In this post I’d like to show you two little tricks concerning 3d printing. I didn’t invent the first one (it’s rather a well known procedure to stick foil to smooth surfaces without bubbles), but as far as I can tell, the second trick is something new.
1. No bubbles, no troubles
When printing with a heated build platform, it turns out, that Kapton tape is a great surface for ABS printing. The only problem is, that normal Kapton tape is rather fragile and easily get ripped off the build platform when removing printed parts. Therefor I use 10x10cm sheets of glass with a layer of Kapton tape on top as exchangeable build surfaces on my heated platform.
One problem is to get the Kapton tape on the glass, well aligned and without bubbles.
The trick is to use soap, water and a scraper. Here’s a short how-to video, I made:
2. Snap-in, not snap-off
I recently designed a printable Tricopter:
One special thing of this design is, that the Tricopter is foldable for easy transport:
For this, the printed center piece (below the plywood platform) has two snap-in hinges for the front arms:
In my first design, I constructed the snap-in mechanism with little noses on the snappers.
But it turned out, that these noses not only are hard to print (due to the relatively small base area), but they’re also far too fragile for the task and easily break off after 3 or 4 times folding/unfolding the Tricopter.
After thinking about the problem for a while, I had the idea to post process the part after printing in order to get an easily printable part, yet maximum stability of the snap-in mechanism.
The trick is, to print the part without any nose at all…
… and then, after printing, to use a heat gun to gently heat up the small wings on the part until the ABS gets soft and then to slightly bend them. The result is an elastic, yet still very strong snapper:
Here’s a video of the bending procedure and of folding the finished Tricopter:
I’m sure, there are several other applications for this technique.
Speaking of technique, slightly off topic, but maybe also interesting:
A “mechanical disadvantage” of Tricopters versus Quadrocopters is, that in order to countervail the unbalanced torque of the three propellers, one of the motors needs a tilt mechanism (Quadrocopters use two CW propellers and two CCW propellers to self balance the propeller’s torque).
This tilt mechanism is usually one of the more complicated parts to build on a Tricopter. Here’s the tilt mechanism I designed for my printed Tricopter:
Besides 3D printing, I have recently started a new hobby: flying a RC Quadrocopter. To be more precise, flying a Quadrocopter with “FPV” (if you’re interested in what lured me into this, watch this video on YouTube…)
Anyway, since I’m relatively new to flying radio controlled stuff, I still crash the thing more than I fly it. Recently things really went out of control and I crash landed my Quadrocopter in a forrest, 450m away from its start position.
About 4 hours search time later (on the next day), my brother in law (who was part of the little search party) found the crashed thing. Of course, since the (LiPo) batteries were (still) connected for about 24 hours, they were fully discharged (and thus damaged). Also the Quadrocopter’s props and frame were damaged. But on the bright side, we were able to recover all motors and the (rather expensive) electronics, including the FPV related stuff (AV transmitter, camera).
Although it might be possible to repair the broken original frame, I decided to rebuild the Quadrocopter from scratch. And of course, I printed all custom plastic parts on my MakerBot :)
There aren’t many parts needed for a Quadrocopter’s frame: It’s more or less just four arms with the motors attached to one end and a center plate on the other end, forming the typical X shape.
The center plate is also where most of the electronics are mounted: the Quadrocopter’s gyroscope controller (which stabilizes the whole thing when airborne), the battery pack and, of course, the RC receiver. The four ESCs (Electronic Speed Controllers), driving the brushless motors, are mounted directly on the arms (i.e. nearby the motors).
In my case, due to flying the whole thing with FPV, there is need for some additional electronic components: an AV transmitter, a camera and the OSD (On Screen Display), consisting of three separate PCBs. The OSD isn’t mandatory for FPV, but it’s quite handy to see the battery’s remaining capacity, the Quadcopter’s GPS position and height and such, overlaid in the transmitted video.
So here’s the design I came up with:
For the arms, I use 10x10mm wood profiles. It’s cheap, it’s light weight and it’s tough!
The four arms (each 25cm long) fit into the holes on the center plate. They are hold in place by M3x25mm bolts, for which I drilled a 3mm hole through each arm after inserting them into the center plate. The exact positions of the holes are already printed into one side of the center plate.
The motors are bolt to small platforms which are attached to the outer end of the four arms:
I used M3x20mm nylon bolts (not printed…) to secure the motor platforms.
The separate holders for the additional electronics (AV transmitter and OSD main PCB) are attached to their respective mounting places on the side and the back of the center plate. The RC receiver and the Gyroscope/Main controller are mounted on top of the platform with double-sided adhesive tape (the Gyro with additional rubber foam padding to reduce vibrations):
The FPV camera is mounted on the front of the center plate. Above it (on the left side in the following picture), the OSD’s GPS receiver is mounted on the top of the center plate (double-sided adhesive tape):
As mentioned before, the ESCs (which control the brushless motors) are mounted directly on the arms. So is the RC receivers additional antenna unit:
On the bottom side, you can see a x-shaped structure. This holds the third (and final) PCB of the OSD, containing the current measurement unit which allows the OSD to measure and display up to 50A current. The x-shaped holder and the velcro tape for later holding the battery pack are bolt down to the center plate with help of the four M3x25 bolts (see above).
