- Basics
- Creating a cylinder ("regular")


Hi, welcome to this second tutorial, in which I will show you an easy way to model "regular" Es-Cage prints.
There are many other ways to model these - here's ONE way to model a cylinder / tube.

We will be constructing this object:



  But first: some Es-Cage printing basics. If you already read these in tutorial #1, you can skip to "CREATING AN ES-CAGE CYLINDER..."  

The main trick of Es-Cage printing is that the printer can print these models in one continuous movement by bridging over the gaps, while the "stages" are connected by "radials", along which the printer zig-zags.
These radials AND the inner and outer shells are all just one single, continuous strand of plastic !

There are two main "flavours" in Es-Cage printing: "regular" and  "OFMS". This has to do with the way we will force the radials of each stage to fit exactly onto the radials of the stage below it.

The easiest way (for modeling) is OFMS, which stands for "Only Follow Mesh Surface". This is the setting in Cura that makes modeling Es-Cage prints a whole lot easier. If you can't or don't want to use Cura, then it depends on whether your slicer can do the same trick - if it can, then you can use the OFMS method as well as the "regular" one. If it can't, then you will have to use the "regular" method, which will be used for this tutorial.

By using OFMS, the center of the nozzle will exactly follow the surface  of the model. This is unusual, as this center normally follows a line which lies a bit INSIDE the model (at exactly half the diameter of the nozzle) so that the outside of the print will come out at exactly the right dimensions, according to the model. Using OFMS the print will be slightly larger than the actual model, because half the nozzle is printing OUTSIDE the skin of the model.

The main hurdle for modeling Es-Cage prints  is that the radials of the stages are switching between being "insides" and "outsides", seen from one direction. So to make the radials fit onto each other, you will have to model some overlap (unless you use OFMS - see Es-Cage Tutorial #1).

Using OFMS causes some limitations: there can be no bottom/top, no skirt/brim, and no retractions. So sometimes "regular" is the way to go.

The main differences between the two flavours:

regular: you can print a bottom, but the model has to be printed at 100% scale

OFMS: no bottom option, but you can easily scale / deform the model.



The first thing you need to do is decide the proportions. You can change some things later, but the amount of "planes" for the stages is decided here.

The cylinder we will be making will have an outside diameter of 40 mm, and a "wall thickness" (i.e. the depth of the gaps) of 5 mm.
For this size, 18 planes per stage will be good (but you can use any other number, as long as it is an even number).
With 18 planes we will get 9 "gaps" and 9 "planes" per stage.

Start by creating a cylinder, (bottom centered at 0,0,0) with 18 sides (no smoothing) and a diameter of 40 mm (radius = 20 mm).
For this example we want the planes to be roughly square. Change the height of the cylinder until the planes look square.
In this case a height of 7 mm takes care of that.



Rotate the cylinder so that two of the ribs line up with the y-axis. (It either should be like that already or else it will probably require a rotation of 10 degrees.)

Next, create a line (at z = 0) that consists of 5 points that roughly looks like this (to form one "notch" that roughly fits one plane of the cylinder).
Don't worry about the exact locations of these points yet - we will set these next.




Move the first point (yellow) to x=0.25, y=15 mm. Move the next one in the line (red) to x=0.25, y=20.

Why 15 and 20 ?   20 is the radius of the tube, and 20 minus the depth of the gaps (in this case 5 mm) = 15.

Why x=0.25 ? This creates the necessary overlap for the "regular" method. In this case, the final model will be printed with a shell of 0.5 mm. (You can do that with a 0.4 mm nozzle - in Cura anyway.) This will make the print stronger than with a shell of 0.4 mm. If you want to print with a shell of 0.4 mm, use x=0.20 instead. Or if you use a different size nozzle, use half the nozzle size - you get the idea.

Now rotate the whole line 20 degrees around the z-axis (clockwise, pivot at 0,0,0). Why 20 degrees? It's 360 degrees divided by 18 planes. So it helps to choose a number of planes like 18, 20, 24, otherwise you have to rotate around a weird angle (although that is possible too, as long as you enter plenty digits...).

So 20 degrees it is - should look something like this now:


  Now adjust the next two points, except this time move the overlap to the LEFT (x= - 0.25, y=15 and 20). Like this:  

  Again, rotate the line 20 degrees clockwise.. Set the last point to x= + 0,25, y=15.  

  Copy this line 8 times (9 in total) and rotate each one by increasing multiples of 40 degrees. If your software has an "array" function, use that.
It should look like this now (you can remove the initial test cylinder) :

  Attach these lines, then select all the corners and weld them together to form a single line. Now you can extrude this line to form a solid object. Extrude by 7mm to form square "planes" (as we checked right at the beginning). That should give you this - the first stage of your Es-Cage model:  

  Now copy this first stage, raise the copy to z=7 mm, and rotate it by 20 degrees to create the second stage.  

  Note how the edges of the gaps have some overlap. That is what makes this a "regular" model - for "OFMS", there would have to be no overlap at these edges (as explained in Es-Cage Tutorial #1).  


  Now copy each stage another 2 times, raising each one to form a stack of 6 stages.
Again: use the array function if you have one.


Your "regular" Es-Cage model is now ready to print.

Suggested print settings: shell 0.5 mm, nozzle 0.5 mm (even with a 0.4 mm nozzle), print speed 35 - 40 mm/s, layer height 0.15 - 0.25 mm. In Cura set “Fix type A” (combine everything) in Expert Settings. It is also a good idea to print using the "spiralized" setting. (It's black magic...)

There are of course many other ways to construct this shape. Next time, do it the way you think is easiest, as long as you end up with this result. Remember: it is crucial that the radials line up perfectly (in the actual print), otherwise the print will be weak.

  Es-Cage models made with this "regular" method can not be scaled, unless you change the shell/nozzle size accordingly.

So for instance, if you used x = +/- 0.25 mm (for shell 0.5 mm), you could scale the model to 80% and set shell & nozzle size to 0.4 mm.

You CAN change the HEIGHT of the model to any scale you like though, as the overlap will remain the same. It is also possible to use some deformations, like "twist" or "skew", but you have to make sure these don't influence the overlap distance for the radials. This makes it a lot harder to create complex shapes than when using the "OFMS" method.

  However, this "regular" method does have some advantages over the "OFMS" method:

- you can add a bottom to the print;

- you can use skirt, brim, raft etc. (all these options are excluded when using OFMS, unfortunately...)

- you can use retraction, which for instance makes it possible to have several separate parts in the model,  and/or add "loose parts" on top of the Es-Cage pattern, like the 4 separate towers and the "loose" battlements on the walls of this Es-Cage Castle:


  One last note: in this tutorial we created a model that consists of 8 solid (watertight) objects stacked on top of each other. This means that the stages have top and bottom planes that might cause problems in your slicer (Cura doesn't care, as long as you set "Fix type A").

If you find these planes are causing problems, then remove all stages except the bottom one, remove the top and bottom planes, and restack the stages so you end up with this (which also works fine in Cura):


  This is also advisable if you are going to use sub-division before applying deformations (to get a smoother result) - this way you can avoid having way too many vertices in the (unused) top and bottom planes.  

That concludes this second tutorial.
I hope you enjoyed it, and I expect you to have lots more fun creating your own Es-Cage prints.

In case you missed it: here's a link to Es-Cage Tutorial #1 - the "OFMS" method.

More Es-Cage tutorials coming soon.



Author: Erik Es, March 2016.