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Journal ArticleDOI

Estimation of filament temperature and adhesion development in fused deposition techniques

TL;DR: In this paper, an analytical solution to the transient heat conduction developing during filament deposition in Fused Deposition Techniques (FDT), which is coupled to a routine that activates or deactivates all relevant local boundary conditions depending on part geometry, operating conditions and deposition strategy, is presented.
About: This article is published in Journal of Materials Processing Technology.The article was published on 2017-07-01 and is currently open access. It has received 180 citations till now. The article focuses on the topics: Protein filament & Deposition (phase transition).

Summary (2 min read)

1. Introduction

  • During deposition, filament deformation and bonding between contiguous filament segments are prevailing process variables (Villalpando et al., 2014) .
  • Céline et al. (2004) estimated the dynamics of bond formation from sintering data of ABS filaments.
  • Sun et al. (2008) and Gurrala and Regalla (2014) analyzed changes in the mesostructure and degree of healing at the interfaces between adjoining polymer filaments.
  • They concluded that fabrication strategy, environment temperature and variations in convection determine the overall quality of the bond strength.

Nomenclature

  • Also, during cooling shrinkage and residual stresses develop, which may induce warping and delamination (Kantaros and Karalekas, 2013) .
  • Bonding was predicted using a wetting-diffusion model based on the reptation theory and it was shown that lower cooling rates promote stronger bonding.
  • The magnitude of the mechanical deformation was also studied.
  • An analytical solution for the transient heat transfer during filament deposition and cooling is proposed, taking into consideration all physical contacts between filament segments during the progressive built-up of a 3D structure.

4. Modeling of filament deposition

  • The building strategy determines the type of contacts taking place (these are identified in Fig. 1 ).
  • Unidirectional and aligned, unidirectional and skewed, and perpendicular deposition modes were considered in the calculations (Fig. 3 ).

c) Computation of filament temperature

  • During building of the part, a filament segment already laid down will be reheated upon contact with a newer one that is hotter, whilst a segment contacting previously deposited neighbours will cool down faster than if exclusively due to convection.
  • Taking these events into consideration implies the simultaneous computation of the temperature of all the filament segments deposited up to a given time, for the thermal boundary conditions updated as explained above.

d) Adhesion

  • At any part location, D h (t) (Eq. ( 11)) is computed while the filament temperature is higher than its glass transition temperature, T g , and also while its value remains lower than unity (threshold for good adhesion).
  • The equation is solved using the trapezoidal method.
  • The temperature computations are carried out in three main steps.
  • For the remaining filament segments of the first row, contacts with adjacent filament segments arise.
  • Fig. 6 shows the filament temperature at various instants of the deposition process (an animated view of cooling can be created).

5.3. Experimental procedure

  • Thus, use of Eq. ( 15) requires knowledge of the filament cross-section, air velocity and air temperature.
  • Its cross-section was determined using a Stereoscopic Olympus Magnifier and the Leica Qwin V3 Software, the air temperature was measured with a type K thermocouple (Hanna Instruments) and the air velocity with a digital anemometer (TES-1340).
  • The calculated and measured values of filament temperature when only heat transfer by convection develops were made to coincide by adjusting h conv .
  • To estimate the coefficient of heat transfer by conduction between filament and support, h FS, the temperature evolution of the filament where contact with the support exists, the crosssection of the filament and the contact area between filament and support were measured.
  • Then, calculated and actual temperatures were made to overlap by adjusting h FS.

6.1. Heat transfer coefficients

  • The segment at the bottom was laid down moving the support in one direction, while the segment on top was deposited moving the support in the opposite direction.
  • The vertical line identifies the instant when contact begins.
  • This is due to the large filament diameter being used in the experiments, which produces a relatively large contact with the support.

