Influence of Liquid Phase Migration on Intermittent Extrusion of Aqueous Al2O3 Paste

2011 ◽  
Vol 189-193 ◽  
pp. 177-180
Author(s):  
Hong Jun Liu
Keyword(s):  
Liquid Phase ◽  
Solid Freeform Fabrication ◽  
Extrusion Process ◽  
Fabrication Process ◽  
Extrusion Pressure ◽  
Strong Impact ◽  
Fabrication Method ◽  
Liquid Content ◽  
Freeform Fabrication ◽  
Paste Extrusion

Extrusion Freeform Fabrication Process (EFF) is an environmentally friendly solid freeform fabrication method that uses aqueous pastes to fabricate ceramic-based components. The Liquid Phase Migration (LPM) causes variation in liquid content and consequently problems in the paste extrusion. To get uniform ceramics parts with desired composition, the LPM should be avoided in extrusion process. This paper investigated the influence of LPM on extrusion process for aqueous alumina paste in EFF process. It shows that the liquid phase migration occurs in Freeform Extrusion Fabrication process and has a strong impact on extrusion pressure. The LPM can be characterized by the extrusion pressure-ram displacement profiles. The liquid phase migration becomes more serious in intermittent extrusion at low ram velocity.

Investigation on Paste Extrudate Features in Ram Extrusion Process

2012 ◽  
Vol 159 ◽  
pp. 146-150
Author(s):  
Hong Jun Liu ◽  
Dong Jian Li ◽  
Ya Min Li
Keyword(s):  
Liquid Phase ◽  
Average Diameter ◽  
Extrusion Process ◽  
Nozzle Diameter ◽  
Considerable Degree ◽  
Extrusion Force ◽  
Liquid Content ◽  
Ceramic Component ◽  
Paste Extrusion ◽  
Experimental Works

The precision of ceramic component gotten by some Solid Freeform Fabirication processes based on paste extrusion is dependent to a considerable degree on paste extrudate. To get clearer understanding about paste extrudate, the experimental works were carried out to investigate some important extrudate features for ram extrusion process in this paper. The velocity, diameter, liquid content and mass of extrudate of alunima paste by ram extrusion were studied. The liquid content of extrudate tests show that the occurance liquid phase migration depends on the ram velocity. Without liquid phase migration, the extrudate velocities have a corresponding relations to extrusion force. The dilation of extrudate occurs in commonly used ram velocities. So extrudate velocities should not be calculated by nozzle diameter but by the average diameter of dilated extrudate. The mass of extrudate in the very end of extrusion is greatly reduced and should not be used.

Cells (MC3T3-E1)-Laden Alginate Scaffolds Fabricated by a Modified Solid-Freeform Fabrication Process Supplemented with an Aerosol Spraying

2012 ◽  
Vol 13 (9) ◽  
pp. 2997-3003 ◽  
Author(s):  
SeungHyun Ahn ◽  
HyeongJin Lee ◽  
Lawrence J. Bonassar ◽  
GeunHyung Kim
Keyword(s):  
Solid Freeform Fabrication ◽  
Fabrication Process ◽  
Freeform Fabrication

LIQUID PHASE MIGRATION IN EXTRUSION OF AQUEOUS ALUMINA PASTE FOR FREEZE-FORM EXTRUSION FABRICATION

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1861-1866 ◽  
Author(s):  
HONGJUN LIU ◽  
MING C. LEU
Keyword(s):  
Liquid Phase ◽  
Dead Zone ◽  
Extrusion Process ◽  
Extrusion Force ◽  
Transient Stage ◽  
Steady Stage ◽  
Paste Extrusion ◽  
Force Data ◽  
Force Profiles ◽  
Key Parameter

Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing technique that extrudes highly ceramic loaded aqueous paste along 3D contours for complex ceramic part fabrication. The phenomenon of liquid phase migration (LPM) in paste extrusion process will result in variation of liquid content in paste and consequently problems in processing and non-uniform properties of ceramic parts. It is necessary to understand the LPM phenomenon in FEF process. In this paper, the effect of liquid phase migration on extrusion of aqueous alumina paste was investigated for FEF process. The water content and extrusion force data were collected for a series of ram velocities. According to the extrusion force profiles, the extrusion process can be divided into four stages: compaction stage, transient stage, steady stage and dead zone stage. The results show that ram velocity is the key parameter for occurrence of liquid phase migration phenomenon and there is a velocity threshold above which the liquid phase migration will not happen.

