File Prep

One of the many differences with modeling for 3D printing is the file prep which must be done.  The model has to be exported as an STL file (Standard Tessellation Language) which is meant for printing and CNC work and describes the surface geometry of the model.  The STL file must also be checked in mesh repair programs which will look for holes in the mesh, duplicate vertices, non-manifold edges (edge which touches more than two faces), inverted normals (flipped geometry faces) and more.  Sometimes additional work will have to be done on a part before it will run through correctly.

I printed in different materials so I had the additional step of dividing out all the parts to their separate materials.  This gets tricky when one part uses multiple materials because each material has to be exported separately and then reassembled in the printing program where the materials are assigned.  Here's a walk through:

Here's half of the body. Notice all the different colors.

Oh Noes! - When the Model Gets Goofed-Up

I was in the process of getting the Octopod ready for printing when I noticed this:

I'm looking along the length of the body where the two halves meet up and noticed that they didn't match.  Somewhere along the way the right half got bumped up by .01mm.  The cockpit lid also got bumped both forward and to the side.  Since all the parts go together with screws and all the holes must line up this could have been a total disaster.  I had to backtrack through 6 different versions of the project to find where the problem started so I could assess what I had to fix.  It sidetracked me for a few hours but I did get it fixed.

Remember to save often and of equal importance is to document what you have done to each file and how they differ.  I have a simple text document in the project directory for this purpose.

The Mr. Miyagi School of Riveting

Rivets! Still messing around with the colors, but you get the idea.

Sometimes there is just no quick and easy way to do something and this was one of those times.  I have been dreading doing rivets on the Octopod because I couldn't think of a way to do it and make it look right without hand placing each one.  I met somewhere in the middle of tedious and super-tedious.

I discovered the cloner function in Cinema which lets you duplicate an object along the edge lines or vertices of an object.  Perfect!  But I immediately ran into problems because I had used a patch sphere for the body.  (A patch sphere is when you start with a cube and smooth it so much that it goes round.  They are good for 3D printing because true spheres tend to have pinched geometry at the poles.)  The problem with the patch sphere is that the edge lines are not perfectly parallel and straight going around the object.  You can see me figuring this out at the beginning of the video.

Update Pix 2 - Now With Even More Update Flavor!

Have hit some major roadblocks when trying to export STL files for printing.  The lesson learned is:

You DO NOT want interior faces left-over from extruding stuff, it will screw up your STL files big time.  Took a while to track down the offending parts and of course they were something small and relatively minor.

All good now, taking some files to the print lab on Friday so we can run test them with the print software.  Will be printing everything in less than two weeks.  Stressing.

A few update pix:

Slight update from previous version.  Portholes and hatches are cut out and windows have some more detail. Adding more hardware and rivets next.  Trying to add nautical stuff that would actually be used and in the right spot.

Update Pix

Wanted to quickly post some renders and screen grabs.

COMPLETED SHELLS AND TENTACLES

Refining the Cockpit Housing Video

I've had a rough layout of the body for a while and now the fine-tuning has started.  The video is primarily of refining the cockpit housing.  The main difficulty was building an odd-ball primitive to build off of.  It was 16 sided but not all sides were the same length and I had to put in some odd loops to accommodate the scoops that go over the tentacles.  I wanted to box-model this piece so it would flow well from the tentacles, up and back to the main body.  Due to the odd shape, putting in edge loops was a challenge as well.

The further challenge will be cutting each body piece to fit with the other, then extruding those pieces so they have thickness otherwise they can't be printed) and figuring out a way that they will all fit together during the physical assembly of the printed model.

The mesh has to be really dense so it will print without showing any polygons.  This part is a good candidate for decimation which will reorganize and reduce the amount of polygons used.

Tentacle Mount Build Video

This is the building of the first tentacle mount. It's been revised but the basic design and methods remained the same.  I tried to speed this up and edit it down but have been having major problems with my screencast software.  A bunch of build videos were corrupted and this is one of the few that I salvaged.

The basic approach for this was to use a knuckle connected to the mount and build a hub that the tentacles would slot into.  Originally I planned on the tentacle having a pivot pin at the base so the whole thing could move but I realized that there wasn't much room underneath for the pins. I also realized that the tentacles are so flexible that the first knuckle could be stationary and there would still be plenty of room to move.  I put the knuckle/mount into an array so they could be positioned evenly.  The hub was then sized to fit the array and slots were booled out.  I had to used a slightly modified version of the mount for booling because the slot has to be bigger  than the original due to mechanical tolerances.