Today was spent researching all the manipulations involved in getting a CT scan into printable form and I managed to get a print out of it. The process starts with DeVide where the dicom data from the CT scan is processed using a dual threshold, decimation filter, and stl writer. The stl file contains a lot of unwanted stuff, in this case, soft tissues inside my head that add triangles but won’t be seen in the print, so those are removed by applying ambient occlusion followed by selecting and deleting vertices by “quality” (which will be very low values for vertices on the interior of the object). This process invariably blows small holes in the desired surface, so you apply a “close holes” filter to fix that (which closed up the nostrils very nicely). Next you open the stl file in netfabb and rotate and clip unwanted external stuff and apply repairs as necessary. Finally, drag it into slicer and scale it. slice and print.
While investigating software to extract bone data from CT scans and turn it into 3D printable STL files, I played with a CT scan of my own head that was used to treatment plan orthodontics. I have been using DeVide to process the data and finding it is not only easy to use, but a lot of fun!
The animated gif was made by sweeping the lower threshold of a dual threshold module from -800 to 900 in steps of 100 with the upper threshold fixed at 1400. The effect is to strip away the lower density tissues leaving only dense bone at the end of the sweep. I saved the result of each run as a png file then converted to an animated gif using an on-line service.
After the mediocre commercial successes of some of my previous audio products, I decided to pursue a project that has absolutely no commercial potential. Although my Automated Gmail Assistant had a 0.1% view to purchase rate, they definitely delighted their new owners! On the other hand, my novel audio surround sound processor, audio-visual processor and audiophile headphones did not produce any revenue, despite being manufactured in an exclusive edition of one each. Not to be discouraged, the goal of this project was to expand on the core idea behind the aforementioned audiophile headphones, but to overcome the main two drawbacks of using headphones: 1) Many people find that headphones are too uncomfortable and impractical for long term listening. And 2) most headphones lack the concert-like visceral bass impact, which is that feeling of the kick drum shaking your chest that only rock and roll shows could provide.
Simply put, the Humorously Maniacal Milwaukee Makerspace Multimedia Machine (HMMMMMM) is a personal sized movie theater, with 5.16 surround sound. That’s right, this theater is like a conventional 5.1 home theater, but with 15 extra subwoofers to delight the senses. While the bass in a live concert can be felt in your chest, the bass in the HMMMMMM can be felt in your soul(!). In addition altering listener’s consciousness, the HMMMMMM will soon be used to screen our yet-to-be-filmed Milwaukee Makerspace orientation video as an integral part of our onboarding process for all new members. The HMMMMMM measures about 7 feet long and about 4 feet wide. An eager movie-goer can simply climb up the integral stairs (shown on the left) and jump in through the 27” diameter escape hatch in the top of the HMMMMMM. Despite its crazy appearance, the HMMMMMM offers a surprisingly comfortable reclining position, much like that of a lazy-boy. Check out this photo of the HMMMMMM under construction for a better idea of the ergonomic internal layout: There is a pillow for one’s head, and ones feet extend to the right. The 27” display is mounted to the angled portion on the top surface, about 24” from the viewer. Eventually, two 24″ monitors will expand the visual experience into the periphery.
The audio portion of the HMMMMMM is a 5.16 system. The high frequencies are played by 5 uninteresting Swan/HiVi speakers that are arranged in a properly boring 5 channel surround configuration. The more exciting portion of the audio system is the subwoofer – well, the 16 (Sixteen) 10″ high efficiency subwoofers that provide that TrueBass™ sensation the masses crave. Its clear from the use of 16 subwoofers that one object of the HMMMMMM was to create an audio system that plays low bass. Playback of really low bass typically requires an extremely large speaker box, and still notes as low as 20 Hz are rarely audible. However, inside any speaker box the bass response is naturally flat to much lower (subsonic) pitches. For more on the sound pressure level inside and outside speaker boxes, check out this link. The graph below is a measurement of the SPL or sound pressure level (how loud it is) versus frequency (pitch) at the listener’s ears in the HMMMMMM.
