Tag Archives: 2.008

Lasers and such (aluminum business cards, wood and paper etching, edge-lit acrylic signs, thermoforming

I’m proud to say that I’ve sunk at least 40 man-hours of other’s people time into nyancat πŸ™‚
(~150,000 views * 1 sec each / 3600 secs/hr  = 41.7 hours)

from 6:20am today (11/8/11) http://imgur.com/HnoAf

Makes me regret not thinking about watermarking my images (free publicity!). Thankfully, these are but brief lapses in my unfailing devotion to laziness.

Meanwhile, I’ve been exploring the joys of the lasercutter. I found some scrap wood sitting around the lasercutter and etched some of my best friend’s art (shout-out to Alice Chung! http://the-crowned.deviantart.com/)

I didn’t know what type of wood it was so I approximated:
material, lens, thickness, ppi, power, speed, description
aircraft plywood        2    1/8″        500    15%        80%        raster
aircraft plywood        2    .17        300    40%        3%        cut ~.17

I also want to make edge-lit signs and found some scrap acrylic. I checked out some real edge-lit signs, the ones used on the newer-style EXIT signs, looking straight up at them, and you can see the individual blips indicating a strip of LEDs. I thought they might have been using a fluorescent tube, which was my other though for lighting — strip out a discarded scanner’s tube and make a lamp ballast for it, then stick it over the acrylic. Todo: buy some nice strips of RGB LEDs. http://www.adafruit.com/blog/2009/09/22/making-an-edge-lit-acrylic-sign/ ~$7: http://ledshoppe.com/Product/led/LE5045.htm

this was .24” thick acrylic:
ACRYLIC (clear)        2    1/2″        500    80%        50        RASTER, 1/32 inch
ACRYLIC (clear)    (tinted)    2    1/4″        500    100%        1.4        cuts through 1/4” (.21”)

I’m sitting in the media lab shop right now helping a friend, Cathy Wu, make business cards for her imminent plane trip to some conference somewhere (_sigh_ smart people…). I was asleep in my room at 11pm when I heard a loud knocking, which turned out to be a hyper Cathy excited about cutting out business cards with the laser cutter πŸ™‚ I had some anodized aluminum let over from the waterjet clock class / Kevin Rustagi, so there we go.
Giraffe design courtesy of Laura Shumaker, another awesome friend.

Settings used:
METAL ENGRAVE    2    n/a        400    50%        10        (Vector) Engraves into most sheet metals. (incl. anodized Al)to confirm: “my impression was that CO2 bleaches the dye in the anodize coating, while YAG actually penetrates the anodize to etch the aluminum”

The 100 watt lasercutter is definitely not awesome enough to cut this out (we tried full power really slow speed high ppi and it looked to have cut to the same depth as the etching). Maybe the BEAM lasercutter? We settled on using the power shears to cut it out.

I also learned that one can etch paper without burning it up!

Construction paper    2    0.01”        500    6%        80%        etch; — @100% speed, 7% min. to etch. @6%, 97% min. speed

thin cardstock — 1mm thick

People online seem to be getting lighter engravings, though, and I can’t figure that out! I tried all sorts of different settings for the construction paper and all I get is the burnt look. The cardstock I know for sure is white through and through and it also gives me this brown color. ??? I need to figure out this mystery:

http://www.epiloglaser.com/tl_paper.htm

Some very useful links:
Different materials at a glance, with examples (look at the dress under textiles! amazing)
http://lasercuttingshapes.com/page/materials
Everything ever about the Universal 100W CO2 laser and all the possible parameters:
http://www.inlay.com/cnc/laser/index.html
Supplier Acrylics, fluorescent (looks edge-lit without needing lighting):
http://www.usplastic.com/catalog/default.aspx?catid=442&parentcatid=443&clickid=searchresults

Ladyada’s examples page:
http://www.adafruit.com/laser/
With more details here:
http://www.ladyada.net/library/laser/settings.html
What people charge for some lasercutting services:
http://www.tree-fox.com/laser-engraved-and-cut-business-card-110.html
And pumpkins! Plastic ones though. We have real ones on hall that I was pondering…
http://www.advancedwj.com/gpage.html1.html

In other news, my surface mount soldering skills have vastly improved with a touch of patience. These all used the: tin one copper pad | tweezer solder the component onto that pad so that it’s straight | solder the other pad on | reflow the first pad. This seemed tedious to me in the past, but it actually goes pretty quickly and helps me place my components correctly (darn lack of silkscreening) since I’ll go through and tin one pad for all the components.

I also printed tiny-to-be-painted-and-turned-into-earring nyancat:

This is the 3d printer:

Meanwhile in 2.008 we thermoformed for the first time. Here’s the thermoform machine:

turned out pretty well, almost none of the webbing we were afraid of.

