RepRap Research Articles

Factors effecting real-time optical monitoring of fused filament 3D printing

This study analyzes a low-cost reliable real-time optical monitoring platform for fused filament fabrication-based open source 3D printing. An algorithm for reconstructing 3D images from overlapping 2D intensity measurements with relaxed camera positioning requirements is compared with a single-camera solution for single-side 3D printing monitoring. The algorithms are tested for different 3D object geometries and filament colors. The results showed that both of the algorithms with a single- and double-camera system were effective at detecting a clogged nozzle, incomplete project, or loss of filament for a wide range of 3D object geometries and filament colors. The combined approach was the most effective and achieves 100% detection rate for failures. The combined method analyzed here has a better detection rate and a lower cost compared to previous methods. In addition, this method is generalizable to a wide range of 3D printer geometries, which enables further deployment of desktop 3D printing as wasted print time and filament are reduced, thereby improving the economic advantages of distributed manufacturing.

3D printing as a means of learning and communication: The 3Ducation project revisited

This research project explores to what extent the utilization of open-source 3D printers and 3D design software could serve as means of learning and communication. The principles of non-formal education aligned with the concept of constructionism are used to create an experimental educational scenario focused on geocultural tourism for persons with visual impairments. This paper documents our experience and presents our findings from a 25-day long project, which took place in Zagori, northwestern Greece. 11 high school students from Portugal designed and manufactured natural and cultural heritage artifacts carrying messages in the Braille language. The objects were then handed to people with visual impairments with a twofold aim. First, to enable the communication among persons with and without visual impairments; and, second, to empower students to participate in training projects through open educational procedures. We conclude that open educational practices can boost students’ active engagement in educational processes. Finally, 3D printing encourages a meaningful communication among people with and without visual impairments via the tangible exploration of geocultural components.

Tensile strength of commercial polymer materials for fused filament fabrication 3D printing

3D printing functional parts with known mechanical properties is challenging using variable open source 3D printers. This study investigates the mechanical properties of 3D printed parts using a commercial open-source 3D printer for a wide range of materials. The samples are tested for tensile strength following ASTM D638. The results are presented and conclusions are drawn about the mechanical properties of various fused filament fabrication materials. The study demonstrates that the tensile strength of a 3D printed specimen depends largely on the mass of the specimen, for all materials. Thus, to solve the challenge of unknown print quality on mechanical properties of a 3D printed part a two step process is proposed, which has a reasonably high expectation that a part will have tensile strengths described in this study for a given material. First, the exterior of the print is inspected visually for sub-optimal layers. Then, to determine if there has been under-extrusion in the interior, the mass of the sample is measured. This mass is compared to the theoretical value using densities for the material and the volume of the object. This two step process provides a means to assist low-cost open-source 3D printers expand the range of object production to functional parts.

The digital code driven autonomous synthesis of ibuprofen automated in a 3D-printer-based robot.

An automated synthesis robot was constructed by modifying an open source 3D printing platform. The resulting automated system was used to 3D print reaction vessels (reactionware) of differing internal volumes using polypropylene feedstock via a fused deposition modeling 3D printing approach and subsequently make use of these fabricated vessels to synthesize the nonsteroidal anti-inflammatory drug ibuprofen via a consecutive one-pot three-step approach. The synthesis of ibuprofen could be achieved on different scales simply by adjusting the parameters in the robot control software. The software for controlling the synthesis robot was written in the python programming language and hard-coded for the synthesis of ibuprofen by the method described, opening possibilities for the sharing of validated synthetic ‘programs’ which can run on similar low cost, user-constructed robotic platforms towards an ‘open-source’ regime in the area of chemical synthesis.