The graph shows that with a sine wave input, the SPL inside the HMMMMMM is 148.6dB at 40 Hz. That means the acoustic pressure on the 27” diameter escape hatch is 45 pounds. Excellent. Note that earplugs in addition to earmuff style hearing protectors are mandatory to safely experience the TrueBass™. To understand this strict hearing protection requirement, lets compare the sound pressure level inside the HMMMMMM to other audio systems that may be more familiar. Note that the loudness of these other audio systems are not visible in the graph above, because essentially all other audio systems (including yours) are inferior. Adjusting the margins of the graph a bit produces the following graph:
The plot shows how loud typical audio systems are, and how low they play. For example, cellphone speakers play only a bit below 1khz, and are ~90 dB if they’re 40cm from you. When a Jambox-type bluetooth speaker is about 60cm from you, it plays ~10 dB louder, and another 1.5 octaves lower, to 200 Hz. Typical bookshelf speakers can get another 5 dB louder if you’re 1.5 meters from them, but only play down another octave to 100 Hz. OEM installed car stereos are a big improvement, but they’re still not in the same league as the HMMMMMM. Yes, the IASCA record holding car is louder than this, but it plays only from 50 Hz to 60 Hz, which isn’t even really bass.
Note that the difference in loudness between a cellphone and a car is 20 dB, while the HMMMMMM is 30 dB louder than a high-performing car stereo. Also note that the frequency range of a piano, with its 88 keys, is about the same as a bookshelf speaker – a bit over 7 octaves. Surprisingly, the subwoofer portion of the HMMMMMM has a 6 octave bandwidth, but it plays the 6 octaves you’ve never heard before! The HMMMMMM plays 6 octaves below what your bookshelf speaker or Jambox calls bass. The HMMMMMM has a +/- 6 dB passband extending down to 2 Hz, with the output at 1 Hz being nearly still above the 120 dB “threshold of pain.”
Disclaimers: For safety, the big 2000 Watt amplifier that drives the HMMMMMM to its full potential is not available when the author is not present. Ironically, the author has taught 75-100 people, the eager early HMMMMMM listeners, how to properly insert earplugs, meaning that the HMMMMMM is actually a learning tool for hearing safety! Finally, the author has some hesitancy in having the HMMMMMM reproduce recordings with 5 Hz content at 140 dB, because typical hearing protection has little effect at these unnaturally low frequencies.
PS: Please don’t hesitate to contact me if you’d like to help with the video scripting, filming or editing.
It seems like just four months since the last Bay View Gallery Night… oh wait, it was!
We’ll once again have a group show, this time titled: More Awesome Things From the Makerspace, which is our way of saying “come check out all the crazy things we do!”
It’s all happening Friday, September 27th, 2013 from 5pm to 10pm. And as always, we’ll have some sort of magical surprise to knock your socks off!
(Or who knows, maybe it’ll be something that gently removes your socks and then carefully places them into the nearest laundry basket…)
As someone who has gone to GenCon quite a few years and knows several of the GMs of major events, I’ve started getting asked to make props… This year I have decided to expand my experiences in molding and casting in order to make one of the props. The prop requested was a “Bracer that looks like it is made of Amber – part of the shell of an insect”. Thankfully I was afforded quite a bit of creative leeway beyond that.
In the past I have used Smooth-on products, but one of the members of the Makerspace mentioned they were a distributor for Alumilite, so I thought I would give them a try. This was my first experience with most of the Alumilite products.
I ordered the following supplies:
Other items I used:
3” Diameter PVC Pipe – Approximately 18” long
3” Diameter Hose Clamp
Disposable Mixing Containers
Steel Wire (to hold the mold together)
I wanted to make a “generic” bracer that would fit either arm, not a right or left arm bracer, so I didn’t want to do a life cast of my arm first – it would be too specific. Instead I picked up a piece of 3” pvc pipe, cut a section out of most of it (leaving a part connected) and then used a hose clamp to tighten the open end down. It turned into a really good stand-in for a human arm. The shape is close enough that it is recognizable, but is not left or right arm specific. (Note that the screws in the picture were added at a later stage)
Once I had the basic form for the arm, I used the synthetic clay to create the shape of the bracer. I was going for an organic look, so I wanted curves and no sharp edges. The biggest challenge I had was trying to smooth out the sculpt. I still need to figure out the right technique. Sadly, I forgot to take pictures of the sculpted bracer.
