Wednesday, December 23, 2015

Yoda In A Box

Initial pass of laser cutting on
the first layer of Yoda
Even though Yoda apparently doesn't get his just due in the latest installment, he's still my favorite Star Wars (tm) character. Wry, witty, lots of character, instantly recognizable. So I decided to memorialize him in a multimedia creation that could serve both as a unique Christmas present and a brief example of how to use a variety of makerspace tools (at Techno Chaos, of course!) and techniques to make something special. I call this story "Yoda in a box".

The ingredients include some digital graphics processing, a few passes in the laser cutter, a quick dash of 3D design and printing, capped off with a nice touch of simple electronics. After finding a good box in a local hobby store, the total parts outlay was less than $5 (but please don't tell my nephew...).

Here's the ambient-light look of the
Yoda box. The pattern created by the 1st
pass of the laser cutter dominates.
The digital graphics processing was the most complex part of this project. This was because of the "wow factor" I wanted for this project: not only would the Yoda image be clearly visible and recognizable under normal ambient light conditions, but it also needed to allow light to shine through parts of the image for a super-cool light-box effect. Because the normal-light image needed sharp lines for clear recognition, I decided to use a laser cutter to apply the image to the box (see the photo above to get the general idea). This would be created by the first pass of the laser cutter over the box (tech notes: this pass was applied with a 40W infrared laser at a speed of 80 inches per minute at about 20% power). Developing the cutting pattern for this step was relatively easy and straightforward, using my current-favorite tool for combined graphics processing and gcode generation laser cutting Inkscape to process a nice clear Yoda drawing I found with an online search. ("Gcode" is the standard "language" to tell computer numerical controlled (CNC) machines like the laser cutter how to move and act. If a pencil in your hand was the drawing instrument of a machine, gcode would tell your arm how to move to move the pencil the correct way to create a pattern or drawing. You don't want to write gcode manually -- the 1st-pass Yoda pattern had 50,000 lines of it! -- rather, you want a software tool like Inkscape that can convert a source graphic to gcode for you. There are more complex programs that can create gcode for a wider range of CNC devices, but I've found Inkscape is all I need for laser cutting. I will publish more tips and tricks about using Inkscape for laser cutting in future blogs.)
Details of the 3D-printed background and
LED electronics installation

The harder part was creating the gcode instructions for the 2nd pass of the laser cutter -- the one that would fully penetrate the wood in the box lid to create the light holes for the wow factor. Anyone with laser cutter experience will recognize that just using the "simple" pattern created for the 1st pass would result in nothing more than a large hole in the box lid resembling the head of Yoda with no features. That might be novel but not very cool. So I adjusted how Inkscape processed the Yoda art so that less than half of the lines remained in the output image, and then I erased additional areas of the artwork to reduce the image to more of an outline effect with hints of a few key features. I also built in bridges where fully-encircled shapes would have been cut out and dropped so the remaining wood would stay in place and visible. And I used good technique to ensure the 2nd pass would be precisely aligned over the 1st pass lines already on the box (tip: I insert an alignment dot at the axis orientation point (also known as origin or "0,0,0") in the lower-left corner of the graphics before applying the gcode generation step, and never rescale the graphics between multiple passes of graphics processing). The resulting 2nd pattern was then applied using the 40W laser cutter with power set high enough to cut all the way through the 1/8"-thick lid; on my laser that's 5 inches per minute feedrate speed at 80% power, just to be sure. (Note: I tested the full process on scrap 1/8" thick plywood twice to get it right before going to the final cuts on the box.)

Yoda shines through with the backlight on -- even more
detail is actually visible than seen from this angle.
The result was excellent! With some quick 3D design and printing a static green backdrop was created and then inserted inside the box to accentuate both modes of Yoda viewing. Then a simple set-up of RGB flashing LEDs (click here for an example source at Amazon) wired in series across a 6 volt coin-cell battery holder with on-off switch (got mine at Adafruit, but they're available in many other places too) was added and locked in placed with the good-ol' hot-glue gun and -- voila' -- we have a lighted glow-through box of Yoda that can be enjoyed day and night!

I hope this story inspires you to think "outside (or, perhaps more fittingly, inside...) the box" for future projects for gifting -- or keeping! Get with us at the Techno Chaos makerspace to get started and for assistance and support.


Santa -- You Can Take That Leaf-Blower Off My Wish List

The main active part -- the turbine fan (in light yellow) -- shows
extensive around the shaft attachment.
It's Fall in South Texas, and that means the leaves are falling. I recently pulled out my battery-powered lime-green leaf blower (bought 4 years ago from you-know-where) only to find it make lots of racket and rattling but no rushing of wind. We have a large yard (this is Texas, after all) and lots of trees, so after some time with a rake gathering leaves I decided it was time to replace the leaf blower. But after a review of my favorite web sites I found that Fall apparently is not a good time to purchase leaf blowers.... And, after perusing a few repair web sites, I came to the conclusion that battery-powered leaf blowers are designed to be disposable items (making me a bit skeptical about how "green" they really are...). So I went to the fall-back plan and called in the go-to guy -- Santa! Surely I've been nice enough to deserve at least a new useful yard tool (note: my wife has agreed not to post on this particular blog...).

