Recap of the 2/4/09 meeting

[Ken]

The evening began with Nick recounting the earlier colloquium by
Andrew Ng of Stanford
about Intelligent Robots. As members arrived we discussed various
aspects of AI and robotics.

Recounting last meeting’s coverage of the Kreg pocket hole jig, Jon
showed us a Kreg jig in a carrying case that he purchased recently and
a shelving project that he did for his wife. He talked about the
challenges and successes of putting together melamine shelves.

Also recounting last meeting’s coverage of mold making and casting,
Ken showed an acrylic project. Using a small plastic film canister and
easily available casting acrylic (fiberglass casting resin, readily
available at home centers is tinted grey and will not work for this,
so Ken recommended Clearlite casting acrylic available from TAP
plastics http://www.tapplastics.com), Ken has preserved wedding cake
for his two son’s weddings as a memento. (Pictures to be posted
shortly.)

Ken also spoke about the use of polymer clays (Fimo or Sculpey) as a
modeling tool for making parts. Polymer clay works well for non-
functional, decorative items, such as moldings or frills, but for
practical parts such as knobs or handles it is too fragile. Instead,
sculpt the item you wish to create in polymer clay, fire it at 250
degrees for 20-25 minutes per ¼”, and use the resulting object to cast
a negative mold. Then recast the object in acrylic (clear or dyed, or
paint it afterwards) and you can create multiple, sturdy items.
Alternatively we also talked about using polymer clay as a one-shot
negative mold for casting acrylic or plaster items. Once the medium
has set up the polymer clay can be ablated away, leaving the cast
object.

Nick showed us the results of his tube-casting, which utilizes the
tube mitering template software that he designed.
http://www.cheaphack.net/2009/01/easily-miter-tubes.html. After
creating a complex design of mitered tubes, printing out the
templates, taping them together using card stock, and then bracing the
tube-template-mold in sand, he filled the tubes with plaster. There
were some voids, and as it turns out the mold was somewhat tilted, but
he ended up with a post-modern sculpture which could be a desk
ornament or a hat rack. One thing he has learned from this casting
experiment is that due to the fine nature of plaster, all of the
seams, tape and even some minutely raised lettering on the cardstock
were imprinted in the plaster.

New member Walter brought us news of a DIY group in Philadelphia
called The Hacktory http://thehacktory.org/. They have a shared space
for working on projects, meet once a month, offer a variety of
classes, and … have just received a 3D printer from a fellow inventor.
Walter told us tales of putting this thing together and making it
work, and then filled us in on his own Arduino/LED matrix projects.
His goal, to make an Arduino driven 90x90 LED matrix that displays
monochromatic grey scale full motion video. As part of his project he
is exploring the design and manufacture of sub-components that can be
daisy-chained together.

Many of us have expressed interest in a “field trip” to Philly to
visit The Hacktory.

Rob has suggested that he will bring in a discarded (but working) B&W
television next meeting for us to experiment with, and if Ken can find
it, he will dig up his Timex/Sinclair to produce RF output for the TV.