Once I had the sculpture complete, I added some screws around the edges as alignment points. I was careful to make sure the heads were close to the PVC so they would not get stuck in the molding material. Then I got to try my first new material – the Mold Putty. I really liked the idea of it – take two parts, hand-mix, then just push it onto the original. It essentially worked exactly that way. I thought the mixed consistency was almost perfect for my application. Unfortunately, the biggest difficulty is being sure not to trap air in it – particularly when placing a second mixed batch next to an already placed batch. I ended up with some imperfections in the final mold because of this. Would I use it again? Yes, but I think I may also try other approaches – either a box and pourable rubber, or brush-on rubber.
Given the way I wanted to cast the bracer – standing vertically – I wanted to make sure that I was able to hold the rubber mold to the arm form well. So, using the plaster bandages, I made a two-part “mother mold” for the rubber mold. First, I coated everything with Vaseline as a release agent, then I covered half of the arm piece with plaster bandaging, making sure the edges were particularly strong, and that the top edge, where I would be creating the second half of the mold, was also quite smooth. After the first half of the mother mold cured, I then coated the edge of the plaster with Vaseline to make sure the other half would not stick to the first half. Once I was done placing the Vaseline, I then coated the other half with plaster bandages.
Once all of the plaster dried, I used a sharpie and drew lines across the edges of the plaster. These lines are so that I could realign them easily after I took the mold apart to remove the original sculpt.
After I removed the original sculpt, I realized I forgot something major… A way to get the resin into the mold. Oops! After a bit of thought, I decided the easiest way to get the resin in would be to drill some holes through the PVC pipe and pour it in that way. Ideally, I would have designed pour holes and vent holes into the original design of the sculpt. Something to remember for the next one! In order to try to control the fluid a bit better, I used straws to extend the holes out. Bendy straws would have been good – I’m not sure how effective straight straws were.
Using the volume of clay from the original sculpt, I did a rough guess at how much resin would be needed to fill the mold (~12oz). I measured out 6oz of each of the two parts, added one drop of red and six drops of yellow to one of them, then mixed it. I used a syringe to suck up the mixed resin and transfer it into the mold. It worked quite well, although it was a bit disconcerting because of the number of bubbles that were exposed during the suction process. Thankfully, as soon as the resin reached normal pressure the bubbles disappeared.
The resin takes 24 hours to cure. 24 hours wondering if it turned out.
And after that full day of waiting, I de-molded it. Quite the pleasant surprise! I think it may have slightly too much red, so I’ll have to correct that for my next iteration. I’m still debating about sanding and buffing it in order to get it to be more glass-like.
We’ve been aluminum casting at the Milwaukee Makerspace since November, and I have cast several things since then. For simplicity, we started by using a lost foam casting method, wherein the form to be cast is fabricated in Owens Corning Foamular 150 (Styrofoam), and is then tightly packed in a reusable, oil bonded sand called petrobond. The molten aluminum is poured directly on the styrofoam, vaporizing it. Because the mold is made of sand, the surface texture on the cast aluminum part has the “resolution” of the grain size of the sand.
Ceramic shell is another technique often used in art casting. The positive of the form to be cast in metal is first created in wax, which is then dipped repeatedly in a silica slurry, that slowly builds up to the desired ½” thickness. The surface detail reproducible is much smaller/better, as the silica has a much finer “grain size.” The piece is then put in a kiln to burn out the wax and harden the silica, thereby forming an empty mold. Typically the mold is cooled, inspected for leaks, patched, and then is buried in regular sand. Note that to avoid fracturing the mold, it must be heated before pouring. With all these steps, this process is relatively time consuming and is also somewhat expensive.
