3D Print of the Month – April 2014
Another month gone by, time for the next 3D printing project. The 3D print of April 2014 is an interesting and practical two piece print: a nutcracker. What makes this print more challenging is that the two pieces need to fit together by the means of a thread which obviously requires a fair amount of precision in order to work properly.
Objective
The reason for picking the nutcracker as 3D print of the month was simply that I wanted to make a functional piece. The design of the nutcracker is such that the nut is being cracked by a screw that pushes against the nut which is held in place by a recess in the corpus of the nutcracker. For these pieces to work together, the thread must be printed accurately.
Sourcing the 3D Model
I first came across the nutcracker on YouMagine, the 3D model repository managed by Ultimaker. The model was developed by user RenatoT and is shared under the Creative Commons – Attribution ShareAlike license.
All models found in on YouMagine are print-ready *.stl files and the nutcracker is no different. It comes in two *.stl files, one for the screw and one for the corpus.
Preparing the 3D Print
I loaded both *.stl files into Cura to set them up for printing. I decided to print each piece individually, not putting both items on the build platform at the same time. Other than modifying the print settings, I did not make further modifications in Cura. Note that the designer of the nutcracker recommends scaling both parts to 85% of their original size before printing. I saw this only after the print was completed hence why the nutcracker I created is a bit oversized.
Switching Cura to ‘overhang mode‘ confirmed the obvious: the most challenging part of the print would be the upper arc of the nutcracker corpus where the printer would need to bridge a gap of around 25 mm without any support material.
Executing the 3D Print
I started off by printing the corpus of the nutcracker. Due to the bridging challenges, I suspected that I might have to print this part a few times to get it right. The lower part of the corpus printed without any issues. Suspense was mounting as the print head started bridging the gap between the two pillars of the nutcracker corpus. The first few strands of filament didn’t look very promising: they were hanging loose between the two extremities of the nutcracker not resembling much of the circular shape they were supposed to become.
However, based on experience, I knew that it pays off to give the printer a chance and not to stop the printing process straight away if a print looks like it is going awry. As it turned out, this was the case for the nutcracker print as well. After a minute or so, enough filament had been placed for the successive layers to find their foothold. Soon enough, the circular shape which represents the ending of the thread started materializing.
Printing the screw was uneventful: this part printed without any hiccups and even while sitting on the print bed it was clear that the thread printed perfectly.
3D print specs:
Filament: 6.62m/52 grams of blue PLA filament
Print time: 2h 41min
Temp: 210°C
Print speed: 25 mm/s
Travel speed: 80 mm/s
Fan: on
Retraction: on
Lessons Learned from the April 2014 3D Print of the Month
In the end, the nutcracker turned out to be a straightforward print. It proved that the Ultimaker is capable of handling bridging quite well. Whereas some of the initial filament strands in the bridging area were hanging a bit loose, the printer quickly managed to build a solid enough base to place the rest of the print on.
Once completed, the body of the nutcracker just needed a bit of post-processing: using a Dremel I sanded off the excess bits of filament. Other than that, the print came out almost perfectly and the screw fit in the thread without any issues.
The nutcracker does not only look good, it also works fine! I used it to open quite a few nuts already.
Have you 3D printed practical items similar to the nutcracker? If so, feel free to share your experience by leaving a comment below. Any suggestions for a future 3D print of the month are also welcome!
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