Sunday, January 30, 2011

SlideTab in 3D

In January, Chris K. Palmer shared on Thingiverse specially-developed tabs to enable paper templates to be folded and joined together into 3D objects. It's also described at (I've previously featured a selection of his Sphericon models.)

Could the concept be translated into 3D models representing the same flat surfaces with slots, tabs, and hinges? At the very least, could it be made compatible with SLS?

I started my efforts by adapting the flat squares that can be assembled into a cube. It eventually worked, but only after I'd reduced the maximum wall thickness to 0.6mm. The hinged tabs required thin spots less than 0.2mm thick, too thin for reliable production by SLS.

Next I adapted the triangle models, which could be assembled into a tetrahedron (pyramid), an octahedron, or an icosahedron. But these required excessively-thin walls, like the cube, so the STLs aren't very share-able.

His "hat" models required even greater flexibility, and hence even thinner walls. It takes a lot of flexing to interlock the tabs.

Here's a partly-assembled Rabbi's Hat model.

It's not very dignified, is it?

So I didn't really meet my goal. The STL files are buildable in LOM because it can exploit the inherent strength of the unbroken source material, but the models aren't portable to other 3D printing processes. An SLS machine could build the individual parts (with careful handling) but I doubt they could be assembled.

Tuesday, January 18, 2011

Bacteriophage by LMDM

Here's an excellent work by someone else:

The Laboratório de Material Didático Multimídia encourages the use of multimedia to promote science education in Brazil, particularly materials sciences. In 2010 they acquired equipment for building solid models including CNC mills, RapMan (from BitsFromBytes), and a Solido SD300 Pro.

Illustrated here is a bacteriophage they assembled on their SD300, using source data created in Google Sketchup!

The model was built as a flat sheet only 5 layers thick, yielding parts that are then folded and glued together.

Consistent with LMDM's philosophy, they produced an animated video that graphically shows viewers how to assemble the bacteriophage model.

Naturally they've posted a YouTube video showing the whole process of building the model, the assembly animation, and the finished model.

Sunday, January 16, 2011

Multi-color 3D printing video

I posted an HD video that illustrates multi-color builds with the SD300...

YOUTUBE: SD300 Pro Multi-color 3D Printing

The thin model in the video is an adaptation of Chris K. Palmer's Slide Tab Polygons that I'm trying to convert to STL. It's 0.5mm at its thickest point, 0.18mm at the thin hinges.

Here's a lower-resolution copy of the video in case you can't access it on YouTube...

Saturday, January 15, 2011

SDPause, a utility for pausing at specific layers

I've been building a lot of multi-color models by swapping out material kits at strategic times during the SD300 Pro's build process. The software didn't allow me to schedule when the machine would pause, so it originally required me to watch the machine carefully.

For my Rox Box model, I built the model upside down starting with the transparent layers first. Once the machine had finished building the transparent 'window' I swapped in the white material and let the machine build the rest of the model. That was simple because I only had to switch materials once.

But Oskar's Cookey Tribute puzzle was over 600 layers thick, and it took almost 30 hours to build because I was building multiple models at the same time. The model entailed multiple color-transitions, so I doubted I would be able to manually intervene at all the right times. I needed something automatic!

So I created a computer program SDPause that watches the SD300's build progress and automatically pauses whenever it reaches the layer entered in the box. That ensures the machine will pause whenever the model requires a different color material. Even if I'm not home, it will pause and wait for me to change the material and manually resume.

Email me if you want a copy of SDPause; my contact info is listed in my profile. SDPause should work with the original SD300, SD300 Pro, and Invision LD.

Some things I've learned about switching material kits:
  • I generally change the glue cartridge with the PVC roll so the materials will be consumed at a predictable rate. This also ensures the installed cartridge always has sufficient glue for whatever PVC roll is installed.
  • I generally don't change the Anti-glue cartridge and pens. Instead I just replace the Anti-glue cartridge when the default material kit needs replacement, or if support material doesn't peel away easily. The machine won't suddenly run out of Anti-glue, unlike the main glue supply.

Thursday, January 6, 2011

Building a custom packing insert

I wanted to ship the parts from my previous Torus project, and they fit very neatly into a small flat-rate shipping box. But I was worried adjacent pieces might slip under each other if the box was bumped, since they're slightly wedge shaped. That could cause them to puncture the container.

So I designed a thin, hinged packing spacer and built it on the SD300. It's less than a millimeter thick, so it barely used any material.

The spacer emerged from the printer in a flat shape, but easily unfolded to form two channels would would keep the parts from overlapping during shipping.

The spacer divided the parts perfectly without occupying any space in the box. I'll probably build custom packing material like this for future shipments, since the material is thin, flexible, and strong in this format.