Search results

The purpose of this paper is to study the influence of changing printing parameters (powder layer thickness and binder saturation) in a three dimensional printing machine (3DP) on the transformation of 3DP printed plaster of paris to hydroxyapatite by low temperature phosphorization.

Plaster of paris‐based powder mixture was used to print specimens using different powder layer thickness (0.080, 0.10 and 0.20 mm) and saturation ratio (1 and 2). Subsequently, density, microstructure, mechanical properties, transformation rate and phase composition were analyzed to compare the influence of such printing parameters on properties.

It was found that printing parameters strongly affect the transformation efficiency and properties of the samples. The sample printed at layer thickness of 0.10 mm and saturation ratio of 1 yielded the highest transformation rate, density and greatest flexural modulus and strength after conversion. This was related to the sufficiently low density structure with good mechanical properties of the as‐fabricated 3DP sample which was suitable for the low temperature phosphorization process. Hydroxyapatite and monetite were found to be the main phases after conversion and the content of each phase depended on the conversion time and on also the printing parameters.

The optimal printing parameters were true for the materials used in this study. In the case of using other materials formulation, the optimal printing parameters might be different from these values.

The results presented here can be used as a guideline for selecting printing parameters in 3DP machine for achieving properties as desired for specific applications or post‐processing techniques.

The paper demonstrates the printing parameters that were needed to be considered for efficient phase transformation and high mechanical properties.

The aim is to investigate the feasibility of increasing the transparency of the samples or models which were fabricated by three dimensional printing technology and study the properties of such developed system.

Polymethyl methacrylate powders were mixed with maltodextrin binders and used as raw materials for 3DP machine to fabricate samples. The samples were then divided into two groups either infiltrating with heat‐cured acrylate infiltrant or subjected to binder elimination prior to infiltration. As‐fabricated and two types of infiltrated samples were characterized to compare the influence of post‐processing on properties such as shrinkage, light transmittance and flexural properties including modulus, strength and strain at break.

It was observed that the combination of binder elimination and resin infiltration showed the greatest increase in flexural properties and transmittance percentage approaching the values of polymethyl methacrylate sheet and stereolithography samples. Infiltration without binder elimination increased the transmittance of samples slightly in comparison to as‐fabricated samples. This is related to the level of porosity in the samples and the difference in refractive index of different compositions within the samples namely PMMA, binder and infiltrant.

Additional step of binder elimination prior to infiltration is needed and this may take time to complete.

The technique presented can be used to fabricate a translucent and strong 3DP models.

This study demonstrates the factors that are needed to consider increasing the transparency and even strength of 3DP models.

The purpose of this study is to evaluate the intra- and post-operative performance and safety of direct three dimensional printing (3DP) porous polyethylene implants in cranial reconstruction.

Prefabricated porous polyethylene implants were prepared by direct 3DP, and cranioplasty implantation was performed. Postoperative aesthetics, patient satisfaction, firmness of the implant, reactions to the implant and 3D computed tomography (CT) scanning were assessed after 2, 6, 12 and 24 months postoperatively.

No complications after surgery were encountered. Excellent aesthetic results were obtained in all cases, and all the patients were satisfied with the reconstruction outcome. Bone density structure was found to ingrowth into these direct 3DP porous polyethylene implants and the content increased with increasing follow-up times.

This study was a pilot study conducted in a single group and evaluated in a short-term period. The bone formation and ingrowth were indirectly assessed by 3D CT evaluation.

This work reported the use and evaluation of direct 3DP porous polyethylene in middle- to large-sized cranial reconstructions. It evidently showed the bonding of implants to surrounding tissues which would result in the long-term stability and infection resistance of the implant.

To study the properties of three dimensional printing (3DP) materials systems which were directly in contact with water or exposure to humidity in order to help in deciding the appropriate system for moisture resistance applications.

Two commercially available 3DP materials namely ZP 100 and ZP 15E were infiltrated with three commonly used infiltrants. All samples were subjected to three storage conditions including dry, room (55 percent RH) and wet (100 percent RH) for 168 h. Then they were characterized to compare the influence of storage conditions on properties such as dimensional change, moisture absorption and flexural properties including modulus, strength and strain at break.

Amongst six material systems investigated in this study, it was observed that the combination of ZP 15E with acrylate infiltrant showed the greatest flexural properties in room and wet conditions. All infiltrated ZP 100 samples were not likely to be as suitable for using in moisture resistance environment as infiltrated ZP 15E samples especially when they were in direct contact with water. Using low moisture absorption infiltrant and 3DP materials that can absorb high amount of infiltration are needed to produce low moisture absorption system.

