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Open Source Grinding Machine Cuts Cost of Pellet 3D Printing

In pursuing the Distributed Recycling and Additive Manufacturing (DRAM) approach to open-source hardware development, a significant challenge lies in addressing the high cost of the compression screw component for alternative 3D printers, such as Fused Particle Fabrication (FPF) or Fused Granular Fabrication (FGF).

Platform solutions such as RepRap and Arduino, have allowed users and professionals worldwide to access or manufacture products or scientific tools themselves, cheaper and more effectively than commercial hardware products. Yet, as Dr. Joshua Pearce, of Michigan Technological University (MTU), notes in his study on the topic, open hardware lags the success of the open software community by about fifteen years. It is initiatives such as Dr Pearce’s Open Lab that are helping to bridge this gap—and in this case, with open hardware solutions that make FPF and FGF cheaper, more accessible, and more efficient than they are at present. The details of the lab’s work on the subject are described in a recent study, “Open Source Grinding Machine for Compression Screw Manufacturing.”

FPF or FGF are more effective than the traditional Fused Filament Fabrication (FFF) for DRAM, since they use raw plastic particles or granules which are more easily available and cheaper, instead of filament, to 3D print objects. Although it is has proven much cheaper and technically viable to produce filament from a variety of waste polymers, using an open-source waste plastic extruder (or recyclebot) – the process degrades the mechanical properties of the filament material over time, and limits its recyclability. In addition, commercially 3D printing filament is more expensive, at $20 per kg, than raw plastic pellets which are priced at $1-5 per kg.

This is why FPF and FGF printers are seen as a more effective alternative for the DRAM approach, and are already being used by academia, maker communities and businesses—the best example for the latter being GigabotX, an open-source industrial 3D printer than can use a range of materials from Polylactic Acid (PLA) to polycarbonate (PC). However, FPF/FGF 3D printers are more expensive, primarily due to the high cost of the precision compression screw, compared to FFF printers, and commercially available screws are not only very expensive (over $700 for the filabot screw) but also limited in handling larger pellets due to their small scale and size.

Image courtesy of MDPI

This is where Dr. Pearce’s open source hardware solves the problem: by providing a low-cost open-source grinding machine, so users of FPF/FGF can fabricate a precision compression screw for about the cost of the bar stock. Users will no longer be limited to commercial designs, and will be able to customize or optimize the screw to suit their requirements in terms of channel depth, screw diameter or length, pitch, abrasive disk thickness, handedness, and materials (three types of steel, 1045 steel, 1144 steel, and 416 stainless steel).

Image courtesy of MDPI

These compression screws will make recycling polymer particles/granules cheaper, more efficient, and flexible for FPF/FGF users, thus strengthening the case for DRAM as it pushes towards a circular economy.

Image courtesy of MDPI

The grinding machine is made using an off-the-shelf cut-off grinder (approximate cost $130, ideally suited only for steel or stainless steel) and less than $155 in parts. It is classified as an outside diameter cylindrical grinding machine. All the 3D printed parts can be made using any desktop printer using PLA (in this case a Lulzbot Taz 6), and the plywood parts were prepared using a CNC wood router.

Dr Pearce has long been an advocate of open source, distributed manufacturing, and DIY solutions for students, businesses, and, in particular, for scientists and researchers. To help accelerate innovation, empower scientists and users dependent on or limited by expensive commercial equipment and supply chains, and to reduce the cost of scientific tools, Dr.Pearce has led the way with his open source software or hardware solutions and initiatives. He has helped develop the Recyclbot, respirators, ventilators, specialized 3D printers, scientific or medical device components, and more.

Among other work, he has also worked to show how DIY 3D printing could impact the toys and game market (reducing costs of simple and complex toys or games by 40-90%), how to develop open-source, affordable metal 3D printing solutions using GMAW, and to 3D print slot die cast parts, that cost thousands of dollars, for just cents. He is also the author of Open-Source Lab: How to Build your Own Hardware and Reduce Research Costs and teaches a renowned open source introductory course in additive manufacturing at MTU, which is now online and free.

