Thursday, June 19, 2014

More iterations on the toolbox

So while I've been working on the 3D printer kit at home, I've continued to play with the 3D printers at work.  Here's my design for a toolbox with a lid that actually opens and closes.  It uses a dimpled hinge concept.  The trick is that there has to be enough flexibility in the end pieces to insert the lid, but without breaking it.

The first try didn't work at all, as I couldn't get the hinge in without breaking the hinge side pieces.  So I modified the design a bit, putting a slot into one of the side pieces as shown below:

This worked better, but with the 4 cm base box length I still ended up bending the end piece and breaking it off.  So I scaled up by 1.5x.  Rationally, one knows that 2x length yields 8x volume, but  I think the picture below really dramatically illustrates what a big difference that makes.  The 1.5x box is huge compared to the original.  But you can see that the right-hand hinge edge still ends up getting bent by the insertion process.

Thickening up the hinge end pieces a bit seems to do the trick, though, and the final version snapsin and works just great.

This was printed in ABS on a Makerbot 2x we have at work.  It has a dual extruder and heated bed, just like my Felix 3.0.  It will be interesting to compare print quality.  A problem did show up with the printing process; one corner sags substantially.

The guy who is responsible for the printer thinks it's sagging because the Kapton tape on the print bed is getting worn, affecting the adhesion of the initial layer.  People on the Felix support boards have talked about similar issues, including deformation of the build plate due to printing of large objects.  The boards didn't explain why the deformation occurs, but I'm thinking it is happening because ABS shrinks a bit while it cools; since it shrinks while still stuck to the build plate it can exert a bowing force.  Even a little deformation can ruin the leveling of the plate and affect the print quality.  One possible fix that is talked about on the boards is using a (cheap) glass plate clipped to the build plate instead of a Kapton covering.

As a final note, here's a photo of the prototype we did up for our Matlab competition's trophy.  This was printed from using their color sandstone option.  The membrane surface is the Mathworks logo, and was created in Matlab and exported directly to a 3D-printable file.  The final version will be bigger, with some writing in the flat square part.  Holding this thing in your hand really brings home the amazing potential of this technology.