Evaluation of the Influence of Parameters of FDM Technology on the Selected Mechanical Properties of Models

Available online at www.sciencedirect.com

ScienceDirect Procedia Engineering 192 (2017) 463 – 468

TRANSCOM 2017: International scientific conference on sustainable, modern and safe transport

Evaluation of the influence of parameters of FDM technology on the selected mechanical properties of models Tomasz Koziora*, Czesław Kunderaa a

Kielce University of Technology, Faculty of Mechatronics and Mechanical Engineering, Department of Manufacturing Engineering and Metrology, al. Tysiąclecia Państwa Polskiego 7, 25-314 Kielce, Poland

Abstract The paper presents experimental results the influence of location and direction of the models on the virtual platform on their selected mechanical properties such as Young's modulus and stress relaxation during uniaxial compression tests. Cylindrical samples were manufactured using the Dimension 1200es machine realizing the fused deposition modeling technology (FDM).. The samples were located on the machine platform at different angles to the printing direction. The material used for the construction of samples was ABS P430. Tests relaxation were made in accordance with ISO 3384: 2002 standard. Tests were performed using the testing machine Inspect Mini. ©2017 2017The TheAuthors. Authors. Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license © Published by Elsevier Ltd. This (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of TRANSCOM 2017: International scientific conference on Peer-review responsibility of the scientific committee of TRANSCOM 2017: International scientific conference on sustainable, modern and safe transport. sustainable,under modern and safe transport Keywords: FDM ; ABS ; Relaxation ; Mechanical Properties.

1. Introduction Additive technologies have become well known since the middle of the 1980s. The first technology involving the layered construction of physical models based on a digital 3D solid model was stereolithography. One of the other layered manufacturing methods invented in the 1980s is the technology of the deposition of molten thermoplastic material. In this technology, input material in the form of a thin plastic rod is passed through the nozzle where it is

* Corresponding author. Tel.: +48-41-342-4453. E-mail address: [email protected]

1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of TRANSCOM 2017: International scientific conference on sustainable, modern and safe transport

doi:10.1016/j.proeng.2017.06.080

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Tomasz Kozior and Czesław Kundera / Procedia Engineering 192 (2017) 463 – 468

heated to a temperature at which it becomes a semi-liquid. Then the material is distributed to the specified crosssection of the current building model. The mechanical properties and dimensional-shaped accuracy of elements manufactured by the aforementioned technology depend on the direction of its position on the building platform, the layer thickness and the temperature of the working chamber [1,2,3]. There are papers [4,5,6], in which authors analyzed both selected mechanical properties, as well as the accuracy of elements manufactured using FDM technology. In spite of this fact there are no studies concerning rheological tests, ie. relaxation, especially in relation to process parameters such as printing direction. In paper [4], the authors determined the influence of the layer thickness and the positioning of the working platform on tensile strength. Samples were designed in accordance with ISO 527 standard and were produced using FDM technology. They determined the most important parameters and their values in regards to tensile strength. The impact of the degree of filling of the sample by model material was tested. Biodegradable material polylactide, PLA was used to build the model. Research on the influence of technological parameters on the surface texture was also described in work [5], where the authors analyzed the impact of printing direction on the spatial parameters of the geometric structure of the surface. In addition, samples were subject to further treatment by using acetone. The confocal microscope Olympus OLS4100 was used to determine above mentioned surface parameters. Analysis of the influence of layer thickness on tensile strength of samples made by FDM technology was also described in paper [6]. The study included three types of samples, which were printed along the three main axis: X, Y, Z and selected thickness of the combined layers. The study confirmed the dependence of the mechanical properties of the selected printing direction during manufacturing. The authors showed that, depending on the location of models on the working platform, different type of filling of support material should be used. Based on this fact, support thickness should be increased or decreased. Due to the fact that most of the elements of machines and mechanisms manufactured by additive technologies [7,8] are subjected to a constant load, the research presented in this paper can be regarded as well founded. 2. FDM technology Fused deposition modeling technology is based on a layered construction of physical models directly from a digital 3D solid model. A printing head locally heats input material in the form of a plastic rod, causing their local melting. Then the head is moved in two directions, X and Y, and spreads a layer of material at the place of the current building cross-section of the model. After completing the layer, the building table is lowered by the thickness of one layer, and the whole process is repeated until the completion of the whole model. Selected mechanical properties of the ABS material which was used to build test samples are shown in Table 1 [9]. Table 1. Model material - ABS P430, selected mechanical properties. Mechanical properties

