Number of Shells Display

by duncan916, published

Number of Shells Display by duncan916 Jul 16, 2015
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This is one of a series of educational displays I made for the Arcade Library in Sacramento to help teach people about 3D printing.

It can be difficult to explain important 3D printing concepts like printing with supports, the effect of the number of shells, resolution, infill percentage and using a raft.

Sometimes all you need is a good visual aid to make things click.

This is a shell display that shows the effect of different "number of shells" settings. A one inch cube is printed ten times with various settings. Cubes with 1-5 shells are on one row and then 10, 15, 20, 25, and 30 shells are on the next row. It is easy to see how the number of shells effects the stability of a print and the translucency.

There is enough space between the cubes to squeeze them to feel how flexible or ridged they are.
It's a great way to quickly find out how many shells you should use for your project.

See the instructions for details on how to make this display for your classroom or wherever else it is useful.


You will need to print the file "25mm cube.stl" ten times.
Print times get longer as you print the cube with more shells, the longest print was 40-50 minutes

Print each cube with 0% infill and 0.3mm layer height.
Print the first cube with 1 shell. Before the print finishes, cancel the print. Do this before the printer seals the top of the cube and you can't see inside of it.

EDIT: It has been brought to my attention that there is a setting called "top layer height" in the advanced settings of MakerWare and Cura. Setting this to 0 will print the block without the top automatically, so you won't need to cancel the print at the end to leave it open so you can see the inside.

When I printed these cubes I put the first cube next to the cube that I was printing near the end of the print, and then canceled the print when it was approximately the same height.

Print the 2nd thru 5th cubes each with 2, 3, 4, 5 shells, 0% infill and 0.3mm layer height.

Do the same with 5 more cubes with the shell settings: 10, 15, 20, 25 and 30 shells.

The next step is printing "Display Row 1-5.stl" and "Display Row 10-30.stl"

I used the settings 5% infill and 2 shells and 0.3mm layer height.

Pick two colors, one for the letters one for the background. Load the filament of your choice for the background and start the print, when the printer starts to print the first layer of the letters and is done with the rest of the model go to "change filament" in the menu of your 3D printer. Then proceed to unload filament you were printing with and load the filament you have chosen for the letters. Then continue the print. Do these steps for both files. I would not recommend printing both files at once in case you make a mistake and have to start over.

Do the same steps for "Number of Shells Display Label.stl" that goes on the front of the display.

Last print the "display steps.stl" file in the color filament of your choosing.
The settings I used were 0.3mm layer height, 2 shells and 5% infill.

Now glue everything together. I glued the cubes down to the display so they do not get lost.

The glue I used is "Model & Hobby Cement" from the dollar store. It's strong but not so strong that you cannot get it apart if you make a mistake.

Enjoy! Teach and spread the knowledge of 3D printing!

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Thank you for your amazing design!!! We wrote about this in our webpage!! http://www.filamentix.com/entendiendo-conceptos-3d-capas-infill-y-soportes/

Jul 20, 2015 - Modified Jul 20, 2015

These are great. However, just to point it out.... your numbering scheme in the infill percentage thing (http://www.thingiverse.com/thing:927750) starts in the front, exactly opposite of this object. For consistency between the two objects it would be nice to have your numbering proceed in the same order on both objects.

Infill Percent Display

The nice thing about these models is you can assemble them however you like when you glue them together if you look at the files.

Truth be told, the shell display was originally in exactly the the same order as the infill display, but I changed my mind. I decided I wanted the 1-5 shells to be at the top because you can really see how translucent the single shell cube is when it is on the top row, instead of the bottom row of the display. It's easier to hold up to the light. So I pulled the whole thing apart, and moved 1-5 shells to the top row.

To be honest it doesn't bother me at all that they are different. I think things that aren't symmetrical make you think about them a little more.

You are welcome to assemble them however you like, whatever floats your boat.

Jul 16, 2015 - Modified Jul 16, 2015

Nice display.

If you make it with Cura, you can use the layer view to work out which layer to stop at.
Then open the resulting .gcode file and look for a line saying ";LAYER:10" for example.
Delete everything after this line down to ";End GCode"
The lines that start with ; are comments, so it does not matter if you keep or delete them.

.gcode is just text, so any text editor can open it, but preferably one that understands linespacing better than notepad.

Jul 19, 2015 - Modified Jul 25, 2015
duncan916 - in reply to MORA99

A much simpler way that someone suggested to me, is to set the "top layer height" to 0 in the advanced settings in Cura or Makerware. I haven't tried it yet, but it would in theory let you print the file without the need to hit cancel at the end so you could see the infill. And you wouldn't need to go in and manually change the gcode.