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ISSN : 1598-6721(Print)
ISSN : 2288-0771(Online)
The Korean Society of Manufacturing Process Engineers Vol.20 No.1 pp.66-73
DOI : https://doi.org/10.14775/ksmpe.2021.20.01.066

Dimensional Characteristics of 3D Printing by FDM and DLP Output Methods

Myung-Hwi Jung*, Jeong-Ri Kong**, Hae-Ji Kim***#
*School of Automotive Engineering, Gyeongnam National University of Science and Technology
**Department of Robot Mechanics, Robot Campusof Korea Polytechnic
***Department of Automotive Engineering, Gyeongnam National University of Science and Technology
#Corresponding Author : khji@gntech.ac.kr Tel: +82-55-751-3647, Fax: +82-55-751-3649
02/11/2020 23/11/2020 30/11/2020

Abstract


In this paper, we analyzed and considered the precision of parts produced by 3D printing methods. For the latch systems applied to the Wingline folding doors, the 3D shape of the door hinge part was printed using FDM and DLP methods. Then, the 3D printed shape was scanned to measure the dimensions and dimensional changes of the actual model. In the comparison and analysis of the 3D printed door hinge parts, because the output filling density is 100% owing to the characteristics of DLP 3D printing, the filling density in FDM 3D printing was also set to 100%.



DLP, FDM 3D 프린팅 출력 방식에 따른 치수 특성에 관한 연구

정 명휘*, 공 정리**, 김 해지***#
*경남과학기술대학교 자동차공학과 대학원
**한국폴리텍대학 로봇캠퍼스 로봇기계과
***경남과학기술대학교 자동차공학과

초록


    Gyeongnam National University of Science and Technology

    © The Korean Society of Manufacturing Process Engineers. All rights reserved.

    This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

    1. Introduction

    With the advent of the Fourth Industrial Revolution and the development of related technologies, various application technologies are being applied to prototyping and dimensional verification using 3D printing technology. For prototyping, 3D printers are used to produce 3D-designed shapes, greatly shortening the product development process[15]. Typically, the fused deposition modeling (FDM) method, a common material extrusion (ME) process, stereolithography (SLA), a type of photopolymerization (PP), and digital light processing (DLP) are most actively used in the polymer series. However, there is a problem in the assembly process due to the change in dimensions based on the materials manufactured by the 3D printer[68]. Dimensional verification and geometric dimension management are required to address this problem. For dimensional verification, techniques for comparing the dimensions of the actual CAD modeling shape and 3D printed shape have recently been applied after 3D printing the 3D design shape and scanning the shape through a non-contact 3D scanner[18].

    This study 3D printed the 3D shapes of the door hinge part in the door latch system applied to a wing-in-ground (WIG) craft by applying two methods: FDM and DLP. The dimensions of the actual model and scanned shape were measured by scanning the printed shape. Subsequently, the dimensional change characteristics were analyzed, and the accuracy of the printed materials was examined for 3D printing methods.

    2. 3D Printing of Door Hinge

    2.1 3D Printer Research Equipment

    In this study, Ultimaker S5, an FDM type printer, and Zbuilder, a DLP type 3D printer, were used to compare 3D printed materials. For the part output of the FDM printer, a polylactic acid (PLA) filament (diameter 2.85 mm, silver) and polyvinyl alcohol (PVA) water-soluble support material (diameter 2.85 mm) were used. Photocurable resins were used as materials for the DLP 3D printer. For the FDM printer, CURA, a dedicated software program, was used, and Materialize Magics Ver.24 and E-stage 7.0 were applied for the DLP 3D printer’s layout and support installation.

    2.2 3D Printing Simulation and 3D Printing for Door Hinge

    This study, for comparative analysis of door hinge parts using the 3D printing method, set the infill density for FDM 3D printing as 100% (the same condition as DLP 3D printing) to proceed with printing because the infill density is 100% due to the characteristic of DLP 3D printing. Fig. 2 illustrates the process from slicing to output after slicing with a 0.1mm stacking height in CURA software for FDM 3D printing of the door hinge.

    Fig. 3 illustrates the process of installing supports using the E-stage of Materialise after setting the stacking direction at a tilted angle to prevent separation from the build plate in the case where the area of the first layer is large due to the nature of DLP 3D printing.

    Fig. 3(b) illustrates one layer of the cross-section of the slicing layer of the DLP 3D printer, and Fig. 3(d) illustrates the output after DLP 3D printing is completed and the support is removed.

    3. 3D Scanning and Dimensional Accuracy of 3D Printed Output

    3.1 Door Hinge Scanning

    This study used an Artec Space Spider 3D Scanner, a non-contact mobile laser scanner from Redmond, to scan the door hinge. This scanner performs the scanning task while moving around the object as if taking a video and obtains automatically-aligned data in real-time at up to seven 3D images per second.

    Fig. 4 illustrates the scanning process of complete 3D printing for the door hinge, which is the 3D scan object in Section 2.2, and the process of converting it into 3D measurement data.

