colored bracelets

Solar System Bracelets

Background Information

Engineers Week

Every year, there is a week called Engineers Week. The idea is to get K-12 students interested in engineering ideas, classes, majors, and careers. Some companies get involved - hosting tours, giving presentations, or otherwise exposing students to STEM.

This week comes from the idea that the earlier children are introduced to engineering, the more excited they'll be to learn about it. To learn more, see the DiscoverE Website.

Girls’ Day

One day within Engineers Week is called Girl Day. The purpose of this day is to introduce a young girl to engineering. The perception that STEM, and specifically engineering, is only for boys is challenged for the girls that participate.

MESA Program

On SDSU's campus, there is a program called the Mathematics, Engineering, Science Achievement (MESA) Program. This program works to help students learn and achieve by providing on-campus resources and events. The MESA Program also engages in outreach events to help younger students become interested in STEM. To learn more about the MESA Program, visit their website here.

On Girls Day 2016, the MESA Program brought 30 middle school girls to SDSU's campus for a variety of STEM workshops and discussions. build IT was one of the locations the girls visited. We hosted the girls for roughly an hour, during which they listened to a presentation on 3D printing, watched some 3D printers print, scanned their friends with our handheld 3D scanner, and painted some 3D printed bracelets. This post is about the design and creation process of the bracelets.

There was a news article about the MESA program and Girls Day! You can read it here!

The Design

Design Requirements

We spent a long time trying to decide what object to print for the girls. We wanted everyone to take something home, and for them to be able to decorate them while they were here. We also wanted the object to be STEM related. Whatever it was, we were going to work in a brief talk on it during our presentation. After discussing various different objects (keychains, planters, and model planes were all considered!), we finally settled on using a flexible filament to create bracelets.

We knew that there were going to be about 30 girls, plus chaperones. We wanted to have enough bracelets so that there was one for each girl, plus their chaperones, plus some extras. We ended up deciding on 45 bracelets.

Next, we knew that we needed to be able to 3D print everything within the three weeks that we had before the event, so the bracelets had to be physically small enough to allow us to print 45 during the hours we were open. In addition to that, we wanted them to use a small enough amount of plastic such that we could get all 45 made from a 1kg spool. (Filament usually comes in spools of 1kg, so the purpose of this was to spend the least amount of money.)

To summarize, our requirements were:
• A bracelet that was entirely 3D printed
• 45 bracelets were needed
• Printable within 3 weeks only during open hours
• Use only 1kg of plastic for all bracelets
• STEM-related in some way

How big is your wrist?

Since we were set on bracelets, the next question was how big do they need to be? We didn't know which grade the girls would primarily be from, just that they were middle schoolers. Middle school in San Diego is grades 6-8, or approximately ages 10-14.

So just how big is a 10-14 year old girl's wrist? There were some websites that had sizing charts for jewelry, like this one, but we weren't sure how accurate they were.

We decided to start polling people who came in to build IT about their wrist sizes. We used string and a ruler and recorded wrist sizes. We decided that the average wrist size was probably close enough for the middle schoolers. It ended up being right around 7 inches, or about 178 mm.

What will go on the bracelet?

One of our design requirements was that the bracelets be STEM-related in some way. We talked about getting rid of that requirement and writing "buildIT" on them, but that seemed too much like self-promotion and not enough like education. We found a very cool bracelet design on Thingiverse, but we wanted the bracelets to be designed by us.

We eventually settled on a solar system. We decided that we would make equally spaced planets that were different sizes. We needed them to be equally spaced, or else it looked very squished, and we couldn't do the sizing to scale because some planets are too small to even appear. We decided to make them so that the larger planets were still larger, but not as much as they really are.

This gave us our talking points - 3D printing, space, and planets.

Which Filament to use?

Decisions, decisions…

We knew we wanted a flexible filament and that we wanted it to be easy to paint. For the second desire, we chose to use the natural color, so that the girls could paint the bracelets without worrying about a base color showing through.

For choosing the actual flexible filament, we had to go through a lot of considerations:
• the printers we had available and their extruders
• how flexible the completed bracelet needed to be
• how sturdy the completed bracelet needed to be

After looking at the various filaments that were available, we decided that we would use the Flashforge Creator Pro because it was open source, meaning we could customize the slicing settings easily, and because the extruder was a direct drive extruder, unlike the See-Me-CNC Rostock, which has a Bowden extruder. The filament choices that we considered were NinjaTek's NinjaFlex and NinjaTek's SemiFlex.

Material Comparisons

Without the change to physically see and compare the materials, we had to do some research. We found that NinjaFlex was the hardest to use by far, and that it often had problems with feeding through an extruder. Since we didn't want to modify our extruder, NinjaFlex was almost immediately eliminated.

