Filament Samples and Customizability

Does the world need yet another filament sampler model? Probably not. But we made one anyway. Along the way we tested out Thingiverse’s new Send to Fusion 360 feature for adding fillets and revisited our Blender Bake method for enabling OpenSCAD to add text to an existing STL file in a way that can be used in the Thingiverse Customizer.

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Why even do this?

When I first got started with 3D printing, I typically used whatever name-brand filament belonged with each type of 3D printer I was using. I figured this could eliminate at least one of the many variables that can lead to failed prints, since Ultimakers might run best with Ultimaker filament, MakerBots might run best with MakerBot filament, and so on, at least at the default slicer settings.

But eventually… I got bored. I wanted to try new types of filament. And new colors. And sparkles. Also, I was running out of all the discounted and free filament that was left over from when I worked at MakerBot and Ultimaker, so it seemed like a good time to branch out.

It got confusing fast. Some filaments worked really well for certain prints, but not others. Some didn’t look the same at all after printing than they did when they were originally on the spool. And there were so many brands and types of filament, not always recorded accurately on the spools. And once a spool was used up, I didn’t have a good record of what the filament was like, so I didn’t always know if I should reorder the same type. And another kicker – half of my printers have their filament loaded *behind* the machine where I can’t see it! It would be nice to have something to put in front of the machine to remind me what’s in there.

There are a number of very nice existing models on Thingiverse for testing and sampling filament, including test cubes, texture and transparency testers, samples for display and to put on chains and loops, and even some that were customizable. Somehow none of these were quite what we wanted. Even our Speed Racer Testbots didn’t seem like quite the right thing.

Design Requirements

Our goal was for the filament samples to be:

  • Elegant, not fussy… but also not just a plain cube or rectangle
  • Descriptive in terms of the color/type/brand of filament
  • Customizable! Of course :)
  • Stackable, with a loop for hanging, and able to stand up on their own (like near a printer or something)
  • Not a 3D printing torture test full of tiny posts, overhangs, and infill samples
  • Rather, a hefty sample that feels good in your hand so you can easily see and feel the filament at a basic level

We settled on the “tombstone” shape shown below. This was the most elegant solution we could think of that would maximize text area and have both straight and curved elements. We chose to emboss the letters because then we could easily color the letters with Uni-Paint pens (these pens tend to bleed into the filament layers a lot less than Sharpies). But letters that stick out of the front and back would make the samples more difficult to stack, so we also included a raised lip around the entire object, effectively making a flat, stackable surface. Here they are both stacking and standing on their own:

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We made the hole really big so the samples would fit over just about anything:

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And especially so that they wouldn’t be fiddly to pick up and carry around!

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Tinkercad-to-Fusion

Tinkercad recently launched a long-awaited feature: the ability to send basic objects from Tinkercad to Fusion 360 for fillets, bevels, and other cool features. Of course, we could always export STL files from Tinkercad and send them to Fusion 360, but those models would be meshes instead of the types of basic geometric objects that Fusion 360 knows how to work with for fillet/bevel modifications. This new feature is really exciting because it allows people to design in a really simple environment (Tinkercad), and then pop over to a more difficult environment (Fusion 360) for just a few simple targeted operations.

The green model on the left below is what we created in Tinkercad, and the gray model on the right is the filleted version that came back from Fusion 360:

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And yes, we *could* have just designed this object in Fusion 360. In fact if you already know Fusion 360 it is easier; you just make some sketches and do some extrusion and a little push-pull. But for beginners whose main design software is Tinkercad, it’s really great to be able to pop into Fusion just for a second and then get out. Here’s what it looked like in Fusion 360 when I was adding the fillets:

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This is seriously great and it’s really exciting this new feature of Tinkercad has launched. HOWEVER, it’s still a bit fiddly; you have to know a few things about Fusion to use it; and you can only apply it to simple designs made with basic shapes. Still, this is the beginning of something fantastic and if you try to keep things simple then this is a nice way to add fillet/bevel options to Tinkercad models.

