Sunday, 8 November 2009

An Open Source licence for Hardware

I'm helping the OSE choose a license for the designs that we produce.

A couple of days ago, I blithely recommended that Marcin license the Liberator compressed earth brick press under the GPL.

Licensing is a largely solved problem in OSS, but on further reading, I found that open hardware licensing is a mess. I'm not a Lawyer (thank goodness :-), but here's by best attempt to understand the situation.

The crucial difference appears to be that physical items are not covered by copyright, which only concerns itself with informational goods.

It's easy enough to do public domain, MIT, or BSD style openness with hardware. These licenses are so permissive that they don't change their behaviour in the new context. They don't need to use copyright to make their provisions enforceable.

The problem comes with the GPL copyleft provisions: Without copyright, enforcing openness of derived works is hard, and I'm not satisfied that any existing license does it well, if at all.

The Open Hardware License (as used by TAPR) was written by a lawyer, but was criticised by Eric Raymond, and I have some misgivings about it too.

There are a substantial number of open hardware projects that are using the GPL as is, and it doesn't seem to be doing them any harm. These include Arduino and RepRap.

I like the obligation to open derived works included in the GPL. I feel that it is politically consistent with the OSE values, and it acts against commercially exploitative freeloading. If it were easy, I would like to enforce that same obligation on anyone selling modified Liberators. I now think that this enforcement may not be possible through copyright.

I also think that it doesn't actually matter very much. We'd like to get the benefit of all modifications to our open designs, but we don't need it. So long as good complete designs and cheap good quality implementations of open hardware are always available then we have succeeded.

So long as there is a community of people using and building our designs the designs will be available and constantly improving. If some people don't share the results of their efforts with us, then that's a shame, but we don't need them anyway. If they're that inclined to be selfish then their grudging cooperation probably wouldn't be that useful anyway.

I think we should go with the GPL for the moment. We can re-license later if we need to.

Tomorrow, I'll contact Eric Raymond, the OSI, and the FSF for advice.

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

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.

Tuesday, 18 August 2009

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
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
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
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.

Monday, 29 June 2009

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.

Friday, 29 May 2009


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.