Snap-Together Bracelet is a Snap (almost)

The Bracelet - a view all around.

After much experimentation with #3DPrinting snap-together parts, I've landed on a design that is almost reliable and almost meeting my criteria for a success in this area.

There are 3 criteria I had:

1 - Easy to print (reliable, minimal likelihood of printing issues due to the design)
2 - Easy to connect the parts together
3 - Hard to come-apart (or at least hard enough that connected parts don't fall apart unexpectedly)

These are hard criteria to balance, but the design I came up with has so far proven to be adequate for at least a simple application - the bracelet.

I started by printing a Pi Bracelet - wearing it a few days (even though one of my best friends didn't approve) and proved to myself that it would not fall off when I didn't want it to. Then I went into the real test - kids' bracelets. I created a full alphabet and a few special emoji-parts and created the name bracelet pictured here for my daughter. More challenging still, was that I reduced the scale to 80% to make it more appropriate for her 8-yr old wrist. The design held up - although the brim material definitely makes the links very stiff at first. A little flexing on each joint and the bracelet was flexible enough to wear.

Still on the print bed. Notice the smiley link is "shadowed",
meaning it got shifted during printing.

This design - 9 links, took 67 minutes to print at a layer height of 0.15mm.
Notice in the picture while the links were still on the printer bed - the smiley emoticon got messed up during printing. Luckily I found a way to salvage the rest of that print job (fodder for another post for sure - adding to my little box of fails) - and simply reprinted just that one link (which took 6 minutes).

COMING SOON - I'll write a post about the link design, as i think it's useful and could be improved by others... and I'll post the alphabet of links so people can print their own bracelets!

Here's the model of the bracelet links. You can see the link design.

My Box of #Fails is a Box of Learning

Right next to my 3D Printer is a small box partially filled with a bunch of my failed prints. Most are partial objects with globs of plastic or streams of spaghetti-looking plastic hanging off. Each one is special. Each one an example of something gone wrong and a reminder of a lesson in how to correct it.

Whenever my kids come to print something or bring their friends by to see the printer, the first thing they see is my box of fails. It intrigues them, and they invariably ask what happened with each one. They also get a good chuckle from the silliness of how each one looks. But the most important part is how they see my pride in my failures, and hear how each one of my fails is a lesson - a step toward success.

Keep your #Fails close by. Share them. Smile when you see them, even if they frustrated you when they happened.

NOTE: This post was inspired by a visit from my daughter and her friend to my printer - after they spent more time talking with me about the Box Of Fails than the successes I was showing off. While I was writing this post, a print I was working on failed. Here it is below before it was even removed from the print bed - and you can see above, as it has already been added to my collection of lessons learned, in my Box of #Fails (although, I must admit, I haven't solved this one yet ;)

3D-Printed Pi Bracelet - Make Every Day Pi Day

I designed a general way to link parts specifically for chaining them together. This design was the best I could come up with so far for making it easy to snap parts together while still giving a firm connection that wouldn't come apart too easily. Not so simple to do since these are opposing needs. Easy to get together, hard to fall apart. Once I had something that worked - and tested with my daughter's name bracelet for a few days of wearing - I had another idea that happened to fall on March 14 - Pi Day. A Pi Bracelet which had a bunch of the digits of Pi chained together.

Model:  on PinShape

Filament:  Ultimachine PLA Gold 3mm

The links are a design that I created from scratch, as I mention above. It requires a quick description - so please read this if you expect to print and use this design so you don't break the connections trying to get it together:

Step 1: Put the male/tenon and female/mortise parts at a right angle to eachother, with the tenon below the mortise.

Step 2: Push the tenon into the bottom of the mortise at the base of the mortise. You should see a small slot where it is meant to be pushed in.

Step 3: Once the tenon is in the mortise, pull the parts to be straight with one-another - slowly opening the 90 degree angle to 180 degrees.

Step 4: Pull the parts away from eachother just slightly until they click - and flex the connection back and forth until it loosens a bit (which is basically clearing some of the residual plastic from printing).

After a while flexing each connection, the links should loosen and naturally flex like a normal bracelet would.

Here's the result - which looked pretty darn good printed in gold - and looks pretty good on your wrist. Traveling back from California, I wore it through security at the airport. The TSA inspector noticed it and said "Nice - I like your Pi" ;)

Printed at 100% (top) and 80% 

3D Printing Snap-together parts - a journey

Early in my journey of #3DPrinting, I started experimenting with modeling and printing snap-together parts. I had a few motivators, as I've mentioned in a previous post, including the ability to make multi-color objects, larger objects and objects which had some dynamic properties, like adjustments in position. Now I was looking more at the functional side - trying to land on a connection design which would give flexibility and easy construction. Here's a summary of the progression I've made so far - which I think is just the beginning of a much longer road ahead (and I'll soon try to post a How-To with design details in 3D Modeling).

1 - Simple Construction

My goal at the start was simply to make a joint which was easy enough to push together but also strong enough to hold. It's a tough balance to reach, since they are opposing requirements. Once I had something good enough, I started pasting the connector bits onto different shapes to see what worked best and what gave building flexibility and fun.

