Gas station without pumps

2021 August 23

Final 3D-printed “quantum dot”

Filed under: Uncategorized — gasstationwithoutpumps @ 14:44
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In 3D-printed “quantum dot” and 3D-printed “quantum dot” revisited, I wrote about my attempts to 3D-print the image from

I finally got good prints from the resin printer at work (they had to clean the optics on the printer) and a decent print of the “stage jewelry” version on my Monoprice Delta Mini printer. I gave away all the prints (including the failed ones) to the physicists who provided the data, except for the one best print in each size.

The STL files from OpenSCAD are ridiculously large (17.8MB and 19.1MB), but they can be reduced using without much loss of detail to under 1MB.

The OpenSCAD program, scaled data file, and two STL files are available at


Here is the resin print, which is 50mm in diameter. The peaks come out clean and sharp, but my only color choices were black and clear (the only two resins BELS had).


The back of the print has the scaling information, but even with sanding the spots from the supports are annoyingly visible.


The stage jewelry version is twice as big, with a diameter of 100mm (I measured it at 104mm—I think my printer calibration may be a bit off).


Again, the back has the scaling information. Using “concentric” for the bottom layers made for some interesting patterning.


Here are the two quantum-dot pendants side-by-side, to show the relative sizes.

2021 July 26

3D-printed “quantum dot” revisited

Filed under: Uncategorized — gasstationwithoutpumps @ 14:55
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In 3D-printed “quantum dot”, I wrote about my attempts to 3D-print the image from, especially how I was unable to get a good print using my Monoprice Delta Mini printer.


Here are two not-very-successful prints using silk-gold PLA filament. There was a lot of stringing and the peaks were too fragile and snapped off.

I decided to try again, but at a bigger scale: 70,000×, rather than 32000× in the xy dimensions, making a 10cm diameter pendant.  My first attempt, using a layer height of 0.14mm was OK for the peaks, but the hanging ring did not fare so well.  Part of the problem was that the ring was too thin, and part was that horizontal circular holes do not print well—the flat top at the inside of the circle is insufficiently supported.

Update 2021 July 28:  I was looking at the original data file today, and it looks like I dropped one of the zeros in the xy scaling (I now think the scaling is 700,000×, not 70,000×).  I need to check the z-axis scaling also.


The image on the right shows the collapsed circular ring on the version printed at 0.14mm layer height. The image on the left shows the redesigned hanging ring and printing at 0.1mm layer height.


Here is the whole medallion at 0.1mm layer height in CC3D silk gold PLA with 20% infill. There was a little stringing and a few “zits” on the surface, but not too bad. I tried printing at 70micron layer height, but pronterface complained about not being able to allocate enough memory, so I gave up on that.

I’ll probably do one more post on these medallions, once I get the resin-printed ones that are printed without support.  The 10cm diameter is a bit too large for ordinary jewelry, but could work as stage jewelry.

2021 July 21

3D-printed “quantum dot”

Filed under: Uncategorized — gasstationwithoutpumps @ 10:40
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Earlier this year, I saw an article at that included a very pretty picture of the scanning-tunnelling micrograph of the trapped electron.  I asked the author (Jairo Velasco Jr) for a copy of the data, so that I could 3D print it.  It took me a few attempts to get the scale and clipping right, but I was unable to get a good print using my Monoprice Delta Mini printer.


Here are two not-very-successful prints using silk-gold PLA filament. There was a lot of stringing and the peaks were too fragile and snapped off.

I finally got around to asking BELS to print one for me on their resin printer.  I had two choices of resin (clear or black), so I picked the opaque one.  The results are much better:


Top view of the black resin-printed electron density.


Somewhat more side view. I’ve played with the darkness here, to make the shape and layering more visible.

Unfortunately, they printed the part with supports, which rather spoiled the back, so I’ll probably order another one without supports.


The back gives the scale: 32,000× in the horizontal direction and 2,000,000× in the vertical dimension. The ripples and dots are from the support structure, which was really not needed.

Correction 2021 July 28: The xy scale factor is incorrectly printed—it should be 320,000×, not 32,000×.  I had an error in my OpenSCAD code in copying the step size from the original data files.  The z-axis scaling is ok.


This is what the support structure looked like after I cut it away from the medallion.

The prints on the resin printer cost me an $11 setup fee, plus $3.64 for resin per print.  I think the tank is big enough to print 6 or 7 at a time, which would reduce the cost from $14.64 to about $5 each.  I’ll want to print a couple as gifts for the physicists who gave me the data. Each medallion is about 4.6 cm in diameter.

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