Make a 3D Printed Japanese Cord Loom (Kumihimo)

I get very excited when I see my kids doing any kind of creative project. Whether it's sewing, painting, Minecraft world building, sand castle building - even cooking. I get even more exciting if that creative activity somehow triggers a 3D printing idea. 

Project Idea 

When I spotted my daughter making a Japanese Cord bracelet using a hand-made cardboard loom, the idea of 3D Printing one was obvious.

Apparently, this is called Kumihimo, officially. There was something magical about using a cardboard Kumihimo loom to make a bracelet - but the cardboard clearly wasn't holding up too well, and I thought we could 3D Model and then print a more durable and colorful loom really easily. We set out to do just that - a basic one to start, and then perhaps we'd customize later.

all parts before subtraction
and construction

Project  Goals

The model is mostly simple looking - but there were some objectives I had to influence the model. First, I didn't want it to just be a solid disk, that would take too long to print. Second, I wanted to make it rather thin, again to influence print speed, but also to make it easy to carry. Third, I wanted it to be rather small, so it could easily fit in a pocket. 

The basic requirements are a hole in the middle, through which the threads form the finished cord, and many slots around the outer rim to hold the thread or yarn material securely.

Making The 3D Model

The ultimate shape I had in mind was like a wagon wheel. It wasn't perfectly obvious how I would achieve that at first. I realized that it would be easier to put two donut shapes together with spokes, than it would be to cut out the sort of holes I envisioned around the "wheel". 

This would take 4 cylinders. First the outer cylinder which was only 2mm high and 35mm radius. That was the outer dimension - 70mm across (diameter). Second, a 6mm radius cyleinder, which I used to cut the hole in the center. Third, a 25mm radius cylinder to cut out most of the inner material in the large cylinder. and fourth, a 12mm radius cylinder to make the inner hub. 

I leave it to the reader (that's you) to figure out the series of subtractions which resulted in two basic donut shaped cylinders - one for the outer part and one for the inner part (hub). Then, using 8 simple 2mm high rectangles, I made the spokes to connect the two donut shaped cylinders. 

To make the slots in the outer rim of the model, I simply created a wedge which I could replicate 32 times around the center of the cylinders, which were now aligned at the center, and then subtract all those from the outer rim. The outer part of the wedge was 1.6mm wide to leave enough room for thicker yarn.

Get The Model

If you want to make these, you can try to replicate the process above (lots of challenge left to the reader) or simply download my model and print away. It is not a very long print given that it is less than 2mm tall. The last resort is to buy one - lots of them on the web if you search for japanese cord loom or Kumihimo - but that takes the fun out ;)

For Valentines Day: 3D Printed Heart Paperclips

Why Paperclips?

I know - paperclips are not particularly romantic, or special, or even interesting - not even a little bit. In fact, some might say they foster the use of paper - which we would never want to do.

BUT - When shaped like hearts, paperclips become about 0.001% more interesting than when they are shaped like paperclips. And when you can say you made them yourself - on your 3D Printer - they become even more interesting (I'll say 1.7% more interesting).

More importantly - when one of these little, boring, uninteresting heart-shaped paperclips can be printed in 2 minutes on your 3D Printer - well - NOW I think think they just got 400% more interesting!

Anything that prints in 2 minutes on my 3D printer and has even the slightest utility, is a winner in my book.

I've written a few posts already on paperclips in a row (the Football for superbowl, the "We Hate Paper" clip) - so you can tell I'm a bit into this theme and I won't get into the details on this model. I'll just say, again, that these babies print FAST. I can print a dozen in under 25 minutes :)

I created these for my 9 yr old daughter to clip onto her Valentine Day cards that she gives to friends at school - so this model has been a winner all around.

There are just so many different designs you can create to appeal to the paper-lover in your life - get creative!

The Model

Here is the 3D Heart-Shaped Paperclip model so you can spend 2 minutes getting one for yourself.
I'm posting this model hopefully with enough time for you to get busy printing hundreds in time for Valentines Day.

Make a Football Paper Clip - Fast, useful 3D Printer Project

In honor of the Superbowl today, I wanted to design a really easy football-themed model which was both useful and super fast to print. Small, useful models which are fast to print are really great for school projects where many kids are often waiting for a single printer, and looking for results within on class period. This model achieves all that.

Design Goals

My main goal was to have a football theme. What better way to achieve than than by using a model of a Football! My second goal was to have the result be somewhat useful - not just a trinket.

You probably know I've done lots of trinkets, and both kids and adults really like those, but I am becoming partial designing and printing more useful things. Third - I wanted this to be a small model which could print fast and reliably.