Comparison on Dimensional Accuracy Using a Newly Developed Nozzle for Open-Source 3D Printer

Fused Deposition Modeling (FDM) or also known as RepRap (Replicating Rapid Prototyper) is a technology that is synonym with 3D printing. This technology has entered a new era with an increasing demand among the community. It has grown commercially in the market of open-source system and it is relatively low cost. Many efforts have been put towards the development of the system in both hardware and software to increase the quality and the performance. The research highlights the development of a new nozzle to evaluate the performance on dimensional accuracy in comparison to the original nozzle. The nozzle emphasizes the die angle for the polylactic acid (PLA) material, the liquefier design which provide constant heat in the liquefier chamber, as well as insulator for the liquefier using highly insulated material. The dimensional accuracies of both nozzles were compared where the result showed that the new nozzle provided better accuracy and stability on the extruding PLA material.

Retrofitment, open-sourcing, and characterisation of a legacy fused deposition modelling system

Rapid prototyping is currently one of the most promising manufacturing techniques in industry, allowing for shorter design cycle times and improved design quality. Traditionally, commercially manufactured machines are locked to use proprietary materials specified by the manufacturer. Should a user require more freedom in material choice and other print-process parametres, open-source printers present a desirable alternative. However, these printers tend to suffer from reduced accuracy and part strength when compared to commercially manufactured machines. Thus, an opportunity exists whereby commercially manufactured print hardware can be retrofitted with open-source software to explore avenues of research that would otherwise be closed. In this paper, a large-format fused deposition modelling printer is used as the base hardware, which is supported by custom circuit boards and software to make the system open source and capable of printing a large variety of materials (for future research purposes). A customised feed system is implemented with dedicated control systems, firmware, and software. These combine to realise a completely open-source 3D printing system. The retrofitted machine is characterised by printing standardised samples, which are printed with acrylonitrile butadiene styrene material, and standard print settings. Tensile tests are performed to evaluate the quality of part lamination. It is found that similar results are attainable for comparable materials on commercial machines, suggesting a successful retrofitment.

ANALYZING THE EFFECT OF NOZZLE DIAMETER IN FUSED DEPOSITION MODELING FOR EXTRUDING POLYLACTIC ACID USING OPEN SOURCE 3D PRINTING

Fused deposition modeling (FDM) is one of the Rapid Prototyping (RP) technologies. The 3D Printer has been widely used in the fabrication of 3D products. One of the main issues has been to obtain a high quality for the finished parts. The present study focuses on the effect of nozzle diameter in terms of pressure drop, geometrical error as well as extrusion time. While using polylactic acid (PLA) as a material, the research was conducted using Finite Element Analysis (FEA) by manipulating the nozzle diameter, and the pressure drop along the liquefier was observed. The geometrical error and printing time were also calculated by using different nozzle diameters. Analysis shows that the diameter of the nozzle significantly affects the pressure drop along the liquefier which influences the consistency of the road width thus affecting the quality of the product’s finish. The vital aspect is minimizing the pressure drop to be as low as possible, which will lead to a good quality final product. The results from the analysis demonstrate that a 0.2 mm nozzle diameter contributes the highest pressure drop, which is not within the optimum range. In this study, by considering several factors including pressure drop, geometrical error and printing time, a 0.3 mm nozzle diameter has been suggested as being in the optimum range for extruding PLA material using open-source 3D printing. The implication of this result is valuable for a better understanding of the melt flow behavior of the PLA material and for choosing the optimum nozzle diameter for 3D printing.

Effect of Infill Parameters on Tensile Mechanical Behavior in Desktop 3D Printing

Abstract The recent creation and growth of desktop three-dimensional (3D) printing has led to a new way of building objects. In the manufacture of pieces using Open-Source 3D printing it is very common to use a range of infill patterns and densities with the aim of reducing printing time and material consumption. However, it is not well understood how these factors influence the characteristics of the pieces obtained. Due to the differences with FDM technology, it is necessary to evaluate the strength of the pieces manufactured with this technology. In this work, the influence of two controllable variables, such as pattern and density of the infill has been evaluated. A series of test pieces with different density characteristics and infill patterns were produced using an open-source 3D printer. The results obtained show that the influence of the different printing patterns causes a variation of less than 5% in maximum tensile strength, although the behavior is similar. The change in infill density determ...

