LaserAccess Updated


Updated the Laser-cutter access control box today. Major changes include.lasercutter_zeit_und_karte

  • Now features a big flat space that will happily hold your RFID access card, token or whole wallet. No more fumbling and trying to get a card to stick to the side of the box
  • Dedicated holder for USB-sticks, the laser-cutter key and the focus distance measurement spacers.
  • Dead-Person-Button – remaining time indicator lights are more diffused by the cover and thus more muted.

The basic logic remains the same.  Once you went through the laser-cutter introduction and got access, just put your RFID token on top of the reader. The beep and the green bar indicates the laser is now hot and you can start cutting. Press the DeadPersonButton while the bar is still green to indicate you are watching and realraum hasn’t burned down yet. Remove the card when you’re done. Beeps and blinks will indicate that laser is now being disabled.

See the wiki for more.

Was lange währt, hängt endlich gut


Not long after realraum moved to it’s current premises, we knew we wanted a curtain in the front windows, just like in the old realraum. Not only to better use the beamer during the day, but also to keep the room cooler in the summer and have a tiny bit more insulation in the winter. There was also hope of it dampening echos and loud noises.

That was about 2 years ago.

finally some sturdy wood
finally some sturdy wood

But how to hang the curtain. The ceiling after all, does not bear any loads. The search for a solution that would allow us to move the curtain freely over the ranges of a 4 and 5 meter wide front window began. The old curtains were both too short and not enough. Where to get nice looking fabric cheap, that is both fire retardant and thick enough to insulate was also an open question. Of course such fabric would be heavy and did I mention the ceiling does not bear any loads.

Now enter a handful of engineers with dwindling spare time, different opinions and varying expertise into the mix and you may begin to see what took so long.

one of two long pipes
one of two long pipes

Quite early, we agreed that spanning two extremely sturdy pipes from one wall to the column to the other wall was the solution to go with. Eventually Christoph procured one for us which was a bit thicker than anticipated. Somewhen, frequent visitor and hobby seamstress Sasa managed to get us between 200 and 300 m² of great fabric for a bit over a 100 Euros. Thank you Sasa for making them into curtains and even putting in the eyelets.

Some very motivated members promised to mount the pipe but went to work more quickly than anyone had anticipated. Miscommunication happened, some mistakes were made. Finally we re-mounted the pipe three times.

zip-ties a smooth sliding curtain not make
zip-ties a smooth sliding curtain not makes

The first attempt had to go because the wood holding up the load was too thin. Instead of the planned U-cut to hold the pipe, an easy V-cut was made. The pressure exuded on the panel in direction of the fibres caused the wood to crack pretty early on. Then, instead of moving away the cable conduit (which later, turned out to be really easy to do), a daring constructions of wooden distance holders bridge was built in order to mount the pipe-holing-wood on top of the cable conduit. While not very tidy, the real problem here was that the screws were too long for the holes drilled. (Understand: were talking about a massive and solid concrete column holding up the whole house. Even with the right equipment that doesn’t drill easily).  Consequently there was an air-gap between the column and the wood holding up the pipe. As we all remembered that day: screws hold stuff in place by way of static friction, i.e. pressing one material onto another e.g.. by pressing a piece of wood against a wall. They are not meant to withstand orthogonal forces and do not like to bear loads that way. Christian was the first to spot the air-gap. Exasperation and learning followed

should brear a few hundred kg
should bear a few hundred kg

Eventually, the sturdy, thicker than what your normal hardwarestore sells, wood we wanted to use in the first place appeared and the pipe-holders got completely redone. Sturdy enough to hang a small car on it. Or, you know.. a curtain and some people that might stumble into it during a party. Gotta plan for everything.

Finally, the pipe was not sufficiently secured against longitudinal movement. Meaning the direction in which you would pull when you move the curtain. Too much and the strings holding it in place might rip and crash everything down. Thankfully Christian also finally drilled holes at the ends and secured them with bolts across and through the pipe.

Don’t exhale yet, we’re not done.  The curtain still had to be mounted, and guess what. Curtainrings that fit a 42mm diameter pipe are really really hard to get. We tried to make due (thanks to Sandra for all the work), it’s really hard to move a curtain that is hanging on 150 tightly bound zip ties. Eventually we found a German shop that sells big metal rings at a surprisingly reasonable price and ordered right away. I don’t even want to explain why it then took 3 months for them to arrive.