The machine is super-straightforward to use. I’ll write it down sometime.

then you use the punch/die to cut out the part you want
some of the injection molded parts. The metal shim actually really affects the shrinking of the part, so our ring and body parts didn’t press-fit together (both used a 3% shrinkage estimate). To be fixed!

Oh, and my food-grade silicone arrived. $17 for a lb off of amazon.

And I shopbot’d a new foam positive. But the silicone negative mold turned out fuzzy :/ with bits of construction foam attached:

Make lots of sacrificial cake until all the foam is melted away? I’m not sure. This silicone will stand up to 400F while the foam melts pretty easily (eg at the hint of a heat gun).

My vending machine coils arrived off of ebay. They definitely look like something I could make by hand.

Also, I learned that ftdi breakout boards are indeed substitutes for ftdi cables. See here for a cool look at what you can do with ftdi:
http://hackaday.com/2009/09/22/introduction-to-ftdi-bitbang-mode/
and some more about ftdi (e.g. vs. avr programmer):
http://www.ladyada.net/learn/breakoutplus/ftdifriend.html

Oh, for 6.131, my final project, some research:
Our normal 6.131 555 pwm generator will not work here. Servo “PWM” signals are very specific — 2 to 4% duty cycle, 20msec period.

http://www.seattlerobotics.org/encoder/200106/16csscnt.htm

use a servo tester then:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=17143 $5
or implement the circuit:
http://www.societyofrobots.com/robotforum/index.php?topic=13833.0

Also, turns out you can totally do diy soldermask (to mask the circuit traces you don’t want to accidentally solder to):
http://retromaster.wordpress.com/pcb-making/ via http://electronics.stackexchange.com/questions/15792/diy-solder-mask-toner-transfer
and a product from seeedstudio:
http://www.seeedstudio.com/wiki/index.php?title=Solder_Mask_Ink

molding and casting research

I conclude that yes, hydrostone and drystone (which mas.863 has lots leftover) can be used for metal casting.

http://www.lagunaclay.com/catalog/pdf/lcc_plaster.pdf
USG PLASTERS & GYPSUM CEMENTS FOR ART, STATUARY & CASTING APPLICATIONS
DRYSTONE Fast-casting gypsum cement that provides strong, durable casts without the need for dryers. Excellent compressive strength and good
impact resistance. Enhanced flexural properties. Low absorption for reduced paint demand. Environmentally preferred to resin-based
alternatives. Available in solid or hollow cast formulas.

HYDRO-STONE Especially suitable where high strength and resistance to wear are necessary. Used in high-quality art and novelty castings, molds, figurines,
modeling material, anchoring material, density fill applications, lamp bases, and die production. Works well in most mold materials, especially
flexible molds. Expansion about two times greater than Hydrocal A-11. Self-leveling when poured and not suitable for hollow cast
applications

http://www.sheffield-pottery.com/US-Gypsum-Plaster-Information-s/38.htm  
DRYSTONE – Fast setting high strength product that needs no drying. An environmentally sound alternative to resin-based products. No hazardous chemicals or waste, no styrene emissions and no required environmental controls.
HYDRO-STONE – One of the hardest and strongest of all gypsum cements. When mixed properly, has a heavy, syrupy consistency ideal for pouring solid models or patterns. Recommended for stretch-press dies where extreme surface hardness is required. Slightly higher setting and expansion than ULTRACAL 30. Used for high quality art novelty and statuary castings.

http://en.wikipedia.org/wiki/Plaster_mold_casting
http://chestofbooks.com/reference/Henley-s-20th-Century-Formulas-Recipes-Processes-Vol1/Casting-Plaster-Molds.html 
plaster is used for metal casting but requires drying for several days

 http://www.artlex.com/ArtLex/G.html
gesso – Plaster or a fine plaster-like material made of gypsum, which is also called whiting, used for sculptures. An especially versatile medium in reliefs, gesso can be either a material cast in a mold or a material of a mold, a material to be modeled, or carved, or attached to something else. When used for molds into which molten metal is poured, it must be hardened with sand as a grog. Gesso may also refer to such a gypsum material mixed with an animal-hide glue and used as a ground for painting. For this latter use, it isWEAR A DUST MASK! usually applied to the surface of a wood panel or sculpture to become the surface on which an artist paints. It was used by Gothic and Renaissance panel painters, and is still used today. Oxgall (or another wetting agent) can be employed MEDICAL ALERT!to eliminate pin-holes in gesso surfaces by mixing it into the gesso before the gesso is applied. Like all other dusts, airborne gesso is hazardous to breathe β€” every user should wear an appropriate dust mask. Also see slip and stucco. 