This latest work shows just how far his lab is going to make manufacturing technology accessible, even down to the compression screw needed for FPF/FGF 3D printing. The design, instructions and files for the device are free, and available here.

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Ireland: Researchers Create Open-Source 3D Printer for Neurophysiology

Researchers Thomas Campbell and James F.X. Jones, both of the School of Medicine, University College Dublin, Ireland, have a created a new 3D printer for the medical field, detailing their work in the recently published ‘Design and implementation of a low cost, modular, adaptable and open-source XYZ positioning system for neurophysiology.’

The authors have created an open-source system that can be customized for a wide range of projects, relying on an XYZ positioning system capable of moving a sensor or probe. Like a gantry crane, this new FDM printer is run by a standard Raspberry Pi 3, Arduino Mega, RAMPS 1.4 motor shield, and NEMA17 bipolar stepper motors. The frame consists of 20×20 mm aluminum extrusion made with 3D printed parts, bolted together by brackets. ‘Entry cost’ for such a 3D printer was calculated at approximately $670.20.

With the integration of the Raspberry Pi 3, the authors were also able to incorporate the Open Computer Vision Library (OpenCV) stating that feature is what makes the system unique in comparison to other XYZ positioning systems. The open-source machine learning software library is used with automated movement, and the creators expect it to transform the exploration of mechanotransduction, the method for sensory neurons to change a mechanical stimulus to an electrical signal.

Movement of the 3D printer is controlled by the Arduino Mega, which in turn is controlled by the Raspberry Pi 3:

“Arranging the microcontrollers in this master-slave configuration permits the automation of complex movement paradigms through the Python3 programming language. The power source for the system depends on the intended use case. For neurophysiology a linear regulated 12 V DC power supply must be used to ensure low EMI how-ever for other applications a 12 V DC switching power supply suffices.”

Campbell and Jones chose PLA for the materials to print components, using a Prusa i3 MK3, modeling the calibration cube in Autodesk Fusion360, and stating that dimensions for each cube were measured with digital calipers six times. Supports were not necessary for any of the fabricated parts, all of which were designed with minimal overhang.

Wiring of XYZ System. (A) RAMPS 1.4 shield (top) and Arduino Mega (bottom). (B) RAMPS 1.4 shield and microstepping jumpers (top). RAMPS 1.4shield with microstepping jumper pins installed (bottom). Note, to enable 1/16 microstepping for each stepper motor, it is necessary to install three jumpers per motor as encircled. (C) A4988 stepper motor drivers shown individually (top) and installed on RAMPS 1.4 shield (bottom). (D) Connecting the LCD screen to the RAMPS 1.4 shield. First, the smart adapter module is seated on the pins at the end of the RAMPS 1.4 shield. Next, EXP1 and EXP2 on the smart module should be connected to their corresponding ports on the reverse of the LCD screen. (E) The Arduino Mega and Raspberry Pi 3 can be connected over USB using a type A male to type B male connector. (F) Wiring of limit switches and stepper motors to RAMPS 1.4 shield. Note both the color orientation for stepper motor wiring and the highlighted pins for limit switch wiring.10T. Campbell, J.F.X. Jones /HardwareX 7 (2020) e00098

Build instructions include:

Y-axis carriage assembly
X and Z axes assembly
Axis alignment
Electronics and wiring
Preparation of and uploading of Marlin firmware
Setup of the Raspberry Pi 3 & OpenCV
Creation of a terminal based operating system

For use in functional neurophysiology applications, the authors tested the machine to see if it was capable of prompting mechanotransduction within the muscle spindle. Activation thresholds were successfully shown for:

Stretch distance
Stretch velocity
Stretch acceleration

Stretching the muscle spindle to study mechanotransduction. (A) Afferent nerve activity from a stretched muscle spindle. Brief pulses of stretch wereapplied to the lumbrical every two seconds in order to elicit mechanotransduction from the muscle spindle. Each Stimulus pulse indicates the initiation of a stretch. Filtered nerve activity is represented in blue, unfiltered in green. (B) Mechanotransduction activation thresholds were assessed with gradual increments in the stretch distance, speed or acceleration. For this filtered unit, activation thresholds were observed at 14.0 mms x 1and 50 mms x 2. Increased stretch distance, speed or acceleration are associated with increased nerve activity (Filtered Spike Rate). (C) Overdraw of filtered nerve activity observed in(B) indicates that this was a single-unit recording. All data was recorded in Spike2 (Cambridge Electronic Design). ENG, Electroneurogram. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)18T. Campbell, J.F.X. Jones /HardwareX 7 (2020) e00098.