That left SemiFlex, or looking into another flexible filament. Many of the reviews we read indicated that SemiFlex could be used on an unmodified direct drive extruder. Our Flashforge Creator Pro is an open source printer with a direct drive extruder, so we thought that would work well. We had also read success stories of its use on that particular printer. The fact that we didn't need to modify the extruder and that the filament had been used on one of our printers is why we chose to look no further than SemiFlex.

SemiFlex is available in quite a few colors. The color we chose is called "Water," which is essentially just a natural, translucent filament color. You can see pictures of the printed bracelets below.

Design Iterations

bracelet v1

Design One

Everything was designed by me on a student license of Autodesk Inventor.

This first design was made with the idea of printing the band in one print, then the planets as snap-on pieces. The students would be able to paint each planet, wait for them to dry, then snap them on to the band for the finished bracelet. The goal was to make flat surfaces for easy printing.

Most of the printing time for this design was spent trying to get the settings for the filament dialed in.

bracelet v2

Design Two

In the second design, we decided to make the bottom of the planets flush with the bottom of the bracelet. This allowed the bracelet to be printed in one piece, and there was no concern of the planets not staying on.

The major issue with this design was that the band was too thick. The flexible filament did bend but only under pressure. As soon as you stopped holding it in a circle, the bracelet would try to bend back into the flat shape. The other issue was that the hook didn't stay in the other end of the bracelet when you tried to clasp it together.

bracelet v3

Design Three

In this design, the band is thinner, and the hook is a closed loop. To allow it to clasp, we used cutting pliers to create a very thin break in the loop, but the hook naturally returns to being closed rather than bending.

The band was lengthened slightly, and the planets sizes were somewhat adjusted. This is the final version that we went with for the students.

The total length is 190 mm. This allows the bracelet to be loose, and for the clasp to overlap. We printed some larger ones at about 220 mm for the adults. If we were to redo this, we should have lengthened all of them - the 190 mm was still too small for the middle schoolers.

The total printing time was about 40 hours, and the total filament usage was practically 1kg.

The Completed STL File

WebGL Error

Downloadable File

In order to download the stl file to print your own, click here.

Printed Bracelets

An Unpainted Bracelet

This bracelet is printed from the third iteration of the design. The ring has already been cut so that the bracelet can hook together.

This image was captured in our light box, made by Rita!

uncolored bracelet

Painted Bracelets

These two bracelets were painted using acrylic paints. You can read more about coloring prints in our post about coloring 3D printed objects.

The one in the back is one of the first iteration prints. It was colored by Rita, who was testing if acrylic would work on the SemiFlex. The one in the front is one of the third iteration prints. It was painted by Jenny as her bracelet to keep as a souvenir from this experience.

This image was captured in our light box, made by Rita!

colored bracelets
lightbox side by side

Lightbox V1.1

Design

Lightbox v1.1 was constructed similarly to our first lightbox, with some minor differences.

lightbox side by side

Left: new lightbox, Right: original lightbox

The new lightbox is also constructed from foamboard, posterboard, and a semi-translucent material. The foam board was joined together with hot-melt adhesive (also known as hot glue) rather than duct tape. To reduce waste, the windows panel frames were made from 2 inch strips of foam board, rather than cutting squares out of whole sheets. The construction method is detailed below.

Construction

lightbox miter uncut

A knife was used to divide sheets of foam board into 2 inch strips, 20 inches long. A 45 degree cut was made on both ends of each strip. In this example, shorter pieces are used to demonstrate the process.

lightbox miter cut

After the ends of each strip are cut, hot glue was used to join the foam edges of the strips to form the corners of the frame.

lightbox miter glued

A square was used to ensure that each strip was joined at right angles to make sure the frames of the box fit together properly.

Details

lightbox corner outside

To join the 5 frame pieces together, hot glue was used to join the edges together. Excess glue was spread along the edges to increase strength.

lightbox inside cloth

In the first lightbox, the fibers in the cloth are visible and the material does not disperse the light as evenly, resulting in a more focused spot of light.

lightbox corner inside

The translucent material used is 0.003 inch thick matte drafting film. For the window frame panels, the film is glued onto the inside of the frame.

lightbox inside film

The drafting film allows the light to diffuse more evenly, resulting in better picture quality.

Raft on Makerbot

Rafts

Before We Begin

Necessary Terminology

Extruder - This is a part of a 3D printer. This is the part that heats up to nearly melt the material so that the material can be worked with. A motor pushes the material through the hot part and out of a nozzle at the end.

Filament - This is the material that is extruded. In the case of buildIT, we use a Polylactic Acid (PLA) plastic filament. For more information, please see the post about materials.

Print Bed/Build Plate - This is a part of a 3D printer. This is the part of the printer that the filament is extruded onto. On some of our printers, this is a heated plate with or without glass on top. On others, it is simply a glass plate.

