Well, this is timely. We saw a lot of things at Midwest RepRap Festival this year on both the printer and the material fronts. We told you about the delicious offerings made possible through remote extruder setups, strong and heavy filaments infused with copper and other metals, and a printer built out of K’NEX. No one was printing with canned cheese, though, and maybe for good reason.
[Andrew] here has created a 3D-printed arm that holds a can of aerosol cheese-like substance in place. A motor causes the holder to move the spout to the side, dispensing the goo. At first he squirts it in a coiled pile on to a cracker. That goes pretty well until it’s time to move away from the cracker. [Andrew]’s later attempt to build up four cheesy walls had us cheering. You can see what we mean after the break.
There are a couple of issues at play. Sometimes the add-on just plain falls off the end of the spout. Other times, air in the can interrupts the flow, just as it does during manual operation. And every once in a while, it just seems that the spout was too close to the substrate.
What do you think about the viability of cheese printing? Would it work better if the extrusion took place remotely, and the cheese was pushed through a thinner tip? Would a cooled print bed help? Let us know.
As far as locations for the Midwest RepRap Festival go, it’s not exactly ideal. This is a feature, not a bug, and it means only the cool people come out to the event. There were a few people travelling thousands of miles across an ocean, just to show off some cool things they built.
Two Colors, One Nozzle
[Sanjay] and [Josh] from E3D came all the way from merry olde England to show off a few of their wares. The star of their show was the Cyclops extruder, a dual-extrusion hot end that’s two input, one output. Yes, two colors can come out of one nozzle.
If you see a printer advertised as being dual extrusion, what you’re going to get is two extruders and two hot ends. This is the kludgy way to do things – the elegant solution is to make two colors come out of one nozzle.
The guys from E3D were showing off a few prints from their Cyclops nozzle that does just that, including a black and red poison dart frog, and a blue and white octopus. The prints looked amazing, and exactly what you would expect from a two-color print.
Rumor has it the development of the Cyclops involved extruding two colors, freezing the nozzle, and putting it in the mill just to see how the colors mixed. I didn’t see those pictures, but there’s a lot of work that went into this hot end.
The extruder uses a normal stepper motor, but instead of the usual knurled or threaded feed wheel and bearing to push filament though, he’s using two counter-rotating feed wheels attached to a planetary gear system. That’s a lot of torque that doesn’t distort or strip the filament. When you consider all the weird filaments that are coming out – ninjaflex, and even 3D printable machinable wax filament, this is extremely interesting.
Even if your filament isn’t exactly 1.75 or 3mm in diameter, this setup will still reliably push plastic; there is a bolt that will move one of the feed wheels in and out 0.4mm.
[Martin] had a pair of his extruders hooked up to a strain gauge, and it’s strong enough to lift your printer off the table without stripping the filament. Here’s a video of that demo from the bondtech page.
It’s been a little over a year since Makerbot introduced their new line of printers, and since then there have been grumblings about the quality of the Smart Extruder that each one of these printers comes with. While there is no 3D printer extruder that will not eventually clog, wear down, or otherwise break, there are reports of the Makerbot Smart Extruder failing in only hundreds or even tens of hours of use. Considering that a single large print can take a dozen or so hours to complete, you can easily see the why the Smart Extruder is so despised and why even the availability of a three-pack of Smart Extruders is a joke in the 3D printing community.
Of course a cheap shot at Makerbot that plays right into your preconceived ideas and prejudices is far too easy. We’re here to solve problems, not just state them, so here’s what we’re working with: to quantify the long-term reliability of 3D printers we need a way to measure the mean time before failure of extruders. This is already a solved problem; it’s just not implemented.
On aircraft and some very expensive engines that power things like buildings and ships, there’s one gauge, tucked away in the control panel, that keeps track of how long the engine has been running. It’s called a hobbs meter, and the idea behind it is extremely simple – when there is power going to the Hobbs meter, it counts out hours on a small clockwork display. The resolution of the display is only tenths of an hour, usually, but that’s good enough for scheduling maintenance and to be mentioned in NTSB accident reports.
Spend enough time with a 3D printer, and you’ll quickly realize the ‘estimated print time’ is merely a ballpark, and with failed prints the ‘total print time for this object’ isn’t exactly a perfect measure of how many hours you’ve been using your extruder. Only by directly measuring how many hours are logged on a hot end or how many kilometers of filament have been sent through an extruder will you ever get an accurate idea of how long an extruder has been running, and how reliable a printer is.
Hobbs meters are available from Mouser, but you’ll be overpaying there. The better option is from a vendor in a different niche; $30 for a meter that can connect directly to the extruder heater. If enough people add this and keep proper logs, there’s a slight chance of improving the state of 3D printers with real data and not the prejudices of people trying to justify their own designs and purchases.
But perhaps that’s too hard; adding a $30 item to a printer’s BOM just for the sake of data is a bit much. Luckily, there’s an even simpler solution that won’t cost a dime. Just measure the time a heater has been on in the firmware, or save the total length of extruded filament in a microcontroller’s EEPROM. Every printer firmware out there, from Marlin to Repetier to Sprinter has in it a way to calculate both the length of time a heater has been on or how much filament has been pushed through a nozzle.
Secondly, if we’re not going with mechanical Hobbs meters there would need to be a ‘total time heater on’ or ‘total length of extruded filament’ variable in the various firmwares. There would hopefully be standardized Gcodes or Mcodes to read and reset this variable.