How to add fillets to a Tinkercad model in Fusion 360

First, read Tinkercad’s blog post about the release of this feature and the basic steps for using it. Once you’re done with that, check out these tips for filleting Tinkercad-made objects in Fusion 360:

  1. You can only use Basic Shapes in your model; if you use a Shape Script then that part of your model will not appear in Fusion 360 after the transfer.
  2. Fillets are really just inherently fiddly things and they don’t always work. Any kind of even mildly interesting geometry like overlaps or corners can unexpectedly make it impossible for Fusion 360 to generate a fillet. If you notice a little red “x” at the bottom right of the window, then Fusion 360 was unable to make your fillet for some reason. Sometimes it helps to choose a smaller fillet radius; sometimes it helps to select many edges to fillet at once; sometimes it helps to select edges just one at a time and in some magical order; and sometimes there is nothing you can do.
  3. Also keep in mind that the design you bring over from Tinkercad might have some weird overlaps or double-edges, and sometimes you won’t be able to see the entire edge you are selecting. If you have a problem getting fillets to work, then I recommend trying a lot of random things to see if something somehow does the trick. If all else fails, try to make your Tinkercad design a little simpler somehow.
  4. For some reason my Tinkercad designs showed up in “Sculpt” mode in Fusion 360. If that happens to you, then you may want to change to “Model” mode from the leftmost square in the toolbar menu.
  5. The fastest way to make fillets in Fusion 360 is to press the “F” key, then select a bunch of edges in sequence, then type a number to set the radius, then press Return/Enter.
  6. Navigation in Fusion isn’t the same as navigation in Tinkercad; in Fusion you Rotate by pressing Shift while dragging with the Middle mouse button and you Pan using the Middle mouse button. If out of habit you press and drag with the Right mouse button, a weird menu or some other thing will pop up; just press “Escape” if this happens.
  7. To export your model from Fusion 360, right-click on the “FusionComponent” text at the top of the Browser list, then select Save as STL. A window will pop up and you’ll have to click “ok” before you can save the file to your computer. Of course you can then print your model, or maybe Import it back into Tinkercad.
  8. If you bring your model back into Tinkercad after filleting or making other modifications in Fusion 360, you won’t be able to ungroup or separate that model anymore. It will act the same way as any imported STL file, as one piece.

After filleting in Fusion 360, you can add text or whatever you like to the sample in Tinkercad. You can try it yourself, and also modify the shape of the object before or after the filleting step, at this Tinkercad link.

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Thingiverse Customizer

If we had made our model in OpenSCAD, then adding text and porting to the Thingiverse Customizer would be pretty easy. And yes, we *could* have just made this model in OpenSCAD, and even acheived most if not all of the fillets with Minkoswki sums and other tricks. But we didn’t; what we have is an STL file from some other program, not a parametrizable model based on OpenSCAD code. We could easily import this STL file into OpenSCAD and add text, no problem. However, the resulting file wouldn’t work in the Thingiverse Customizer, because it would involve an external file. There is currently no way to import an existing STL file into the Customizer.

However, there is a way to embed an STL model into OpenSCAD as a list of mesh/triangle data that generates a polyhedron in the shape of the model… and once you’ve done that, everything is self-contained in one OpenSCAD file, just like the Customizer wants. This method was shown to me by atartanian and uses a Blender plugin written by graphicsforge. You can read a step-by-step in my previous post Beefy Trophy – Baking meshes into OpenSCAD from Blender. Basically it involves importing your STL file into Blender and then using the plugin to export it as text that can be used inside an OpenSCAD file:

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Here’s what the model data looks like after opening it in OpenSCAD:

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And now we can use the model inside OpenSCAD by calling the polyhedron anywhere we like within our code. Note at the top we have user-modifiable parameters for three lines of text and for font size; these are the elements that people will be able to change inside the Thingiverse Customizer.

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When we upload to Thingiverse we have to include the .scad file and click the “This is a Customizer” button.

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This activates the “Update in Customizer” button on the front page of our model on Thingiverse (see the bottom right of the screenshot below):

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Pressing this button takes the user to a screen where they can change the text and font size parameters:

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3D design for everyone

Notice the running theme here of creating hacks that enable people to do things above their current design skill level:

  1. First, the Thingiverse Customizer enables even beginners to modify the filament sample text, without having to work with any of the actual OpenSCAD code.
  2. Second, the new Tinkercad-to-Fusion feature enables beginner designers to leverage some of the tools in Fusion 360 without having to get too deep into that more complicated software.
  3. And finally, the Blender Bake method enables Customizer designers to use OpenSCAD to modify existing models, or models that they created in other software, without having to design from the ground up with OpenSCAD code.

