If I’m printing an object with a 0.5mm thickness, chances are the very first time there’s a slight overhang it will go pear shaped. When the walls are that thin, there’s almost nothing underneath even a very slight 20-30 degree overhang.
Duh.
Category Archives: Design
Printable Sonic Screwdriver progress
STL sheet for printable sonic screwdriver
Sketch of Screwdriver
Off to the left is a picture of what the finished sonic screwdriver should look like. Here’s a picture of the parts I’ve designed so far. Assembled properly, these parts should be able to be assembled into the lower half of the sonic screwdriver.
I’ve arranged the parts so that they have a less than 60mm x 60mm footprint on the build platform. I would really like it if the final product could be printed all on one build plate and assembled without tools or additional non-printed pieces.
After my recent design-print fail, I’m going back to the drawing board (slightly)1 wiser. If nothing else, I like to think what I have so far is pretty neat. 2
Design-print fail
I’ve been slowly working on the design of a printable (and fully MakerBottable) sonic screwdriver. This model of the sonic screwdriver is built up of a number of concentric cylinders, has several significant overhangs well in excess of 45 degrees, and is larger than the MakerBot’s built capacity. In order to deal with these design problems, I modeled it in sections.
In order to make the overall result something I could just pop/snap/slide together I designed it making some sections which were split vertically and other sections which slide around those sections to keep them together. In order to make the parts quickly printable I designed all the parts at around 0.5mm thickness.
About 40% of the way through the print one of the vertical sections wasn’t coming out properly – probably because it was too thin. The parts were too thin and flexible and ended up tearing between layers and just being too flimsy.
I also noticed something odd – the extrusion was too thin on that side of the model. I can’t be sure why this is happening – but I suspect it’s due to the extruder not getting a good enough grip. Perhaps I need to floss the extruder pulley or install a new extruder idler wheel. However, it doesn’t explain why the extrusion was too thin on just that one side and no other spots.
Suggestions?
3x2x1 Rubik’s Cube Production File
My prior copy of this 3x2x1 Rubik’s Cube was printed a few parts at a time – I’d print one part, test it, print up another, etc. Last night I was able to use my production file to generate all seven pieces in one go. It took 1 hour and 45 minutes to complete the print job, but well under three minutes to clear most of the pieces of the raft off the parts and assemble the puzzle. In order to help people modify and improve upon my design, I’ve upload the original Sketchup files, the STL I used, as well as my own GCode.
Owenscenic on Thingiverse asked,
I am interested in trying your gcode, how did you generate it? How well does it minimize strings between the printed parts? I’ll look at is to see how it starts and the temp…
In case you’re wondering too, the answers are as follows:
- I generated the Gcode using my slightly tweaked RepG v18 built-in Skeinforge settings for ABS with a raft, with a build temperature of 220C.
- The Gcode does pretty well with minimizing stringing. However, some of the credit has to go with the part placement in the STL production file as well as the nature of the object. As soon as you assemble it and start to rotate the parts, most of the remaining strings and little blobbies will pop right off.
Owenscenic, please let me know how your print of this turned out! Please post a picture!
3x2x1 Rubik’s Cube assembly pictures
The design should be pretty intuitive. However, I went ahead and took some pictures of the assembly anyhow.
-
- All seven parts of the 3x2x1 Rubik’s cube puzzle, as they came off the MakerBot build platform
-
- All seven parts of the 3x2x1 Rubik’s cube puzzle
-
- 3x2x1 Rubik’s cube puzzle, center barbell/axle installed
-
- 3x2x1 Rubik’s cube puzzle, all cubes slotted together
-
- 3x2x1 Rubik’s cube puzzle, fully assembled
-
- 3x2x1 Rubik’s cube puzzle, partial rotation
As I mentioned in an earlier post, I think this one came out really really well. :)
Tyvek Sled Kite… from office supplies
Tyvek Office Supply Kite
The picture to the right is of a kite that I built several weeks ago and only got around to actually flying this weekend. It’s basically made out of office supplies. :)
Originally I just wanted to make the Tyvek sled kite from the Howtoons shown in Craft Magazine, Volume 8. 1 But then I wanted to see how much of the kite I could assemble just using things from the office. The answer is, basically all of it.
The Howtoons calls for:
- A large sheet of Tyvek
- Tyvek tape
- A washer
- Ruler
- Scissors
Instead I used:
- Tyvek from Tyvek office envelopes, rather than a large sheet or roll of Tyvek house wrap. My office is sent dozens of these things a day. It didn’t take long to collect 30 plus.
- Clear packing tape. I used this instead of Tyvek tape. Tyvek tape would have worked a LOT better, but I have no complaints.
- Rather than use a washer, I used a spare keyring. I had other various office supply bits hanging around in case this didn’t work out. Paperclips, binder clips, etc.
- Yardstick.
- Scissors.
Since the envelopes are significantly smaller than the sheet of Tyvek rolls, I had to either make my kite smaller or stitch them together into a larger sheet. I did both. I scaled the plans down to about 2/3rds the size from the diagrams and then used packing tape to put them all together. To get the most surface area out of each envelope, I burst all of the envelopes at the seams and then taped them up. Once I had a 36″ tall sheet, I started cutting it into the pieces I needed, re-taped it back together as indicated by the diagram, and then set it aside for weeks while I didn’t fly it. :)
On the day of the launch I made the tail out of strips of leftover envelopes taped together with the gluey bits from some of the envelope flap sealants and more packing tape. I punched a hole in the three ribs using a pen, ran the line through each of the three ribs, reinforced it with more packing tape… and launched.