2 - Smaller, Simple Links

In this phase, I realized that it was fun and simpler to have small links that I could construct into many things. Mostly it was a straight link, but I experimented with 90 degree angles to give more flexibility to build. Here is where I realized - mostly through watching my kids try these, that jewelry-making was a good direction.

3 - Basic Bracelets

Once the simple link was working, I tried some more decorative links to make it more engaging for kids. The goal here was to provide a template on top of which kids could model their own "jewels" and bracelet designs.

Personalized Name Bracelets became easy(ish)

4 - Decorative Designs

I got more fancy at this stage and tried larger and more personalized designs. You can see where this led - making a name bracelet for my daughter. This stage will lead to many prints, I can tell... I already have a list of must-do projects for other kids.

5 - Product Logo Bracelets

It's beginning to feel that all my projects end here - with Google Docs, Sheets and Slides logos being re-purposed. Actually, I was simply trying to prove here, that my new link connector could be re-used with almost any other object. This worked pretty well.

Next Steps

Soon, I'll post a few things to follow this up...

• The actual letter link 3D Models - so people can print their own name bracelets.
• A description of my experience creating the connector parts themselves - this was the main challenge of this project.
• The current design and 3D Model of the connector parts stand-alone (this will help you create your own custom links). I'd love to see people sharing their own custom links to inspire kids to get creative!

7 tips when starting 3D Printing

Our tech club at middle school recently had the fortune of receiving a donated new 3D Printer. We're also fortunate enough to have an ambitious 8th grader with some experience 3D Printing at home who took the lead in recommending, ordering and seting up the 3D Printer. After it was all set up (Flashforge, dual Extruder!), of course the printing fun began - and so did the learning.
The minor lessons we learned seemed worth sharing:

1 - Don't rush the printer set up

This one truly is more than just one tip - but too involved to give details here. Let's just say A 3D Printer is not a toaster - you likely won't be able to take it out of the box, turn it on, and just start toasting stuff. There are key things to get right, and if your printer company doesn't explain it well (you shouldn't have bought that particular printer, and) you should go right to YouTube or the web and find people who have done it before. Bed-leveling, Software setup, Printer configurations for the filament you have, filament loading, and especially bed preparation to make sure your models will stick to the bed. This can get pretty complicated - so have an experienced person on hand if at all possible. We found bed adhesion to the be the trickiest part - so be ready to get some painters tape or kapton or hairspray (yes, hairspray).

early modeling is key

2 - Start Modeling Early

Way before you get a printer, try some #3Dmodeling apps and create things that you will eventually print. I use Autodesk 123D Design. Tech Club uses TinkerCad - both very easy. A very large portion of the learning is in the modeling, not just the physical printing. Kids who have any expectation of printing custom objects, parts, kits, etc, will need this skill. The father of the 8th grader who set up the school's printer has a great rule at home - "If you didn't model it yourself, you can't print it". That's a motivational rule I really like for schools.

Small logo keychain - 20 minutes

3 - Print Small Models

There's usually more than one person waiting to print something - and if you print something that takes hours to print,  1) you'll decrease the motivation for those waiting to print. 2) you'll simply reduce the experimentation and learning efficiency. You learn more with every print - so print lots of projects, not fewer large projects, and 3) You'll waste resources - since failures (perhaps common in the early days) will take lots of material and time.

4 - Start Simple (e.g. no dual extrusion)

There are lots of ways to make a project more complex - but save those for later. If you happen to get a dual extruder (we were so lucky!) - it means you can print in two colors - but don't! wait until you get the hang of simple things. If you are tempted to use a sculpting app which takes 360 view of your principal and prints her - don't! save that for week 2 (or week 22). Get the basics down, then advance.

5 - Start with PLA Filament

While I don't have any useful data or facts here - there is the belief that ABS, since it is petroleum-based, gives off bad smelling fumes more than PLA, which is corn-based (and actually smells sweet when it extrudes). Again - no data here - but it seems PLA has less concern than ABS, especially if the printer is in an un-ventilated space.
Some articles I found on this topic range from the not so scary to the worst-thing-since-poison. I think there needs to be more facts here, which leads me to believe a conservative approach is best to start.

6 - Model and Print semi-useful things

Motivation on the part of students and team members - to learn modeling and work through problems - will be much more easily maintained if they can experience real benefits from their efforts. Cute trinkets for your desk will only last a little while - but even a pencil holder or a pegboard hook will

Pegboard hook!

give a greater sense of accomplishment and will even wow the parents.

7 - Document your failures and successes

Start a journal - could be a blog, a spreadsheet, a folder with project write-ups and results - to give the people modeling and printing a place to share what they learn and to constantly build up the knowledge of the team and others. This is also great to teach the scientific method. Ask students to form a hypothesis each time they change something in their project and document the results. You'll be amazed at the amount of experimentation you end up doing.

That's likely just a starter list - and I'll add to it as we learn more.