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:


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:


And when finished:



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:


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:


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… :)

Multicolor 3D Printing, from Tinkercad to XYZ

Today’s post is about something that is flat-out easy and in addition somehow actually works. Specifically, we have some good news: You can create color 3D designs in Tinkercad and import them directly into the XYZ da Vinci Color 3D printer for printing! I know, that sounds obvious, but in general color printing is hard and even getting the right kinds of files exported can be a tricky business. This is one case where somehow the stars align and life is easy…

Here’s an example of a very simple design we made in Tinkercad, and the same design opened in XYZmaker and ready to 3D print in color:


XYZmaker vs. Tinkercad

XYZmaker is both a slicer and a rudimentary design program. Like any 3D printer’s slicer/software, you can use it to scale, place, translate, and rotate an imported design. But in addition, you can add geometric shapes, text, and symbols to the build platform, and combine them to make simple designs. It works a lot like Tinkercad, sort of like an alternate-universe version of Tinkercad. In XYZmaker it is easy to assign colors to each imported design and each element you build from scratch, and those colors will actually be printed when you send your design to the XYZ da Vinci Color Printer.

On the other hand, lots of people are already Tinkercad masters. For those people, the easiest way to create and print a color object would be to create and color something in Tinkercad, export it from Tinkercad, import it into XYZmaker with colors still intact, and then slice and print the design. Is this possible? Amazingly, YES! You can export any color design from Tinkercad into an .obj file, and have your design colors preserved and printable when you bring them into the XYZmaker software.

Multicolor 3D Design and Printing for Beginners

For people totally new to 3D printing, here is the basic process:

  • Get a Tinkercad account, create a new design, and design a model that uses colors.
  • In Tinkercad, select all the parts of your object and click the Group button, then click on the grouped object, press the Solid color button, and check the Multicolor box.
  • In Tinkercad, press the Export button and choose the filetype .obj; this will download a .zip file.
  • Unzip the .zip file; you should see a folder with two files, obj.mtl and tinker.obj.
  • Open the XYZmaker software and use File/Open in that software to open the tinker.obj file.
  • In XYZmaker use File/Print, choose your settings, then click Prepare and Save to send the design to the USB drive, then put the USB drive in the XYZ da Vinci Color printer, and print!

Blended Color

Will it blend? Well, with the Tinkercad technique outlined above, the answer is no; if you export from Tinkercad, then you’re going to get discrete areas of color, with only 36 possible colors. You won’t be able to blend the colors together to make new colors or smooth transitions. You can print in full blended color on the da Vinci Color printer, but you will have to use a different design program like Meshmixer or Blender to create the files.

Color Testing

Of course, the color of a 3D design on your screen may or may not faithfully represent the color of the resulting 3D-printed object, even if you’re using a full-color printer. To get a preview of what the Tinkercad colors look like printed on our XYZ printer, we created the Tinkercad color palette in Tinkercad (meta!):

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Then we printed this color palette on the da Vanci Color printer:


Other Ways to 3D Print in Color

You can create multi-color prints with dual-nozzle printers like the Ultimaker 3, or with filament-splicing add-ons like Mosaic Manufacturing’s Palette, but with those types of solutions you are still restricted to a small number of colors determined by the colors of plastic that you load into your machine. The XYZ da Vinci Color is just one example of a 3D printer that prints material that is then colored with ink. For example, the Mcor ARKe colors and cuts layers of paper to create 3D designs. If you have access to an ink-based color 3D printer, then you can test the colors on your printer by downloading and printing our Tinkercad Color Palette design from Thingiverse:

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At Shapeways, you can upload a digital color design and have it printed on a fancy 3D printer in Full Color Sandstone, with layers of gypsum powder sprayed with a binding material and ink. Unfortunately, you can’t currently export Shapeways-friendly files from Tinkercad, at least not with Beta/current design files. If you have been using Tinkercad long enough to have a Legacy Tinkercad design in your collection, then you can create models in that file and export them in VRML format as .wrl files, which can be printed directly in Full Color Sandstone at Shapeways. To test out the colors, you can order our Tinkercad Color Palette from our geekhaus Shapeways shop:

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For more information on full-color 3D printing with the da Vinci Color, look back at our previous posts Full Color Desktop 3D Printing?! and Full Color Un-Manufacturable Part.

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!