High-Force Soft Printable Pneumatics for Soft Robotic Applications

This work presents a novel technique for direct 3D printing of soft pneumatic actuators using 3D printers based on fused deposition modeling (FDM) technology. Existing fabrication techniques for soft pneumatic actuators with complex inner geometry are normally time-consuming and involve multistep processes. A low-cost open-source consumer 3D printer and a commercially available printing material were identified for printing soft pneumatic actuators with complex inner geometry and high degree of freedom. We investigated the material properties of the printing material, simulated the mechanical behavior of the printed actuators, characterized the performances of the actuators in terms of their bending capability, output forces, as well as durability, and demonstrated the potential soft robotic applications of the 3D printed actuators. Using the 3D printed actuators, we developed a soft gripper that was able to grasp and lift heavy objects with high pay–-to-weight ratio, which demonstrated that the actuators were able to apply high forces. To demonstrate the ability of the actuators to achieve complex movements, such as bidirectional bending movements, we also developed wearable hand and wrist exoskeletons that were able to assist finger flexion and wrist flexion–extension. The proposed technique is the first-in-class approach to directly 3D print airtight soft pneumatic actuators for soft robotic applications using FDM technology.

The cloud factory: Making things and making a living with desktop 3D printing

ABSTRACTThis paper presents a case study of an open-source 3D printer called ‘Rep-rap’. 3D printing derives from computer numerical control machinery, a technology first introduced against a background of industrial conflict. This historical fact reactualises labour process theory as a theoretical resource. However, the hobbyists in the Rep-rap project are located ‘outside’ the typical setting studied in labour process theory, that is, the workplace. The case study is, therefore, suitable for examining the limits of labour process theory. Its key tenet regarding structured antagonism between labour and capital is put to the test when the ‘point of production’ is located in a community and ‘labour’ consists in non-remunerated contributions by hobbyists (i.e. non-employees). Drawing on theories of the social factory and free labour in the cultural sector, the article argues that this is changing as hobbyists, fans, makers, etc., are put to work by start-up firms and venture capital in the so-called “sharing economy.”

3D Printing, Intellectual Property and Innovation Policy

Three-dimensional (3D) printing technologies differ from traditional molding and casting manufacturing processes in that they build 3D objects by successively creating layers of material on top of each other. Rooted in manufacturing research of the 1980s, 3D printing has evolved into a broad set of technologies that could fundamentally alter production processes in a wide set of technology areas. This article investigates how 3D printing technology has developed over the last few decades, how intellectual property rights have shaped this potential breakthrough innovation and how 3D printing technologies could challenge the system of intellectual property rights in the future. Patent protection seems to have played an important role in the industrial 3D printing sector. In the newly emerging personal 3D printing sector, the intellectual property system faces new challenges. Developers of personal 3D printing systems and services have to cope with large-scale infringement by end-consumers, a situation well known from digital content technologies. At the same time, the expiration of key patents on 3D printing has arguably contributed to a flourishing ecosystem of open source 3D printer hardware and software. As in other areas of innovation policy, the role of the intellectual property system in fostering innovation in 3D printing technologies is a complex one. It played a beneficial role in some instances (sometimes intended and sometimes unintended), and it may have played a neutral or detrimental role in other instances. Studying the progress of 3D printing technologies thereby also informs us about the intricate relationship between intellectual property and innovation.

