Lost-PLA Aluminum Casting

Last Sunday, several Hackerspace members came over to check out my David Gingery-style aluminum casting setup.   We tried “lost-PLA” casting, and it worked out pretty well!

Aluminum Yoda

Lost-PLA: Works, It Does

 The test target was the 3D-printer-classic Yoda head.  It was printed on a RepRap in PLA and bedded directly in sand.  Molten aluminum was poured straight into the PLA, vaporizing the plastic as it filled the mold.    Overall, this process makes for a shorter, simpler route from a virtual 3D model to a solid aluminum object than anything else I’ve done or heard of.

Jim printed Yoda on his RepRap Mendel with minimal infill.    In order to put the sprue on the bottom it was cast upside-down.  So I started by setting the plastic model on a molding board, and rammed up the drag (packed in sand) around it.  Rolling over the drag, I set a 1″ sprue pin on the exposed base of the pattern, and rammed up the cope around that.

The actual pour was somewhat exciting (that’s a bad thing), as you can see in this video Seb shot.  On the initial pour, it appeared that the aluminum failed to enter the pattern at all.  (Castings fill wildly faster than I expect, plus I was distracted by the sudden eruption of fire.)   The flames died down, revealing a gas-filled bubble of aluminum rising from the sprue.  This is a bad sign, so I tried pouring in a bit more aluminum.  This is generally pointless and never does any good, but it’s hard to resist trying.  So the extra just filled up the sprue a bit more, expanded the puddle on the surface, and torched the strap holding the flask together.

After the pour, we were all convinced the experiment had been a complete failure.   As we  knocked the casting out of the sand, I fully expected to find a misshapen, formless blob.  So convinced was I of failure, that with the casting still too hot to touch without heavy gloves and covered in burnt sand & plastic residue,  I assumed we were looking at scorched PLA.  I had just begun to speculate about how the plastic could have survived so entirely intact when Jim grabbed a stick and whacked Yoda on the head: Ding!  Surprise victory!

Overall, the reproduction quality is excellent.   In spots you can even make out the fine striations from the 3D printer.  The parts that didn’t work:

  • Yoda’s long, thin ears didn’t fill, which was entirely expected.  This might be resolvable with the addition of gates & vents so that the aluminum can come in from the bottom while vaporized PLA escapes upward.
  • The wide flat-bottomed base of the shoulders didn’t fill.  Upside-down this became a wide flat-roofed space, which trapped a big enough bubble of escaping gas that it couldn’t get out through the  bottleneck at the base of the sprue.  If I’d realized this ahead of time, I would have made a bigger sprue covering the entire base and this wouldn’t be an issue.

In any case, I’m pretty excited about the possibilities with this process.   It eliminates lots of tedious pattern making and at the same time radically expands the variety of things I can cast.

 

Here is a picture from Jim of the pattern mid-print; showing off the fancy 10% hex infill:

 

 

Hackerspace a’ rumblin

So things have been going really well at the Hackerspace lately. We’ve had some people join, including another Ross (which is a little weird for me) which is just awesome. Every person that is part of the space brings their own unique attributes and contributions which help make the space that much better. Heaven forbid I say something like “synergy” but that is what it is. As a group we are more then the sum of our parts. Anyways, along with new people we’ve also had some new equipment come our way via some wonderful donations (thanks Anne!) and some savvy shoppers and yard sale wanderers (you know who you are!).

For those of you who have been to the space before this last week, you should come back. Last Saturday there was a huge re-organization to separate out the computer working areas and all the machining tools.

We’ve taken over the front half of the space we were in which is now the main computer / meet and greet space.

The back end is still getting organized as we’ve got some machines that need to be put on tables which still need to be built.