Dual-Phase Materials Extrusion Process for Rapid Fabrication of Ceramic Dental Crown

2010 ◽  
Vol 97-101 ◽  
pp. 4050-4053 ◽  
Author(s):  
Dong Bin Zhu ◽  
An Ping Xu
Keyword(s):  
3D Model ◽  
Solid Freeform Fabrication ◽  
Extrusion Process ◽  
Human Tooth ◽  
Dual Phase ◽  
Positioning System ◽  
Forming Process ◽  
Freeform Fabrication ◽  
Rapid Fabrication ◽  
Dental Crown

A novel ceramic forming process, dual-phase materials extrusion process based on solid freeform fabrication (also known as rapid prototyping), has been developed. It is a kind of selective slurry extrusion (SSE) technique previously proposed in our group. The dual-phase materials extrusion machine was constructed with micro-extrusion system and 3-axial positioning system. To demonstrate the usability of this machine, a functionalized dental crown was directly fabricated with support material and dental material from 3D model (STL format) of a human tooth. The fabrication time is usually in 20-50 min.

Effect of Preheating on the Delamination and Crack Formation in Laser Solid Freeform Fabrication Process

2008 ◽  
Author(s):  
Masoud Alimardani ◽  
Ehsan Toyserkani ◽  
Jan Paul Huissoon
Keyword(s):  
Thermal Stresses ◽  
Crack Formation ◽  
Solid Freeform Fabrication ◽  
Fabrication Process ◽  
Experimental Results ◽  
Stress Fields ◽  
Thin Wall ◽  
Freeform Fabrication ◽  
Micro Cracks ◽  
Laser Solid Freeform Fabrication

This paper presents a numerical-experimental investigation on the effects of preheating the substrate on the potential delamination and crack formation across the parts fabricated using the Laser Solid Freeform Fabrication (LSFF) process. For this purpose, the temperature distributions and stress fields induced during the multilayer LSFF process, and their correlation with the delamination and crack formation are studied throughout the numerical analysis and the experimental fabrication of a four-layer thin wall of SS304L. A 3D time-dependent numerical approach is used to simulate the LSFF process, and also interpret the experimental results in terms of the temperature distribution and the thermal stress fields. The numerical results show that by preheating the substrate prior to the fabrication process, the thermal stresses throughout the process domain substantially reduce. Accordingly, this can result in the reduction of potential micro-cracks formation across the fabricated part. Preheating also decreases the transient time for the development of a proper melt pool which is an important factor to prevent poor bonding between deposited layers. The experimental results are used to verify the numerical findings as well as the feasibility of preheating on the reduction of the micro-cracks formed throughout the fabrication process.

Novel Highly Potential Initiators for the Two-Photon-Induced Photopolymerization Process

2009 ◽  
Vol 1179 ◽  
Author(s):  
Niklas Pucher ◽  
Valentin Satzinger ◽  
Arnulf Rosspeintner ◽  
Georg Gescheidt ◽  
Volker Schmidt ◽  
...  
Keyword(s):  
Solid Freeform Fabrication ◽  
Photophysical Properties ◽  
Fabrication Process ◽  
Freeform Fabrication ◽  
Structure Activity Relationships ◽  
Two Photon ◽  
Triple Bonds ◽  
Processing Window ◽  
Structure Activity ◽  
Donor And Acceptor

AbstractThe development of new optimized photoinitiators for the two-photon induced photopolymerization (TPIP) is essential in order to obtain high resolutions in this solid freeform fabrication process. Herein, we present the syntheses and characterizations of a series of efficient photoinitiators, comprising of a cross conjugated D-π-A-π-D system. The different donor- and acceptor functionalities of the investigated photoinitiators as well as the synthesis of targeted derivatives containing double and triple bonds in the conjugated backbone allowed the evaluation of structure-activity relationships. The basic photophysical properties as well as the activity and ideal processing window under TPIP conditions were investigated for each initiator and compared with typical commercially available one-photon initiator and with two highly potential initiators well known from literature. These tests figured out that the new chromophores are highly potential even at concentrations down to 0.05 wt%.

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