Fabrication and characterization of gels with integrated channels using 3D printing with microfluidic nozzle for tissue engineering applications

The lack of a simple and effective method to integrate vascular network with engineered scaffolds and tissue constructs remains one of the biggest challenges in true 3D tissue engineering. Here, we detail the use of a commercially available, low-cost, open-source 3D printer modified with a microfluidic print-head in order to develop a method for the generation of instantly perfusable vascular network integrated with gel scaffolds seeded with cells. The print-head features an integrated coaxial nozzle that allows the fabrication of hollow, calcium-polymerized alginate tubes that can be easily patterned using 3D printing techniques. The diameter of the hollow channel can be precisely controlled and varied between 500μm - 2mm by changing applied flow rates or print-head speed. These channels are integrated into gel layers with a thickness of 800μm - 2.5mm. The structural rigidity of these constructs allows the fabrication of multi-layered structures without causing the collapse of hollow channels in lower layers. The 3D printing method was fully characterized at a range of operating speeds (0-40m/min) and corresponding flow rates (1-30mL/min) were identified to produce precise definition. This microfluidic design also allows the incorporation of a wide range of scaffold materials as well as biological constituents such as cells, growth factors, and ECM material. Media perfusion of the channels causes a significant viability increase in the bulk of cell-laden structures over the long-term. With this setup, gel constructs with embedded arrays of hollow channels can be created and used as a potential substitute for blood vessel networks.

Spatially controlled photo-patterning of multi-material bioactive hydrogels

Event Abstract Back to Event Spatially controlled photo-patterning of multi-material bioactive hydrogels Bagrat Grigoryan1*, Jonathon D. Roybal2, Paul T. Greenfield1, Alexander J. Zaita1, Samantha J. Paulsen1, Jacob L. Albritton1, Anderson Ta1, Don L. Gibbons2, 3 and Jordan S. Miller1 1 Rice University, Bioengineering, United States 2 The University of Texas M.D. Anderson Cancer Center, Thoracic/Head and Neck Medical Oncology, United States 3 The University of Texas, MD Anderson Cancer Center, Molecular and Cellular Oncology, United States Introduction: While fabrication of simple microenvironments to study cell fate and function has been achieved using soft lithography and photolithography techniques, mimicking the complex, heterogeneous patterns of native tissue in vitro remains challenging due to lack of available simple, automated patterning technologies[1]. To this end, we developed a stereolithography (SLA)-based 3D printer for automated fabrication of hydrogels containing microstructures composed of multi-materials for applications towards understanding the lung tumor microenvironment. Materials and Methods: We developed and characterized our custom SLA-based 3D printer to spatially control the patterning of multiple materials within a single layer and across successive layers. We performed photorheological characterization of prepolymer formulations containing poly(ethylene glycol) diacrylate (PEGDA) and lithium acylphosphinate (LAP) photoinitiator to quantitatively understand the gelation kinetics and modulus of a single layer of hydrogel. Patterned entrapped fluorophore molecules facilitated characterization of the fidelity of multi-material patterns. To demonstrate biocompatibility of our technology, we added hMSCs into the prepolymer solution and performed LIVE/DEAD staining of printed cell-laden hydrogels at various time points. We further demonstrate the biocompatibility of our technology by adding a murine metastatic lung adenocarcinoma cell line, 344SQ, into the prepolymer solution to fabricate bioactive PEG-based gels containing cell-adhesive CGRGDS ligand and MMP-sensitive peptides incorporated into the polymer backbone[2]. We investigated cell viability and function by monitoring the innate ability of 344SQ cells to form into aggregates and lumenize over time in the proper microenvironment. Results and Discussion: The photorheological assay provided us with information on the exposure duration needed for a certain layer thickness as a function of PEG molecular weight, PEG concentration, and LAP concentration in the prepolymer formulation for reproducible fabrication of hydrogels (Figure 1A). Fluorescent microscopy images demonstrated fabrication of features as small as 300µm in diameter as well as precise spatial control in photo-patterning of multiple materials within the same plane (Figure 1B). Encapsulation of cells in bioactive PEG-based gels demonstrated cell viability greater than 90% after 2 days of culture (Figure 1C-Top). Encapsulated 344SQ cells retained their biological activity by forming into aggregates and lumenizing throughout the 2-week long culture (Figure 1C-Bottom). Conclusion: We have developed an open-source SLA-based 3D printer that enables us to automatically fabricate hydrogels containing bioactive microstructures with spatial control of multiple materials at a medium-high throughput. We utilized this technology to encapsulate hMSCs and metastatic cells in PEG-based hydrogels with high cell viability and function. We believe the automated nature of our developed system will enable researchers to recapitulate intricate microenvironments for studying complex cellular interactions in vitro without facing difficulties associated with precisely aligning masks with traditional photolithographic techniques. Thanks to the Open Source Hardware Association, RepRap.org, and related projects and companies that support worldwide, open standardization of 3D printing. This work was supported in part by NSF Graduate Research Fellowship (BG).