“The main limitations of the XYZ positioning system are mechanical in nature,” concluded the authors. “In our implementation, the X & Z axis assembly is tall and heavy and as such we opted to reduce the Y and Z axis travel speeds to 2 mms x 1and 5 mms x 1respectively. This reduction in speed preserves positional integrity of the system by reducing the likelihood of stepper motors stepping erroneously. However, the assembly can be adjusted to the desired specific use case and a simple reduction the size of the Z-axis would greatly reduce its inertia and permit positional accuracy at greater travel speeds.”

“All components and software utilized were open-source, free to access or available at low cost. Given the ease with which these components can be accessed and the potential that such a system offers, it is believed that other research groups may find this system an attractive and useful experimental tool.”

3D printers are being used—and created—for many purposes in medical applications like dental, bioprinting, also offering a wide range of tools for doctors and surgeons like medical models and instruments. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: ‘Design and implementation of a low cost, modular, adaptable and open-source XYZ positioning system for neurophysiology’]

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Michigan Tech Researchers Recycle Wood Furniture Waste into Composite 3D Printing Material

A) PLA during mechanical mixing with wood-waste powder, B) PLA and wood-waste powder-based WPC after mixing and cooling to room temperature, C) chipped WPC, and D) homogeneous WPC material after first pass through recyclebot.

From artwork, instruments, and boats to gear shift knobs, cell phone accessories, and even 3D printers, wood has been used often as a 3D printing material. It’s a valuable renewable resource that stores carbon and is easily recycled, so why wouldn’t we think to use it in 3D printing projects?

A trio of researchers from Michigan Technological University recently published a paper, titled “Wood Furniture Waste-Based Recycled 3-D Printing Filament,” that looks to see how viable a solution it is to use wood furniture waste, upcycled into a wood polymer composite (WPC) material, as a 3D printing feedstock for building furniture.

The abstract reads, “The Michigan furniture industry produces >150 tons/day of wood-based waste, which can be upcycled into a wood polymer composite (WPC). This study investigates the viability of using furniture waste as a feedstock for 3-D printer filament to produce furniture components. The process involves: grinding/milling board scraps made of both LDF/MDF/LDF and melamine/particleboard/paper impregnated with phenolic resins; pre-mixing wood-based powder with the biopolymer poly lactic acid (PLA), extruding twice through open-source recyclebots to fabricate homogeneous 3-D printable WPC filament, and printing with open source FFF-based 3-D printers. The results indicate there is a significant opportunity for waste-based composite WPCs to be used as 3-D printing filament.”

While a lot of wood is wasted by burning it, it may be better to upcycle it into WPCs, which contain a wood component in particle form inside a polymer matrix. These materials can help lower costs and environmental impact, as well as offer a greater performance.

A) 0.15 mm layer height drawer knob being 3D printed with a screw hole for attachment. B) Completed drawer knob fully attached on left of wood block with example pre-printed hole on right of block, 30wt% wood furniture waste.

“There is a wide range of modification techniques for wood either involving active modifications such as thermal or chemical treatments, or passive modification, which changes the physical properties but not the biochemical structure,” the researchers wrote. “However, WPCs still have limitations due to production methods, such as producing waste material or orientation reliant fabrication, which may be alleviated with alternative manufacturing techniques such as additive manufacturing.”

While lots of PLA composite manufacturers are already in the market to make virgin, wood-based 3D printing filaments, the Michigan Tech study investigated using wood furniture waste as a 3D printing feedstock for WPC filament, which could then be used to make new furniture components.

