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:


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.


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.


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:


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:


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.


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!


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.


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.


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:



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


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:


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:


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!


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


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:


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


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!

Triple Check Knit

Today we’ll take a break from digital 3D design and do some good old-fashioned analog knitting. Here’s a stitch we’ve been working with recently, in progress as part of a simple scarf:


If you think there’s something weird about that stitch, you’re right: If you look across each row you’ll see that… there really aren’t any rows? The stitches kind of zig-zag up and down as you move from one side to the other.

The really cool thing about this stitch is that it is completely reversible, and in fact looks exactly the same on both sides:


So what is this crazy stitch, and where did it come from? We call it the Triple Check, and it’s a stitch we made up to solve a design problem. Maybe it’s new, maybe it isn’t; we aren’t sure yet, although we haven’t been able to find anything like it on the web or in our knitting books. If you’ve seen this stitch before, please let us know!

Designing by Deduction

Our design problem was to find a simple knit stitch pattern for multicolor reversible scarves that we could knit during math talks and committee meetings. Specifically, we wanted a stitch that would satify all of the following conditions:

  1. Reversible, preferably identical on each side
  2. Uses multiple colors but NOT floats, double knitting, or carrying more than one strand of yarn at a time
  3. Must be a simple stitch with a short repeat that one could easily knit without looking or counting while at a math talk; no brioche or fancy stuff
  4. Preferably the knitting procedure would be the same on the right side and the wrong side, to avoid confusion/mistakes if knitting while multitasking
  5. Weaving in ends is tedious, so minimize the need for this
  6. Finished piece should lie flat and not curl up

Of course the first thing we tried was finding such a stitch in the existing literature; no need to remake the wheel if there are already perfectly good wheels! However, in this case our literature search came up short, so we wondered… could we construct a suitable stitch pattern by deducing certain things from our list of desired conditions?

Somehow we did; here’s how the deduction process panned out:

  • One way to satisfy the multiple-colors-one-at-a-time condition (2) is to use slipped stitches. We decided to riff off the slipped-stitches trick for knitting vertical stripes in the round, with each color traveling across the knitting one at a time, slipping stitches to skip over stitches in the opposite color. But in our case we wanted to have a reversible fabric, and to knit on straight needles.
  • A really easy way to satisfy the reversibility condition (1) is to use some kind of rib stitch. That would also have the added benefit of satisfying our lay-flat condition (6). We didn’t want something too stretchy so 1×1 rib seemed like a good idea.
  • Conditions (3) and (4) basically mean that we have to keep it simple, so we started thinking about the simplest possible way to have a 1×1 rib that slips over other colors. After a bunch of dead ends the most obvious thing ended up working: basically, doing 1×1 rib and then slipping twice to leave a gap for a piece of 1×1 rib in another color.
  • The key that made the whole thing come together was using three colors instead of two. With two colors on straight needles, you’d have to knit across and back each row to get back to the other strand of working yarn. But with three colors and straight needles, the parity works out perfectly: knit across with Color A and leave it there, then pick up Color B and knit back on the wrong side, then pick up Color C and knit across, and then pick up Color A from where you left it and bring it back along the wrong side.
  • The three-color method above also satisfies condition (5) because there is no need for weaving in ends every time you change colors; all the colors just travel up the sides of the work with no ends.
  • When you slip stitches, the carried yarn has to go somewhere. If it goes in front of a knit stitch or if its color peeks through another color, then your work is not going to look good. The final piece of the puzzle was to figure out how to slip stitches so that the carried yarn was hidden inside the work. We’ll show a picture of the method that ended up working after we describe the stitch.

Triple Check Stitch

Here’s the simple, reversible, three-color “Triple Check” stitch that resulted from our deductions:

  • In Color A, loosely CO a multiple of 4.
  • Pick up Color B and [K1, P1, s1wyib, s1wyif] to end of row.
  • Repeat: Pick up Color C and do the same four-stitch pattern for one row. Then pick up Color A and do it again. Then Color B. Then Color C, and so on.


All slipped stitches should be purlwise, whether the yarn is held in back (wyib) or in front (wyif); see the video Slip stitches wyib vs wyif for a demonstration.

Note that in each color we are only traveling along the knitting one time, in one direction; not going across the knitting and back again. At the end of the row just drop the color you are using and pick up the next color, which will be waiting for you.

Hiding the slips

So where is the carried yarn hiding under the slipped stitches? In the close-up image below we’re just done the s1wyif step, slipping a black stitch with the white yarn held in the front:


What happens next is that the white “yarn in front” strand needs to be wrapped over the black slipped stitch to the back of the work. Here’s the exciting part: When we wrap the white yarn over the black stitch, the carried yarn will make a white bump that lies exactly over an existing white bump from a previous perl stitch!

Every slipped stitch in the Triple Check pattern wraps over a bump of the same color in this way, either in front or in back of the work. The carried yarn under the slipped stitches is basically copying the “knit, purl” stitch of the 1×1 rib below it (which is luckily of the same color as the carried yarn), but without making any actual stitches. This color-matching on the slipped stitches is the secret sauce of the Triple Check pattern, since all of the slipped stitches end up invisible inside the work.

Triple W Stitch

The Triple W variant below is actually the stitch we discovered first (originally we called it “The W”), but it makes more sense as a variant of the Triple Check. The stitch pattern is pretty much the same as for Triple Check but twice as wide, with pieces of 2×2 rib followed by four slipped stitches.

  • In Color A, loosely CO a multiple of 8.
  • Pick up Color B and [K1, P1, K1, P1, s1wyib, s1wyif, s1wyib, s1wyif] to end of row.
  • Repeat: Pick up Color C and do the same eight-stitch pattern for one row. Then pick up Color A and do it again. Then Color B. Then Color C, and so on.


Triple Check and Triple W are good stitches for stash-busting projects that use up your random yarn scraps and leftovers, because you can change colors gradually as you knit. For a gradient/morphing look, change just one of the three colors at a time, leaving two of the colors alone for a while before changing again. Here’s a Triple W scarf-in-progress with a color-morphing rainbow look:


Again, if you’ve seen the Triple Check or the Triple W stitches before, then please let me know! These stitches are so simple that I feel like they have to exist somewhere, but I haven’t been able to find them. Or, maybe we found a piece of low-hanging fruit that everyone else somehow missed, stumbling on that rare combination of easy, interesting, and new? In any case, happy multicolor reversible multitask-knitting :)



  • Triple Check is now a project on Ravelry.
  • Holly (@antimonia on Twitter) found something by Nancy Marchant that looks just like Triple Check on one side. It’s brioche so much more difficult, and not identically reversible, but the front side matches perfectly!
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  • Another good catch from Holly: You can get a reversible “tiny hearts” stitch by knitting two strands in white and one in red. After a couple of rows I started knitting/perling into the backs of the loops of the red stitches, to make them come to a sharp point and look more like hearts:
  • Trammell Hudson and Rod Bogart did some bind-off experiments and found that K1,P1 is a good bind off for the Triple Check:
  • More samples from Jacqueline Jensen-Vallin and Rod Bogart‘s wife. Love all the different color looks!
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