang
1,2,
* , Ke Hu
1
, Yang Zhan
3
, Chunyu Zhao
1,2
and Xiaopeng Li
1,2
1
School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, China;
hukehuk@163.com (K.H.); chyzhao@mail.neu.edu.cn (C.Z.); xpli@me.neu.edu.cn (X.L.)
2
Key Laboratory of Dynamics and Reliability of Mechanical Equipment of Liaoning Province, School of
Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, China
3
Department of Cultural Foundation, Guidaojiaotong Polytechnic Institute, Shenyang 110023, China;
19218793@163.com
* Correspondence: jiangsj@me.neu.edu.cn
Abstract:
Material extrusion (ME), one of the most widely used additive manufacturing technique,
has the advantages of freedom of design, wide range of raw materials, strong ability to manufacture
complex products, etc. However, ME products have obvious surface defects due to the layer-by-layer
manufacturing characteristics. To reveal the generation mechanism, the three-dimensional surface
roughness (3DSR) of ME products was investigated theoretically and experimentally. Based on the
forming process of bonding neck, the 3DSR theoretical model in two different directions (vertical
and parallel to the fiber direction) was established respectively. The preparation of ME samples
was then completed and a series of experimental tests were performed to determine their surface
roughness with the laser microscope. Through the comparison between theoretical and experimental
results, the proposed model was validated. In addition, sensitivity analysis is implemented onto
the proposed model, investigating how layer thickness, extrusion temperature, and extrusion width
influence the samples’ surface roughness. This study provides theoretical basis and technical insight
into improving the surface quality of ME products.
Keywords:
material extrusion; surface roughness; bonding neck; theoretical model; experimental
tests; sensitivity analysis
1. Introduction
Additive manufacturing has gradually developed from the initial prototype manu-
facturing to direct manufacturing and mass manufacturing, which has a wide range of
important application prospects [
1
–
3
]. Material extrusion (ME) is one of the most popular
additive manufacturing technologies, which create three-dimensional (3D) solids through
layer-by-layer manufacturing process [
4
,
5
]. It is inherently less wasteful than traditional
subtractive methods of production and holds the potential to decouple social and economic
value creation from the environmental impact of business activities [
6
]. However, due to the
stratified nature of manufacturing characteristic, there is a big gap between ME products
and those fabricated by traditional processing methods in terms of surface quality [
7
]. Since
surface roughness affects the wear resistance, fatigue strength, and corrosion resistance of
ME products, it needs to be as small as possible to maintain stability and extend the service
life of the products for application in the field of automotive, electronics, aerospace, etc., [
8
].
Up to now, the surface roughness of ME products has been mainly assessed by per-
forming iterative experiments at varying processing conditions. A lot of investigations
on the optimization of processing parameters [
9
–
12
] have been performed to improve the
surface quality of ME products, but the improvement is limited due to the small adjustment
Polymers 2022, 14, 293. https://doi.org/10.3390/polym14020293 https://www.mdpi.com/journal/polymers