Value

Unit

Standard

Young’s modulus

2320

MPa

ASTM D638

Tensile strength

37

MPa

ASTM D638

IZOD Impact, notched

106

J/m

ASTM D256

3. Research methodology Stress relaxation in compression testing, according to ISO 3384: 2002, was performed on samples of cylindrical shape with an identical diameter and height equal to 10 mm. Samples were designed in SolidWorks, and their digital models saved as an STL format file. Approximation parameter models were as follows: tolerance of 0.01 mm, tolerance angle 5°. The samples were located on the working platform in three characteristics angles, ie. 1(0°), 2(45°), 3(90°). All types of samples were manufactured in 5 pieces. Location of the models on the building platform using the Catalyst software are shown in Figure 1. Catalyst software also allows to calculate building time and

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Tomasz Kozior and Czesław Kundera / Procedia Engineering 192 (2017) 463 – 468

materials consumption. These values for presented research were respectively 6 hours and 14 minutes, 94.02 cm3 and 10.55 cm3.

Fig. 1. Samples on the working platform of the Dimension 1200es machine (a) 0°; (b) 45°; (c) 90°.

The study of the effect of the printing direction on the stress relaxation in compression in uniaxial test were carried out using the testing machine Inspect Mini 3kN. Relaxation tests consisted of rapid loading of the sample, so as to reach the set displacement value of compressive deformation and then maintain it within a predetermined time, carried out to the end of the test. The whole test was controlled by the program LABMASTER [10]. Test cycle parameters were in accordance with ISO 3384 standard [11], respectively, test time 1800s, compressive deformation 1 mm (10%), loading speed 30 mm / min. 4. Identification of the rheological model parameters To describe the rheological properties ie. stress relaxation or creep various types of rheological models can be used [1, 12], the parameters of which, however, must be determined in an experimental way. Due to the high degree of complexity of the experiment, whenever it is possible, the rheological model should be simplified. All of the parameters depend not only of the amount of deformation, but also its speed. Theoretical description of the test results can be performed by using well known rheological models eg. Maxwell, Kelvin-Voigt, Standard I or Burgers. In this paper the Standard I rheological model was used to describe the rheological properties. Figure 2 shows the mechanical model of Standard I.

Fig. 2. Rheological model Standard I.

V

K E1  E

V

E1E KE H H E1  E E1  E

(1)

where: E, E1 – elastic modulus, K – viscous modulus. Assuming a jump-like strain step equal H H1H (t ) from the differential equation (1), we can determine a change in (relaxation) stress in time, equation 2.

466

Tomasz Kozior and Czesław Kundera / Procedia Engineering 192 (2017) 463 – 468 E E ª EE  1 tº E 1  e K » « E1  E E1  E » ¬ ¼

V (t ) H1 «

(2)

where: H1 – set strain value, H(t) – Heaviside'a function. On the basis of the measurement results obtained from the experiments, the stress relaxation function can be approximated as exponential function 3.

V (t ) a  be kt

(3)

where: a, b, k – approximation function parameters From (2) and (3) equations can be determined parameters (modules) of rheological model Standard I (4) [12]:

E1

a (a  b); E b

a  b; K

ab§ a· ¨1  ¸ k © b¹

(4)

5. Research results The test results of stress relaxation are shown in figures 3-6 and tables 2 and 3. Digital data analysis was performed using LABMASTER Science software and the calculation program Origin. In figures 3-6 the number 1 represents the original curves obtained during the test, and number 2 the approximations curves obtained from test results, using equation 4 shown above. Table 2. Research results. Sample number

ߪ [MPa]

ߪ଴ [MPa]

1 90°

21.159

24.102

2 90°

20.764

23.873

3 90°

22.548

23.898

4 90°

22.484

23.796

5 90°

22.981

24.268

mean

21.987

23.987

6 45°

20.828

24.089

7 45°

19.847

23.809

8 45°

19.096

22.726

9 45°

19.529

23.503

10 45°

18.790

23.338

mean

19.618

23.493

Tomasz Kozior and Czesław Kundera / Procedia Engineering 192 (2017) 463 – 468

Fig. 3. The relation of stress versus time for a sample at an angle of 0° relative to the building platform

Fig. 4. The relation of stress versus time for a sample at an angle of 45° relative to the building platform

Fig. 5. The relation of stress versus time for a sample at an angle of 90° relative to the building platform