Yesterday, then, the long road had an end, the project finally got done. Our junior member David took up heart and down the pipes, replacing the zip-ties around the pipe with well moving (and sounding) metal rings.

no more sliding rods
no more shifting rods

So end of story. Finally. Or is it? Because we also ordered clips to hang the curtain from it’s eyelets to the rings. We ordered new eyelets with a bigger inner diameter because the clips would not fit in the very small ones we had when Sasa and Sandra put them in. (Never believe the online-shopping product description). Right now the curtain and the clips/rings are still connected with zip-ties. So the question remains… do we still care? Or did anybody even read all the way down?

Debian on ZFS: It’s alive… It’s alive, it’s moving, it’s alive, it’s alive, IT’S ALIVE!

zfs_aliveLast night, r³ saw, as a world première, the first boot of the first computer running pure Debian with ZFS-on-Linux.
There definitely were some before, using third-party packages (including my other laptop), by this is an important step for native ZFS support in Debian.

I will probably be involved, in the coming weeks, in squashing ZFS bugs and making sure that Debian Stretch users get a smooth ZFS experience.
Don’t hesitate to drop by and ask questions if you are curious about ZFS, or borrow the ZFS books I added to the library  ;-)

The whole install is described here and on a post to the pkg-zfsonlinux-devel mailing-list.

All the drawers are belongmade by us


Our shelf next to our electronics corner, aptly named TESLA, is getting a bit crowded. Luckily we have our own lasercutter. Why not make drawers? After today’s lasercutter workshop, nothing would be more obvious. So I made the beginning and created the first. The basic idea now is:

If everybody who doesn’t know where to put stuff any more, makes just one drawer, we will end up with a cool and individualized shelf.

Everybody is invited to use the drawers in this github repository to get started quickly and add their own designs.


wpid-dsc_5227.jpgIn other News: H sponsored earphones, so people watching videos on Würfel, our pc directly connected to the room’s stereo, no longer need to play to an audience.

The long road to fixing our TAZ4 3D Printer


Around the end of Februar 2016 prints with our trusty only 11 months old TAZ4 3D Printer started to fail. Specifically the extruder just stopped extruding mid-print, while everything else was working along as if nothing had happened.

After some investigation, we discovered the problem, the extruder stepper motor was getting waaayyy tooo hot. Each time, about 10 to 15 minutes into a print, the extruder/feed stepper would reach 91°C and just stop moving. As no more filament was being extruded, prints were getting ruined.


Fixing It – First Attempts

First I ran a print with the filament removed, the filament tension mount relaxed in order to reduce any resistance the stepper might encounter. Still it overheated. Obviously we tried attaching a heatsink, but of course that just bought a few extra minutes.

My first idea was to trim the micropotis on the controller board and reduce the motorcurrent. Alas, there were no potis to be found. Then equinox suggested it might be a mechanical problem since everything was working fine the last eleven months.

So we took the extruder apart twice. Second time around an hour later, we discovered that the M10 nut of the bolt conveying the filament which has the big cog on it’s other side, was way too tight. Presumably someone wanted to improve things by tightening the screw.
The result being, that the washer pressed on the bearing and put the brakes on the extruder motor.

Additionally I discovered that the screw afixing the steppershaft to the PLA cogwheel was loose. Possibly the hot motor softened the PLA enough for the shaft to slip through and cause the motor to turn by itself.

Sadly, none of these fixed solved our problem. Our NEMA17 still overheated, with 90°C being far outside it’s absolute maximum rating of 60°C (Specs) and even further away from the 42°C operating temperature reported on the internet.

Read more The long road to fixing our TAZ4 3D Printer

Visit from Counter Culture Labs


Mary Ward from Counter Culture Labs in Oakland, California is currently visiting Graz. Today she gave a talk @ realraum about her idea of doing microfluidic mRNA assay in space. Those were some really great ideas and nice example of putting existing stuff together to make even more exciting stuff.

Since we already have a lot of experience with microfluidics and building space-worthy satellites, this turned out to be the perfect topic for our space. Beautiful discussion and knowledge exchange ensued and will continue on Sunday. :-)