Basically right now in the back we’ve got

  • Soldering station with microscope inspection tool (can’t see it in the image, to the left you can see the table, barely)
  • Radial Arm Saw (Liz)
  • Small Drill press (Anne!)
  • Large Pneumatic Band Saw (sort of working, needs a new switch / fuse) (Anne!)
  • 1 donated lathe – semi working, needs stand and some cleanup not to mention tooling (Anne!)
  • 1 on loan lathe (thanks Edwin)
  • 1 on loan belt sander (Edwin)
  • 1 on loan grinder (Edwin)
  • 1 corded drill (Dan Z.)
  • Lots of hand tools, saws, clamps, bits etc.
  • Some spare lumber
  • A nice bike maintenance stand (thanks, don’t know who brought it)

Right now we’ve got a great bike lighting (POV) workshop being organized, stay tuned for more details. But as a teaser here is some video 🙂


link to video on YouTube

Also, it looks like were going to be having a BBQ on Saturday the 14th at 5pm. So bring your hacking spirit and eat some foods!

Project Update

There’s been a lot of activity at the space lately and here are just a few of the awesome projects happening here:

Plans are underway for us to hold a light-your-bike workshop on a Saturday afternoon in May. We are thinking of having 2 projects people can choose from, one pretty easy for novices in need of an intro, and the other ultimate fun for those already somewhat technically inclined. Details will follow soon. We are also planning a party which will probably be held in late June.

John E and Edwin are working hard on their Musical Universe of Faux Fur Flowers (they did receive some grant money – yay!) and to a lesser extent their costumes for Burning Man / Apogaea.

Spring has brought renewed interest in Autoponics (a fully automated aeroponic system). Dan Z and Lindsay are also practicing worm husbandry plus growing hundreds of seedlings at their apartment. They are looking for foster farmers who can offer spare land and watering when their crop is ready to transplant.

The Solar Steam Engine project has lost a little steam lately but is always a hit with visitors. Some solar panels and a voltmeter told us the solar power concentration is about 30% greater through the Fresnel lens than with normal sunlight.

Joel is working on several projects, including a lunch-box light show that consists of lasers and mirrors all self-contained in – you guessed it – a lunch box. His Ardouija will be a hands-off Ouija Board powered by an Arduino. He has one dimension going and was working on refinement plus adding and integrating the second dimension. He also just brought in various rocket parts and related paraphernalia for people to hack away on.

Ardouiji

Ardouiji

John M bought some Sifteo cubes which we were playing around with a couple weeks ago and will be thinking about possibilities for.

Sifteo

Sifteo

Ross has been hard at work building a heat-forming machine which will take a sheet of plastic which with a mold, heat and a vacuum will allow creation of various things. One application could be for Halloween masks or related props. Employing a CNC machine to make molds will broaden the possibilities considerably.

Dan D-B found a YouTube video a couple weeks ago of someone using spray paint to create a painting in about 40 seconds and wanted to try it out himself. Scrounging up various cans in various colors that were recently donated, he created a bunch of paintings one Saturday afternoon out in the parking lot. Liz tried one too and we now have more paint and props so expect more of this.

Spray paint art

Spray paint art

Liz is still working on improvements to her LED coat but dropped that temporarily to work on some flower power – adding simple yet elegant white LEDs to a floral print dress. She has plans for a few more projects like this but also is thinking about Apogaea / Burning Man plus ahead into fall and ideas for us hosting a Haunted Hacker House.

At this past Tuesday’s meeting, Juan from SparkFun attended and intended to photograph general goings-on at our space, but also got roped in to doing some light painting with Liz and her LED coat on rainbow mode.

Light painting

Light painting

We are expanding in to more of the building! Which is fortunate as our stuff has accumulated and we’ve attracted more people. In addition to all our fun projects we will be spending some time reorganizing and moving things around to better accommodate our needs.

I know there are some things I’ve missed so these are just a few of the projects going on at Solid State Depot. Come check us out on a Tuesday evening or see if we’re around on a Saturday afternoon! (But maybe not this Saturday 4/23 – instead go see our friends at SparkFun for their Autonomous Vehicle Competition!)