A few years back, there were some studies on the chemical and particle emissions coming out of the hotends of 3D printers. Although they galvanized a lot of people in the community, the science wasn’t entirely conclusive — one paper made it sound like you needed a hazmat suit for 3D printing, and the other suggested that cooking a meal in a kitchen was worse for you. That’s because they were measuring different things.
This new research paper on the emissions of 3D printers covers all the bases. They examined a variety of different materials printed in different printers. They also measured both chemical emissions and Ultrafine Particles (UFP) which can be hazardous even when the material itself is not.
There was no significant variation across brands of 3D printers. (Duh?)
ABS and similar materials outgas styrene at levels you should probably be worrying about if you’re running your printer for a few hours a day in an unventilated office.
PLA emitted significantly less overall, and most of it was a non-hazardous chemical, lactide. PLA doesn’t look like a problem.
All of the materials resulted in increased UFP exposure. These levels are above normal household background levels, but lower than certain “microclimates” which (if you follow the references) include principals’ offices with carpet, automobiles, restaurants, and rooms with burning candles or running hair dryers. In short, the UFP exposure doesn’t look like it’s going to be a big deal unless you’re sitting right next to the printer and running it continually.
So what would we do? It now looks like it’s prudent to print ABS only in a well-ventilated room. Or enclose the printer in a box and vent whatever you can outside — which can also help prevent breezes cooling the piece down unevenly and adding to ABS’s warping problems. Or just stick to PLA. It looks essentially harmless.
Despite tuning my extruder steps perfectly, and getting good results instantly on larger prints. I was still having a ton of trouble with smaller parts. PLA is the favored printing material for its low odor, low warping, and decent material properties. It also has many downside, but it’s biggest, for the end user, lies in its large glass transition temperature range. Like all thermoplastics, it shrinks when it cools, but because of this large range, it stays expanded and, getting deep into my reserve of technical terms, bendy for a long time. If you don’t cool it, the plastic will pile up in its expanded state and deform.
I am working on a project that needs a tiny part, pictured above. The part on the left is what I was getting with my current cooling set-up and temperature settings. It had very little semblance with the CAD file that brought it into this world.
The bond between layers in a 3d print occurs when the plastic has freshly left the nozzle at its melting point. Almost immediately after that, the plastic crosses from the liquid state into a glass state, and like pressing two pieces of glass together, no further bonding occurs. This means that in order to get a strong bond between the print layers, the plastic has to have enough thermal mass to melt the plastic below it. Allowing the polymer chains to get cozy and hold hands. Nozzle geometry can help some, by providing a heat source to press and melt the two layer together, but for the most part, the fusing is done by the liquid plastic. This is why large diameter nozzles produce stronger parts.
What I’m getting at is that I like to run my nozzle temperature a little hotter than is exactly needed or even sensible. This tends to produce a better bond and sometimes helps prevent jamming (with a good extruder design). It also reduces accuracy and adds gloopiness. So, my first attempt to fix the problem was to perhaps consider the possibility that I was not 100% right in running my nozzle so hot, and I dropped the temperature as low as I could push it. This produced a more dimensionally accurate part, but a extraordinarily weak one. I experimented with a range of temperatures, but found that all but the lowest produced goopy parts.
After confirming that I could not get a significant return on quality by fine tuning my temperature, I reduced the speed of the nozzle by a large percentage. By reducing the speed I was able to produce the middle of the three printed parts shown in the opening image. Moving the nozzle very slowly gave the ambient air and my old cooling fan plenty of time to cool the part. However, what was previously a five minute part now took twenty minutes to print. A larger part would be a nightmare.
So, if I can’t adjust the temperature to get what I want, and I can adjust the speed; this tells me I just need to cool the part better. The glass state of the plastic is useless to me for two reasons. One, as stated before, no bonding occurs. Two, while the plastic remains expanded and bendy, the new layer being put down is being put down in the wrong place. When the plastic shrinks to its final dimension is when I want to place the next layer. Time to solve this the traditional way: overkill.
A while back my friend gifted me a little squirrel cage fan he had used with success on his 3d printer. Inspired by this, I had also scrounged a 12v, 1.7A fan from a broken Power Mac G5 power supply. When it spins up I have to be careful that it doesn’t throw itself off the table.
I printed out mounts for the fans. The big one got attached to the Z axis, and the little one rides behind the extruder. I fired up the gcode from before and started to print, only to find that my nozzle stopped extruding mid way. What? I soon discovered I had so much cooling that my nozzle was dropping below the 160C cold extrusion cut-off point and the firmware was stopping it from damaging itself. My heated bed also could no longer maintain a temperature higher than 59C. At this point I felt I was onto something.
I wrapped my extruder in fiberglass insulation and kapton tape, confidently turned the nozzle temperature up, set the speed to full, and clicked print. With the addition of the overkill cooling I was able to get the part shown to the right in my three example prints. This was full speed and achieved full bond. Not bad! Thus concludes this chapter in my adventures with cooling. I was really impressed by the results. Next I want to try cooling ABS as it prints. Some have reported horrible results, others pretty good ones, I’m interested. I also wonder about cooling the plastic with a liquid at a temperature just below the glass state as it is deposited. Thoughts?
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.