Comparison of Two Different Rapid Prototyping System Based on Dimensional Performance Using Grey Relational Grade Method

In this research, an attempt has been made to find out the influence of the process parameter along with their interactions on the dimensional accuracy of part fabricated using two different rapid prototyping machines namely fused deposition modelling machine, and a low cost open source 3D printer. 3D open source printer (3D-OSP) is one of the newly developed rapid prototyping (RP) process for part fabrication. It has been observed from previous research that the contribution of parameters such as raster width, slice height, and path speed are the most significant to the dimensional accuracy of 3D open source product while raster width, slice height, and tip dimension are the most influencing factors for fused deposition modelling machine. Taguchi parameter design of experiment method has been used to find out the optimum parameters level to minimize percentage change in length (L1), length (L2) and height (H) of test specimens fabricated by each of these two rapid prototyping machines. Experimental result revels that there is different optimal parameters level setting for each dimensional characteristics namely change in length (L1), length (L2) and height (H). Therefore, grey relational method is used to obtain optimum factor level of each dimensional characteristic simultaneously. Dimensional accuracy of parts fabricated by two different technique namely 3D open source printer and fused deposition modelling machine is within a desired range. Appropriate controls of machine process parameters improve the dimensional accuracy of parts. It is concluded that a low cost 3D open source printer gave sufficient amount of part accuracy when it is compared with the industrial based fused deposition modelling machine.

Optimization of Poli(ɛ-caprolactone) Scaffolds Suitable for 3D Cancer Cell Culture

Fused Deposition Model (FDM) as Additive manufacturing (AM) technologies may offer a viable and simpler alternative to manufacture scaffolds for different purposes such as tissue engineering and cells culture. Existing commercial FDM machines are currently being modified to improve their accuracy, capabilities and use. However, for biocompatible and/or bioimplantable materials such as Poli (ɛ -caprolactone) PCL there is still a lot of work to do to set up process parameters. Cells culture had been carried on 2D without being a proper and real midst. In fact cells do not grow only in two flat directions but in all directions making strong net. Since cells responses to proteins or drugs is important for knowing proliferation or enrichment more real culture in 3D is needed. This work focuses on the study and optimization of open-source 3D printer machine, called RepRap, employed to manufacture biocompatible scaffolds for 3D cells culture of Triple-Negative Breast Cancer (TNBC). It has been shown that scaffolds culture can enhance the Cancer Stem Cell (CSC) population, responsible in part for tumour recurrence after chemotherapy. Mammosphere Forming Index (MFI) was defined in all cell lines to evaluate this population in TNBC cell lines sensible and resistant to chemotherapy. Enriching TNBC cells with CSC after scaffold culture will help to study new therapeutic treatments directed to this population. Several process parameters are tested to manufacture scaffolds and cells culture had been carried out in order to validate the results. Results show that porosity plays an important role in scaffolds manufacture having low cells adhesion and growth. Lower porosity values should be tested to further evaluate MFI index after scaffold culture as cell growth and enrichment indication.