Will this happen? Of course not. Organization isn’t a strong suit of the RepRap project, and any company that implements Hobbs meter functionality will probably lock that up in proprietary obfuscation. However, Makerbot isn’t dumb, and given they’re selling three-packs of extruders, I would bet they have some data on the MTBF of their extruders. A community-based measurement of the most common cause of broken printers is certainly possible, but like all problems it’s one of organization, not technology.
3D Printering is a semi-weekly column that digs deep into all things related to 3D Printing. If you have questions or ideas for future installments please sending us your thoughts.
In the past month, a few patent applications from MakerBot were published, and like everything tangentially related to the prodigal son of the 3D printer world, the Internet arose in a clamor that would be comparable only to news that grumpy cat has died. That’s just an analogy, by the way. Grumpy cat is fine.
The first patent, titled, Three-dimensional printer with force detection was filed on October 29th, 2013. It describes a 3D printer with a sensor coupled to the hot end able to sense a contact force between the nozzle and build plate. It’s a rather clever idea that will allow any 3D printer to perform software calibration of the build plate, ensuring everything is printed on a nice, level surface. Interestingly, [Steve Graber] posted an extremely similar design of a bed leveling probe on October 6th, 2013. In [Steve]’s video, you can see his bed level probe doing just about everything the MakerBot patent claims, all while being uploaded to YouTube before the patent application.
When it rains it pours, and the Quick-release extruder patent application, filed on October 28, 2013, bears this out. It claims an extruder that includes, “a bistable lever including a mechanical linkage to the bearing, the bearing engaged with the drive gear when the bistable lever is in a first position and the bearing disengaged from the drive gear when the bistable lever is in a second position.” Simple enough, a lever with two positions, where one presses a bearing against a drive gear, and the other position disengages the bearing from a drive gear. Here’s something that was published on Thingiverse in 2011 that does the same thing. Hugely famous RepRap contributor [whosawhatsis] has weighed in on this as well.
It is important to note that these are patent applications. Nothing has been patented yet. The US Patent and Trademark Office does seem to have a lot of rubber stamps these days, so what is the average Internet denizen to do? Here are easy to follow, step-by-step instructions on how to notify the USPTO of prior art. Remember, just because prior art does not completely invalidate a patent application’s claims doesn’t mean you shouldn’t send it in. It is a patent examiner’s job to review the prior art.
So there you go. MakerBot applies for patents, people complain, but not to the USPTO. Highly relevant video and transcription below.
The current crop of 3D printers are technically four-axis machines, with three axes of movement and a fourth for the position of the filament. [Bas] had an entirely different idea – why not link the speed of the extruder to the speed of the nozzle? It turns out this technique gives you more ‘plasticy-looking’ prints and a vast reduction in blobbiness.
[Baz] has been working with LinuxCNC, a BeagleBone Black and the BeBoPr-Bridge cape, and there’s been a lot of development with that system in turning many straight lines into one smooth arc. This led him to adjusting the flow rate of a nozzle while the printer is running, but this is difficult if the extrusion is controlled by position as in a traditional printer setup. A new configuration was in order.
What [Baz] ended up with is a config that calculated the speed of the extruder based on the speed the nozzle is moving over the print surface. This gave him the ability to add live nozzle pressure adjustment, and as a result, a near complete disappearance of the little blobs that appear at the start of each layer.
For a well calibrated machine, it’s only a small difference between the ‘normal’ and ‘velocity’ methods of controlling an extrusion rate. It’s a noticeable difference, though, and one that vastly improves the visual quality of a print.
Once you have a 3D printer able to build a few objects in a single color, the next logical upgrade is a dual extruder. A dual extruder allows for multiple color prints, and by adding a dissolvable filament, the ability to print object that would otherwise be impossible. Fitting a dual extruder on an existing 3D printer presents a problem: simply by using a second stepper motor, you reduce the print area of your printer significantly. That’s the problem Dglass 3D aims to solve with their extruder. It’s a dual filament extruder that uses only one stepper motor and takes up less space than some other single filament extruders.
This isn’t the first time the guys at Dglass 3D have tried Kickstarting a dual filament extruder; last year we saw a very similar mechanism that used a single stepper motor to feed two filaments. This older model lacked retraction, though, meaning two colored prints would range somewhere between messy, inaccurate, to impossible.
The new extruder uses a servo to ‘latch’ the filament and drive it into the hot end. This means retraction of the filament is possible and from the sample prints with this extruder, the results look pretty good.
Below You’ll see a few video demos of the dual color/retraction extruder printing an object in black and white filaments at the same time. It’s very cool, and with the addition of a dissolvable filament means very complex objects can be printed very easily.
For how many can be found on the workbenches and in the toolboxes of makers and hackers the world over, finding a glue gun that does more than just heat up and drip glue everywhere can be a challenge. [Ben Heck] finally solved this problem with a hot glue gun that’s more like an extruder from a 3D printer than a piece of junk you can pick up at Walmart for a few dollars.
By far, the most difficult part of this project was the glue stick extruder. For this, [Ben] used a DC motor with a two-stage planetary gear system. This drives a homemade hobbed bolt, just like the extruder in 99% of 3D printers. The glue stick is wedged up against the hobbed bolt with a few 3D printed parts and a spring making for a very compact glue stick extruder.
The electronics are a small AVR board [Ben] made for a previous episode, a thermistor attached to the hot end of the glue gun, a solid state relay for the heater, and analog controls for speed and temperature settings. After finishing the mechanics and electronics, [Ben] took everything apart and put it back together in a glue gun-shaped object.
The finished product is actually pretty nice. It lays down constistant beads of hot glue and thanks to a little bit of motor retraction won’t drip.
You can check out both parts of [Ben]’s build below.