All of these things make 3D design a little bit more accessible, at different levels. Will someday this stuff just be… easy? Maybe. But for now, baby steps.

tl;dr

Hey, here is a new model for making filament samples. You can easily customize the text yourself on Thingiverse at this link: Customizable Filament Samples. Or, play with the model in Tinkercad, at this link: Filament Samples and Tinkercad/Fusion test. Or, learn how all of that came together by scrolling up :)

SONY Paper for Reading Technical Mathematics

I brought nearly 1000 research papers and over 200 books with me to Peru this spring. Not in heavy stacks and stapled packets, but on a SONY Digital Paper, a large-format e-reader that is basically the size of a thick piece of standard 8.5 x 11 paper. Here is the Paper in action with some excellent Peruvian food at a cafe in Monumental Callou:

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The Paper is the first electronic device I’ve used that is suitable for reading technical mathematics research papers.  Unlike a tablet, the screen real estate is large enough that you can actually see notation and diagrams. Unlike a laptop, it’s in portait mode (taller than it is wide), just like a real printed-out research paper. Although it holds over 11GB of documents and has a very large screen, it’s thin and light and you can bring it anywhere without even noticing that it’s in your bag.  It’s easy to hold and use, shown in action here on the long flight home:

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The Paper is a replacement for… Paper

The Sony Paper is well-named. It’s not a tablet. It’s not a laptop. It doesn’t connect you to the internet or let you read your email. It is truly a replacement for paper. Stacks and stacks and stacks of paper. I had already digitized my physical-paper library so I had a huge collection of nearly a thousand mathematical research papers already in PDF form on Google Drive. It was easy to transfer this library to the Paper by dragging the PDFs into the Digital Paper App on my desktop computer while the Paper was plugged in by USB. Here’s what the Digital Paper App looks like:

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You can organize documents into folders with the desktop app, so that they are easier to find when using the Paper:

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It is really a joy to read mathematics on this device. I’m so sick of being in front of my computer or laptop all the time, but I don’t want to carry around a heavy library of research papers everywhere I go, especially when I’m traveling. Ths screen is really great for diagrams and readable text, entire pages at a time:

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In addition to research paper PDFs, my digital collection included more than 230 full mathematical textbooks, which I also transfered to the Paper in just a few minutes. Even with hundreds of books and many hundreds of papers on the device, I still have almost 4GB of space left. Here’s part of Fulton’s Intersection Theory, which I can now carry with me everywhere just in case:

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Functionality: Search and Stylus

The Paper does only very specific things, but they are most of the things that you would want a technical e-reader to do. You can swipe left and right to change pages, pinch to display thumbnails of a document, tap to jump to hyperlinked references, and even do full-text searches within a document. You can’t do full-text search across ALL documents (yet?), but you can search your full set of documents by title words; for example, here is the document search result I got for “Foisy”:

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With the (very expensive! do not lose!) Stylus you can mark up documents, make comments and highlights, and even mark asterisks and stars within documents that you can search for later. If you want to make whole pages of notes starting from blank templates, then you can do that too, and even display those notes side-by-side with a research paper in a two-page view. The stylus works well and you can train it to your style of writing angle. You can also use the stylus to spot-erase notes, a feature which I use all the time as I resolve questions or rewrite thoughts. (This is one of the few ways that the Paper physically surpasses Actual Paper, since I usually use pens and therefore cannot erase.) Here is the Paper in action with lots of notes, marks, and highlights.

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Is the Digital Paper better than having Actual Printed Research Papers? Yes and no. In terms of traveling/weight/accessibility, definitely yes. But still nothing beats having a printout of a paper and writing all over it in the margins, working out examples, and so on, with an actual pen. Navigation on the Digital Paper is sometimes a little clunky, and it certainly isn’t as easy as spreading out a bunch of printouts all over your desk and having six books open at once. On the other hand, with the Paper you can’t lose that one printout with all your notes on it, or have to reprint a paper that you already printed at home but now want to look at in the office, or bring a messy stack of papers with you on a trip only to find out that what you really want is some other paper in your library that you didn’t think to bring. I’m an analog girl most of the time for things like this, but the power of having my entire library with me all the time is still amazingly cool.

Should you buy this?