Ultrahigh-throughput generation and characterization of cellular aggregates in laser-ablated microwells of poly(dimethylsiloxane)

Ultrahigh-throughput generation and characterization of cellular aggregates in laser-ablated microwells of poly(dimethylsiloxane)

On the Geometric Accuracy of RepRap Open-Source Three-Dimensional Printer

In the field of additive manufacturing (AM) processes, there is a significant lack of scientific data on the performance of open-source 3D printers in relation to process parameter values. The purpose of this paper is to assess the impact of the main process parameters on the accuracy of a set of typical geometric features, as obtained with an open-source 3D printer, the RepRap Prusa-Mendel I2. For this purpose, a benchmarking part was set up, composed of elementary shapes, representing a series of different geometric features. By means of a DoE approach, it was possible to assess the effects of two process parameters—layer thickness (Lt) and flow rate (Fr)—on five geometric features: cube, sphere, cylinder, cone, and angled surface. A high resolution Laser Scanner was used to evaluate the variation between the acquired geometric feature and the corresponding 3D computer-aided design (CAD) nominal model. On the basis of experimental results, it was possible to analyze and discuss the main effects of the above-mentioned process parameters on each geometric feature. These results can help RepRap users in the correct selection of process parameters with the aim of improving the quality of prototypes.

Streamlined, Inexpensive 3D Printing of the Brain and Skull.

Neuroimaging technologies such as Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) collect three-dimensional data (3D) that is typically viewed on two-dimensional (2D) screens. Actual 3D models, however, allow interaction with real objects such as implantable electrode grids, potentially improving patient specific neurosurgical planning and personalized clinical education. Desktop 3D printers can now produce relatively inexpensive, good quality prints. We describe our process for reliably generating life-sized 3D brain prints from MRIs and 3D skull prints from CTs. We have integrated a standardized, primarily open-source process for 3D printing brains and skulls. We describe how to convert clinical neuroimaging Digital Imaging and Communications in Medicine (DICOM) images to stereolithography (STL) files, a common 3D object file format that can be sent to 3D printing services. We additionally share how to convert these STL files to machine instruction gcode files, for reliable in-house printing on desktop, open-source 3D printers. We have successfully printed over 19 patient brain hemispheres from 7 patients on two different open-source desktop 3D printers. Each brain hemisphere costs approximately $3–4 in consumable plastic filament as described, and the total process takes 14–17 hours, almost all of which is unsupervised (preprocessing = 4–6 hr; printing = 9–11 hr, post-processing = <30 min). Printing a matching portion of a skull costs $1–5 in consumable plastic filament and takes less than 14 hr, in total. We have developed a streamlined, cost-effective process for 3D printing brain and skull models. We surveyed healthcare providers and patients who confirmed that rapid-prototype patient specific 3D models may help interdisciplinary surgical planning and patient education. The methods we describe can be applied for other clinical, research, and educational purposes.

Understanding Process Parameter Effects of RepRap Open-Source Three-Dimensional Printers Through a Design of Experiments Approach

With a view to enabling additive manufacturing (AM) processes, today, open-source, low-cost 3D printers are systems with great potential. However there is a significant lack of scientific data on the performance of open-source 3D systems and on the selection of adequate process parameters that can help to improve the quality of the parts. The purpose of this paper is to assess the effects of the main process parameters on the dimensional accuracy of a specific open-source 3D printer, the RepRap Prusa-Mendel I2. This study consisted of a benchmarking part, involving elementary shapes representing a series of different features. By means of a full factorial DoE (Design of Experiments), with three factors (layer thickness, deposition speed, and flow rate), three levels, and three replications, 81 parts were obtained. Subsequently, a laser scanner (D700 Laser Scanner—3Shape, Denmark) was used as high resolution reverse engineering system in order to evaluate the variation between real parts and nominal geometry. The impact of the main process parameters was evaluated and optimal combinations were analyzed. On the basis of the results obtained in the experiments, practical suggestions for the settings of common process parameters were formulated. Test results serve to improve the quality of AM parts through the most appropriate selection of the main process parameters.

Fabrication of paper-based microfluidic analysis devices: a review

As the main advantage of μPADs is compact and low-cost, we suggest that three kinds of technology could be utilized to develop the prototype of μPADs-based instruments rapidly, including open source hardware-Aduino, smart phone and 3D printing.