Love the TIMESQUARE DIY Watch kit and have a great idea for a custom watch body you would like to fabricate to house the electronic parts? The watch kit already ships with style to spare, but that's no reason to limit yourself to the included watch band when you can make one.

Here are the steps I took to create the "Circling the Square" TIMESQUARE Watch Body. As I guide you through the steps I followed, I will share plenty of tips and tricks for how you can design your own! 

Take advantage of the tools I created for this model kit to help you design faster! Check out this TIMESQUARE Sketch Guide (PDF) that you can use to sketch out your ideas. Or download this TIMESQUARE Dummy (STL) object to import into your modeling tool as a handy reference -- or as a boolean operations tool to punch an electronics cavity into another object you have designed!

Before You Get Started

Prepare the watch electronics first. Check out Ladyada's Learning System tutorial: TIMESQUARE Watch Kit.

Print a test object from your design software. As a first stage to design, create and export a small file with easy to measure parts on x, y, and z axes. Print this as early in the process as possible and use digital calipers to measure how the physical object compares to the measurement settings in your digital design file.

Selecting 3D CAD / Modeling Software

For this project, I selected Rhino OSX (work-in-progress) because it is a dependable, affordable solution for transforming my reference sketches into surfaces. Particularly useful are dimensional and object "snaps" (ways to lock elements to each other according to user-selected criteria) to ensure that I can build parts separately, joining them at a later stage in the design.

You might might have equal luck with another solution, from open source apps such as Blender, Wings3D, and OpenSCAD to free options such as TinkerCAD  123D Design, and Sketchup  Other popular commercial modeling tools includes Solidworks, Maya, modo, AutoCAD, and 3DS Max.

Here are a few specs to consider when selecting a solid modeling tool for 3D printing:

• Dimensionally accurate. 2D vectors and 3D models can be imported and exported and will remain precisely the same all the way through a project.

• Multiple layers that can be shown, hidden, and locked. While versioning the design file itself is essential, the ability to break up the parts of your design into multiple layers allows you to keep around reference curves from earlier stages in the design to help you make adjustments later in the design process.

• Ability to create objects from points, curves, surfaces, and solids -- and explode them back into the faces, curves, and points they are made from.

• Grid and object snaps. Grid snaps are handy for making approximations early and late in the design process to adjust to the real world. Object snaps should be user configurable and aid the designer with establishing clear relationships between parts of a model: this line is a tangent to this curve, this surface is perpendicular to that surface, this point is the center of this circular object, etc..

• Ability to export manifold STL mesh models directly. While there are plenty of handy tools such as Meshlab to import files from a variety of computer graphics formats (cloud data, obj, stl, etc.), having an export option to create from your design software directly what your 3D Printing software / CAM requires reduces the complexity of the process. (Luckily, formats like STL are very old and most CAD software supports it.)

Selecting a 3D Printer:

I used a MakerBot Replicator 1 and Replicator 2 for this project, but every day, new affordable desktop 3D printers are released that offer the qualities you need to print electronics enclosures efficiently and inexpensively. As a reference to help you select one, consider the MAKE Ultimate Guide to 3D Printing, to which I contributed.

Here are characteristics to consider when selecting a desktop 3D printer:

• Layer height. Often described as "resolution" or "z-axis resolution.

• Thread width. How wide is the filament extrusion coming out of the extruder nozzle? (Or in other methods of 3D printing, the grain size for powder printers and x-/y- axis resolution for laser and UV curing projects. This factor affects the size of "smallest discernable detail" which affects how thin walls and details can be on the surface of objects in terms of x-/y-axis.

• Layer-to-layer registration. When looking at a printed part, are there pronounced layer ridges or do flat/smooth parts only have layers upon close inspection? The more dependable desktop printers are designed to make sure registration is accurate to allow for smooth, organic curved surfaces.

• Repeatability. From job to job, do the calibration settings and dimensions of the results remain the same within a very narrow tolerance? The best way to learn this is to consult a longtime user of the machine. User-assembled kits tend to require user expertise with a painstaking process of establishing a baseline configuration -- but gaining this experience with your printer can allow for more control over print job settings.

• Print materials. Will the print material handle the heat, weight, torquing, pressure, seal, etc. that you require from your final piece? And most importantly, how will this material interact with the other elements you need to place up against it and to the process of gluing two parts of this material together?

For printing services, contact your local hackerspaces and university fab labs or visit the Shapeways or Ponoko services online to have your final models shipped to you. 

Here are the steps I took to create the "Circling the Square" watch body.
Click any of the stage titles to head directly to that subtopic.

A Few General Modeling Tips

While I will mention many of these elsewhere in this guide, it is worth gathering here the general modeling tips you will return to again and again.