Design Details

One of the things I dislike most about classrooms today is the continuous and heavy use of paper. There's just so much more that can go digital but hasn't yet - and paper often adds a burden in paces where it is unnecessary.

That said, I decided to design a paper clip - ah.. the irony.

I've noticed in previous flat-model printing I've done that the printed PLA in heights of 1-2mm is quite flexible. I figured I could create a paperclip-like structure quite easily on a flat surface, in practically any shape I wanted.

I tried a football shaped design. Here's the steps I used to create this:

1 - Sketched an oval with 6 points using the "Spline" tool in 123D Design - getting a Football shape pretty easily. It was about 30mm wide and 50mm long.

2 - Extruded the football to 1.4mm deep.

3 - Duplicated and reduced the size to about 75% the original.

4 - Shelled out the original to make it just an outline of about 3mm width.

5 - fit the smaller football inside the larger outlined football leaving approximately 1-2mm gap between the two (that's the space the paper will fit when it's a paper clip).

6 - create a connecting rectangle which is 3mm wide, long enough to bridge the gap between the objects and 1mm high. I place that at the tip of the football connecting the two parts.

7 - Use short rectangle pieces which are 1mm wide and 1mm tall - to create a "laces" pattern on top of the inner football (see the picture to understand what this looks like).

3D Printed Results

After a little tweaking, I ended up making the inner football slightly higher than the outer outline shape and gave it rounded edges (using the Filet tool) just to make it look better. I also did a bunch of experimenting with height to get the right balance between strength and flexibility.

The Model

In case you don't feel like starting from scratch to make this yourself, and just want the immediate satisfaction of printing a few (or a few dozen) of these now, I've posted the Football Paper Clip model on Pinshape for you to use.

If you're having people over for the superbowl today, print a few and give them out to your friends ;)

And just in case you think I've created this model because I like paper, I've also created this other paper clip design, shown here, to clarify my position...

I think I'll give these out by the dozen at my kids' schools :)

Here's that "We Hate Paper" Paperclip Model - also free on Pinshape - in case you want to inspire your school to reduce the waste and time innefficiency ;)

3D Printing Chinese Characters

My son is learning Chinese as a freshman in high school. For the holidays, he wanted to give a personalized gift to a friend who is also taking Chinese - so he decided a 3D Printed version of her name in Chinese would be worth a try.

Design Goals

The goal is to create an object - basically a name tag or placard - which will stand up on a desk. In this case, my son said he wanted each character to be it's own distinct object. This was a pretty basic idea - one which we've covered mostly in a prior post about 3D printing text - using extrusions of english text.  But what if the language or characters you want to print are not available in the text objects of your 3D modeling tool?

Design approach

I decided the best bet would be to use the "tracing" method with Google Draw to trace over the characters - creating sketches of each character, then extruding them into 3D objects. This is super easy once you can get an image of the characters into Google Draw. My son did this part by changing his keyboard language to Chinese, using Pinyin to enter the words he wanted, then using a text object in Google Draw.

Once the characters were on the drawing canvas, I basically just traced over them using the Polyline tool. Then, once the whole thing was traced, and after deleting the text object, I use the "download as SVG" option to get something my 3D Modeling tool can import (Autodesk 123D and Tinkercad both support .SVG files).

The Challenge

The name we were creating - Wang May Hua (in english) - is actually three individual characters (in Chinese) - but two of them were multi-part characters with parts which were not physically connected. Here was he main challenge - and basically I referred to all the learnings in my "3D Printing Text" post to make this work.

the two part character connected using small rectangles

I decided the end product should be the individual characters - in their positive form rather than negative subtractions from a block - standing up on a base. That dictated what process to use to connect the individual parts of each character.

Making it work

To connect the individual parts of each character I placed a small rectangle connecting the parts, but offset it 2mm lower than the surface of the characters so that it was less obvious.

To make the characters stand up, I added a base that stood out in front of the characters - about double the thickness of the characters - so my 5mm thick characters had a 10mm thick base, which when stood up would only be 3mm high.

The result came out quite nice - and while I started with objects which are only about 30mm x 30mm, my son is hoping we can "print these now around 10 times that size!". I guess that's a good sign.

More Holiday 3D Printing - The Snowflake

The holidays are a great time for gift giving, and if you have a 3D Printer, nothing is more fun (exaggeration warning) than 3D Printing a gift for someone you love (or just like a little). My previous post which featured the Christmas Tree ornament/decoration was a simple way to start - and then I then posted the Snowman design which followed the same pattern. This new design - the Snowflake - has a slightly more interesting base design with circular symmetry and offered an opportunity to change to a more complex construction model too.