But wait -- I'm a Maker with a lot of 3D design experience. I most often apply these skills to robotics, but why not appliance repair too? It would be a tough application with all that rotational speed, but what's life without a good challenge (or two)?
Close-up of the turbine fan with shaft-mount cracking


So I dove into a bit of device dis-assembly and problem analysis. (Note: always remove any power source BEFORE attempting to open power tools and equipment.) Removing a few screws quickly revealed the source of the problem: the turbine fan shaft mount had fractured in multiple places, so that it was no longer able to rotate. Fortunately the motor appeared to still be in good condition, and all the electrical components still operated fine. So, if I could design and 3D-print a replacement for the turbine fan, there was a good chance this tool would blow again.

I chose to 3D-print the replacement turbine fan because I had multiple 3D printers available in the makerspace capable of printing a variety of materials with potential to stand up to the mechanical stresses. But this would be a challenging design, since there was no large flat surface in the original part structure to support reliable 3D printing. And there are many, many curves in the turbine fan structure!

But with some design decomposition I landed on a 2-part component, both with the requisite large flat areas for 3D printing: (1) a flat shaft collar on the bottom,  and (2) the working part of the turbine fan structure with all the curved blades and functional cavities. I decided to use ABS as the 3D printing material for best wearability and glue adhesion.

Now came the "fun" part: designing the turbine fan section! I decided to use TinkerCad (an excellent free online 3D design tool designed for beginners but with 80% of the power of top-end Autodesk tools, in my opinion) so I could share this model with students in the future. With TinkerCad it was relatively easy to create and shape the curved parts -- it just requires a little bit of mental dexterity with the concept of cutting primitive shapes with other shapes. Intermediate and final results of the design are shown in the pictures.

The 3D-printed replacement turbine fan
Perhaps the most difficult part of the 3D design was implementing the reverse blunt threads needed to install the 3D printed parts onto the motor shaft. TinkerCad has a nice library of user-created shape generators that yielded a reverse-thread shape, but it took 2 test prints with smaller test pieces to get the fit right despite my use of a micrometer to measure the shaft. The successful dimensions were then applied to the turbine fan design.




Now it was 3D printing time! Despite the large flat surface on the bottom, I was concerned about how well the bridging (unsupported horizontal surface areas) would print given the all the curves (printing the curves reduces 3D printer speed, which increases printing sag -- which is not good). I decided to try the PolyPrinter 229 I'm currently testing because of its high bridging speed and was very satisfied with the results -- OK, I was actually surprised. The replacement turbine fan was good to go after the first print, needing just a little bit of cleanup with a sharp knife.

After test-fitting the 3D-printed parts onto the motor shaft, I decided they'd operate better with additional bonding and applied a good amount of resin epoxy glue. Both parts (the shaft collar, in orange, and turbine fan) went on well and fit correctly. And everything fit back into the leaf blower just fine (yielding an initial stage of relief....) Then I aligned parts to reduce wobble when rotated and gave the epoxy an hour to fully set.

After reassembly it was time to test. A few power cycles confirmed the 3D-printed parts were indeed attached to the motor shaft. And the tool now generated a rush of air -- enough to scare any lingering dust bunnies in the Techno Chaos makerspace. But would it be enough to move a Texas-sized accumulation of leaves? After taking it home and trying it in the "real world" I can confirm the answer is "YES!!!!"

video
So Santa -- I know you're busy right now -- but if you're listening you can take that new leaf blower off my wish list because I have one that works just fine now! (I estimate it produces about 75% of the air speed of the original part, probably due to the increased weight of the turbine fan and slightly-thicker fan blades for the 3D-printed part. But as the video shows it definitely works!)

And in case you and the Lead Elves get bored after the Big Day, we have some classes in 3D printing coming up soon! You'll find them useful for many things back at the North Pole...    ;-}

Tuesday, December 22, 2015

"Hello World"

Hello World! I'm an active Maker blessed with full access to a well-equipped makerspace (Techno Chaos, in Sugar Land, Texas) my wife and I own and operate. Actually, I consider myself a life-long Maker, having grown up in the 60s idealizing the US space program and building models, electronic devices and an array of weird contraptions. Despite the strong influence of the race-to-the-moon and the pro-science and -engineering environment of those days, I believe the here and now is the best time to be an inventor and creative -- ever! Yes, I really do mean in all of human history. And it's only going to get better. The purpose of my blog is to talk about my "adventures", projects and learnings as I dive deeply into the world of Making and inventing! And perhaps I'll share insights into my other "hobbies" and activities along the way...