Sony gave me this device for beta testing, feedback, and an honest product review on this blog (whether good or bad!). Without being given this device I would not have been able to justify a personal expense for such a limited-use device, and I think very few people would; it’s fairly costly at $599. However, I think that’s at least a hundred dollars less than what it cost six months ago, and as with all technology, I’m sure that the price will continue to come down. Although I probably wouldn’t have spent so much money myself on this device, at this point you’d literally have to fight me to take my Paper away.

Honestly, what you should do is get your department to buy this for you, or maybe work it into a grant. I’ve found it to be an invaluable device for being able to take my research with me everywhere, and I think you could argue that it would make you a more productive and happy scholar who can literally work all the time everywhere (that’s what the Dean wants, right?).

It’s great if you travel a lot, because it’s lighter than acutal paper and books, and it works even when you’re in places that might not have great internet access for your laptop, like airports, restaurants, and foreign countries. Over the past few months I’ve taken the Paper to colloquia, research meetings, restaurants, and my back porch, as well as traveled with it to Chicago, Atlanta, Kansas City, Brooklyn, Lima, Johannesburg, Cape Town, and a ton of other places. I’ve smushed it into my luggage and thrown it into my bag without it being in a case, and it’s still in one piece and working great. I did lose the stylus on a flight a month ago, and it cost me a lot of money to replace it, so if you do buy this then look after the stylus or you will be sad. (I heard someone say once that the worst thing about cutting yourself when preparing food is the knowledge that you are an idiot for whatever you did to cause the accident; that’s how I feel about losing the pen! I can still hear that “thunk” as something hit the floor of the plane and thinking “oh, that’s probably nothing”. No, it was an $80 stylus, dumbass!)

Just remember what the Paper is, and what it isn’t: it’s not a tablet or a computer; it does basically ONE THING — lets you carry around and work with stacks of papers and books on a lightweight large-format device — but it does that one thing very, very well.

Knitting Machine Punch Card Trials

We’re finally getting back to our Brother KH-881 punch card knitting machine project (check out our previous knitting machine post)… and it’s time to make some punch cards! The KH-881 reads 24-stitch repeat punch cards, and uses the punched holes to determine where stitches are slipped, tucked, or knit in a differerent color, depending on the settings on the machine.

Some punch cards come standard with the machine, like the one on the left in the photo below. You can also hand-punch custom cards, like the one shown on the right:

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It’s not difficult to make interesting custom designs by hand-punching cards. Here are some test patterns that I made using a special punch card tool, and two-color test swatches for each pattern:

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Punching Faster

So, that’s nice and everything, but it turns out that punching cards is a PAIN. I thought it would be kind of fun, but after about a quarter of a punch card it is no longer amusing; there is a lot of squinting my eyes and lining up the punch and hunching over the card. And errors are a pain to fix; you have to tape the tiny holes back in if you punch things by mistake! In addition, I really want to be able to “fail faster;” if one trial of a punch card design isn’t quite right, I want to be able to modify it and try the new version again relatively quickly. Repunching an entire card is a slow and irritating way to do this iteration.

So, as if an antique knitting machine wasn’t enough of a craft money hole, I decided to get a Silhouette Cameo 3 cutting machine. As you can see from the marketing image below, the Cameo is a hobbyist-grade craft cutter that people use for scrapbooking and other artsy paper/sticker/vinyl projects. My goal is to use this machine to create knitting-machine-readable punch cards.

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First Iterations on the Cameo

People so often show just their finished designs or products, but the story of iteration and failure behind every project is perhaps even more useful. So I took pictures as I learned to use the Cameo to make punch cards. Here’s the first thing (well, the first successful thing) I made with the Cameo:

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The knitting machine punch cards are made of some kind of flexible plastic or laminated material. I went to the Michael’s big box craft store and got a handful of different types of paper to see what it would work. All of them were awful, including this crinkly one:

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The only other type which came close to working was the original cardstock I had tried. But even that material only sometimes let me cut out the holes the whole way, even after adjustments to the cutter setting. In addition, the cardstock stuck to the cutting mat and was obviously not durable enough for the knitting machine:

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Dura-Lar Iterations

At my local craft store an actual live person recommended that I try Dura-Lar. It turned out to be perfect, so here is a picture of it in case you want to order your own. (I think this product on Amazon is comparable, an just a little thicker.)