Painters Tape - This may not seem like it, but this is an important part of 3D printing in buildIT. This material is the exact same as the one you would purchase for painting a room in your house. The tape is placed on the print bed so that the material has a rough surface to adhere to. If the tape wasn't there, the material would have a much harder time staying in place.

Layer Height - This is the amount the extruder moves vertically between each layer of the print. This number is usually a fraction of a millimeter for our printers. For more information, please see the post about resolution and layer height.

Warping - This is something that can happen to a print. In some prints, the edges of the part will curl up, away from the build plate. This can happen for a variety of reasons, including the part being too big or too thin. Usually, a part will need to be reprinted if the warping is severe enough.

What is a raft?

Technical Description

A raft is an extrusion at the beginning of a print to help a part better adhere to the build plate. Prints that fail due to warping or detachment usually require reprints with rafts.

Explanation

A raft is some extra plastic that a 3D printer lays down before starting the actual part. The printer lays down about 3 layers in a very simplistic pattern on the build plate. The reasoning is very simple - even with the painters tape, plastic sticks best to other plastic. The idea behind a raft is to give the plastic something solid to attach to before creating the part. The layer height between the raft and the bottom layer of the part is larger than the rest of the layer heights. The idea is to make the raft easy to remove from the part when the part is done.

In the simplest terms, a raft is temporary, extra plastic that the printer lays down before starting the actual part to help the part adhere to the build plate. It is meant to be removed immediately after the print finishes.

When should I use a raft?

Steps to determine if a raft is necessary.

Once you gain some familiarity with the printer you're using and you've printed a few things, you'll start getting a sense on whether a part needs a raft before you try printing it. I'll discuss certain types of objects that usually need rafts below. Until you get an intuitive feel about rafts, though, there's an easy process to follow to figure out if you need a raft.

1. Try printing the object on the build plate without a raft. Consider adding glue if you have any doubts!

2. If the object doesn't stick to the build plate, becomes detached after a few layers, or starts warping, cancel the print immediately.

3. Assess why the print didn't go as planned. Did the printer have trouble extruding? Did you not use glue? Is there some mechanical problem that might have caused a failure?

4. If you've determined that there was no failure other than a lack of raft, add a raft and reprint!

Typical prints that require rafts

There are some prints that almost always require a raft in order to succeed. As stated above, getting a good sense of what needs a raft and what doesn't only truly comes from experience.

A raft is typically needed if:
• the object is smaller than about 10 mm in any direction at the base
• the object is thinner than about 3 layers at the extremities
• the object is larger than about 80 mm in any direction at the base

Essentially, a raft is needed if a part is too big, too small, or too thin.

What does a raft look like?

Raft on Makerbot

On the Printer

This is a picture of an object being printed on the Makerbot with a raft. This object is tc_fea's Miniature Castle from Thingiverse.

You can see that there is a large flat part, and a smaller part that extends further vertically. The large, flat part is the raft. The smaller part is the object. They are connected for now.

Part with Raft

Off the printer, on the part

At this stage, the part and the raft have been removed from the printer but not separated. It should be very easy to remove the raft from the object.
Part and Raft

Off the printer, off the part

The raft and the object have now been separated! At this stage, the object is completed. The raft is now trash. It can be disposed of in a trash can or in our plastic waste bin.

Remember to clean up after yourself!

How do I add a raft?

Adding a raft is easy!

The way you add a raft depends on the 3D printer you're using and its associated software.

A quick reminder on software association with printers:
• Rostock uses Cura
• Flashforge uses Cura
• Makerbot uses Makerbot Desktop
• CubePro uses CubePro

To add a raft using Cura

The two pictures show screenshots of Cura.

The picture on the top shows a green circle around "Platform Adhesion Type." Click on the dropdown selector next to "Platform Adhesion Type."

The picture on the bottom shows a red circle around the dropdown options. Click on "Raft."

Cura Raft 1
Cura Raft 2

To add a raft using Makerbot Desktop

The two pictures show screenshots of Makerbot Desktop.

The picture on the top shows a green circle around "Settings." Click on Settings.

The picture on the bottom shows a red circle around the checkbox on the settings menu next to "Raft." Click so that the checkbox has a checkmark in it.

Makerbot Raft 1
Makberbot Raft 2

To add a raft using CubePro

The two pictures show screenshots of the CubePro software.

The picture on the top shows a red circle around "Build." Click on "Build" to begin changing settings.

The picture on the bottom shows a red circle around the "Sidewalk Material" and a green circle around "PLA White." For the CubePro, "Sidewalk Material" simply means the material the raft will be made out of. The CubePro allows the user to select the color and filament material for the rafts, which is why we have a color option. As we only load one cartridge of filament at a time, simply select whatever color it offers.