The moisture absorption experiment was done at 168 h. The values obtained from the report for some testing conditions, i.e. room environment may not be able to extend to long‐term performance.

The results presented here can be used as a guideline for 3DP materials selection for moisture resistance applications.

This study demonstrated the governed factors that were needed to consider for using 3DP models in moisture resistance applications.

The purpose of this paper is to characterize mechanical properties (tensile, compressive and flexural) for the three-dimensional printing (3DP) process, using various common recommended infiltrate materials and post-processing conditions.

A literature review is conducted to assess the information available related to the mechanical properties, as well as the experimental methodologies which have been used when investigating the 3D printing process characteristics. Test samples are designed, and a methodology to measure infiltrate depths is presented. A full factorial experiment is conducted to collect the tensile, compressive and bending forces for a set of infiltrates and build orientations. The impact of the infiltrate type and depth with respect to the observed strength characteristics is evaluated.

For most brittle materials, the ultimate compression strength is much larger than the ultimate tensile strength, which is shown in this work. Unique stress–strain curves are generated from the infiltrate and build orientation conditions; however, the compressive strength trends are more consistent in behavior compared to the tensile and flexural results. This comprehensive study shows that infiltrates can significantly improve the mechanical characteristics, but performance degradation can also occur, which occurred with the Epsom salts infiltrates.

More experimental research needs to be performed to develop predictive models for design and fabrication optimization. The material-infiltrate performance characteristics vary per build orientation; hence, experimental testing should be performed on intermediate angles, and a double angle experiment set should also be conducted. By conducting multiple test scenarios, it is now understood that this base material-infiltrate combination does not react similar to other materials, and any performance characteristics cannot be easily predicted from just one study.

These results provide a foundation for a process design and post-processing configuration database, and downstream design and optimization models. This research illustrates that there is no “best” solution when considering material costs, processing options, safety issues and strength considerations. This research also shows that specific testing is required for new machine–material–infiltrate combinations to calibrate a performance model.

There is limited published data with respect to the strength characteristics that can be achieved using the 3DP process. No published data with respect to stress–strain curves are available. This research presents tensile, compressive and flexural strength and strain behaviors for a wide variety of infiltrates, and post-processing conditions. A simple, unique process is presented to measure infiltrate depths. The observed behaviors are non-linear and unpredictable.

The purpose of this paper is to investigate the adoption of rapid prototyping (RP) technology using three dimensional (3D) printer for infusing agility in traditional manufacturing environment.

The computer aided design (CAD) model of a knob of an electronics switch is developed using Pro/E software. Keeping this model as a reference, CAD models of new six knobs are developed. A 3D printer is used to build the prototypes of five of those CAD models. The receptivity of the practitioners over adopting CAD models and 3D printer for achieving agility is investigated.

The sensitisation of the industry captains and employees of traditional manufacturing sector is the imperative for exploiting the power of 3D printer and achieving mass customisation.

The paper reports an original research in which the practicality of using 3D printer is investigated with the objective of enabling the traditional manufacturing companies to imbibe agile characteristics.

The effects of infiltrant-related factors during post-processing on mechanical performance are fully considered for three-dimensional printing (3DP) technology. The factors contain infiltrant type, infiltrating means, infiltrating frequency and time interval of infiltrating.

A series of printing experiments are conducted and the parts are processed with different conditions by considering the above mentioned four parameters. Then the mechanical performances of the parts are tested from both macroscopic and microscopic papers. In the macroscopic view, the compressive strength of each printed part is measured by the materials testing machine – Instron 3367. In the microscopic view, scanning electron microscope and energy dispersion spectrum are used to obtain microstructure images and element content results. The pore size distributions of the parts are measured further to illustrate that if the particles are bound tightly by infiltrant. Then, partial least square (PLS) is used to conduct the analysis of the influencing factors, which can solve the small-sample problem well. The regression analysis and the influencing degree of each factor are explored further.

The experimental results show that commercial infiltrant has an outstanding performance than other super glues. The infiltrating action will own higher compressive strength than the brushing action. The higher infiltrating frequency and inconsistent infiltrating time interval will contribute to better mechanical performance. The PLS analysis shows that the most important factor is the infiltrating method. When compare the fitted value with the actual value, it is clear that when the compressive strength is higher, the fitting error will be smaller.