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The Dura-Lar material is strong and flexible but doesn’t damage easily; it’s really sturdy. The holes cut perfectly into this material, but the pen refused to draw on it half the time, and was smudgy:

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Replacing the Cameo pen with a Sharpie did the trick, but with this new pen, the drawing and cutting tools didn’t seem to be aligned properly:

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The heart of the problem was that the Dura-Lar could only be drawn on with Sharpie pens, but those pens were not exactly the correct diameter for the Cameo pen holder. Luckily, the knitting machine doesn’t give a crap about the printed lines, and only cares about the holes.  So even though our next trial still had messed-up lines, we could use it to knit a pattern swatch with the KH-881; it worked!

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Playing with cutting settings and alignment to try to get things to match up only made things worse:

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At this point we realized we could do our tests with much smaller pieces, and save material. We tried using tape to build up the pen case width, and we tried using a custom pen holder. After many adjustments we almost got things to line up correctly.

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Stay Tuned…

Although we did almost get things to work, the alignment process was really fiddly and sort of random. Worse, it wasn’t clear that the process was even going to be repeatable for future designs. Time for a break, and to wash all the dots off our cutting mat:

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In our next post, we’ll solve our problem with (what else) some 3D printing…

Rainbow Triple Wrap Bracelet

For the last six months I’ve worn this 3D-printed Triple Wrap Bracelet all day and all night, and it’s great:

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It’s super flexible when going over your hand, but keeps its shape and fits snugly around your wrist. The version in the photo above was printed on a super-fancy HP Jet Fusion printer at Shapeways, and would be a pretty nasty torture test for any desktop 3D printer.

We decided to put our XYZ da Vinci Color printer to the test! The Shapeways version of the bracelet is way too thin to print on a desktop machine, so we made a slightly thicker version from our OpenSCAD code. The thicker version is the same thing we printed for our previous post Dissolvable Support Interface is Everything You Need. Now, how to add color?

Adding color with Meshmixer

Now, how to color it? It’s easy to color 3D models with the Meshmixer Sculpt tool. To do this, set the top Sculpt selector set to Surface, and set the Brush tool to PaintVertex. Then just select colors and paint around the curve. When you’re done, you can switch your Brush tool to SmoothColor to blend the colors together, if you like:

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Printing on the XYZ Color

Obviously this model needed Raft and Support, so we selected that in the XYZmaker software. We also turned the Infill up to 50% to keep the model strong, and selected Thick Shells since we believe the model gets more saturated color that way. Here’s what the model looked like while printing:

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And when finished:

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Post-Processing

Most of the supports were easy to remove, but remaining bits of support and rough areas of the print would make the bracelet uncomfortable to wear, so we also sanded things down with a sandpaper file. The finished design held together surprisingly well:

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This version of the Triple Wrap Bracelet is a little bit flexible, but it doesn’t open up as wide as the Shapeways-printed version. Be careful not to break it!

Hex Bowls for Settlers of Catan

Settlers of Catan + Cities and Knights + Expansion Pack + House Rules = Complicated. To help mitigate the chaos we keep our settlements, cities, roads, and knights in tidy 3D printed hex-boxes:

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The boxes have snap-fit lids with a slot to help with opening. We 3D printed a lot of boxes, to hold our standard Catan pieces, our Extra Catan pPieces, our 3D Catan Numbers, and some extra bits and pieces we use for our House Rules. The bowls are designed to be the same size as the land hex tiles in the game, for maximum matchy-ness.

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The closed hex-bowls fit sideways in the Catan box, together with our Catan Card Holders, to keep things organized in one box so we can set up quickly when we want to play.

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These bowls were designed in Fusion 360. To get started using Fusion 360, check out our article Tutorial Tuesday 15: First Steps with 3D Design Software Fusion 360. Or, if you just want to print these same 3D models, you can download the 3D-printable STL files from Thingiverse. Have fun, and best of luck against the barbarians and robbers!

Getting Started on the Brother KH-881 Punchcard Knitting Machine

Just before the new year we bought a punchcard knitting machine from the 1980’s from eBay. It’s a Brother KH-881, one of the last Brother models before electronics were added to the machine. Our plan is as follows.

  • Step 1: Figure out how to use a punchcard knitting machine
  • Step 2: Push things as far as we can go with mathematics and design

Needless to say, we are still on Step 1 and we’ll be there for a while. This is the first in a series of posts to catalog this journey and maybe make it slightly easier for anyone else that wants to walk the same road.