The first version of the design is the simple two-part construction, but the second version creates a much fuller final product by using three parts fit together at 60 degree angles rather than 90 degrees.

The first, too-complicated, design
but I will print this one too soon.

Design Goals

As in the previous holiday decoration designs, I was aiming here for simplicity and ease in printing as well as creating a mode symmetrical model that could eventually be constructed using 3 parts. The mostly flat parts are designed to easily fit together to form three-dimensional objects - something easy to hang on a tree or stand up on a shelf. Both Snowflake models in this post meet that objective.

Snowflake Design Overview

The snowflake took me a few tries to come up with a method that worked well. I tried drawing it with a sketch, but couldn't get it to look right. I knew I would need to use a duplicating method to get the symmetry no matter how I modeled it. I finally just used long rectangles overlapping with some shelled outlines of rectangles at the outer edges. 

This looked amazing - but was much bigger than I had hoped. I simplified that design starting from scratch, and used a simple cylinder in the middle around which the single crystal of the flake I designed could be repeated in a circular pattern. I knew I could use this basic design with both the 2-part and the 3-part final design, so I focused on getting this right first.

Snowflake Details

The tool in 123D Design to get that symmetrical circular pattern is the "Pattern" tool. Selecting "Circular Pattern" lets you repeat the single set of crystal objects in a circular pattern around the diameter of the center cylinder object - which is selected as the "Axis" of the pattern.

This tool was perfect for the job - and I could see how I could create many different designs with the same base set of objects. With the simpler and smaller crystal pattern, and repeating it 6-times around the center cylinder, I was able to get a simple, small design to try.

The final step was to create a slot in the center to allow two of these "flakes" to fit together at right angles. I simply duplicated the design, turned one 90 degrees and moved it half the distance off the other so that each would have a slot halfway down the middle. 

Note: I actually made that slot 0.3mm deeper than halfway to allow for a bit of printing imprecision, as always. The design also required that I had enough room between the crystal legs to allow the two parts to fit together.

The More Complex 3-Part Snowflake Design

I realized with this two-part design, that it could actually look much better with 3 parts fit together. I took some time to figure out how to actually accomplish this, but the math seemed straight forward. With three parts crossing at the center, there would be 6 sections, which means each would be separated by 60 degrees around the circle to create the full 360 degrees.

I accomplished this by creating center slots which, instead of cut perpendicular at 90 degrees, were cut (subtracted) at an angle of 60 degrees. The tricky part was that 3rd piece.

The first two (which are actually exactly the same) fit together nicely since they had slots cut halfway up the center on each - but the 3rd piece now needed a place to go. I achieved this by extending the center of the 3rd piece and cutting a slot which was the full length of the centers of the first two, and by cutting TWO 60 degree angles in that same slot. This allowed the 3rd part to fit over two other parts in the center.

There was one problem - at that shallower angle, the extended parts of each flake overlapped and didn't let the parts slide together. I had two options - either cut the slot through those parts too, or, make the height of the model shallower overall. I decided on the latter, reducing the height of each flake part from 2.0mm to 1.6mm - getting to that number only through experimenting until the flakes didn't overlap.

view of the center where 3 parts
come together

The image included here shows the center where the 3 parts come together, showing the angles a little more clearly - and the other image describes the differences between the parts (the first two are actually exactly the same). 

The Models

As always, here are links to the 3D Models:

Snowflake - 2-part - One part which should be printed twice to fit together (and stands on it's own or hangs from a tree quite nicely.

Snowflake - 3-part - Three parts (even though 2 of them are the same) included in this file to be printed at once. You can also hang each part as it's own decoration, or put them together to create a beautiful ornament or decoration for a shelf.

The 3D Printed Snowman Ornament

The positive results on the Christmas Tree decoration design inspired me to create additional holiday decoration models. The natural next step in designs which are vertically symmetrical seemed to be a snowman for sure. I experimented with it in the prior post - so this time I'll describe the whole 3D Snowman model.

Design Goals

I was aiming here for simplicity and ease in printing as well as just extending the simple design I already proved in the prior christmas tree model. That is, two mostly flat parts designed to easily fit together to form a three-dimensional look, and something easy to hang on a tree or stand up on a shelf.

Snowman Design

tiny version with filled parts

The Snowman is simple - just 3 circles, reduced in size from bottom to top and put together at their tangents. I added a top hat for design detail, a hanging loop above the hat and a small tab at the base so that it can fit into a stand. The stand didn't have to be designed, as I just re-used the one from the prior Christmas Tree design.

