Thursday, April 26, 2012

Elaborate box-insert

Every SD300 supply kit includes a little cardboard box that has a self-locking lid.  I've been carelessly tossing the box into my cardboard recycling bin, but it's a nice box so I really ought to re-use it.

Last year I had designed a simple hinged insert to help pack lots of small parts into a box.  Taking inspiration from that, I devised this elaborate insert for protecting one of my homebuilt puzzles for mailing.

My custom-built insert consists of hinged panels, folded into shape after they're built on the SD300.

The folded insert slides into the box. Winged tabs hold it securely at the corners of the box.

Thanks to this plastic insert, my puzzle fits neatly into the cardboard box and it's held safely for mailing.

Friday, April 13, 2012

Fluctuating Build Economy

I've produced a ton of test models for my Cooksey's Griddle puzzle of the past month because I discovered how to build them cheaply with relative ease.  That's quite a change from my experience in February, when I had so much trouble building prototypes of it that I gave up and submitted the model to i.Materialise to build it for me--but they couldn't build it either.  (Bad STL file, I think.)

But I didn't really set out to build so many test models, it just happened.  The first model worked fine but someone suggested a nice improvement so I built another.  Then someone suggested another change, and I built another to try it out.  Eventually I built over a dozen test models, each with minor differences from the last.  There are so many that I'll discuss the details of the puzzle in another post.

In this post I'll concentrate on the surprising economy of this particular model...

Originally this puzzle was designed as a flat slab with a 16mm round disc attached.  Above, the diagram shows it with a rectangular outline around it showing the volume of material the SD300 would build to create this model.  Much of the area above and below the slab is just empty space, but the SD300 would consume that much material in order to support the slab while it built the disc.  This would consume less than $30 worth of material, much cheaper than sending it to a 3D printing service...even deep-discount Shapeways.

But material costs (and build time) were reduced by two-thirds if I built the disc as a separate piece to be glued onto the model after building it.  As shown above, no volume would be wasted above or below the slab.

I could realize a further savings by building two models at a time.  That gave me two complete puzzles in each build job, complete with all their accessories, for less than $10 per puzzle.  Each job consumed only 6% of an SD300 material kit; I could build 32 of these puzzles with 1 box of SD300 material.

Particularly critical was the use of a precision probe, like this Moody Tools set, to peel material out of the narrow grooves.  These probes are also excellent for clearing small holes without marring the model, especially in narrow or deep locations where the standard Solido-supplied tweezers aren't optimal.

Wednesday, April 4, 2012

A Same-day Repair

Here's a true story just like the 3D printing hype I see in magazines and newspapers.

This morning the Snooze button didn't work on my twenty-year-old Westclox 22651.  It wouldn't move, it didn't click, it didn't do anything.  I tried to buy a new clock, but my local store didn't have any suitable replacements.

Could I fix it myself?  I disassembled the clock and found the cause of the problem: the snooze button was supposed to click against a membrane switch, but the plastic pin had broken off so the button was non-functional.

Hey!  That would be easy to fix by building a little spacer to replace the pin.  I brought out the calipers and took measurements: the rib is 2mm wide and 3mm high, the cavity is 5.8mm wide, and the required distance from the top of the rib to the membrane switch is 4mm.  Easy.

Too easy, in fact.  In less than an hour I had designed a new part on the computer, built it, and installed it in the clock.

It worked perfectly, without requiring any adjustments...nor even glue!  The spacer fits neatly between the button and the circuit board, held in alignment by the rib on the underside of the button.

If you've got a similar clock that needs repair, just download the model from Thingiverse.

Funny, I didn't even lose any sleep over it.