Blazing fail.

August 23, 2012

This is a failure of a Seej Masonry Bloxen.

I stuck an LED inside it to highlight the software-generated infill pattern.

ReplicatorG does this cool thing when preparing the model for printing, generating a honeycomb pattern for large solid volumes. Presumably this feature was designed to save plastic and printing time.

It’s like magic the first time you see it in action.

This is a PLA print at 10% infill. One hundred percent infill would print a solid block of plastic.


Raftless Printing with PLA

August 8, 2012

I’m no expert at 3D printing, but through a lot of trial and error I’ve discovered a few nuggets of information that I wish I’d known a few months ago.

A few weeks ago I said I was chasing a raftless print. I’ve finally got it, at least with PLA and ABS, printing Seej bloxen.

This comparison isn’t entirely fair, since the bloxen are sourced from different models, but the difference between a hot, rafted print on the left and a cool, raftless print on the right should be pretty clear. Both of these are printed from the same roll of 1.75mm PLA.

Here’s what I’ve learned.

PLA likes a cool build platform, somewhere around 45° C: My MakerBot Replicator ships with a heated build platform, and ABS plastic seems to stick nicely around 115°.

When I first started printing with PLA I just assumed it was more or less like ABS. When prints started shifting off the platform I kept cranking up the temperature on the HBP, eventually resorting to elaborate raft structures with painters’ tape.

It never occurred to me that lowering the HBP platform temperature was the solution.

Changing the build temperature in gCode is easy: just find a line that looks like:

M109 S100 T0 (set HBP temperature)

And change S100 to S45. This assumes that you’re using ReplicatorG to generate your gCode.

There’s one other change that seems to be helping: print a nice, gooey first layer of PLA, and then back off the printing temperature to maintain the model’s integrity through the rest of the print. The gCode for this isn’t much more complicated, but you have to get it in the right place. First, set the extruder temperature at the beginning of the print, close to the top of the gCode:

M104 S240 T0 (set extruder temperature)

Change 240 (or whatever it is in your gCode) to 210.

The last step is to find the point in the gCode where the first layer stops and the second layer begins, and back off the temperature a bit.

In the other two instances there are existing M codes that tell the machine to wait for the extruder or bed to reach the specified temperature before proceeding. You’ll have to put those codes in yourself for this line.

Find the first example of:

M73 P1 (display progress)

and add these lines after the next <layer> tag:

(*custom gCode here*)
M104 S190 T1 (set extruder temperature)
M6 T1 (wait for toolhead, and HBP to reach temperature)
(*end custom gCode*)

That should drop the extruder temperature down to 190° and then resume printing. The delay can be a little unexpected the first time your Replicator just seems to stop printing abruptly, but then your forebrain will kick in and you’ll realize it’s just doing what you told it to do.

The usual warnings about bricking your Replicator or burning down your apartment building apply. Use this code at your own risk, and you should probably own couple of fire extinguishers anyways.

The Virtuous Cycle of Fail

August 2, 2012

This is a failure of an Seej Tournament Bloxen print. Seej is an open source tabletop wargame based around 3D printing.

After a minor success with custom gCode yesterday I started experimenting with altering printing temperatures on the fly.

I tried cooling off the raft a bit and lowering the extrusion temperature; the raft worked great, but the rest of the print didn’t want to stick to the raft anymore.

PLA can be a little fussy, and tends to lose its shape if it’s printed too hot. The next thing I’ll try is feathering off the extrusion temperature layer by layer; hot and sticky at the raft layer, and then successively cooler until I get to a minimum print temperature.

Filament gets gummed up in the extruder at 170° C.

Experimenting leads to failure. Failure leads to knowledge. Knowledge leads to experimenting.

And here’s a Seej Ourobouros Guardian fail. Plenty of tries on this one before I got something that printed correctly.


Seej at Maker Faire Detroit 2012

July 31, 2012

There are splintered shields and broken hopes among the solder blobs on the ground at the Henry Ford, site of Maker Faire Detroit 2012.

