There currently is a Fablab
being established at Friedrich-Alexander-University (site
is in german, see
Wikipedia for an explanation of fablabs in general).
Although they're not fully equipped yet, they recently
got their laser cutter/engraver. Naturally, such a "toy
for big boys" was something I desperately
wanted to try out - but I needed a project where I could
make use of it. Just doing the usual, cutting and engraving
a sign out of a piece of acrylic glass and then lighting
it with some LEDs, does certainly look cool, but has
been done about a gazillion times already in the week
since the laser was delivered. I found it too boring.
After a week, I finally had the idea that I needed a spice
rack, and while there are certainly better ways to build
a spice rack than with parts cut out of acrylic glass, it
was not a terribly bad idea.
I measured the place where
I wanted to put it, and then constructed it so that would
exactly fit that spot. I also made the construction so
that it would hold together without any glueing. While
I intended to make it more stable by glueing, the basic
structure would hold without any of it. 5 millimeter thick
acrylic glas was to be used, as that would provide the
needed stability and ease construction.
Turning my construction into reality started off with
a few technical difficulties:
First of all, I had planned
for the rack to be 4 stories and 60 centimeters high.
However, the acrylic glas available in the fablab only
was 50 centimers long, thus only permitting 49 centimeters
of height. The top level thus had to be cut off.
The
second problem was the software: The lasercutter has
a not-so-great windows driver, and usually "Corel
Draw" is used to send data to it. I had created
my design with "QCAD" (community edition),
which saves files in DXF format. Importing those
into Corel Draw was absolutely unproblematic. However,
when sending it to the cutter, the printer driver
created nonsense cuts because it only has two modes for
vector sorting. The "inside out" mode (that had to
be used because there were holes to be made into the
parts before they were cut out) gets confused with
the outer border of the part, and randomly cuts individual
lines of the outer border. Luckily, corel draw has a
function to combine multiple connected lines into one
continuous object. That also causes them to be sent to
the printer driver as one object, eliminating the
problem. Of course, it would be a very useful feature
for the printer driver if it could do that internally.
After that, cutting the parts went pretty smooth - but
problems continued during assembly: The laser currently
seems to be a little misaligned, meaning that it does not
do cuts through the material at an 90 degrees angle, but
more like 80 degrees. Also, the acrylic plates from
which I cut have a pretty high tolerance themselves:
a "5 millimeters" thick plate is somewhere between
4.1 and 5.9 millimeters in reality. Both these problems
meant that I needed to use a lot more force than planned
and - in one case - a rasp to get the parts together.
On the pro side, after finally putting the parts together,
they were really stuck, making the construction rock stable.
I still decided to glue the most important parts together
as originally planned. I used Dichloromethane for that -
it essentially melts the acryl together and should create
almost perfect connections. The problem here was that I had
read the german
Wikipedia article on Dichloromethane - and as a result,
I was very very veeeeery cautious with it. In the end, I
used way too little, and my "glue points" did not hold.
I decided to skip a second attempt - as mentioned, the
construction was stable enough without glueing.
There was one more FAIL worth mentioning: I had
misconstructed the mount points for the bars at the
front and the back that prevent the spices from falling
out. They were 5 mm too high due to a little miscalculation.
Instead of lasering the big side parts again with the
mount points in the right places, I just made the bars
(which I had not lasered yet) 5 mm larger so they
would fit. In the files below, the .cdr file
has the wrong mount points and the larger bars. In
the .dxf file, the error has been corrected, so
bars and mountpoints are as intended, but not as I
built it.
In the meantime, the spice rack is in full operation.
Unfortunately, it is too small, I can't fit all my
spices in due to it only having 3 instead of 4 floors.
I'm still pondering ways to add the missing one.
Though I had constructed a bar for screwing it to
a wall, that was not done: The construction is attached
to the wall only through a Tesa Power Strip that
has been cut into two halves.
As usual, here is a collection of stuff from the
project, in the hope that some of it might be useful
for others:
[Photos from
the construction]
[Corel Draw file - this contains what was
actually built]
[QCAD / .dxf file - what was originally
planned]
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