Introduction
Pepakura models are designed to be cut and folded out of paper. This causes a few challenges when you try to 3D print them. First, they have no thickness, so we will have to create the interior walls in order to give them some volume. Secondly, they are usually composed of few polygons, so we will need to smooth the surface.
This guide was written specifically for my build of a MK III Iron Man suit, but I think it could be useful for any sort of costume.
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To do this, go to
File > Export > Texture Editing > 3D Model with UV Info
.
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First you will want to delete all the objects in Blender's default scene. To do this, press
A
until everything is selected, then pressX
to delete them. -
To import the OBJ file, go to
File > Import > Wavefront (.obj)
. Select the file you exported in step 1.
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Here are the basics of getting around in Blender.
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Drag MMB
(Middle Mouse Button): Rotate view -
Shift + MMB
: Pan view -
Scroll wheel
: Zoom in/out -
RMB
(RIght Mouse Button): Select an object
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Select the group by right clicking on it.
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Move it to the center by dragging the arrows on each axis.
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You can also move things by pressing
G
. -
To make things easier, you may want to reset the object's origins. To do this, go to
Set Origin > Origin to Geometry
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At this point you will probably also want to save the model with
CTRL-S
.
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In Pepakura Designer, go to
2D Menu > Change Scale > Set Scale
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Copy the scale value.
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In Blender, right click on your model to select it and then press
N
to bring up the Object Transformation panel. -
Change the scale of all three axes to what you copied from Pepakura.
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Select the group and switch to Edit Mode, if you are not there already.
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Press
A
until nothing is selected, then right click on one piece to select one of its vertexes. -
Press
CTRL-L
to select the entire piece (all linked vertices). -
Press
P
then chooseSelection
to separate that piece from the group.
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Select a piece and go into Edit Mode.
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Switch to Face Select mode.
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You can select faces of the support structures by right clicking on them individually, but I find it easier to use Circle Select.
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Press
C
then click to select faces touching the circle. -
You can use the scroll wheel to increase/decrease the size of the circle.
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When you are done selecting, press
ESC
. -
To delete the faces, press
X
and then selectFaces
.
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The easiest way to do this is with the Solidify modifier.
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Select your object, then go to the Modifiers tab of the Properties editor.
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Click
Add Modifier
and then chooseSolidify
from theGenerate
section. -
Increase the thickness to whatever you think is best. I think 3.0 is a good starting point.
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If you want to make the changes permanent, you can hit
Apply
. This is not really necessary, though. You can leave it as is, which will allow you to edit the modifier later.
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Go into edit mode and press
A
to select everything. -
Press
E
to extrude. This will make a copy of the mesh that is linked to the original around the edges. You can move this copy around with the mouse, but in this case we want to keep it in the same place so just pressESC
. -
Now press
S
to scale down the copy. We are going to turn it into the inside surface. -
We want the inside of this tube to be just as tall as the outside, so press
SHIFT+Z
to tell blender not to scale the Z axis. Conversely, you could pressZ
if you wanted to scale only the Z axis but not any others. The same goes for the X and Y axes as well. -
Move the mouse until the tube is the right thickness, then press
ESC
when you are done.
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You can use
ALT+B
to slice open the mesh and see inside of it. -
Here you can see a part of the inside that's sticking through the outside. I'll need to fix this by deleting faces and moving things around.
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This part is also very thin and might not print well.
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You can also switch the view to wireframe mode, to make everything transparent.
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We need to select the line where the cut will be made. Select one edge and then keep selecting more using
SHIFT
orCTRL
. -
CTRL
makes it easy by selecting the shortest path between the first line and the one you click on. -
Press
V
andESC
to rip the mesh along the line you selected. -
Press
CTRL+L
to select the entire linked section, then move it away from the rest. -
Press
P
to ungroup it from the original.
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Select all then go to
Mesh > Normals > Recalculate Outside
. If you see any faces change color slightly, it means they were reversed before. -
Go to
Select > Select All by Trait > Non Manifold
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Any parts of the mesh that are now selected have issues. You will need to manually fix these. The best way is to probably delete those faces and reconstruct that area.
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One thing that often leads to non manifold geometry is vertices which are very close to each other but not actually linked. To fix these, select all and then go to
Mesh > Vertices > Remove Doubles
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To smooth things out we are going to use Blender's Subdivision Surface Modifier. Open to the Modifiers tab and then go to
Add Modifier > Subdivision Surface
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The setting you want to play with now is the number of subdivisions (
View
, notRender
). I generally like to do 3 or 4. The more subdivisions, the smoother the surface. However it will also make more polygons which means larger file sizes and slower performance.
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Lets start off by temporarily disabling the Subdivision Surface modifier. You can do this by clicking the eyeball icon.
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Now lets select the edges we want to crease. An easy way to do this is by going to
Select > Sharp Edges
. This will select all edges with a sharp angle. -
Play with the sharpness threshold until it looks like it has most of the important edges. It does not have to be perfect. We can add or remove more later. This is just to give you a good starting point.
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Crease the edges by pressing
SHIFT+E
then type1.0
and pressENTER
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To uncrease an edge, you would type
-1.0
instead -
You can now unhide the modifier to see how it looks, then go back and crease/uncrease more edges as needed.
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Thats it! You now have a model thats ready for printing. Go to
File > Export > Stl (.stl)
to export the currently selected object. -
Now bring it into your favorite slicer and start printing.
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