therefore gesso is probably food safe.  so if I coat my pink foam model (which can cause sensitivity with prolonged exposure — cue architecture student horror stories) with gesso and then cast it with food-safe silicon, should be good.

overview of molding techniques
http://miniatures.about.com/od/techniques/tp/moldputtylist.htm

discussion of 3d-printing plaster molds
http://forums.reprap.org/read.php?171,37834,3783

Nyancat party! in aluminum, egg, foam, silicone, hydrostone, and drystone

MAS.863, Fall 2011
Week 6
Molding and Casting — Nyancat party! in Egg, Silicone, Plastic, Hydrostone, Aluminum, and Foam

We can use molding and casting to easily replicate a design.
The analogies between this manufacturing process and internet memes are clear.
Thus, I am compelled to make nyancats!

nyanweight? nyancoaster?

Aluminum paperweight. File done in solidworks, export as DWG to Mastercam, turned on CNC lathe (daewoo puma) and milled with engraving tool to 0.02’’ depth on CNC mill (EZ trak). Used as mold positive.


Smooth-on OOMOO25 used as silicone mold (negative). 100 parts A : 130 parts B by weight, pot time ~15 minutes, cure time ~1 hour.
 
Masking tape used to form β€œwalls” for negative mold.

Released fine (no releasing agent used). Fine features (0.02’’) reproduced cleanly.


Hydrostone casting, positive.

Final result: one nyancat party.

nyanegg?
Just for fun: some egg?
 
End result:
 

Not so great. I await the shopbot 3D mold.

hot glue mold: jello legos
Previously on Bad Ideas:
 

Hot glue is nontoxic, right? Legos used to create positive for hot glue. Crisco applied as releasing agent — did not release well, had to pry out legos, destroying them. Jello poured in — very nice, can even see the β€œLEGO” lettering on the bumps. Jello lego’s had flat bottoms though, since this is a one-part mold.

nyancake?
On Saturday, I learned that I now have media lab shop access and can now devote my entire weekend to MAS.863! Yay!

I made the model in Solidworks while still hoping I could get my hands on some food safe silicone. This didnt happen, though IαΈΏ not sure why. Ah well. I went ahead anyway and cut my model on the shopbot out of foam
.
1/8´’ bit, though later I remember I had resized my model specifically for a 1/4´’bit which could have cut my time down by half. After 1.5 hours of cutting I had my mold (the partworks estimate was 45 minutes). The deepest parts the shopbot just barely cleared (that was nervewracking!). The cut-out toolpath the shopbot most definitely did not clear — I was prepared and hit the e-stop button immediately.


There were a lot of burrs and the finish quality was less than what Id expected. But IαΈΏ not complaining, since IαΈΏ using a shopbot to cut out an internet meme…

I attempted to deburr with a heat gun but stopped immediately when I realized I was rounding out my beloved sprinkles. I ended up using an air compressor and getting pink sprinkles all over myself.
Then I cast a negative mold with smooth-on silicone, in this case mold star slow since the arch shop was out of oomax 25. Pot time 50 mins, cure time 4 hours. After 1.5 hrs I took my mold with me instead of waiting. Mold turned out fine. Probably used half a smooth-on set of material.


I had to commit some violence to the mold original in order to get the silicone out, simply due to the geometry of the piece. The silicone separated from the foam just fine.

Drystone casting followed. Required almost exactly ~1.5 cups of material. (500grams?)

Oh, this reminds me, IΒ΄ve done sand casting before too. We helped sand-cast a cement health-friendly stove in La Vaquita, Mexico. This was a government initiative of some sort.

Files coming soon. [edit: 4 Sept 2012. So maybe not soon. But I’ll try to get around to it. Also I would like to point out to blog readers that I went on to make nyancake and nyanjello! πŸ˜€ http://www.orangenarwhals.com/search/label/nyancake

centrifugal switches (spin activated yoyo electronics)

doing some research for 2.008 instead of freaking out over 6.131 lab

Edit 10/17/2011: Found it! Thanks to Charles.

See explanation of “tilt sensors,” which include both mercury and rolling-ball type ones, here: http://www.ladyada.net/learn/sensors/tilt.html

http://www.adafruit.com/products/173

Cost: $2.00.
(octopart search: http://octopart.com/partsearch/#search/requestData&q=tilt+switch&rangedfilters%5Bavg_price%5D%5Bmin%5D=0.54&rangedfilters%5Bavg_price%5D%5Bmax%5D=2 can maybe get it for $1)
http://smparts.com/-Switches-Rolling-ball-switches-%28AT%29/c0_2_561/index.html — but no prices listed, hah.