Well, that’s about it, so far:
The feet in the above picture are currently simply four pieces of 6mm aluminum pipe. I plan to replace these by 6mm carbon rod, with nice, printed landing plates:
Unfortunately, these aren’t ready, yet. I’d like to build these with some kind of suspension in order to soften rough landings. But I’m still in process to design a simple, light weight and effective way to build this…
That leaves me with a last important question:
Will it blend fly?
The whole Quadrocopter, including the full FPV equipement, battery pack and preliminary feet weights only about 650 gramms, which is well under the theoretical maximum flying weight (including payload) of the original Gaui 330XS hardware.
Unfortunately, it’s raining outside, so I couldn’t test it in the wild. But I couldn’t resist to do a short hovering test in my living room. You must know, that my living room is rather small and stuffed with furniture, so it’s kind of hard to do test flights there, especially for a not-so-experienced pilot as myself.
But see for yourself:
Well, this looks promising!
So far I’m quite happy with the results of 3D printing structural parts for a Quadrocopter. The parts are quite sturdy, yet light weight. And if I’ll brake any part of the Quadrocopter in the future, the replacement is always just a quick print away!
A minor problem with this object is, that Bradley Rigdon, the creator of this design, owns a couple of Dimension 3D printers. Since these professional printers automatically print with support material, large overhangs and such are no problem for them. And there are some large overhangs in the iPhone 4 tripod design…
It’s no secret, that the standard MakerBot Cupcake doesn’t have a second extruder for printing support material. Nonetheless, some people (including yours truly) recently started experimenting with Skeinforge’s built-in support stucture feature. It turns out, that these support structures don’t necessarily need a second extruder with dedicated support material.
Keen to experiment, I turned on the support feature in Skeinforge and sliced the downloaded STL (BTW, which needed resizing by factor 25.4, since the original STL was exported in inches).
In the relatively old version of Skeinforge, I still use for several reasons (v2009-11-06), the support settings are part of the Raft preferences:
I printed the generated gcode in white ABS with my -more or less- standard MakerBot.
Removing the support structures after printing is relatively easy as long as you choose “Support on Exterior only” in the above settings.
Besides the relative coarse bottom side (which was likely more a problem with some Skeinforge settings unrelated to the support structure), the main problem with the printed object was the tiny wall on one side. You’ll know which wall I mean and what’s the problem when you compare the following picture with the object’s STL-screenshot above:
One thing I learned in the last year, printing 3D objects with my MakerBot: avoid printing single, tall, thin walls in upright position, unless you want to break them away later (intensionally or unintensionally…).
The missing wall on the above object broke away when I tried to attach the object to my iPhone for the first time.
The easiest solution for such a problem is usually to print the object “on its side”, i.e. rotate the whole thing by 90°:
But in this case you’d run right into the next problem: Now you’d need to manage the 90° overhang (marked with the red circle). In order to use Skeinforge’s support structures for that, you’d need to switch the “Support Material Choice” setting to “Support Everywhere” (instead of “Support on Exterior only”). But removing those “inside” supports after printing isn’t easy and the support structures would likely degrade the surface of the rail on the upper side of the object, critical for the fit of the iPhone.
My solution for the dilemma was to print the object only slightly rotated:
I started with 30° rotation from the upright orientation. Since I used support structures anyway, the weird angle shouldn’t be a problem to print. By choosing a rotation angle smaller than 45° the resulting additional overhangs of the former vertical walls shouldn’t need additional support (Skeinforge automatically don’t generate support structures for those overhangs; see “Support Minimum Angle” in the above settings).
By rotating the object, the iffy wall is now also sliced in an angle, which greatly improves its stability:
The print looked ok on first sight…
… and the stability of the printed object was indeed greatly improved.
But unfortunately, printing the 30° overhangs didn’t work very well:
I did some additional adjustments in the Skeinforge settings:
To give the curved lower part more plastic to stick on, I changed the “Thread Sequence Choice” (Fill Preferences) from the default value “Perimeter > Loops > Infill” to “Loops > Infill > Perimeter”.
I also reduced the rotation of the object from 30° down to 15°, which still should be enough to give the front wall sufficient stability:
This time, the print looked good:
The refined settings seem to do the trick.
Here’s the printed part after breaking away the support material:
And here’s a comparison of all three different prints (left to right: 15°, 30°, 0°):
The stability-improved vertical (diagonal) structure (from left to right: 0°, 30°, 15°):
One more lineup (left to right: 0°, 30°, 15°):
And now to an interesting question: Does the part work?
See for yourself:
Looking good!
After the successful first test, I coated the whole thing with liquid rubber (Plasti Dip):
The rubber coating isn’t needed for grip (of the iPhone). But I thought, a little bit color couldn’t hurt. And also I like the rubbery texture on printed objects :)
In this post I’d like to show you two little tricks concerning 3d printing. I didn’t invent the first one (it’s rather a well known procedure to stick foil to smooth surfaces without bubbles), but as far as I can tell, the second trick is something new.