The first version had filled-in circles, but in the final design, I hollowed out each circle to make it lighter and slightly more elegant (who am I to judge)... Ok, I really did that to make it print super fast ;)

To hollow out the circles, I used the "Shell" tool in 123D, but there are two tricks: 

First, to get a thick enough shell, you might have to initially thicken the height of the object, as the modeling tool won't let you have a shell width that is greater than the height of the object (since it is also trying to shell the bottom). 

Second, once you have the shell, to get rid of the bottom layer, you simply select that inner bottom face and "Pull" (actually, Push) that face in the negative direction beyond it's thickness and it will simply disappear.

The Model

Here is a link to the the model:

The Snowman - Three parts in total - two snowman parts and a stand.

Creative Building with 3D Bot Bits

I've done lots of experimenting with connecting parts for both functional and fun purposes. The fun creative-building goal is admittedly more fun sometimes - and this latest experiment seems to have finally produced a reliable, creativity-inducing design that I'll keep enhancing.

I call these "3D Bot Bits", since most of the resulting creations are robot-looking.

Design Goals

There were a few things I knew I wanted to achieve in this design:

1 - Give the joints as much range of motion as possible

2 - Make the joints tight enough to have friction to hold specific positions (not collapse with gravity)

3 - Allow the joints to flex a bit without breaking

4 - Allow for customization - so new parts could easily be designed and added to kits

Basic Design Principle

The premise of this design is a simple ball-joint. One side is a round ball, and the other is a socket with the inside diameter just big enough to firmly hold the ball, with enough clearance to let it move around.

While it's pretty easy to make these two parts, what added to the challenge was making them in a way that gave them a flat enough base to print reliably (I don't like using rafts and supports) and let them snap together and apart without too much effort.

Detailed Design Process

With these design goals and principles in mind, here's a general description of how I went about the modeling:

1 - Created a sphere of around 10mm radius then duplicated it and scaled up the duplicate to a 12mm radius. The smaller sphere is now inside and centered with the larger sphere.

2 - Flattened both spheres by taking away approximately 4mm from the bottom and 4mm from the top (to make them more like bulging puck shapes).

3 - Subtract the smaller sphere from the larger, so that the larger sphere becomes a shell.

4 - Create some gap between the outer surface of the inner smaller sphere and the inner surface of the outer shell - I used about 0.3mm radius here by pushing the inner surface of the outer shell to be bigger, but you could also just scale the X/Y of the outer shell object too.

5 - Create a break in that outer shell object so that it can stretch to allow the inner sphere to be snapped in and snapped out in the finished object.

6 - Add a connector "axel" between the parts which is 1-2mm smaller than that break in the outer shell so that it fits into the break easily for connecting parts.

Strength and Stretch

The position of the part during printing is actually quite important - which is why I designed it this way. The part that grabs onto the ball - the "Gripper" - is where most of the stress will be. As the ball is snapped in and out when the parts are put together and taken apart, the Gripper will stretch. If that stretch was done along the Z-axis part of the built part (the up-and-down axis), the prt would break quite quickly given that is the weakest part of 3D Printed parts. But with the Gripper part printed laying down, it makes it much stronger and actually allows it to flex quite a bit without breaking.

A Custom Bot Bit: Robot Hand

Customizing Bot Bits

Once I had a simple ball and gripper pair working well, I started creating some alternative parts with different configurations and shapes.

One technique I use when building models like this is to never permanently merge the component parts of an object - or to keep copies of the component parts so they can be re-used.

This made it super simple to make new connecting Bot Bits which were shaped like a "T" or with two grippers on either end, or an "X" shape to allow more complex builds.

Since my initial creations looked like Robots (hence the name Bot Bits), I decided to make some super-custom parts too - like hands and sneakers and face parts. This is where I see the most interesting potential of this design - allowing others to create their own Bits to make specific types of Bots.

The Bot Bit Kit

With a good feeling about the most simple "complete" robot that can be built with these Bot Bits, I created a simple Bot Bit Kit - which contains all the parts needed to make the basic Bot. This can be printed in one shot on my Lulzbot TAZ4 in 2.5 hours very reliably.

The basic parts in this kit can also be put together in different ways to make many other creatures or designs - take a look at the pictures at the end of this post for some ideas.

Here is a link to the Bot Bit Kit model. If you print it, please comment back here with some pictures of the creation you made with this kit!

