half-dog: The 3D printer that we ordered
from Shanghai on a Sunday
in June made its way to South Carolina on Friday of the same week. The
CR-10S Pro required only minor assembly, and was ready for alignment in
half-hour or so. Alas, that is when the trouble began. We didn’t fully
understand the alignment and leveling instructions, although these were
well-illustrated in the small user manual. Initial testing,
sample file that came with the printer, produced globs of twisted
filament. Our best result on that first day is
affectionately remembered as ‘little half-dog’.
The next morning we revisited alignment
of the hot-bed, taking care not to overlook any detail in the
This effort produced a small dog that was not headless. (no photo—the
is presently in the hands of a grandchild.)
From not working at all, to producing a
satisfactory print most of the time, was not a linear progression. Over
time we learned some ‘tricks’
or maybe superstitions that seemed to improve the likelihood of
success. At one point we tried
glue that promised to cause objects to adhere better for printing, and
also to release more easily when finished. However, after several days
we concluded that while the
glue did not help significantly, it did contribute to the post-print
useful print: While waiting for the printer to be
delivered I had worked through a few FreeCAD
tutorials, and had also created my first ‘original’
object. In the electronic parts closet were several small (2-inch)
speakers from Jameco.
These 8 ohm speakers produce decent sound in the frequency range of
they do not have any sort of mounting frame—There are
holes. After measuring diameters and depths etc. I designed a custom
bracket, shown on the right as rendered in FreeCAD.
The completed result was
encouraging. I have since included this 3D-printed bracket in two
projects, one being the example enclosure pictured at the top of this
match: In the past I relied on manufactured project
for most small electronic projects. The boxes themselves are fine.
challenge has been to drill holes and make smooth cutouts for switches,
pushbuttons, LCD’s or OLED’s etc. I do not have machine tools or the
skill required to use them, and the scroll saw does not make a clean
in project box plastic, at least not in my hands. For some reason I did
immediately consider 3D-printing a complete project enclosure. Instead
to replace the lid or top of a manufactured enclosure, the part that
holes and cutouts.
measurement: The photo (left) shows the inside corner of a
manufactured (Steren) project box. The edge that mates top to bottom
has three levels. I used micrometer calipers to measure
their widths. Then I placed an index card along the lip
made a pencil mark on the card for the middle part height. There are
surely other ways to measure small things precisely. The point is that
in order for
a 3D-printed top to fit a manufactured bottom, the measurement should
be nearly exact.
Notwithstanding the care taken, I
imagined it was unlikely this
try would work, and therefore made a design cutout in the top to
conserve filament and
printing time (right). As it happened, the lid did fit. It was only
file the corners a little, as I had not thought to filet them in the
the test top snugly in place on the manufactured bottom, I thought of
another idea. Instead of reprinting a no-cutout top, with holes and
project components, it would be more efficient to 3D-print a separate
panel that could be
inserted into the large test cutout. In that way, if there
were mistakes, only the
panel insert would need to be reprinted. By this stage of
experimentation the original filament spool had run out, and a
different color PLA had been loaded. The result is shown in the photo
(below left). It is a little rough, but everything fit.
epiphany: Different projects come in different sizes. It
seemed there should be a way to specify overall dimensions
independently of other details, so that the same design (corner
screw posts/holes, top-bottom mating, etc.) could be reused. I Googled
this question and found an immediate answer. FreeCAD has a built-in
spreadsheet. It is there for the looking, but I tend not to look very
deeply when fiddling with something new. So I re-did the enclosure top,
and also a bottom, which is nearly the same as the top except
for depth, but this time parameterizing the primary dimensions in
Spreadsheet format. While FreeCAD’s
built-in spreadsheet is not Excel, it does include some very useful
features. One can define expressions to compute derivative values, for
example. And any value (cell) can be
given a symbolic name or alias, so that if additional rows are
inserted, or if rows are removed from within the populated part of the
it is not necessary to pay attention to shifting cell ID’s. Another
virtue of the FreeCAD spreadsheet is that it can serve to document a
design, recording what each value means, or how it was obtained, etc.
digression: I thought it would be fun to construct a
canonic illustration of spreadsheet usage in FreeCAD. This led to a
digression having nothing to do with radio or electronics projects. In another article I described a game
called Pentominoes invented by professor Solomon W. Golomb and popularized
by Martin Gardner in his Scientific
American column (ca. 1957). The game involves fitting
Pentomino pieces on a checkerboard (or chessboard). In order for the
game to work,
the unit square size of Pentomino pieces must correspond exactly to
the board square size. Of course boards come in all
sizes, so a set of Pentominoes constructed for one board will not fit
a different sized board.
The printer had idle time—not much, but some! Why not print a set to
fit our chessboard, during hours when the printer had
to do. The design could be generalized to allow reprinting pieces of
any reasonable size. Over time this aside project produced a
multi-colored set of the twelve pieces. It may be worth remarking about
something that is conspicuous in the ‘T’ Pentomino print photo (left).
piece itself has a border called a ‘brim’ that is generated as an
option in the slicing software Cura. Brims help adhere flat
objects securely to the printer hot-bed. (Another support structure
called a ‘raft’ performs a similar function for objects that do not
have a flat bottom.)
downloads: As one might guess, a great many 3D print files
are available for download from a variety of Internet sources, the
best known of which is Thingiverse.
Some downloadable 3D print objects make intriguing demonstrations.
Others are merely ‘cute’.
Truly useful objects are perhaps a minority. One from the
latter category is an enclosure for the Atomic Pi. My wife downloaded and
printed an enclosure for her Pi (right). This downloaded enclosure is
complex than any we have designed ourselves.
Typically before completing the design of a full-scale project
enclosure we test the fit of individual parts. For this we
make a small plate or bracket that accommodates just the part and
nothing else. Then for the main project it is only necessary to
replicate measurements from the verified test in the main project. The
composite image below shows one such test, where a capacitor shaft must
be positioned to align precisely with the Vernier dial (or conversely).
Mounting holes for both components must also be
It may take a
to obtain a precise fit, but little material or time is wasted in
testing. Occasionally it may be more efficient to test two or more
things at once.
pieces: While I have seen some impressive multi-part
constructions that were 3D-printed all in apiece, it is also possible
print parts of a thing separately and glue or otherwise join the pieces
together. I have done this a couple of times. For example, the photo at
the top of this article shows the GPS antenna slotted in an ‘L’-shaped
bracket on the side of the enclosure. That bracket was printed
separately and glued on. This approach is similar to gluing a panel in
a cutout, or a recessed tube in a hole.
and detritus: So far I have tried only PLA filament.
to its manufacturer, the filament we are
using is ‘earth friendly’ and ‘biodegradable’. It is certainly tough,
but warps at high temperature. Higher
temperature filaments would serve better for some purposes, but are
challenging to work with. Some require venting the printer, which would
be a project in itself. While
PLA would not be suitable for making (outside) antenna parts,
as I once
considered, I do plan to test its durability in a limited outdoor
setting, namely on our small sailboat, but only for short day sails.
this stage, having been
introduced to 3D printing just two months ago,
we remain focused on basics. FreeCAD has
many features that I have not examined or studied yet. The slicing
has options we haven’t
tried. 3D printing is not ‘plug and play’. There
is much to learn!
following photos show test or finished prints at various stages of
conception and execution, and sundry related stuff.
Project descriptions on this page are intended for entertainment
only.The author makes no claim as to the accuracy or completeness of
information presented. In no event will the author be liable for any
damages, lost effort, inability to carry out a similar project, or to
reproduce a claimed result, or anything else relating to a decision to
use the information on this page.