Fig. 6. The relation of stress versus time for three type of directions: 1 - 0°, 2 - 45°, 3 - 90°

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Tomasz Kozior and Czesław Kundera / Procedia Engineering 192 (2017) 463 – 468

Table 3. Approximation function parameters and rheological for three printing directions. Printing direction °

a

b

k

Chi^2

R^2

E [MPa]

E1 [MPa]

K [Ns/m2]

0

22.172

1.014

0.00225

0.003

0.954

23.187

506.65

238959

45

20.886

1.626

0.00206

0.008

0.955

22.513

289.048

246043

90

21.210

1.578

0.00208

0.006

0.964

22.789

306.139

249698

Quantitative analysis of the test results shows that the lowest value of the Young's modulus in uniaxial compression tests presents samples at an angle of 90°, samples No. 3. The difference in results in comparison to other types of samples is only 4%. This indicates that the printing direction is not the key technological parameter which affected on the value of Young's modulus in FDM technology. Analyzing the modules of adopted rheological model can be observed that in the case of elastic modulus E1 location on the working platform of the machine is the key influence on its value. In the case of samples located at an angle of 0°, the value of this module is 506.65 MPa, which is almost twice time more than in the case of other types of samples. Also the value of E modulus for this type of placement assumes the greatest value equal 23.187 MPa. With regard to the third module, ie. viscosity, value of these parameters for all tested samples are on the same level. 6. Conclusion The test results allow us to conclude that the print direction is a key parameter influencing in particular on the rheological properties of materials. Examination of the test results can formulate the following general conclusions: The highest value of Young's modulus were obtain for the location samples on the building platform at an anle of 0°. It is the most preferred placement for the models during their printing in FDM technology. Determined rheological properties show that the location of the sample at an angle of 0° results in the highest value of the modulus of elasticity E and E1 in rheological Standard I model. Location of the samples in accordance with the variant 2, ie. 45 ° provides the lowest resistance models for constant loads and the lowest value in all above mentioned modulus. References [1] Cz. Kundera, J. Bochnia, Investigating the stress relaxation of photopolymer O-ring seal models, Rapid Prototyping Journal, 20 (6) 533-540, 2014. [2] Cz. Kundera, T. Kozior, Research of the Elastic Properties of Bellows Made in SLS Technology, Advanced Materials Research, Volume: 874 pp. 77-81, 2014. [3] S. Adamczak, P. Zmarzły, K. Stępień, Identification and analysis of optimal method parameters of the V-block waviness measurements Bulletin of the Polish Academy of Sciences Technical Science, 64 (2), pp. 45-52, 2016. [4] C.A. Griffithsa, J. Howarthb, G. de-Almeida Rowbothamb, A. Reesa, Effect of build parameters on processing efficiency and material performance in fused deposition modelling, Procedia CIRP 49, pp. 28 – 32, 2016. [5] T. Bartkowiak, J.T. Lehner, J. Hyde, Z. Wang, D. Bue Pedersen, H. Norgaard Hansen, C.A. Brown, Multi-Scale areal curvature analysis of fused deposition surfaces, Proceedings - Achieving Precision Tolerances in Additive Manufacturing, pp. 77-82, 2015. [6] A. Bagsik, V. Schöppner, Mechanical properties of fused deposition modeling parts manufactured with ultem*9085, 69th Annual Technical Conference of the Society of Plastics Engineers, USA, 2011. [7] M. Li, A. Ghazanfari, W. Li, R.G. Landers, M.C. Leu, Modeling and analysis of paste freezing in freeze-form extrusion fabrication of thinwall parts via a lumped method, Journal of Materials Processing Technology, Vol. 237, pp. 163-180, 2016. [8] M.C. Leu, N. Guo, Additive manufacturing: technology, applications and research needs. Frontiers of Mechanical Engineering, Vol. 8 Iss. 3, pp. 215-243, 2013. [9] www.stratasys.com [10] Inspekt Mini, Universal Testing Machine Inspekt mini 3kN - User’s Guide, Hegewald & Peschke, Meß- und Prüftechnik GmbH, 2011. [11] ISO 3384: 2002, Rubber, vulcanized or thermoplastic – Determination of stress relaxation in compression at ambient and at elevated temperatures, 2002. [12] Cz. Kundera, Seals of rotating systems, Monograph M53, Kielce University of Technology, Kielce, p. 286. (in Polish), 2013. [13] J. Skrzypek, Plasticity and creep, (in Polish) PWN, Warsaw, 1986.