The botswarm is expanding. We’re looking to hire on a new person for our team, and this time we’re looking for someone to help us on the virtual side of things. Besides making Thingiverse an awesome place for the 3D printing community, there is a lot of backend software needed to run a hardware company. We’re looking for a talented and brave soul to help us continue rocking the free by democratizing manufacturing.
Is this you? Is this someone you know? If so, check out our job posting for the job requirements.
Joel Belouet and Catarina Mota have collaborated on what may be my favorite (and delicious) MakerBot project of all time. Using a MakerBot + Frostruder + Heated Build Platform they have managed to 3D print and cook a real cookie. That’s right: your MakerBot is capable of autonomous cookie creation from start to finish. MMM. Oh yeah, and check out the their hilarious documentation site.
MakerBot is looking to expand. The next person we’re looking to hire is an electrical engineer. We’re looking for someone with a deep and masterful understanding of the workings of electrons and how to control them. If you are the type of person who ends up boring people at dinner parties talking about Boron and other doping agents, you may be our person! This position will be focused on building the latest and greatest open source electronics for MakerBot, so we’re really looking for someone with experience in mechatronics. The role will primarily be electronics based, but they will be controlling things such as motors, relays and other mechanical beasts.
If this is not you, but describes someone you know, please send them our way. If you refer us someone we end up hiring, we’ll hook you up with 5lbs of plastic.
Check out the craigslist posting for full details on the position and details on how to apply.
We’ve been working very hard in the MakerBot R&D lab lately. The thing that has been our main focus lately is the Plastruder. As many of you know, it can be a bit finicky at times. One of the failure modes of the extruder is that the drive pulley will strip the filament. Drawing on excellent research by Nophead and others in the open source 3D printing community, we’ve developed an improved drive mechanism: the MK5 Drive Gear. In fact, this drive pulley pushes about 2x harder than the old MK3/MK4 Drive Pulley. We jut got 700 of them in the MakerBot Store.
The design is pretty simple: there is a chunk of Stainless Steel 304 with a knurled groove that has the same diameter as the old drive pulley. Therefore, this part is a drop-in replacement for the old pulley. Since it is stainless steel it is very difficult to damage the pulley, even if you tighten it down too far. Furthermore, since the knurling on the pulley is so fine, it has a limited ability to self-clean as any stripped filament will typically fall out of it. If you’re feeling hardcore, you can download it from Thingiverse and make it yourself.
As sexy as this new pulley is, we wanted to be able to prove that it was indeed better than the old system. So, we turned to our trusty friend, Science! We formed a hypothesis (that the MK5 drive gear is better than the MK3 Drive Pulley). We created a test rig and we ran a bunch of tests. We tested the MK4 with both the new and old drive pulleys at a variety of spacings. As we had hoped, the new MK5 drive pulley came out on top.
For the force measurements, we used a very nice yet affordable Dillon GL-500 Force Gauge. This gauge has a few really nice features: a 500N capacity (~50kg) with an accuracy of 0.2N (~20g). Besides being nice and accurate, it can also measure both pull and push forces. It can record peak force, and even has RS-232 output which we could use to record measurements digitally. It is also a really solid, well built device.
The test rig was lasercut from some plywood and bolted to a chunky 2×6. If you want to replicate our results at home, you can download our template and lasercut it. The test process was pretty straightforward. We typically repeat this process 10x per setup to get a decent sample size.
The design is pretty simple: there is a chunk of Stainless Steel 304 with a knurled groove that has the same diameter as the old drive pulley. Therefore, this part is a drop-in replacement for the old pulley. Since it is stainless steel it is very difficult to damage the pulley, even if you tighten it down too far. Furthermore, since the knurling on the pulley is so fine, it has a limited ability to self-clean as any stripped filament will typically fall out of it.
Unclamp filament drive, remove the motor, and clean the teeth.
Re-attach motor, and set the filament idler wheel distance.
Clamp down extruder filament drive with output hole right against the force gauge probe.
