The strength of object printed on filament-based 3D printers varies by the plastic used, the G-code used by the printer, the percent infill, and even the temperature the plastic was extruded at. Everything, it seems, has an effect on the strength of 3D printed parts, but does the color of filament have an effect on the stress and strain a plastic part it can withstand? [Joshua M. Pearce] set out to answer that question in one of his most recent papers.
The methods section of the paper is about what you would expect for someone investigating the strength of parts printed on a RepRap. A Lulzbot TAZ 4 was used, along with natural, white, black, silver, and blue 3mm PLA filament. All parts were printed at 190°C with a 60°C heated bed.
The printed parts demonstrated yet again that a RepRap can produce parts that are at least equal in material strength to those produced by a proprietary 3D printer. But what about a difference in the strength among different colors? While there wasn’t a significant variation in the Young’s modulus of parts printed in different colors, there was a significant variation of the crystallization of differently colored printed parts, with white PLA producing the largest percent crystallinity, followed by blue, grey, black, and finally natural PLA. This crystallinity of a printed part can affect the tensile properties of a printed part, but [Pearce] found the extrusion temperature also has a large effect on the percentage of crystallinity.
Even though the pewter is hot enough to melt the PLA, it doesn’t appear to be a major problem if you quench the piece fast enough. According to [bms.had], a slower quench will melt some PLA although that creates a smoother surface. You can see the 0.31 mm layer lines in the cast, though, although you can use any layer height you like to control that. Creating the mold is simple (the videos use Tinkercad, although anything suitable for creating 3D models would work). You essentially attach a funnel to your part and make the entire part a hole inside an enveloping shape.
Every little plastic bauble you interact with has some sort of recycling code on it somewhere. Now that we’re producing plastic 3D printed parts at home, it would be a good idea to agree on how to recycle all those parts, and [Joshua Pearce]’s lab at Michigan Tech has the answer; since we’re printing these objects, we can just print the recycling code right in the object.
The US system of plastic recycling codes is particularly ill-suited for identifying what kind of plastic the object in question is made of; there are only seven codes, while China’s system of plastic identification uses 140 identification codes. This system for labeling 3D printed parts borrows heavily from the Chinese system, assigning ABS as ‘9’, PLA as ’92’, and HIPS as ‘108’.
With agreed upon recycling codes, the only thing left to do is to label every print with the correct recycling code. That’s an easy task with a few OpenSCAD scripts – the paper shows off a wrench made out of HIPS labeled with the correct code, and an ABS drill bit handle sporting a number nine. 3D printing opens up a few interesting manufacturing techniques, and the research team shows this off with a PLA vase with a recycle code lithophane embedded in the first few layers.
[Johannes] wanted to develop an unusual way to display time on a custom wristwatch. LED’s were too common, and mechanical indicators with small engines were too expansive, but Nixie tubes were just right. His design for the Numitron Geekwatch utilized two boards that were soldered together at a right angle, with a 3D printed enclosure made of semi-transparent PLA.
Future designs of this will improve on the button functionality as well as the housing of the wristwatch to protect the fragile tubes from external forces.
After the break is a video (in German) with [Johannes] going through the steps needed to make one of these of your very own:
Oculus, as we know, was acquired by Facebook for $2 billion, and now the VR community has been buzzing about trying to figure out what to do with all this newly accessible technology. And adding to the interest, the 2nd iteration of the development kits were released, causing a resurgence in virtual reality development as computer generated experiences started pouring out from of every corner of the world. But not everyone can afford the $350 USD price tag to purchase one of these devices, bringing out the need for Do-It-Yourself projects like these 3D printed wearable video goggles via Adafruit.
The design of this project is reminiscent of the VR2GO mobile viewer that came out of the MxR Lab (aka the research environment that spun out Palmer Lucky before he created Oculus). However, the hardware here is more robust and utilizes a 5.6″ display and 50mm aspheric lenses instead of a regular smart phone. The HD monitor is held within a 3D printed enclosure along with an Arduino Micro and 9-DOF motion sensor. The outer hood of the case is composed of a combination of PLA and Ninjaflex printing-filament, keeping the fame rigid while the area around the eyes remain flexible and comfortable. The faceplate is secured with a mounting bracket and a pair of aspheric lenses inside split the screen for stereoscopic video. Head straps were added allowing for the device to fit snugly on one’s face.
At the end of the tutorial, the instructions state that once everything is assembled, all that is required afterwards is to plug in a 9V power adapter and an HDMI cable sourcing video from somewhere else. This should get the console up and running; but it would be interesting to see if this design in the future can eliminate the wires and make this into a portable unit. Regardless of which, this project does a fantastic job at showing what it takes to create a homemade virtual reality device. And as you can see from the product list after the break, the price of the project fits under the $350 DK2 amount, helping to save some money while still providing a fun and educational experience.
If a 3D printer is interrupted during a print, it will usually result in a junk part. Resuming the print can be very difficult. A group of researchers at MIT have built an add-on for 3D printers that uses a laser scanner to evaluate the state of the print, and allows the printer to restart.
While this will allow you to salvage some partially competed prints, the interesting application is switching between materials. In the image above, the lower piece was printed in ABS. The print was interrupted to change materials, and the top cube was printed in PLA. This allows for prints to mix materials and colors.
The add-on was tested with the Solidoodle 3D printer, and can be built for about $60. It requires a laser mounted to the print head, and a low-cost webcam for performing the measurements. While the group will not be continuing work on this project, they plan to open source their work so others can continue where they’ve left off.
After the break, we have a video of the printer performing a scan and resuming a print.
Yeah I am still a little pissed that the competition is still around and we aren’t, and by “we” I mean Commodore Business Machines (CBM). It was Commodore that had the most popular home computer ever in the C64 (27 Million) and it was a team of MOS engineers after all, that had the idea to make a “micro” processor out of a 12 square inch PCB.
Of course they did work at Motorola at the time and “Mot” did not want anything to do with a reduction of the profit margin on the pie-plate size processor. Of course MOS got sued by Motorola but that was an average Tuesday at MOS/CBM. I absolutely credit CBM with buying the MOS Technologies chip foundry, as together we could make our own processors, graphics chips, sound chips, memory controllers, and programmable logic.
With this arsenal at our call we didn’t have to make compromises the way other companies did such as conforming to the bus spec of an industrial standard 6845 or having to add extra logic when a custom extra pin would work. We could also make sprites.
The compromise we did have to make when designing was cost, and I mean the kind of cost reduction where finding a way to save a dollar ($1USD) saved millions in the production run. I knocked $.90USD out of a transformer one day and I couldn’t focus the rest of the day due to elation.
Cost reduction is a harsh mistress however as you can’t just do it a little some of the time or only when you want to. The mental exercise of multiplying anything times a million was always there, it made it hard to buy lunch — I’d be blocking the lunch line while figuring the cost of a million tuna sandwiches FOB Tokyo Continue reading “Programmable Logic I – PLA/PAL”→