Recently, I read a blog post about a quick and low cost ceramic shell alternative that substitutes one or two coats of watered down “Hamiltons White Line Drywall Texture mix” for the tedious ceramic shell process outlined above. While I couldn’t find that exact product, 4.5 gallon buckets of Sheetrock brand lightweight drywall joint compound (DJC) are omnipresent. Note that some bags of quick setting drywall joint compound are actually just plaster, and cannot be substituted. I first assembled all the parts needed to make a quick test of the process. I decided to make some aluminum packing peanuts:
I hot glued the pyramid shaped sprues to the round cup and to the peanuts themselves:
I removed half of the 43 Lbs of DJC from the bucket, and poured in 10 lbs of water, taking care to mix it thoroughly with a spiral paint mixer connected to a drill. Then, I just dipped the whole styrofoam assembly into the bucket, let it dry overnight, and dipped it in a second time. Immediately after the first dip, I took care to brush the surface of any especially undercut areas, to prevent air bubbles from sticking to the surface. In the future, I may consider pulling a vacuum on the bucket of DJC to de-gas it. This may help prevent the formation of air bubbles on the surface of the styrofoam parts. In addition, I could have first dipped the assembly in surfactant. After two dips, the 1/8” thick shell on the assembly looked like this:
It was a week before the next aluminum pour at the Makerspace, during which time I poured a half ounce of acetone into the mold to dissolve the polystyrene packing peanuts and styrofoam, producing an empty mold. This step is only necessary when casting packing peanuts, as their polystyrene tends to rapidly expand out of the mold and catch fire, while the pink styrofoam (also polystyrene) is made for homes, and so is much better behaved. I buried the now-empty DJC mold in ordinary sand, and Matt W fired up the Bret’s furnace, melted a #16 crucible of aluminum, and poured it (Thanks guys!). After fifteen minutes, I pulled the mold out of the sand, and found the DJC was a little darker. The act of pulling the mold out of the sand an leaving it to cool over night left it somewhat cracked:
The DJC crumbled off so easily that I didn’t even need a brush. Also, I noticed that there is more yellowish surface tarnish on pieces left in the DJC to fully cool. I recommend removing the DJC immediately after the aluminum solidifies.
After making a few more, I’m almost ready to safely pack valuables, such as my “Marquis, by Waterford” crystal stemware:
Finally, check out the phenomenal surface detail that this process can reproduce. For scale, this peanut is 1.5” long. The surface texture on the front face is about ~0.002”!
Thanks to Jason G for this last photo. Also, a big thanks to Dave from buildyouridea.com for letting me know that one or two dips will do it!
Summer is just around the corner, and that means it’s time for the first Bay View Gallery Night of the year, and now that Milwaukee Makerspace is located in the heart of Bay View, we just had to get in on the action, so we’re inviting you to join us in what we sometimes refer to as “16,000 sq feet of Art”.
And hey, it’s not all art, as we do a zillion things at Milwaukee Makerspace, as long as it involves being creative and making things, we do it. We’ll have plenty to see and experience, including our group show titled: Awesome Things From the Makerspace.
If that’s not enough to convince you, we’ll also be hosting a show from our friends at the Bay View Arts Guild, so yeah, even more art!
It’s all happening Friday, May 31st, 2013 from 5pm to 10pm. And as always, we’ll have some sort of magical surprise to knock your socks off!
(Note: If you’re not wearing socks, we can’t be responsible for what might happen to your feet. You’ve been warned!)
The idea was simple: make something to help keep track of our supplies so we know when we’re running low on the essentials. After weeks of kicking the idea around and various rough doodles, this project finally took shape. Two days after the first cut on the laser cutter, it was complete.
Made from multiple layers of acrylic, cardboard, and wood, the “Milwaukee Makerspace Consumables Super Analog Status Board” is a clipboard-sized device with nine sliders installed in enclosed slots. Sliding the tabs right displays more green to indicate “full” or “lots” and sliding left reveals the red acrylic below to indicate “empty” or “low.” The user can carry the board around the Space with them as they check on supplies and when done, a large hole centered at the top allows the board to be hung up and displayed on a wall.
The hardware holding the whole thing together can be loosened and the layers disassembled. The cardboard insert that the text resides on can be swapped out should we decide to change the list of items we want to keep tabs on. The supplies being tracked currently include:
- Toilet Paper
- Paper Towels
- Hand Soap
- Welding Gases
- Welding Wire
- Duct Tape
- Painter’s Tape
A digital version may or may not be planned for future release.
If you happen to be out and about on Friday, April 19th, 2013 you might want to swing by Milwaukee Makerspace at 2555 S. Lenox St. in Bay View.
While we aren’t officially part of any gallery night events this time around, we’ll be open to the public on Friday from 6pm to 9pm for anyone who wants to stop by and take a tour, or check out some of the art (and art making tools!) we have at our space.
And if you want to see us in full art swing, you’ll only have to wait until the end of May. ;)