Hmm. So I know there was at least one previous design in 2.008 that used these switches. They put two on each side (top and bottom), facing outwards. Then, when the yo-yo spun, both switches would contact (and presumably switch on LEDs). Apparently they had issues with the thermoform shrinking and squeezing the ball switch and preventing it from switching though. All in all, I’m a bit iffy about these rolling ball switches. There’s no way to adjust their sensitivity (although I guess regardless PoV yoyo requires a microcontroller anyway, but the less pin-count the better), so what if it switches on when the the switches are rotated to (left right) and the yo-yo is slightly tilted? We’d be stuck with 100 useless switches.

I like Paulina Mustafa’s design of a flexure switch, she was prototyping this at MITERS (but I can’t find a blog for her). Looks sort of a like a ying-yang design, and the tips are flung outward and make contact with the sides when the yo-yo is spun. She’s using copper-tape, but I think something like conductive glue would be easier to apply.
http://www.instructables.com/id/Conductive-Glue-And-Conductive-Thread-Make-an-LED/step1/Make-Conductive-Glue-Conductive-Paint-and-Conduc/

=====
Earlier Research

via
http://www.helifreak.com/showthread.php?t=33567 “DIY Night Blades”

centrifugal switches:
http://www.atomicmods.com/Categories/Tutorial-1-28-Mini-Z-Rim-Light-Installation.aspx
(spring inside a brass tube)

The batteries are wired in series with the LED and the centrifugal switch. The centrifugal switch is simply a tiny spring inside a brass tube. When you accelerate, the spring swings to the outside and makes contact with the brass tube turning on the lights. It is really quite simple and very reliable. This also makes the batteries last a long time since they are only on while you are driving and you will never forget to turn them off.

types of switches and design of switch contacts (including mercury switch aka “tilt switch”): http://www.allaboutcircuits.com/vol_4/chpt_4/1.html

quora question
http://www.quora.com/Mechanical-Engineering/What-centrifugal-switches-are-suitable-for-use-in-a-yo-yo

still failing to find suppliers o.o

mercury switch:
http://mondo-technology.com/yoyo.html

paperclip style:
http://www.make-digital.com/make/vol22?pg=115#pg117

abusing CNC mills for internet memes

It’s official. CNC mills are sexy. Even decades-old bridgeport model ones that take giant floppies.

So a while back I was all like “I’mma mill me some nyancat for my 2.008 paperweight.” (http://www.orangenarwhals.com/?p=187)
Oh yea, my partner for this lab is the awesome Cappie Pomeroy. He did all the lathe work o.o so don’t ask me about that.
So I got around to milling it.
look, nyancat got fatter so that you can fit a 1/16” end mill between it’s crevices!

(The way I did it is I did a Tools>Sketch Tools>Sketch Picture, then resized that reference nyancat picture until it looked appropriate. I then put a Tools>Options>Grid>Major Grid 0.07 / minor grid off. System Snaps>check Grid. Also, make sure Units>IPS, InchPoundSomething. Then just trace it with lines).

However, my resizing and retracing ended up not mattering, since I decided to engrave it. This was because we had to make a 15 minute version, and no matter how I tweaked Mastercam (using 0.02” depth instead of 0.1”, using a wide endmill to clear it and then remachining with the 1/16”), there was no way the full 3D paperweight was milling out in 15 minutes.

Yea so there are really dumb ways to make a path in Mastercam. 
See the X’d out paths to the left — I was tracing all the paths by hand, essentially. Then Pat, the shop instructor, came by and showed me the magic of the the “polygon” tool which will automatically apply a function (in this case, engraving) to everything within that polgyon. It created some weird paths, like you get on a lasercutter which doesn’t recognize your vector as one shape but as individual lines*, but it gets the job done. In other words, he finished in 10 minutes what was taking me hours to do… hah.
*aka it doesn’t trace them continuously but rather jumps back and forth between different lines in the drawing
See link below for g-code / mastercam / solidworks files.

The jig was made by the instructors for the class, along with the “offset” used in Mastercam to make sure the blank is positioned correctly.

gahhh technical difficulties. Yes, I used my phone to take a picture of picture on my camera.  You really don’t want to know.

Nyanweight documents:
https://docs.google.com/leaf?id=0B9r0HZeoMbmgZjgzMTkyOTEtOTU4OS00MDhjLWJlMmYtNTQzMjc2YmJlMzkx&hl=en_US
where “base/lab1” docs are for the CNC lathe and “engraving” docs are for the CNC mill.


Software used: solidworks (.sldprt, exported to .dwg), mastercam

Todo next: Mill out the actual thing.