6.2. Representative results

  • The effect of changing the extrusion temperature on the evolution of the filament segment temperature deposited on top (at Fig. 16 analyses the deposition of a vertical stack of 3 filament segments.
  • This cross-section was laid 6.7 s after the equivalent one in the middle and 17.6 s after the one at the bottom.
  • Temperature readings performed during the deposition of the segment on top are in good agreement with the predictions, which encompassed the entire deposition sequence (on average errors were smaller than 1.3 C).
  • The deformation of the filament influences the fractions of its perimeter that will contact other segments or the support.
  • This can be easily accommodated in the modeling routine, since these are input values.

6.4. Application example

  • Since the theoretical predictions are in good agreement with the measurements of filament temperature and adhesion, it seems fitting to demonstrate the use of the computer code for the analysis of a representative part manufactured by FDT.
  • The process parameters and material properties presented in Tables 1 and 2 remain valid, with the exception of the environment temperature, which was changed.
  • The unidirectional and aligned building strategy was adopted.
  • This would be easily accommodated by the model which, at each location, updates the pertinent material properties.
  • Fig. 17 identifies (in lighter gray) the regions of the part where insufficient adhesion between filament segments is anticipated.

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Citations
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Journal ArticleDOI
TL;DR: Fused deposition modeling (FDM) is one of the most widely used 3D printing techniques that utilizes polymers to create models, prototypes or even end products as mentioned in this paper, and since 2009, the demand for FD...
Abstract: Fused deposition modeling (FDM) is one of the most widely used 3D printing techniques that utilizes polymers to create models, prototypes or even end products. Since 2009, the demand for FD...

190 citations

Journal ArticleDOI
TL;DR: In this article, the authors measured the tensile strength of interlayer bond lines in ABS coupons printed in two orientations and found that a plateau of 22MPa was observed for a normalized contact length greater than 0.6 independent of print orientation.
Abstract: Interlayer bonds pose regions of weakness in structures produced via melt extrusion based polymer additive manufacturing. Bond strength was assessed both between layers and within layers as a function of print parameters by performing tensile tests on ABS coupons printed in two orientations. Print parameters considered were extruder temperature, print speed, and layer height. An IR camera was used to track thermal history of interlayer bond lines during the printing process. Contact length between roads was measured from mesostructure optical micrographs. Print speed was found to have a large impact on tensile strength with high speeds generally yielding lower strength. A plateau in tensile strength of 22 MPa was observed for a normalized contact length greater than 0.6 independent of print orientation.

174 citations

Journal ArticleDOI
TL;DR: In this paper, a two-stage thermal and sintering model is developed to predict the bond formation process between filaments in 3D printed polymeric components with custom properties, directly in terms of manufacturing settings.

169 citations

Journal ArticleDOI
Geng Peng1, Ji Zhao1, Wu Wenzheng1, Wenli Ye1, Y. Wang1, Shuobang Wang1, Shuo Zhang1 
TL;DR: In this article, the effects of extrusion speed and printing speed on the microstructure and dimensions of an extruded PEEK filament in 3D printing were investigated and a control algorithm that mathematically replaces the nozzle diameter with the diameter of the extruded filament was proposed.

163 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a numerical model to simulate the extrusion of a strand of semi-molten material on a moving substrate, within the computation fluid dynamics paradigm, and quantified the effect of the gap distance and the velocity ratio on the size and the shape of the strand.
Abstract: We propose a numerical model to simulate the extrusion of a strand of semi-molten material on a moving substrate, within the computation fluid dynamics paradigm. According to the literature, the deposition flow of the strands has an impact on the inter-layer bond formation in extrusion-based additive manufacturing, as well as the surface roughness of the fabricated part. Under the assumptions of an isothermal Newtonian fluid and a creeping laminar flow, the deposition flow is controlled by two parameters: the gap distance between the extrusion nozzle and the substrate, and the velocity ratio of the substrate to the average velocity of the flow inside the nozzle. The numerical simulation fully resolves the deposition flow and provides the cross-section of the printed strand. For the first time, we have quantified the effect of the gap distance and the velocity ratio on the size and the shape of the strand. The cross-section of the strand ranges from being almost cylindrical (for a fast printing and with a large gap) to a flat cuboid with rounded edges (for a slow printing and with a small gap), which substantially differs from the idealized cross-section typically assumed in the literature. Finally, we found that the printing force applied by the extruded material on the substrate has a negative linear relationship with the velocity ratio, for a constant gap.