Inspiration: Electroknitting

Before we ever knew we wanted, or could want, a punchcard knitting machine, there was Fabienne “fbz” Serriere. Fabienne is a celebrity in the mathematical community for her successful Kickstarter project KnitYak: Custom mathematical knit scarves, in which she obtained an industrial knitting machine to produce a large number unique mathematical scarves based on elementary cellular automata. For example, this KnitYak scarf was generated by Rule 90, with multiple pixels in the generating row:

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Before her Kickstarter project, Fabienne Serriere had experience hacking electronic consumer knitting machines so that they would accept design patterns from a computer instead of from manual pixel selection. In this video Fabienne’s Hacked Knitting Machine Creations!, she explains how she got started:

In this video Art Zone: KnitYak – Mathematical Knitwear you can see what she is doing now with her 3,000 pound industrial knitting machine and celluluar automata:

If you’re interested in hacking a small-scale electronic knitting machine to accept computer patterns, check out Becky Sterns’s adafruit tutorial for Hacking the Brother KH-930e Knitting Machine, in which she shows you how to use a Python floppy disk emulator to feed patterns for fair isle knitting into the electronics of the machine:

All this is well and good, but for me it seemed… difficult! I’m don’t have a lot of computer/hacking/arduino skills, and the thought of having One More Project On The Computer was just exhausting. So I’ve watched these projects with interest in the same way that I watch videos of rocket launches. It’s cool, but I didn’t intend to try to do it myself. Until…

Analog knitting in Estonia

My family is from Estonia and a bunch of us met up there last summer as a reunion. While we were there we stopped in a knitting shop that sold beautiful Estonian-style fair isle scarves and shawls, and in the shop was this curious machine:

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I was told that this was a “knitting machine”, and that the punchcard determined the pattern that would be knit into the scarf. Here’s a picture of one of the punchcards that could be fed into this mysterious machine:

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This was awesome! What the heck is this! Whatever it is, it seemed like something I could actually maybe figure out how to do. When we returned to the states I consulted the magical internet and figured out how to get one of these machines. The Brother KH-881 I ended up getting from eBay is really close to the machine I saw in that Estonian shop. In fact, one of the scarves I bought in that shop turned out to be created using a standard Brother punchcard that came with my machine. So… maybe not a traditional Estonian fair isle patten after all :)

Setting Up the Brother KH-881

The eBay auction I won was for a Brother KH-881 plus a ribber and lace carriage and a bunch of other things that I still don’t know exactly what they are. The knitting machine was shipped to me in two boxes, each with just a few pieces of bubble wrap that were completely popped by the time they got to me. Here’s the box of “miscellaneous parts” that was included in the shipment. Oh boy.

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If you get a knitting machine and it doesn’t ship with the manual, then the first thing you should do is find the manual online. After going through the parts list carefully I determined that about a third of the things I was shipped were part of the Brother KH-881, and the rest were incomprehensible attachments to deal with later. It also turned out that I was missing five or six relatively key pieces, all of which I could order from eBay.

After the manual, the next best resource for machine knitting is YouTube. There are a HUGE number of videos online that you can watch to get your bearings and to learn how to manage specific problems. Two very good sources of video tutorials are the YouTube videos by June Clark and the YouTube videos by theanswerladyknits.

One thing in particular is that whatever kind of knitting machine you get, you’re almost definitely going to have to replace the “sponge bar”. Knitting Couture’s video on How to Replace the Sponge Bar helped me through this process, which turned out to be pretty gross:

If you’re feeling like nobody you know is also trying to figure out how to work a punchcard knitting machine, check out the amazing Facebook group Machine Knitting Beginners Circle, with well over 4,000 members! The admins have posted lots of videos and documents, and lots of people ask and answer questions every day. I’ve learned so much just reading the posts that pop up each day in this group.

After lots of cleaning, pulling out and replacing broken needles, and figuring out how everything goes together by watching videos on YouTube, here’s how my new friend looks!

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Another long battle with the machine and the manual got us to the point where we could Actually Knit Something Successfully (this learning process really is a lot like what I went through with 3D printing, I’m discovering), I finally got a tiny knit swatch! Along the way I learned that it is possible to impale your thumb on one of the needles and that it is not fun when that happens.

