
Hi, welcome to this tutorial, in which I will show you an easy
way to model EsCage prints.
There are many other ways to model these, but let's start with
this one.
We will be constructing this object: 











But first: some EsCage printing basics. 





BASICS
The main trick of EsCage 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 zigzags.
These radials AND the inner and outer shells are all just one
single, continuous strand of plastic !
There are two main "flavours" in EsCage 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 EsCage 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 either
start using Cura or skip this tutorial and read
EsCage Tutorial #2 about
the "regular" method.
PLEASE NOTE: THE OFMS OPTION IS AVAILABLE IN
CURA VERSION 14.07. IT DISAPPEARED
IN LATER VERSIONS.
You can download version 14.07
here
(go to "see all versions").
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 EsCage 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.
However, 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. But modeling for OFMS EsCage prints
is easier, so we'll start with that.
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. 





CREATING AN ESCAGE CYLINDER USING
THE "OFMS" SETTING IN CURA
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).
ORIENTATION: XAXIS =
LEFT TO RIGHT, ZAXIS = HEIGHT
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
yaxis. (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, y=15 mm. Move the next one
in the line (red) to x=0, 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.
Now rotate the whole line 20 degrees around the zaxis (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 like this now: 











Now adjust the next two points (x=0, y=15 and
20). Like this: 











Again, rotate the line 20 degrees clockwise., and set the last
point to x=0, 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 first EsCage 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 fit exactly on top of each
other. That is what makes this an "OFMS" model  for
"regular", there would have to be some overlap at these edges 
more about that in EsCage Tutorial #2. 











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 first EsCage model is now ready to print (using OFMS).
Suggested print settings: SINGLE SHELL 0.4  0.5 mm (with nozzle 0.4 mm,
else set shell to nozzle size if you use another size 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.
And don't forget to switch on the "Only Follow Mesh Surface"
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, otherwise the print will be
weak. 





You can now group the objects together and scale and/or deform
this group. For instance, if you add two more stages, scale y to 55% and apply a
twist, you end up with this: 











As you can see, this causes the square planes to become 2
triangles at slightly different angles. For a more sophisticated
approach, you can first apply a subdivision to the model to get
a smoother result like this: 











Before subdivision, it is useful to remove the top and bottom
planes of the stages, to avoid ending up with too many vertices.
Cura doesn't need these horizontal planes anyway, so it is best
to remove them to save memory. Go back to the first stage
(delete the others), remove the top and bottom planes and
restack the stages. Then apply subdivision and transformation(s). 











That concludes this first tutorial.
I hope you enjoyed it, and I expect you to have lots more fun
creating your own EsCage prints.
Next tutorial:
EsCage Tutorial #2  the
"regular" method.
More EsCage tutorials coming soon.



Author: Erik Es, March 2016. 





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