158 citations


Cites methods from "Estimation of filament temperature ..."

  • ...Thermal models have further been coupled to a sintering model [14] (driven by the capillary forces) and healing models [12,15,16] (driven by the intermolecular diffusion), to predict the local bond formation between adjoining strands....

    [...]

References
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Journal ArticleDOI
TL;DR: In this article, the properties of FDM parts fabricated by the FDM 1650 were analyzed using a Design of Experiment (DOE) approach, such as raster orientation, air gap, bead width, color and model temperature.
Abstract: Rapid Prototyping (RP) technologies provide the ability to fabricate initial prototypes from various model materials. Stratasys Fused Deposition Modeling (FDM) is a typical RP process that can fabricate prototypes out of ABS plastic. To predict the mechanical behavior of FDM parts, it is critical to understand the material properties of the raw FDM process material, and the effect that FDM build parameters have on anisotropic material properties. This paper characterizes the properties of ABS parts fabricated by the FDM 1650. Using a Design of Experiment (DOE) approach, the process parameters of FDM, such as raster orientation, air gap, bead width, color, and model temperature were examined. Tensile strengths and compressive strengths of directionally fabricated specimens were measured and compared with injection molded FDM ABS P400 material. For the FDM parts made with a 0.003 inch overlap between roads, the typical tensile strength ranged between 65 and 72 percent of the strength of injection molded ABS P400. The compressive strength ranged from 80 to 90 percent of the injection molded FDM ABS. Several build rules for designing FDM parts were formulated based on experimental results.

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Book
01 Jan 1960

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TL;DR: In this paper, five important process parameters such as layer thickness, orientation, raster angle, Raster width and air gap are considered and their influence on three responses such as tensile, flexural and impact strength of test specimen is studied.

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Journal ArticleDOI
TL;DR: In this article, the authors investigated the mechanisms controlling the bond formation among extruded polymer filaments in the fused deposition modeling (FDM) process and showed that the bonding phenomenon is thermally driven and ultimately determines the integrity and mechanical properties of the resultant prototypes.
Abstract: Purpose – The purpose of this paper is to investigate the mechanisms controlling the bond formation among extruded polymer filaments in the fused deposition modeling (FDM) process. The bonding phenomenon is thermally driven and ultimately determines the integrity and mechanical properties of the resultant prototypes.Design/methodology/approach – The bond quality was assessed through measuring and analyzing changes in the mesostructure and the degree of healing achieved at the interfaces between the adjoining polymer filaments. Experimental measurements of the temperature profiles were carried out for specimens produced under different processing conditions, and the effects on mesostructures and mechanical properties were observed. Parallel to the experimental work, predictions of the degree of bonding achieved during the filament deposition process were made based on the thermal analysis of extruded polymer filaments.Findings – Experimental results showed that the fabrication strategy, the envelope temper...

949 citations

Book
11 Feb 2010
TL;DR: In this paper, the authors present animated illustrations of the working principles of today's key Rapid prototyping processes, the available models and specifications, and their principles, materials, advantages and disadvantages.
Abstract: Rapid prototyping (RP) has revolutionized how prototypes are made and small batch manufacturing is carried out. With rapid prototyping, the strategies used to produce a part change a number of important considerations and limitations previously faced by tool designers and engineers. Now in its third edition, this textbook is still the definitive text on RP. It covers the key RP processes, the available models and specifications, and their principles, materials, advantages and disadvantages. Examples of application areas in design, planning, manufacturing, biomedical engineering, art and architecture are also given. The book includes several related problems so that the reader can test his or her understanding of the topics. New to this edition, the included DVD-ROM presents animated illustrations of the working principles of today's key RP processes.

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