• Print a test object from your design software. As a first stage to design, create and export a small file with some easy to measure parts on x, y, and z axes. Print this as early in the process as possible and use digital calipers to measure how the physical object compares to the measurement settings in your digital design file.
• Use Many Layers. Get to know the layers in your application and develop a practice of duplicating all of the elements that you will use for joins, 
• Create "Reference Layers." The simple points, curves, and surfaces that you use to produce solid parts by combining, lofting, slicing, and boolean operations are of crucial value later in the design process as a reference for how you created complex shapes. Create separate reference layers and copy and paste the elements you use as tools before running operations on them so that you can retrieve them later if something goes wrong and you need to roll back the clock.
• Build a Mechanical Tolerance Plan. Anytime you use a fabrication tool to produce a physical object from a digital design, there are slight differences between the "ideal" digital model and the accuracy of the machine used to create the printed object. When you create printed parts that interface with real world objects you need to plan to accomodate this by getting to know the technical specs for your machine and job settings -- and by printing frequently. See "Creating a Dummy Object" for a great practical example.
• Create "Reference Cages." You will find that you will create geometry separate from your design primarily as a reference for position, compare, or separate objects. A good "reference cage" includes both geometry to reference the "dummy object" and workplane and the workplane of the object being modeled. (Here's a hint -- a reference cage for a cavity emphasizes the points and curves inset from boundary between cavity and dummy while a reference cage for an outer surface emphasizes the points and curves offset from the boundary of the object.) 
• Learn the keyboard commands. You will rarely use all of the modeling tools from a CAD package within one project, just a small subset. Learning the keyboard commands won't just speed up the process of modeling, it will help keep you in more intuitive creative mindset than if you are constantly stopping to mouse over to a menu item.
• Print Often, Measure Once, Twice, Thrice! Take every opportunity to print your model, or parts of your model, available to you. You will learn quite a bit about your model by holding it physically in your hand. And if you use each opportunity to measure and compare your real world model to your digital one, you will make sure you detect faster whether any of your modeling operations has shifted your design off of the baseline you established creating the dummy object.
• Print Parts of your Model. To save time and print material, it is worth creating new layers with version of your project that are trimmed down to only the element you are currently working on, so that you can export and print those. Examples include how a button and button cavity will function. 
• Adjust your model, not your job settings. While it is tempting to tweak your print job settings with lots of tiny scale and position changes in your CAM tool to just "make it work," those you share your printable model with after the design process will not benefit from what you learned about your model from printing it unless you go back into the design file and make adjustments there, upstream from your printable files.
• Fused Filament Fabrication prints shrink as they cool. And by a factor of about 1%-2%, depending on your plastic vendor. You will get the hang of this over time, but as long as you accomodate this when planning for engineering tolerances your design should remain accurate to the world.

GOAL:

Take detailed measurements of the electronics parts to be inserted into the watch base and create an accurate 3D model that matches its real world counterpart when produced by the intended desktop 3D printer.


The first (often overlooked) stage for the design of a 3D enclosure, model, or bezel: measure your electronics and create a digital "dummy" object that is an accurate match for it's real world counterpart. 

The creation of dummy objects is a long-standing tradition from the world of fashion, craft, and industry -- typically used to optimize how multiples of an object will be assembled. This process has added relevance to the digital designer within the wider open source / open hardware culture of today: 

• Make use of the efforts of other people who have tackled these components before you.
• Share back digital models to help others print and tune your project for other, novel purposes.
• Why should anyone recreate the wheel when they can make a better functioning, better looking wheel by studying the wheels of others?

It is worth going through the process of re-making your physical objects in the digital world so that you can take the measurements you need to discover essential shape and position information to help you construct an artful, intentional design to interface with it!

GOALS:

Leaning on the accurate model produced for the dummy object, sketch out ideas for the watch body design and take notes how you design references the electronic parts.

From hand draw notes to vector-based illustration ready to drop into your CAD application, any pathway you find to capture your ideas to aid you during the 3D modeling process is acceptable. However, when making a tight enclosure for electronics I find it is helpful to do your sketching at this stage in the order: after creating your "dummy" object.

GOALS:

Import sketches for faceplate into 3D CAD tool and use reference measurements and notes where parts interface to model the first part of the watch body.

GOALS:

Work with Faceplate test prints to determine placement of buttons and how they should interface with the enclosed electronics.

5. Preparing for Wrist Straps

Create and implement a cutting tool for routing wrist straps / pocket watch fob. Create snap-fit strap bar for easier handling.

GOALS

Model the backplate to closeup back of watch body, to insulate the electronics, and to accomodate wrist straps.

Surface Finishing Techniques

• Sanding
  
• Dremel polishing - Abrasive buffs rather than sanding discs or grinders.
  
• Plastic polishing compound
  
• Heat - annealing the surface
  
• Solvents