“The process uses grinding and milling of two furniture waste materials – boards scraps made of both LDF/MDF/LDF (where LDF is light density fill and MDF is medium density fill) and melamine/particleboard/paper impregnated with phenolic resins. A pre-mixing process is used for the resultant wood-based powder with PLA pellets,” the researchers wrote. “This material is extruded twice through an open source recyclebot to fabricate homogeneous 3-D printable filament in volume fractions of wood:PLA from 10:100 to 40:100. The filament is tested in an open source FFF-based industrial 3-D printer. The results are presented and discussed to analyze the opportunity for waste based composite filament production.”

Surface contours of a personalized drawer handle with the Herman Miller emblem. A coloration change from the outside to the center is shown due to induced temperature changes during printing to provide a tree ring.

The team received wood-based waste material, in both sawdust and bulk form, from several furniture manufacturing companies, and completed some important steps to turn the wood waste into WPCs for 3D printing filament:

Size reduction from macro- and meso-scale to micro-scale
Mix fine wood-based filler material with matrix polymer
Extrude feed material into filament of homogeneous thickness and density

Then, the material was loaded into a delta RepRap 3D printer, as well as an open source Re:3D Gigabot 3D printer, to make a high-resolution drawer knob that was “attached to a printed wood block using a wood screw threaded through a pre-printed hole.”

“The wood screw was easily twisted through both objects with a Phillips screwdriver and the resulting connection withstood normal forces expected in everyday use. Additionally due to the flexibility of 3-D printing orientations a unique or personalized surfaces may be printed onto objects,” the researchers wrote.

“This is shown through the particular geometries or print directions which may be modified directly by altering gcode, or more conveniently by changing parameters in slicer programs. This enables mass-scale personalization of not only furniture components with wood, but any 3D printed part using recycled waste-based plastic composites.”

Once an optimized 3D printing profile was obtained, the recycled wood furniture waste-based WPC filament was able to produce parts without too many errors. However, there was a greater frequency of filament blockages and nozzle clogging with this material, when compared to pure PLA.

Five desk cable feedthrough parts 3D printed consecutively, 30wt% wood furniture-based waste.

“This study has demonstrated a technically viable methodology of upcycling furniture wood waste into usable 3-D printable parts for the furniture industry,” the researchers concluded. “By mixing PLA pellets and recycled wood waste material filament was produced with a diameter size of 1.65±0.10 mm and used to print a small variety of test parts. This method while developed in the lab may be scaled up to meet industry needs as the process steps are uncomplicated. Small batches of 40wt% wood were created, but showed reduced repeatability, while batches of 30wt% wood showed the most promise with ease of use.”

The researchers wrote that further work on creating waste-based WPC filament should include quantifying the material’s mechanical properties after the first cycle, and then comparing it to other materials, such as pure PLA and modified wood fiber powder. Additionally, industrial equipment and grouped 3D printing nozzles should be evaluated in terms of scaling up the process.

Co-authors of the paper are Adam M. Pringle, Mark Rudnicki, and Joshua Pearce.

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Researchers Build Inexpensive Open Source Bioprinter for 3D Printing Branching, Hydrogel-Based Vascular Constructs

While 3D bioprinting is not yet able to fabricate full human organs just yet, it can be used to manufacture several different kinds of human tissue, such as heart and bile duct. One of the main barriers of forming viable tissues for clinical and scientific use is the development of vasculature for engineered tissue constructs, mainly due to generating branching channels in hydrogel constructs that can later produce vessel-like structures after being seeded with endothelial cells.

But thanks to 3D bioprinting, it’s now possible to 3D print complex structures on multiple length scales within a single construct. This enables the generation of branching, interconnected vessel systems of small, vein-like microvessels and larger macrovessels, which couldn’t be done with former tissue engineering methods. However, the best sacrificial material for fabricating branching vascular conduits in constructs based in hydrogel has yet to be determined.

A team of researchers from the University of Toronto recently published a paper, titled “Generating vascular channels within hydrogel constructs using an economical open-source 3D bioprinter and thermoreversible gels,” in the Bioprinting journal. Co-authors of the paper include Ross EB Fitzsimmons, Mark S. Aquilino, Jasmine Quigley, Oleg Chebotarev, Farhang Tarlan, and Craig A. Simmons.

