January 2010 Archives

All the endmills are now in this cigar box, which lives near the Modela. Grab the SVG file for the insert here.

My press-fit construction kit:

The parts have come out! Here they are separate:

Attempting to cast one out of urethane plastic with a layer of soap scum failed, as I hadn't mixed the plastic enough and weird white blobs of goo got stuck in the mold. I'm currently making another mold from the wax original after having stuck the bit that came off back on.

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I've been in L.A. for about a week now and I'm really eager to get back to the lab. I have so many ideas about how to incorporate every lesson thus far into my big project, especially making molds to cast multiples of tiny body parts for the characters I've been sculpting. I'll also be molding some 3-D rendered forms. Complicated and interactive automata dioramas!

I hand- sculpted the heads above in Cernit. I flameworked the glass eyes, and the "hair" on the right is made of trochus shells.

Jonathan's machine uses flexible couplings:

Decided to print an "old school rocket" from thingiverse for the lab:

Seen here in front of Jenine's "Providence" sign.

For my final project -- a pinball machine themed on an opera whose libretto is written by monkeys on typewriters -- I want to have a central chorus pit with five or six monkeys on typewriters. This seems like a perfect application for the molding and casting unit. My wife (Jill Colinan) is making the monkeys, so I thought I'd cast the typewriters for this assignment.

The Fluxamacutter is a design for a simple vinyl cutter that satisfies these criteria:

• Inexpensive ($50-$100 in parts)
• All parts can be cut on a 24"x12" laser cutter
• All press-fit construction: minimize hardware fasteners
• No precision parts required: all hardware cheap and widely available
• Arduino-compatible
• Plug-and-play replacement for existing HPGL-speaking cutters

The initial cutter will be able to take 15"-18" rolls, and will be designed to scale to 24" rolls.

After seeing David Carr’s political map relief I was inspired to do something similar. I thought it would be cool to model the Boston skyline. Since I also wanted to see how fine I could get the resolution, I took a jpg, and using the GIMP program, made it a black and white image with 50 colors and then put it through cad. I had it create a file with the following specs:

z min: -.75″

nz: 50 (one pass for each color)

tool size: 1/32

At 20, 20 speed the file was going to take about 12 hours. I was still going to try to cut it but Shawn pointed out to me that our 1/32″ bit didn’t have a long enough shank to cut at -.75″.

I went back, edited the file down to 10 colors and filled in the sky so as to leave just the buildings.

Then I created a .rml file in cad using a 1/16″ bit, .-.5 z min, and 11 nz.

After about 2 passes, the machine did a dramatic z drop and I had to stop it. Shawn suggested that I use more nz steps so I created a new file with 30 steps.

I piped the .rml files directly to the serial port through the command line as the computer thats hooked up to the mini mill has older software.

I piped the .rml files directly to the serial port through the command line as the computer thats hooked up to the mini mill has older software.

My 3D Modeling and Casting project is to make a model of the outside of the TARDIS. I used the scale and dimensions from G. Hartley’s plans to make an 8 inch model TARDIS.

G. Hartley’s Original Plans

The Fab Academy Assignment

• design a 3D model of a potential semester project
• render it
• extra credit: physically model it

The Project: 3D model of TARDIS

Skills Learned

• Learned how to create a 3D model
• learned to think in three dimensions - advance planning of how objects are put together before modeling.

Tools Used

• Google Sketchup

I used these plans to create a 3-D model in Google Sketchup

However, as the milling machine cannot carve out negative space, the faces on the sides or the model could not be created. In order to create a machinable mold, I had to take the 3D model apart into three sections: the roof, the front door and a side (3 of the sides are the same).

In addition, I also removed some details that were in the original 3D model, like the light on top of the box and the all of the “Police Box” lettering. The light was not transferring properly into the CAD file and the lettering would be too fine for the bit on the milling machine. (I plan to create a sticker or letter by hand). I also scaled the model down from 8 inches high to 4.8” so it could fit within the block of machinable wax.

Shawn Wallace suggested that I cast an LED into the model and use it for the light on top of the box. Brilliant.

The Roof, Side Door and Front Door

Sketchup exports .stl ASCII files and I needed them to be in binary. I opened the files in Meshlab and then exported them as .stl binary files. Next I ran the .stl files through stl2png.py to convert the depths to grayscale.

The final result (roof not shown)

The next steps are: 1. Mill out the 3 of the mold pieces 2. Cast with rubber, making 3 casts of the side view 3. Create a laser-cut box that will hold the mold together when it is being cast with hydrastone. 4. Cast with hydrastone.

Creating a bzr repository:

First, inform bazaar as to your personage:

bzr whoami "Mr. Foo <mrfoo@as220.org>"

Then, make a directory for your repository: mkdir repository

Initialize the repository:

bzr init

Add the current directory:

bzr add *

Make the first commit:

bzr commit -m "Hello World"

Now, every time you want to add files, run

bzr add <files>

again, and

bzr commit -m "Message".

To check out your repository

start an ssh server (openssh-server in ubuntu, check the box in the preferences window in OSX), and run

bzr branch  sftp://user@ip-address/path/to/directory

Then

bzr pull

To update the repository, bzr commit again and then

bzr push

Have fun!

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Elliot and Shawn were debugging the modela, Elliot bet $1 that switching zmin to a negative number wouldn't fix the contouring problem (even though it'd been his suggestion to do so) and then Shawn bet $1 that adding a white background would fix Elliot's contouring problem. Shawn won both bets. I still haven't finished building Jonathan's machine, I cut another threaded rod that was too short, and our chemical filter isn't working. Susan, however, installed a new, quiet fan, so the leafblower has been obsoleted.

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