The red arrow points to the old washer, the green arrow points to the new one.

-John

*I can’t quite take full credit, as I had to leave before I could finish the job by closing the covering.

As I do not have one major project i am working on, this month I mainly just did what i could to help with other peoples projects. I came to 023 two or three times per week, here is the breakdown of what I spent my time on.

Week 1
This week i mostly focused on projects that were given to me last year, specifically on casting lenses. I worked on my design and decided I needed a vacuum chamber before I could do anything else. I quickly found an old vacuum chamber, and was able to use the smaller laser cutter’s air compressor as a vacuum. Unfortunately, the chamber did not have a rubber gasket and did not create a seal. I eventually created my own gasket using Dragon Skin, which worked quite well. Turns out, the compressor wasn’t powerful enough to create bubble-free mixtures, so i’ve been meaning to order a more powerful one.

Week 2
This week I did various odd jobs among the grad students, strip some wire, mill out this, help assemble that. Some projects I helped out on include a milling a circuit board for a new stepper motor controller and spending most of a day assembling a hollow-replica making machine (you spin a partially filled negative along it’s x an y axis).

In addition to the above projects, I spent almost the majority of my time talking. Though talking does not lend itself as well to logs or progress reports, I believe it to be the most important thing I can do for myself. After almost every conversation, I feel like I know just a little bit more. Which is exactly my reason for being at 023, to learn. And I am learning more here than anywhere else.

Amy created an awesome pdf file, here are some images from it.

-John

Dragon Skin
I used Dragon Skin to create molds off all the sizes of gears. The smaller ones came out slightly worse than the larger ones, but I don’t think that could have been helped no matter what material I used. I was impressed by the dry time for it, around 10 min in the oven. It also felt very durable, a good quality for a mold to have.

OOMOO
I used oomoo to create a mold of middle-sized gears. I encountered no problems, and the molds came out very nice. Working with it was almost exactly like Dragon Skin, except it was easier to draw up a syringe. It had similar drying times to Dragon Skin, and had a similar flexibility as Dragon Skin.

Task 3
Task 3 was neither outstanding nor terrible. It did take quite a while to set, almost an hour. Besides that, working with it felt like working with Task 2 ripoff of slightly less quality.

Smooth-Cast 300

Smooth-Cast 300 made decent gears, but it set almost as fast as Task 8. Actually, it felt about 4 minutes slower, but that’s still too fast for mass use.

Smooth-Cast 310
Smooth-Cast 310 went quite well, and the only real fault I can think of is the long dry time, about as long as Task 3.


Bottom line, I think Dragon Skin is the best for mold making, despite the fact OOMOO comes in a cool color, and Task 2 is still best for casting.

-John

On Wednesday and Friday I spent my time at 023 molding and casting gears. I experimentally tested 4 different materials for casting the gears. This is a post of my results and observations. The 4 materials were Task 2, Task 8, Task 9, and Urethane. I mixed every material in a plastic cup B first then A, filling B in up to the bottom lip of the cup, and the same amount (everything was done on a scale) of A. I then used a syringe tofill the molds.

Task 8 and Urethane

I am putting these in the same category because in practice, they were effectively the same. When both were mixed , they were clear, however, within 2 minutes they became an opaque tan and hardened. I had to make two batches of Task 8, as my first batch hardened so quickly it stuck my syringe in the cup where I mixed it and was drawing it up. They both hardened almost completely in around 20 min without heating. The gears made were decent, but not fantastic.

Task 9
Task 9 took a much more reasonable time to harden and created some nice gears, however, Task 9 had a few major flaws.
1: It got REALLY hot. The leftover got hot enough to warp the plastic cup it was mixed in.

_The warped plastic cup._
2: Two batches failed…..spectacularly. I suspect it came from not having an even mix in these batches or from the fact that it recommends being under positive pressure when hardening (which it wasn’t).

3: The batches that failed…. They also ruined those molds.
4: The instructions call for positive pressure. They seem to work fine as long as the weight of itself holds it down, but I suspect if I try to cast smaller gears I will have the same problem I had on the upside-down molds that failed.

Task 2
Task 2 was the best casting agent I used. It had around a 8 minute working time, which is plenty of time for filling many molds, and around a 25 minute hardening time in the oven. It created nice looking gears with not too many bubbles, and I think the perfection of the process would decrease the bubbles even further. The only problem i ran into was with the mold i used, and the fact I didn’t use enough mold release.

Task 2 was also what i used to create this:

The white one is Task 2
It went quite well, with the only problem being once again, too little mold release.

So, bottom line of my experimenting: Task 2 is my favorite for casting, and mold release is your friend.

-John

I also created and uploaded a tutorial on using parab.m to generate a frame with a parabolic cut out to the fablab.is wiki.

But I did manage to create the tutorial, however, I have not yet added it to the fabfolk wiki as I feel it is too rough and sparse in some areas to actually post it as a real tutorial. That said, here it is.

== How to create a paraboloid using cam.py and parab.m in octave ==

==== Step 1: Setup ====
Install Octave
If using Ubuntu/Debian, type “sudo apt-get install octave3.0” (no quotes) in Terminal
If using another distro, install from here

Download the other files: parab.m and cam.py and move them to your /home/(username)/

==== Step 2: Configuring parab.m ====

Open parab.m using your favorite text editor. I am using gedit in this tutorial so I will “gedit /home/john/parab.m”

The highlighted text is what you modify to change the final figure.

Once you are finished, Save the file.

==== Step 3: running parab.m====

In terminal, run octave by typing “octave” (no quotes). Then run parab.m by typing “parab.m”

You will see a bunch of windows pop up,they sometimes close, but if they don’t, close them. You will now have an svg file in your home folder.

==== Step 3: Editing parab.svg ====

In Terminal, “gedit parab.svg”
Now remove the highlighted section in this photo:

Now delete the highlighted area in this photo:
Save that file.

==== Step 4: Using cam.py====

In terminal, run “python cam.py parab.svg”

Now use cam.py to print your Paraboloid

________________________________

Before I add this to the wiki, I feel like I should include how to set up the epilog and how to use cam.py. I don’t mind writing up how to set up the epilog (once I have some time), but  I was hoping cam.py already has a tutorial i could link instead of writing my own. Does anybody reading this now where such a tutorial is?

-John Williams

As for what I did today, I learned to use the epilog to the extant that I feel comfortable cutting out any basic shape right now, and learned that with vector drawing you seem to have a better chance than with pixel drawing of the shapes you draw being cut exactly as you want them with the laser printer. I also learned that I should get into a habit of having a reason for everything I say or do, as it seems like it will make me of more useful and productive.

My first epilog creation: Stickman             My second epilog creation: Mini-wash

Mini-wash is a mini-human-powered washing machine (like in MAKE mag)