MakerBot Industries was kind enough to give me the opportunity to talk about Seej at their booth on Saturday. Afterwards I hung around and played Seej against passers-by, losing more often than not.

While I was playing I realized that players need a way to commemorate their games. I usually travel with a backpack full of tools, including a Sharpie. So I signed and dated a few bloxen and left them with the booth crew.

Unfortunately there’s not a lot of room to write on most of the current designs. This is remedied with the Tournament Bloxen; it sports a large, flat plaque upon which players can immortalize an event:

Flagrant stagecraft alert: I didn’t have this tournament bloxen at the Maker Faire, but if I had, this is exactly what I’d have written on it before handing it over to a victorious opponent.

I’d like to accumulate a mantel full of these, signed by different Seej players.

The gentleman in the Makerbot t-shirt is Matt Griffin from MakerBot Industries, all-around nice guy and excellent child wrangler, refereeing a match.

The younger kids seemed mostly interested in building structures out of bloxen. MakerBot had printed a few dozen bloxen of various kinds and colors, so there was plenty for them to work with. Look at the size of this stack protecting a young Seejmaester:

This kid destroyed me in about five turns.

Note: if you and/or your child appears in one of these photos and you’d like it removed, please notify me immediately.

Download the Tournament Bloxen from Thingiverse.

All work and no PLA makes Zheng a dull boy

July 27, 2012

I’m headed off to Maker Faire Detroit in a few hours, and I needed a new Penny Ballista to take on the crew from MakerBot in a no-models-barred Seej match. So I personalized the nock on this one and gave it a go printing with PLA.

The Replicator can print in (at least) two kinds of plastic: ABS, which is the stuff LEGO bricks are made of, and PLA, which is a biodegradable wonder plastic made from corn.

PLA works better than ABS at lower printing temperatures. I’ve been lowering the extruder by 1° every time I print something new, and still haven’t found the floor.

This is my first set of prints with PLA, and I like what I’ve seen so far. I bought this roll from JetJet2004 on Amazon a couple of weeks ago, and I haven’t been disappointed with it yet.

I also printed some Seej Bloxen, Riveted, which aren’t available on Thingiverse: if you want one, you’ll have to solve the
Cryptstone Challenge.

So! Find me walking around with a ballista in my pocket at Maker Faire Detroit on Saturday. I’ll be the pale geek in cargo shorts and a t-shirt.

Benzene, done that.

July 24, 2012

I’ve always liked the anecdote about Friedrich August Kekulé von Stradonitz and his fevered daydream about the chemical structure of benzene, and apparently I’m not alone.

Regardless of how much truth there is to Kekulé’s story, I try to sneak the word “ouroboros” into conversation as often as possible. It’s a lot easier for me now that I can say, “Hey, check out the ouroboros I designed on Thingiverse.”

You can see some rectangular bits of sprue protruding from the base of the model in the photo above; they exist to keep the model from toppling if the extruder tip nicks the top layer of the print. The sprue isn’t in the final model.

I have a dual-extruder replicator. The unused nozzle in this single-color print kept bumping into the right prong of the snake’s body as the extruder traversed the X-axis. This tells me my nozzles are out of calibration by a micron or two.

I solved this problem by rotating the snake 45° around the Z-axis so the prong tips moved out of X alignment, which is a handy cantrip to have in one’s grimoire.

This is a fairly fast print so I was able to go through lots of iterations to get it right:

This model is future-proofed, at least for a while. There’s some detail in the eyes and mouth that is going to have to wait for the next generation of extruder technology to be fully realized. You’ll also note some slight nickeling in the curve of the body, but I designed it to be smoothed easily so we can squeeze another few years out of it.

The tail and mouth are connected by a couple of polygons– this is the one artistic change I really didn’t want to make but I just couldn’t get the model to print reliably when they were separated.

I’ve got the serpent broken out as a separate model, so maybe if I get the time she’ll be transincarnated as cobra.

1.75mm ABS Green
10% infill
Feedrate: 25
Layer Height: .2
HBP Temp: 116°

Just a normal day at the office

July 19, 2012

New Seej model coming soon. Couldn’t resist the pun.