How to Make 3D Printed Building Sticks

Early on in my 3D Printing experience, I immediately became interested in designing connecting parts. After some fails, some lessons and minor success, I took a break. I came back to this project and now created some simple connecting parts I call "Building Sticks".

The goal for the Building Sticks was two-fold. First, I wanted something that would be fun for kids (and me) to build stuff - like a construction toy. Second, I wanted something I could use to build or prototype simple functional things - like phone stands or business card holders or even just ideas for larger custom objects.

Design Size

One project I had in mind for the Building Sticks was quite large - a printer enclosure - but I've learned that starting small is smart until the design is right. I also knew that the size of the model I created would have an influence on the connector design - particularly the clearances between parts (more on this below). I decided to start quite small - with sticks that were 5mm square around the waist (width and height) and around 30mm - 60mm long (although that measurement would not influence the connector at all).

Connector Design

Before I even finalized the shapes and angles of the objects to be connecting, I needed to get the connectors right. The main goal was to make sure they snapped together easily but also provided a firm hold. Not an easy balance to reach. From prior experiments, I decided on a mortise and tenon design. Here's the basic steps I took to get this done:

• Model the tenon on a small block that was the same length as the width of the Building Sticks. This would allow the tenon to be inserted both straight on and from the side for 90 degree connections.

• Add a "bump" on both sides of the tenon - perfectly in the middle of the tenon - as the method to provide a more secure "snapped in" connection on the mortise (which would have an opposite indent to receive the bump). I did this by overlapping a sphere onto the tenon, perfectly centered, then sizing it so it stuck out approx 0.50mm from each side.

• Create the mortise on a separate block by subtracting a copy of the tenon from an equally sized block (5mm wide and high). This created the exact negative shapes on the inside of the mortise, including the bump, which is now an indent.

• Create clearance between the Mortise and the Tenon to allow for smooth fit. Open up the mortise - and the indent - by just a small amount to give clearance so that the tenon is not too tight. THIS IS THE CRUCIAL STEP. I do this using the "Push" command in 123D Design on the inside walls of the mortise and the indent - and/or on the outer walls of the tenon (in the opposite direction). 

Clearances on the Connector

As mentioned above, the clearances given between the connecting parts is the most important part of this whole design. I found that at this size, clearances between touching parts should be somewhere in the 0.25mm to 0.30mm range for each side touching. That means for the mortise and tenon, the sum of those clearances became 0.60mm - which was to allow for 0.30mm for each side of the connection. The diagram below shows all the clearance values I ended up with.

Your Printer May Vary!

Once I "perfected" my connector design, I started printing on two different printers, and quickly found that the clearnace values I used for the Polar3D did not work well on the TAZ4. The TAZ4 has a flatter first layer and therefore pushes the filament wider than the Polar3D - so the parts were too tight. Make sure you test on the same printer you intend to use for printing final parts. That also means that if you end up using my models, you may need to adjust and customize the mortise and tenon sizes to fit better for your printer.

Shapes and Angles

The fun part of this design came after I had the connector working well. I could now experiment with all sorts of Building Stick shapes and angles. The only limitation was really "printability" - that is, making sure the shapes I dreamed up would actually print well on my print bed (reducing overhangs, etc). I found that printing both the mortise and tenon along the bed sideways worked best. Building upwards a tenon or mortise was ok, but not as clean, and not as strong (given the grain of the print layers were now perpendicular to the weakest part of the print (vertical layering).

I started with some basic shapes and will expand that as I get experience with what I need in my building. That's the best part - that I can customize these shapes for precisely what I might decide to build. I ended up with straight sticks in two sizes (30mm and 60mm), single height right angles, double-height right-angles (these are magical ;) and the "H with arms" - which are basically 4-way connectors that allow straight and right angle connections in any 4 directions.

Polishing the Design

Sharp corners on 3D Printed parts often come out sharp enough to cut skin. I learned this the hard way when my Pi Bracelet gave me a significant cut on my wrist when it got caught between me and my backpack. Now I almost always try to round the edges on designs which have high-touch. I do this simply using the "Filet" tool in 123D Design, which makes this super simple. A filet radius of 0.5mm worked well on the Building Sticks in the size I was printing.

That's really the only finishing touch I added to this design, but you can add all sorts of other touches if you want to spruce these up - even personalization embossed into the sides of the sticks.

Now What?

My main goal here was to get a basic design for connection which was reliable at one size. I'll now try the following things:

• scale the design larger to use it as building blocks for a printer enclosure.
• Create fun toy designs - perhaps hands, heads, feet, tails and other parts to let kids create their own characters.