The only non-office supply things used in the construction were:
- Crayons for coloring the kite (hard to see)
- The ruler – I don’t have a yardstick at work
- The kite line, purchased from Amazon
It flew pretty well.
- I found a copy of all three pages after googling around a little. Howtoons: Sled on a Thread pages 1 2, 3 [↩]
3x2x1 Rubik’s Cube – done!
I’m so happy with the way this has turned out.
I’ve made a bunch of changes since the last revision of this printable 3x2x1 Rubik’s Cube puzzle:
- I’ve totally redesigned the center barbell connector. I simplified the design, removed the five support struts for each end and replaced it with a single support strut and a flat hexagon in the center of the piece. The purpose of the hexagon is to give the barbell more contact area with the raft. One of the earlier drafts didn’t have as many supports or this flat hexagon, and it tore off the build platform partway through the build.
- I increased the diameter of the tube between the barbells. This enabled it to print easier, made it a little more sturdy, and decreased the wobbliness of the barbell when everything is assembled.
- I also shortened the entire barbell by 1mm, so that the entire puzzle is held together more closely.
- I made the flat semi-circular tabs slightly thinner so they rotate a little more freely.
- I significantly redesigned, thickened and simplified the two brackets that the barbell snaps into. It’s been able to easily withstand numerous couplings/decouplings as well as numerous rotations. With a few rotations, all parts now rotate easily.
- All of the parts fit together SO much better than my first draft held together with a nut and bolt.
- There is a slight bit of sideways flex that can occur with the use of the barbell. It is really minor and it actually seems to help the puzzle be more forgiving as you manipulate it. I see this more as a benefit than a design flaw.
The was one design choice on which I waffled. I considered making the center cubes non-identical, with one having half a barbell stick out and with the other having the internal connector you see now. This would have removed much of the sideways flex – since the barbell would be stationary. I did not go with this design choice because whether the puzzle used one barbell and two connectors or male/female center cubes, there would always be some flex caused by the use of a connector rather than a static pin. And, to be honest, I much preferred the symmetry of having everything assembled out of just three unique parts.
I know I’ve mentioned this before, but I really like the idea of a MakerBot printable toy that can be printed in one go and then assembled without tools or any additional hardware. I also think this would make a great MakerBot print demonstration.
I’ll post some pictures of the parts a little bit later.
New 3x2x1 Rubik’s cube design – totally printable!
X-Ray view of the 3x2x1 puzzle cube
This is easily my most intricate digital design for the MakerBot yet. It’s a 3x2x1 variation on the Rubik’s cube puzzle I had posted earlier.
This version incorporates the prior improvements as well as designing a connector system inspired by R3bbeca‘s beco block connectors.
This has enabled a totally printable toy. This just makes me happy. 1 The idea that I can crank out a set of these parts, clean them up a little, and just snap the toy together is just amazing.
TomZ‘s original 1x2x3 “friendlier” Rubik’s cube designs were also totally printable – but required a printed pin that was later glued in place. I like the ideal of all printed parts – but strongly prefer a design that can later be disassembled easily. And, as I mentioned above – the ability to hand assemble the toy is important to me.
I wasn’t able to recreate R3bbeca’s female connector designs2 so I made a simplified version that should suffice.
The simplified connection mechanism is essentially two plastic fingers that will (hopefully) pinch the barbell into place. This was made by designing the outline of the gripping “fingers,” creating a horizontal cylindrical hole slightly larger than the intended end of the barbell, then creating a vertical cylindrical hole in the center for the barbell to be inserted through, then a bit of cleanup.
The biggest potential problem is that this design will require a carefully tuned ‘bot. The center cube pieces have a lot of stuff packed in there – semi-circular slots for the semi-circular tabs, connectors for the barbell, and thin walls separating things. With those thin walls and interior overhangs, this may be a difficult design to print.
I think Bender is up to the task, but we’ll see in a few hours. :) I can’t wait to print this!
For me, having a MakerBot is like waking up to Christmas every morning.
Oh, and before I forget, if you want one of these – leave a comment or send me an e-mail through the Contact page. Make me an offer.
- Perhaps a little prematurely, since I haven’t actually printed this yet… [↩]
- I believe I’ve already sufficiently lamented my inability to understand women and their mysterious lady ways. [↩]
Improving on the 3x2x1 Rubik’s Cube
I’ve been fiddling with the designs for the 3x2x1 Rubik’s Cube incorporating some of the changes I had considered:
- I’ve widened the holes for the nut and bolt.
- I’ve made all of the cubes solid. I think it will just work better with solid parts. I had left the four end cubes mostly hollow to:
- Improve printing time
- Use less plastic
- Possibly make an interesting hiding place for something very small
- I’ve shortened the “stem” that connects the semi-circular tab to the end cube to allow for a more snug fit.
- I’ve made the semi-circular groove in the center cubes narrower, to allow for a more snug fit.
- Make these cubes solid so that they slide against each other easier.
- I’ve noticed that the nut and bolt I installed into either side of the center cubes were pushed sufficiently well inside that they don’t want to come out or rotate. This is a very good thing for this design! It turns out that if you rotate it too much in one direction, you can just rotate it back a few times and it will be tightened back up! It also makes for easy disassembly/reassembly – just rotate the puzzle until it comes apart and rotate it back together to reassemble.
Designing with a MakerBot
After playing with this puzzle for a few days I’m really happy with how it turned out and I think the above improvements will make the next version a little bit better. This reminds me of Forrest Higgs’ recent commentary on engineering with a RepRap in the design cycle. It’s so easy to test out a new design that I don’t hesitate to whip something up, print it off, SEE and FEEL how it works and any unintended nuances of that design, and then redesign with these revelations in mind.