    3.2 Alignment of Door Hinge Design Model and Scan Model

    For comparing the design model’s dimensions and the 3D printed shape of the door hinge part, the design model and scan model of the door hinge part were aligned using Geomagic Control X software. Figs. 5 and 6 illustrate the alignment process of the door hinge printed using DLP. As depicted in Fig. 5, datum alignment was performed after performing initial and best alignment because an alignment error between the design and scan models was identified. Fig. 7 illustrates a graph of the alignment and consistency between the scan model outputs from the FDM method and the design model. Tables 2 and 3 present the detailed analysis tables of the consistency for DLP and FDM.

    3.3 Comparison of 3D Printing Dimensions of Door Hinge

    Based on the final alignment shape of the scan and design models for the door hinge part of Section 3.1, the 3D printing dimensions of the WIG craft`s door hinge were compared for the FDM and DLP 3D printing methods. For the dimensional inspection, the inspection function of Geomagic Control X software was used. The dimensional tolerance was set to ±0.1 mm to perform the 3D comparison analysis of the design model and the scan model, and 2D comparison analysis used the cross-section of the part. Fig. 8 illustrates the results of the 3D comparison analysis of DLP and FDM methods. Based on Fig. 8 and Table 4, the standard deviation of the design model and the scan model for DLP is 0.2166, which is lower than 0.2331 for FDM, although the overall consistency is high. In contrast, based on the color distribution diagrams depicted in Fig. 8(a) and 8(b), FDM has a wide color distribution, whereas various colors are observed throughout the part in DLP. This result suggests that the FDM method, compared with the DLP method, induces a dimensional difference due to the influence of relatively high surface roughness, exhibiting a consistent dimensional range.

    Figs. 9 to 10 illustrate the results of the dimensional inspection on the bottom and side sections of the door hinge part. According to Tables 5 and 6, the range that satisfies the tolerance of ±0.1 in the bottom section is 14% for DLP and 30% for FDM, and the range for the side section is 24% for DLP and 66% for FDM. These results indicate that the FDM 3D printing method has higher dimensional accuracy than the DLP method.

    Figs. 11 to 12 illustrate the measurement locations set for the door hinge. Tables 7 and 8 present the dimensional inspection result values for each location, indicating that the FDM method has higher dimensional accuracy than the DLP method.

    4. Conclusions

    This study applied the design model of a door hinge part in the door latch system of the WIG craft in a 3D printer and scanned the door hinge shape printed through the FDM and DLP methods. The dimensional change of the printed shape by design model and method was examined using the inspection software, thereby drawing the following conclusions.

    • 1. The FDM method has consistent dimensional accuracy compared with the DLP method.

    • 2. In the dimensional inspection of the bottom and side sections, the FDM method exhibited relatively higher dimensional accuracy than the DLP method.

    • 3. The FDM method, compared with the DLP method, produced weak dimensional errors due to the effect of high surface roughness, exhibiting higher dimensional accuracy.

    Acknowledgments

    This work was supported by Gyeongnam National University of Science and Technology Grant in 2020~2021.

    Figure

    KSMPE-20-1-66_F1.gif
    DLP, FDM 3D printer
    KSMPE-20-1-66_F2.gif
    FDM 3D printing process of door hinge parts
    KSMPE-20-1-66_F3.gif
    DLP 3D printing process of poor hinge parts
    KSMPE-20-1-66_F4.gif
    3D scanning process of door hinge part
    KSMPE-20-1-66_F5.gif
    DLP 3D printed door hinge alignment
    KSMPE-20-1-66_F6.gif
    DLP 3D printed door hinge part datum alignment
    KSMPE-20-1-66_F7.gif
    FDM 3D printed door hinge alignment
    KSMPE-20-1-66_F8.gif
    Dimension 3D comparison analysis result with design model and 3d printed model
    KSMPE-20-1-66_F9.gif
    Dimension 2D comparison analysis result with design model and 3D printed model
    KSMPE-20-1-66_F10.gif
    Dimension 2D comparison analysis result with design model and 3D printed model (2mm offset from Right Side Surface)
    KSMPE-20-1-66_F11.gif
    2D dimension measurement point of door hinge with 2mm offset from bottom surface
    KSMPE-20-1-66_F12.gif
    2D dimension measurement point of door hinge with 2mm offset from right side surface

    Table

    3D printing condition
    Dimensional datum alignment analysis of design model and scan model
    Dimensional alignment analysis of design model and scan model (Unit, mm)
    Dimension 3D comparison result with design model and 3D printing model (Unit, mm)
    Dimension 2D comparison result with design model and 3D printing model (2mm offset from top surface) (Unit, mm)
    Dimension 2D comparison result with design model and 3D printing model (2mm offset from right side surface) (Unit, mm)
    Dimension 2D comparison result with design model and 3D printing model(2mm offset from top surface) (Unit, mm)
    Dimension 2D comparison result with design model and 3D printing model (2mm offset from top surface) (Unit, mm)

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