CubePro Raft 1
CubePro Raft 2
layer-height-1

Layer Height

Definition

The 3D printers in build IT create 3D objects by depositing layers of material incrementally to build a 3D object.

The thickness of each layer of deposited material is called the ‘layer height’.

For Fused Deposition Modeling, or FDM, printers like the ones in build IT, one variable that affects the final quality of a 3D print is the layer height. Typical layer heights are between 0.1 millimeters and 0.5 millimeters. The surface quality of the finished part is proportional to how small the layer height is; smaller layer heights result in smother surface finishes.

Different layer heights affect the time it takes a 3D print to finish.

For FDM printers, the number of layers is one indicator of how much time a 3D print will take. Choosing a smaller layer height will divide a 3D model into more layers, increasing the print time. For example, an object printed at 0.4mm layer height would take half as much time as an object printed at 0.2mm layer height, because there are half as many layers. Due to machine limitations, the minimum layer height for all prints done in build IT is 0.2mm.

Different layer heights are appropriate for different 3D models.

Objects without fine surface details do not benefit from smaller layer heights, so printing them at a larger layer height (closer to 0.4 mm) reduces print time without sacrificing strength or quality. Smaller layer heights (closer to 0.2mm) are only recommended for prints which require better surface finishes, but this limits their overall size because the increased number of layers will take longer.

Example

This object was printed at four different layer heights, indicated by the text on the object. You can see how the quality differs between each section.

layer-height-1

Software

Changing the layer height setting in the model slicing software

cura layer height

Cura

The layer height settings can be found on the first tab under the 'Quality' heading on the left side. Cura will indicate if an improper value is entered in this field.

makerbot layer height

Makerbot Desktop

The layer height settings can be accessed via the 'Settings' window, on the left side. Selecting either Low, Standard, and High quality using the dropdown menu selects different default layer heights.

all benchys

Coloring 3D Printed Objects

Adding Color

A comparison of coloring 3D printed objects

all benchys

Natural PLA

natural pla benchy

Red PLA

red pla benchy

White PLA

benchywhite

How to color what's 3D printed in build IT

photo of all the paint used

Acrylic Paint

Painted with Sax True Flow acrylic paint in Fire Red

photo of paint
Acrylic

Pro:

  • Easy to apply

    • Con:

  • Paint coverage

    • How many coats is applied?

    Two coats of acrylic paint.

    Acrylic Paint with Spray Paint

    Painted with Sax True Flow acrylic paint in Fire Red and sprayed with Krylon Acrylic Crystal Clear

    photo of paint
    Acrylic Crystal Clear

    Pro:

  • Little shine
  • Fix the paint coverage from the acrylic

    • Con:

  • Long process

    • How many coats is applied?

    Two coats of acrylic paint and one coat with acrylic crystal clear.

    Spray Paint

    Painted with Rust-Oleum Gloss Apple Red

    photo of paint
    Spray Paint

    Pro:

  • Fast Process

    • Con:

  • Glossy
  • Does not paint small inside areas
  • Dull

    • How many coats is applied?

    One coat of spray paint.

    Sharpie

    Colored with Red Sharpie

    photo of paint
    Sharpie

    Pro:

  • Less materials
  • Fast process

    • Con:

  • Can not reach small inside areas

    • How many coats is applied?

    One coat of sharpie.

    Nail Polish

    Painted with Zoya LC Red

    photo of paint
    Nail Polish

    Pro:

  • Easy to apply
  • Glossy

    • Con:

  • Heavy smell

    • How many coats is applied?

    One coat of nail polish.

    Skateboard rack

    Skateboard Rack

    by Doug Brantley, 2015

    Materials

    Wood

    Processes

    Design Goals

    Challenges

     

    Plastic Google Cardboard

    Plastic Google Cardboard

    by Joey Casabar, 2014

    Materials

    Plastic

    Processes

    3D modeling, 3D printing

    Design Goals

    To design a more sanitary and sturdy Google Cardboard

    Challenges

    The original Google Cardboard design changed. Finding suppliers of the lens.

    structure sensor 3d scanner

    Getting Started with 3D Scanning

    Learn how scan physical objects and create digital files you can send to a 3D printer. In this workshop you’ll get hands-on experience with a number of 3D scanning technologies available in build IT and learn how to edit and refine your scans using Meshmixer.

    IMG_20160223_161519

    Introduction to Simple 3D Modeling

    This workshop will cover the basics of using 3D design software and creating designs suitable for 3D printing at build IT. Participants will learn about the variety of options available for 3D design, downloading and modifying free online 3D designs, and get hands-on practice with Tinkercad, a free, easy-to-use software.

    IMG_20160223_162033_scaled

    3D Printing Demystified

    Curious about how 3D printing can fit your needs? Join us to explore the history of 3D printing, the basics of hardware and software, and other local resources available to you. In this hands-on session, participates will find a design that can be printed in build IT.