How do you tell if an open source project is successful

After a bit of musing, I came up with the following metrics:

Good structures

version control system for code

bug tracking system

documentation for developers and users (might be in a Wiki or similar)

mailing lists or equivalent

discussion fora or equivalent

Active Developer Community

traffic on developer mailing list or forum or similar

high rate of code commits to VCS

low bug fix latency

high bug fix rate

high new feature rate

full release calendar (lots of releases are being made)

Active User Community

traffic in user fora/mailing lists

download rate of installers

output produced (type depends on project)

professional support services

job openings for skilled users

Can you think of any others?

Working on Open Source Ecology

I'm contributing to the OSE effort, where my fabrication efforts have a chance to deliver enormous social benefits. Finally, I've got a something concrete to do that can have a widespread beneficial effect. It's very exciting.

The best place to read about it is http://openfarmtech.org/weblog/.

I'll be continuing with posts about fabrication soon, but I'll also be posting about open source hardware, and other related subjects, as I'm stimulated to write by my interactions with the other OSE contributors.

Vacuum Degassing PU resin experiments 00-02

I have some Smooth On resins that are past their use by, including Task8 that's 15 months old and some other that are ~2 years old. They are supposed to be used within 12 months of manufacture, so they're a bit dodgy.

These resins are interesting materials with a lot of promise, so I did some experiments to get a feel for them.

I'm interesed in Reaction Injection Moulding (RIM), which can including injecting the resin under pressure into a mold under vacuum to reduce trapped air bubbles. This doesn't work with the resins I tried, because they seem to evolve a gas as they cure, after they gel, and vacuum causes them to foam hugely. This might be because my samples are old, but I suspect that it's a 'feature' of the material.

Experiment 00

Mixed ~180 ml
Put in in to degass after about 1:30 of mixing
degassing happened late in the cure
Result: cup full of hard cured coarse partly open foam


Experiment 01

Mixed ~240 ml
Put it in to degass after ~50s of mixing, in two cups:
~70ml on two layers of Biaxial glass fiber mat
~160ml on its own
Degass happened early in the cure, but post gel
Result:
Large cup overflowed.
Cured as solid, not foam, but surface of both very uneven. Partly clear amber which is interesting because this resin is supposed to cure opaque tan. Is the opacity a volatile reaction product that is causing foaming under vacuum?
Resin appears to wet out mat well.
Thin section was strong, but breakable by hand. Showed evidence of delamination, probably from part cured layers touching as the gelled foam colapsed.

Experiment 02

pre-degass 2 minute
mix 120ml
Vacuum half of it after 30s, keep under vaccum during cure
Result:
Vacuumed half overflowed cup and produced rubbery Clear amber mess with large bubbles in it
Unvacuumed half foamed very sightly and set to rubbery tan.


Experiment 03

same, but with 2 year old Smooth Cast 326
Result:
The half cured under vacuum had a totally clear and nearly colourless bottom part and a tall deck of hard coarse foam on top.

The half cured at room pressure had a bunch of pinhead bubbles.

I suspect that a little gas was evolved during cure.

Awesomely huge 3D printing in stone

Big. 3x3x3m is the small scale demo.

The final version will be 10m tall.

Sand or ground rock with "inorganic binder".

Pretty sweet.

http://www.dezeen.com/2009/06/22/radiolaria-pavilion-by-shiro-studio/#more-33059

Noisebridge

While I was in the San Francisco Bay Area (where I'd like to live eventually), I hung out with a wonderful buch of hackers at Noisbridge. Massively inspiring, and constantly bubbling over with creativity and skill.

Just for example, some are working on a McWire RepStrap, and another created this bit of kinky steampunkery.

If you get the chance, check it out.

Moving to Zurich

I'm in the process of Moving to Zurich in Switzerland. I've got a job with Google there.

Over the last couple of months I've packed up my house, shipped my stuff to a warehouse, been to California, and I'm now in temporary accomodation in Zurich while I wait for my appartment to become available.

I should be moved in within a fortnight.

Amazingly easy CNC touch off

Very often I need to measure the length of a tool in the spindle or the hight of a piece of stock. With a feeler gauge or similar this takes ages.

How can you do it quickly precisely and easily?

As far as I know this is the simplest thing that that works: an electronic touchplate. If the tool tip is at IO signal ground, it is easy to detect when it touches a conductive plate, but attaching a pull up resistor to the plate and detecting its logic level.

Many spindles have grounded collets anyway, most CNC controllers have signal ground and mains ground at the same voltage, and tungsten carbide is conductive, even if it is coated with TiAlN, so the first part is usually automatic. If your controller has a small signal ground (0V) that is isolated from mains ground, or your spindle electrically isolates its collet, YMMV.

My spindle is not grounded at all (single phase mains and neutral, double isolated, plastic case, no ground), but it does have a metal collar for clamping it to the Z table. This collar is electrically connected to the collet, so I added a connection between the ground for the Z servo encoder and the Z table.

Connecting the touchplate was pretty easy too. My controller is not electrically isolated: it uses direct connections from the PC parallel port. I connected a 10k pull up resistor between the 5V supply from the PC and pin 15. Then I soldered a long wire between pin 15 and a blank PCB, which is 1.58 +-0.02mm thick.

I used the EMC Halscope to observe parport.0.pin-15-in. This does indeed go false when I touch the reference panel to the tool, and is true otherwise.



I can now run this program to set the z=0 level to the surface that the touchplate (the blank PCB) is resting on:


(restore offsets)
G92.3
(make this Z=20)
G92 z20
(probe down for a maximum of 10mm or until contact is made, at 50mm/min)
F50
G38.2 z0
(assume that we made contact, and set z=0 to be the surface that the touch off contact was resting on)
G92 z1.58
(back off so that we can get the plate out)
G0 z10

(end, which clears all the offsets)
M2