Rest the force gauge to record Push force in Peak mode
Run the filament drive forward at 255 PWM (full-on)
Wait until the filament reaches the force gauge probe and fails (you can tell because the force gauge numbers climb and eventually stop at the peak.)
Record the peak force reading
After a bit of testing, some pretty clear results emerged: the MK5 drive pulley can generate a much stronger push force before failure by a solid margin. Since it is made from Stainless Steel, it is also much stronger and more durable than the Aluminum pulley which can easily suffer damage to its teeth when setting the gap. A word of warning: if your hot end does jam, the new drive pulley is strong enough that it may actually destroy your insulator retainer. You should definitely print out some replacements before you begin using with the new and improved MK5 Drive Gear.
If you would like to get your hands on this new hotness, they are available right now in the MakerBot store. Hot off the lathe. The kit comes with a new drive pulley, a 3mm set screw, and a new spacer stick so you can get the best force out of your drive pulley.
For the curious, here is the data we generated during our testing:
Charles Pax of NYC Resistor has been experimenting with a conveyor belt design that would allow him to fully automate the build process and create a ‘print queue’ of sorts. Here’s his latest results:
NASA is currently taking ideas from the public for about the next week or so at http://opennasa.ideascale.com. People can submit their ideas and vote on the ideas of others.
I submitted an idea for NASA to get involved with the desktop manufacturing / 3d printing movement. It can be seen here.
Desktop manufacturing and 3D printers are beginning to emerge as a growing industry. See RepRap – http://www.reprap.org/ and Cupcake CNC – http://www.makerbot.com/ for two examples. The technology allows you to design a model and have it manufactured in a device about the size of a large inkjet / laser printer. Instead of ink it extrudes plastic onto a platform. By layering the plastic objects can be created.
NASA could work with the desktop manufacturing community to design models for use in 3D printers. There are any number of items that could be modeled – rockets, satellites, the Shuttles, the International Space Station. The designs could be released into the public domain for anyone to use.
NASA engineers could also look into helping to develop the technology behind the 3D printers to make them better.
Inspired by Nophead’s excellent work, I decided to do my own testing. I had the folks up at Najet make me a prototype and pitted it against the existing timing belt pulley from SDP-SI. As with Nophead, I found the worm-gear style pulley to be much superior.
My process was pretty simple. We’re testing the pull strength of the extruder only here, so it involved hooking up the filament drive portion to a force meter (fish scale) and running it until it either stopped or failed. Here’s my setup.
Force Meter
A fish scale 50lbs / 23 kg. I couldn’t figure out how to make it do metric. FAIL! It still worked reliably, and I got a rough sense of what forces were involved. Now that I know my range, I am purchasing a much nicer digital force meter. (Its held down by capa / shapelock… I know, I should really have printed that part)
Filament Harness
Since we’re measuring how hard the extruder pulls on the filament, we need a way to hook up the filament to the force meter. I ended up bolting the filament between two washers and then looping that over the hook. I only rarely had problems after that.
Extruder Drive System
No need for the hot end or anything like that for this test. I laid the electronics to the side. Then I just clamped it to the wood, making sure to clamp in the middle of the dinos and not too hard. The bolts dug into the wood after a bit and made it snap right into place.
Then I just did a bunch of test and measurements. The fish scale did not have a very fast update rate at all (5 seconds?) It also did not have a peak weight or anything like that. I just watched it and tried to remember the highest number. This was a big deal because sometimes the filament itself would either break or elongate and deform. There readings could be slightly low because of that. It was also a bit chilly in the Botcave (its late december but I’m not going to go that deep on ya.
Here are the results as a google doc:
As for the extruder pulley, yes we will have these eventually. No idea on the timeframe, but having to wait is the price we pay for being as open as possible. I also made the silly mistake of making the diameter of the threaded parts different from the diameter of the current pinch wheel teeth. Its not much of a difference, but I’d like it to be a drop-in replacement. Its a really daunting thing to go into production on a part without a prototype, so it means I’ll probably need to get a new one made. I might have a few other variants made and see how they match up with the results from this one.
but I’m not going to go that deep on ya.