The research will have extensive applicability and practical significance for powder-based additive manufacturing.

The impact of the infiltrating-related post-processing on the performance of 3DP technology is easy to be ignored, which is fully taken into consideration in this paper. Both macroscopic and microscopic methods are conducted to explore, which can better explain the mechanical performance of the parts. Furthermore, as a small-sample method, PLS is used for influencing factors analysis. The variable importance in the projection index can explain the influencing degree of each parameter.

This paper aims to study the influence of the binder saturation level on the accuracy and on the mechanical properties of three-dimensional (3D)-printed scaffolds for bone tissue engineering.

To study the influence of the liquid binder volume on the models accuracy, two quality test plates with different macropore sizes were designed and produced. For the mechanical and physical characterisation, cylindrical specimens were used. The models were printed using a calcium phosphate powder, which was characterised in terms of composition, particle size and morphology, by X-ray diffraction (XRD), laser diffraction and Scanning electron microscopy (SEM) analysis. The sample’s physical characterisation was made using the Archimedes method (porosity), SEM, micro-computer tomography (CT) and digital scan techniques, while the mechanical characterisation was performed by means of uniaxial compressive tests. Strength distribution was analysed using a statistical Weibull approach, and the dependence of the compressive strength on the porosity was discussed.

The saturation level is determinant for the structural characteristics, accuracy and strength the models produced by three-dimensional printing (3DP). Samples printed with the highest saturation showed higher compressive strengths (24 MPa), which are over the human trabecular bone. The models printed with lower saturations presented the highest accuracy and pore interconnectivity.

This study allowed to acquire important knowledge concerning the effects of shell/core saturation on the overall performance of the 3DP. With this information it is possible to devise scaffolds with the required properties for bone scaffold engineering.

The purpose of this paper is to characterize and evaluate a new 3D‐printing process based on Poly(methyl methacrylate) (PMMA).

A benchmark part and standard parts were designed, printed by a 3D‐printer and characterized.

3D printed PMMA parts have a tensile strength of 2.91 MPa and a modulus of elasticity of 223 MPa. The mechanical properties can be improved by infiltrations with epoxy (tensile strength: 26.6 MPa, modulus of elasticity: 1,190 MPa). The surface quality of the parts can be improved by infiltration with wax for usage as lost models. The minimum feature size is 0.3 mm.

The PMMA‐based 3D printing process can be used for manufacturing concept models, functional parts and lost models for investment casting.

This is the first paper investigating a PMMA‐based 3D printing process.

This paper aims to propose a vacuum-assisted post-processing method for use in binder jetted technology. The method is based on six key technological parameters and uses standard, commercially available consumables to achieve improvement in tensile strength, as well as the microstructure and porosity of the infiltrated matrix.

Six key technological parameters were systematically varied as factors on three levels, using design of experiment, i.e. definitive screening design. Surface response methodology was used to optimize the process and yield optimal tensile strength for the given range of input factors. Thus obtained, the optimized factor settings were used in a set of confirmation runs, where the result of optimization was experimentally confirmed. To confirm improvement in microstructure of the infiltrated matrix, SEM analysis was performed, while the reduction of porosity was analyzed using mercury porosimetry.

The obtained results indicate that, compared to its conventional counterpart, the proposed, optimized infiltration method yields improvement in tensile strength which is significant from both the statistical and engineering point of view, while reducing porosity by 3.5 times, using only standard consumables. Scanning electron microscopy examination of fractured specimens’ micrographs also revealed significant morphological differences between the conventional and proposed method of post-processing. This primarily reflects in higher surface area under hardened epoxy infiltrate, which contributes to increased load capacity of specimen cross-section.

At the present stage of development, the most important limitation of the proposed method is the overall size of models which can be accommodated in standard vacuum impregnation units. Although, in this study, the infiltration method did not prove statistically significant, further investigation is required with models of complex geometry, various sizes and mass arrangements, where infiltration would be more challenging and could possibly result in different findings.

The most important practical implication of this study is the experimentally verified result of optimization, which showed that tensile strength and matrix microstructure can be significantly improved, using just standard consumables.

Improved strength contributes to reduction of material consumption, which, in a longer run, can be beneficial for environment protection and sustainable development.

Based on literature review, there have been no previous investigations which studied the tensile strength of infiltrated specimens through design of experiment, which involved specimen preheating temperature, level and duration of vacuum treatment of infiltrate mixture and infiltrated specimens and infiltration method.