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Fair Isle Knitting with Punchcards

We figured out how to use the punchcards to make two-color designs with the help of the manual and a series of YouTube videos by Tricotosing (which aren’t in English, but you can do auto-translation closed captions for a rough translation). This video from Tricotosing about machine knitting two-color punchcard designs on a Brother KH-881 was particularly helpful:

Here’s one of our first successful fair isle swatches next to the punchcard that was used to make it. After knitting you have to “block” or steam the fabric so it won’t roll up, but we were too lazy to do that so instead we 3D printed a snap-together swatch holder to keep the fabric flat.

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You can download the .stl files for our large and small swatch holders from Thingiverse and 3D print them for your own use. We made them in Tinkercad, so you can also modify them yourself from the public file if you want a different size or style:

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What’s Next?

Next time: punching our own custom punchcards, figuring out that punching punchcards is a serious pain, and ordering a Silhouette Cameo 3 to speed up the process… stay tuned :)

Dissolvable Support Interface is Everything You Need

I’m totally in love with dissolvable supports for complex models, but… the dissolvable PVA material is (a) expensive, (b) increases my print times, and (c) takes a long time to dissolve. In this post we’ll discuss a tip that a helpful Ultimaker friend (thanks, Luis!) shared with me about how to make all three of those things better.

First, let’s see what it looks like in Cura when you print normally with dissolvable supports. We’ll be printing an FDM version of our Triple Wrap Bracelet, since this is exactly the type of fragile, internally complex model for which regular supports might be problematic. With the standard “Fast” settings, this model would take nearly five hours to print:

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That’s a lot of support material, and that costs time and money!

One simple change can decrease the amount of PVA material used to an absolute minimum. If you think about it, the dissolvable material is really only needed at the interface between the support and the model. Sensibly, this is the part of the print called the Support Interface. We can set the dissolvable support nozzle to print just the Support Interface, but let the regular PLA material nozzle print the rest of the supports!

If you don’t see an option for Support Interface Extruder in your Cura settings, then hover over the right hand side of the grey bar that says Support, click on the gear that should appear there, and then activate the checkboxes to make that option visible.

Here’s what it looks like in Cura using the support nozzle only for the interface:

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Now the clear dissolvable PVA material is only being used in a thin curve just above and below the model itself, and the model and the majority of the supports are printed using the less expensive black PLA material. This means less need for filament swaps (and also I think the supports print differently and faster?), so our print time is cut to under 3 hours.

Sometimes there can be problems with PVA adhering properly to PLA, or vice-versa, but for this example we had no problems:
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Success!

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To tell you the truth, most of the PVA interface actually just slid right off the model when we snapped off the PLA supports:

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This means that very little PVA was left on the model to dissolve away:

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After a relatively short time soaking in a bucket, here’s how our finished Triple Wrap Bracelet came out:

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The PLA version of the bracelet can stretch out somewhat so that you can open it up to sneak over the large part of your hand; this allows you to have a much closer-fitting bracelet than if you had to slip an inflexible bangle over your hand.

If you want a REALLY flexy version you can order one from Shapeways in HP Jet Fusion or Strong & Flexible Nylon:

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Don’t try such extreme flexing with the desktop-printed PLA version or the bracelet will snap! In fact, if you look very closely at my final photo you can see that I did in fact try this with the PLA version and then had to glue the model back together… :)

Three-Sided Cylinder Coins

Today we 3D printed some cylinder coins for students and classrooms to experiment with after watching Matt Parker’s video How thick is a three-sided coin:

These “fat coins” can land on their edges as well as their faces. Try out different thickness-to-diameter ratios and search for the fairest three-sided cylinder coin!

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We made coins for five popular ratios with Tinkercad: the two ratios tried in the video, plus three inbetween:

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We also made a parametrized version in OpenSCAD so you can try any ratio you like:

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If you don’t have access to a 3D printer, you can purchase 3D printed sets of coins from our Shapeways shop, in the same ratios as shown in the Tinkercad photo above, or as a set of 10 coins that range in ratio evenly between the 1:2*sqrt(2) and 1:sqrt(3) ratios shown in Matt Parker’s video. To save on per-part costs, the 3D printed coins print in a cage which you can break open after shipping:

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Here’s what the 10 variable-ratio coins look like after removal from their cage:

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Students, educators, and experimenters: if you want to get involved and add data to Matt Parker’s collection, check out Matt Parker’s follow-up video Help me find the thickness of a three-sided coin!..

Happy flipping!