Creating a hollow cube with a hole: 3D print tutorial problem

Hi

I have been following this tutorial http://www.youtube.com/watch?v=zHxs4uerHjw

The author creates a hollow cube and then cuts a hole in it (about minute 10:20 I think). But however closely I follow the instructions I always end up with a hole in the outside surface of the hollow cube but not the inside surface.

The author uses a cylinder made to pass through both surfaces and then uses a boolean operation to cut the hole.

I’ve tried doing the operation twice, once on the outside surface and then the inside but it never ends up right.

Any help much appreciated

You have provided almost no information on what you did… post your file here to get more help unless you’ve figured it out already.

I guess you’ll have to invert face normals. Object outer shell face normals have to point outwards and inner shell face normals have to point inwards.

Ok, I am using Blender 2.7 on Ubuntu 14.04 LTS with 64 bit OS.

Objective: create a hollow cube with a hole as an exercise in using Blender to create files that can be 3D printed.

Steps employed (according to the tutorial):

-Select cube
-Set scene units to metric (and set the scale to 0.001)
-Scale by a factor of 10 (cube is now 2cm x 2cm x 2cm)
-Apply the scale
-Create cylinder mesh
-Scale it to appropriate size (to use to create a hole) and locate it just beneath cube
-Select cube, and in wireframe view, duplicate it and then scale so that it now forms the inside of the hollow cube
-Move the cylinder vertically through both surfaces of the hollow cube.
-Reselect the cube (presumably the outside cube surface?)
-Go to modifiers, select add modifier and select boolean
-Select the cylinder as the object and difference as the operation and click apply
-Move the cylinder down again (and can be deleted).

This is the point where what I get starts to differ from the results in the tutorial. I have uploaded the file created from this as: ‘cube test for Blender Artists 9-7-14’

In the tutorial the tutor proceeds to delete the protruding vertices leaving two holes: one in the inner cube surface and one in the outer cube surface. Then he looks for non-manifold vertices and bridges across the holes to create a ‘watertight’ object that is ok to 3D print.

I hope that is enough info and thanks!

Thanks -I’ll have to look into how to do that!

Hello, You can cut any holes in plane or in object, using Boolean or Knife Project. Please take look at two videos 1 and 2. Another example - cut hole in plate, next extrude plate with hole.

Thanks I will check those out…I’m very new to this so making very slow progress! …It seems like there are a number of ways of doing everything in Blender…What is troubling me is not being able to do what the guy is doing in the tutorial…That’s what I want to work out.

It is great Blender feature, that you can model on different ways. If you want to use Boolean Modifier it is good to know how to easy omit boolean errors.

  1. add Cube (SHIFT+A)
  2. duplicate cube (SHIFT+D) for create new Cube.001 and leave it in the same place (RMB)
  3. scale (S) for create smaller inside Cube.001 and accept change (LMB)
  4. apply new Scale for Cube.001 (CTRL+A)
  5. select outside Cube and add Boolean modifier - opeartion: Difference, as object choose inside Cube.001 (you can hide/unhide inside Cube.001 for check effect) and Apply if OK
  6. remove Cube.001 (X)

Now Cube is empty inside.

  1. Add e.g. Cylinder, scale, rotate and move it to place that it should create a hole.
  2. Apply new Rotation and Scale for Cylinder (CTRL+A) - You can switch wireframe preview (Z) and back to Solid (Z)
  3. Select your empty Cube and add Boolean Modifier - opeartion: Difference, as object choose inside Cylinder (you can hide/unhide Cylinder for check effect) and Apply if OK
  4. remove Cylinder (X)

hope it helps.

Attachments


Hi

Thanks again…It worked and all looked good to me.

[ATTACH=CONFIG]320084[/ATTACH]

I did a test for non-manifold effects (as the other guys tutorial had suggested). So I then exported it as an .stl. I just uploaded it (http://i.materialise.com/3dprintlab/instance/57d6b9b2-2ca3-443e-b068-27ba6488fc8a) to see if it works and can be used to get a quote for 3D printing but I got the same error message:

“An error in the model prevents us from offering an online price. Please request the price. We will check your model manually and contact you with an offline price.”

Any ideas? Thanks again…

Isn’t that unnecessarily complicated? Why don’t you just…

  1. …add cube (Shift-A),
  2. Tab into Edit Mode, select all (A) and duplicate the geometry (Shift-D),
  3. scale (S) the copied geometry to form the inside of the cube,
  4. Flip the normals of the inside polygons with Ctrl-F > Flip Normals and Tab out of Edit Mode.

Then continue with your step 7 - that totally eradicates the need for the first boolean operation.

My guess is that the OP had a) the outside and the inside of the cube as separate objects and b) did not flip the normals of the inside geometry, just as JuhaW has already pointed out. That’s why his result deviated from the tutorial.

IkariShinji, you are right, works great… Solidify Modifier also replace 2-6

Good call!

Thanks…I’ll try that…I just wonder why the guy in the tutorial didn’t think this stuff needed mentioning…?