The abstract reads, “The advent of 3D bioprinting offers new opportunities to create complex vascular structures within engineered tissues. However, the most suitable sacrificial material for producing branching vascular conduits within hydrogel-based constructs has not yet been resolved. Here, we assess two leading contenders, gelatin and Pluronic F-127, for a number of characteristics relevant to their use as sacrificial materials (printed filament diameter and its variability, toxicity, rheological properties, and compressive moduli). To aid in our assessment and help accelerate the adoption of 3D bioprinting by the biomedical field, we custom-built an inexpensive (< $3000 CAD) 3D bioprinter. This open-source 3D printer was designed to be fabricated in a modular manner with 3D printed/laser-cut components and off-the-shelf electronics to allow for easy assembly, iterative improvements, and customization by future adopters of the design. We found Pluronic F-127 to produce filaments with higher spatial resolution, greater uniformity, and greater elastic modulus than gelatin filaments, and with low toxicity despite being a surfactant, making it particularly suitable for engineering smaller vascular conduits. Notably, the addition of hyaluronan to gelatin increased its viscosity to achieve filament resolutions and print uniformity approaching that with Pluronic F-127. Gelatin-hyaluronan was also more resistant to plastic deformation than Pluronic F-127, and therefore may be advantageous in situations in which the sacrificial material provides structural support. We expect that this work to establish an economical 3D bioprinter and assess sacrificial materials will assist the ongoing development of vascularized tissues and will help accelerate the widespread adoption 3D bioprinting to create engineered tissues.”

3D Bioprinter Hardware.

Existing 3D bioprinters have different technical advantages and deposition methods, which influence their prices and available applications. Extrusion-based 3D printers are good for tissue engineering, but the cost is usually too high for the field to experience significant growth.

For this experiment, the researchers chose to create their own open source 3D bioprinter, which costs roughly $3,000 and can be used for lower resolution applications, such as 3D printing perfusable microvessels in tissue constructs.

Printer operational overview.

Both the chosen method and material have to meet a certain number of requirements to successfully 3D print complex branching vessel systems within hydrogel constructs. First, sacrificial materials, which need to be non-toxic and maintain a uniform filament diameter during printing, have to be deposited in the desired vascular design during printing, then flushed away once the construct is done.

In addition, the 3D printer needs to have enough resolution to print all the channels – even those that will act as the small artery vessels of ~0.5–1 mm. It also needs to be able to deposit at least two materials, though more is better when it comes to creating heterogeneous tissues with different regions of varying cell and hydrogel composition.

The team investigated formulations of gelatin and PF127 due to their potential advantages as sacrificial materials in hydrogel-based tissue constructs. Gelatin, which has been used in several biomedical applications, is a thermoreversible (the property of certain substances to be reversed when exposed to heat) biopolymer of several hydrolyzed collagen segments, and can be 3D printed at ~37 °C, which is a temperature compatible with cells.

PF127 is a surfactant, meaning that it could have potential cytotoxic effects on embedded cells. But, it has inverse thermal gelation, which means it can be 3D printed at an ambient temperature, and then removed at ~4 °C to create void vascular channels.

According to the paper, “By using our custom-built printer in order to assess the printability of these materials and assessing mechanical properties, we aimed to establish which may be the best option for creating branching vascular channels within engineered tissues.”

The team’s modular 3D bioprinter includes extruding systems, 3D printed out of ABS on a MakerBot 3D printer, which were designed specifically to hold commercially-available, sterile 10 mL syringes, instead of custom-made reservoirs that would need to be specially made and repeatedly sterilized. An open-source Duet v0.6 controller board controls the system, and the print heads are isolated from the XYZ movements executed by the lower part of the chassis.

Fabricating perfusable channels.

For testing purposes, water droplets were 3D printed in a defined pattern with each extruder system, and the average distance between the droplets’ centers in the X and Y directions were measured; then, the mean distances were compared to the pre-defined CAD model distances.

“In conclusion, we found that PF127 is generally superior to gelatin as a sacrificial material for creating vascularized tissues by merit of its filament uniformity during printing and its greater compressive modulus,” the paper concluded.

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