Research Papers

Analyzing the Effects of Temperature, Nozzle-Bed Distance, and Their Interactions on the Width of Fused Deposition Modeled Struts Using Statistical Techniques Toward Precision Scaffold Fabrication

[+] Author and Article Information
Prashanth Ravi

Department of Mechanical and Aerospace
The University of Texas at Arlington,
Box 19023,
Arlington, TX 76019-0023
e-mail: prashanth.ravi@uta.edu

Panos S. Shiakolas

Department of Mechanical and Aerospace
The University of Texas at Arlington,
Box 19023,
Arlington, TX 76019-0023
e-mail: shiakolas@uta.edu

Avinash Dnyaneshwar Thorat

Department of Industrial, Manufacturing and
Systems Engineering,
The University of Texas at Arlington,
Box 19023,
Arlington, TX 76019-0023
e-mail: avinash.thorat@mavs.uta.edu

1Corresponding author.

Manuscript received October 28, 2016; final manuscript received January 30, 2017; published online March 8, 2017. Assoc. Editor: Zhijian J. Pei.

J. Manuf. Sci. Eng 139(7), 071007 (Mar 08, 2017) (9 pages) Paper No: MANU-16-1576; doi: 10.1115/1.4035963 History: Received October 28, 2016; Revised January 30, 2017

Fused deposition modeling (FDM) is currently one of the most widely utilized prototyping technologies. Studies employing statistical techniques have been conducted to develop empirical relationships between FDM process factors and output variables such as dimensional accuracy, surface roughness, and mechanical properties of the fabricated structures. However, the effects of nozzle temperature (T), nozzle-bed distance (NBD), and their interactions on strut width (SW) have not been investigated. In the present work, a two-way factorial study with three levels of T and NBD in triplicates was undertaken. A fixed-effects model with interaction was proposed and remedial measures based on the error analysis were performed to obtain correct inferences. The factor main/interaction effects were all found to be statistically significant (p < 0.05) using analysis of variance (ANOVA). Multiple comparisons were conducted between treatment means using the Tukey's method. A multiple linear regression (MLR) model (R2 = 0.95) was subsequently developed to enable the prediction of SW. The developed MLR model was verified experimentally; by (1) the fabrication of individual struts and (2) the fabrication of single-layer scaffolds with parallel raster patterns. The percentage error between the predicted and observed widths of individually fabricated struts was 3.2%, and the error between predicted and observed SW/spacing for the single-layer scaffolds was ≤ 5.5%. Results indicate that a similar statistical methodology could be potentially employed to identify levels of T and NBD that yield defined width struts using open architecture, personal or commercial FDM setups, and existing/new materials.

Copyright © 2017 by ASME
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Fig. 1

(a) The in-house developed CMMB with different modules and (b) the FDM module highlighted with important components adapted from Ref. [25]

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Fig. 2

A representative experimental run shown with the initialization, transition, and actual regions counterclockwise from top-right

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Fig. 3

Plot of SW versus T (a) with average SW data for each T level within inset text box, SW versus NBD (b), and SW versus treatment no. (c)

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Fig. 4

Residuals (e) versus fitted values (ŷ)

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Fig. 5

Normal probability plot (NPP) of SW residuals (e) versus normal scores (z)

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Fig. 6

Residuals (e) versus fitted values (ŷ) for the transformed data

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Fig. 7

Normal probability plot (NPP) of SW residuals (e) versus normal scores (z) for the transformed data set

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Fig. 8

Interaction plot of factors NBD and T. Note: NBD in mm

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Fig. 9

Representative cross-sectional SEM image of a strut printed with T = 200 °C and NBD = 0.18 mm using a 0.4 mm nozzle. The deformed cross section is clearly visible as a result of the strut being sandwiched between the bed and nozzle.

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Fig. 10

Line plot summarizing results from pairwise comparisons of the nine μij treatment means using the Tukey's procedure. Nonsignificant differences are connected by lines. Out of the 36 total pairwise comparisons, eight were found to be nonsignificant at 95% family confidence, simultaneously.

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Fig. 11

A representative single layer scaffold 3D printed with a targeted strut–strut spacing of 600 μm (T = 220 °C, NBD = 0.2 mm) visible with the initialization and transition regions starting from the top-right corner. Scale bar 1 division = 1 mm.




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