A quick note to say that these are only preliminary images! I will be uploading a video of the watch in action, as well as better renders and more descriptions next week but unfortunately I'm out of time this week. Watch this space to see how it all works!

In this instructable I'm going to show you how to print your own pocket watch! The thought of trying to make one is probably quite daunting, and in fact, it is quite the challenge, but lucky for you, I've already suffered through it so you won't have to!

Basic Pocket Watch Movement from Matthew "Rick" Shaw on Vimeo.

We'll need to look at how a mechanical pocket watch works so we know what we're getting ourselves in for. There are a few good videos online, this one is short and explains it very well, though it is just a demonstration and doesn't quite explain everything, while this one is considerably longer, but is still completely accurate and extremely useful for figuring out what we need to make. In case you don't want to watch them, or don't have the time, I'll give a quick explanation here:

The Balance Wheel is the key to the watch. It is attached to a spring, and is pushed by the Fork Pin. When pushed, it spins a little before the spring pulls it back, knocking the fork pin on it's way past, which gives it an extra little push to continue the momentum. By doing this, the fork pin is able to quickly move from side to side, allowing two paddles to catch and release a wheel with long pointed teeth called the escape wheel. This is the ticking sound you hear from watches, and is what controls the speed of the watch. A series of gears are attached which pass the motion on in a way that gives the correct rate for each hand. The power for the watch comes from a second spring inside the barrel of another gear. When you wind the top, the spring is tighetened, and releases slowly, pushing the chain of gears.

So, now that we have an idea of how the watch works, we can begin to look at how we're going to make it and some important facts to keep in mind.

Note: It is of course, impossible to entirely print a watch as there are two springs required which cannot be 3d printed as then they would not have tension. The spring for the balance wheel must be careful made to ensure the correct motion of the balance wheel. Similarly, if you want a glass front, you'll obviously need to get the separately, although with the rise in 3d printing, many companies are offering a clear material.

Step 1: 3D Printing Notes

There are a few limitations, as well as a few things to keep in mind when 3d printing an object. If you've printed before, or have a good knowledge of how it works then you can probably skip these notes and move on to the mechanics of the watch. Otherwise, it is important to know how to make an object ready for printing and the options available.

Types of Printers
There are two main different types of 3d printers; FDM (Fused Deposition Modelling) and STL (Stereolithography). These names sound overly complicated, but they're basically; Melted plastic printed in lines, and liquid resin solidified by a laser. As you can imagine, lasers are far more accurate than a nozzle head extruding plastic, so Stereolithography printers are far better, and as a result, far more expensive. These are generally professional standard, so for home printing then you'd want a FDM, like the MakerBot Replicator 2. However, if you really really want an STL, MIT researchers have developed a small relatively cheap one called the Form 1. Now when I say relatively cheap, it is still about twice the price of the MakerBot, and with a smaller print bed, so keep that in mind if you're picking your own printer.

3D Printing Companies and Materials
Never fear however, there are plenty of online options for ordering 3d prints of your own designs (And even sites where you can download other peoples creations for 3d printing, like Thingiverse). Companies like Shapeways and i.materialise offer a range of materials that you can print your designs in too, which gives you much more control over the final look than printing something from home. It is important to note the specifications of the material you want to use though. Due to the nature of 3d printing, every material will have a minimum thickness and minimum detail it can print. Always check for the limitations before designing something in that material or you may lose important detail. With something as small as our pocket watch, we need as much detail to be kept as possible, so the High Detail Stainless Steel from i.materialise would be ideal, with a minimum detail of .1mm!

Sending Objects to Print
As for sending a file to print, there are a few important things to keep in mind. For those unfamiliar with 3d programs, objects are made using vertices, edges and polygons (Though they may be given different names depending on the program). Vertices are the points, edges connect them, and polygons are the surfaces that fill in between the edges. However, polygons can be deceptive. While in 3d they may look smooth and correct, in reality they may be trying to connect impossible shapes. Here are some key things to look out for (With further explanations below):
  • Objects will be divided into triangles for printing, so make sure surfaces have enough detail, and are made of all quadrangles or triangles.
  • Smoothing will not be printed, make sure objects are set to hard edges to see their true form.
  • Holes in meshes will confuse the printer, make sure there are no gaps, and that everything has some thickness.
  • Intersecting or Multiple objects will not be joined, but will confuse the printer as to which part is to be printed, and what is empty space.
  • Surfaces have an outwards direction called normals, which must all point out from the object.
  • Overlapping geometry will cause problems, make sure the mesh is clean.

Polygons and smoothing
Place a sheet of paper flat on your table. This is our polygon. Now lift up two opposite corners. See how the paper curves? Our polygon is trying to create a flat surface that connects those points. In reality, we would need to fold the paper diagonally to keep the surfaces flat while lifting those corners, which is really creating two triangles. For this reason, it is always best to keep your models made of a maximum of four sided polygons, and ideally in triangles to see it's true shape, as this is how it will be divided up when it goes to print. Also, do not be fooled by any smoothing that the program does. Many programs will try to adjust the surfaces to give an illusion of a curve when it's made of tiny squares. Turn off this to give it hard edges so you can see exactly what will print.

Holes in Objects
When printing something like a cube, The program understands that the interior is to be filled. However, if you remove one of the sides, the printer will not know where the printing should stop and will provide messy results. Ensure that there are no gaps in your model. If you need to have an opening, you will need to fill in any interior detail (eg, if you want a hole in a block, you will need to make the interior tube connecting the two sides, and have it attached).

Intersecting Objects
Similarly, intersecting objects will confuse the printer as to what is 'inside' and what is 'outside'. Always make your object out of one mesh, or print it in separate parts that you can attach together later. Boolean functions can add/subtract multiple objects, but the resulting meshes can be very messy and require some cleaning up to ensure there are no gaps or incorrect edges/vertices.

Surface Normals
Another problem that can cause these messy prints are the normals of your surfaces. Normals dictate what direction a surface is facing. Taking our box example, if the normals point outwards, it will print the box with a filled interior. If they point inwards, it will consider what we see as inside the box to be outside, and will consider the entire rest of the printing area as the 'inside'! (However, without another surface to tell it where to stop, it will be confused and likely just make a mess!).

Overlapping Geometry
Sometimes when creating edges/vertices/polygons you can easily accidentally create ones on top of one another. The printer will try to print all of these, so you'll get some very bad results. Selecting all vertices and welding at a very low value is useful for removing any double vertices (and often their adjoined edges). Programs like 3ds max have options like XView (in the Tools menu) for checking for any irregularities on the object.
<p>Detail № 22 (Click) can be set in Detail № 3 (Bottom Plate).</p><p>No fixing and openings (see the difference in the video and presented in detail format STL)</p><p>Furthermore, Detail №13 (Intermediate Wheel) hangs in the air and has balanced rotational axis.</p><p>The author complete the work... please. Very interesting work.</p>
<p>Hi, </p><p>I tried printing this with my school's makerbot mini with standard plastic filament.</p><p>Sure this is not your fault, but the plastic broke off around the teeth quite often. Another thing you might want to consider is changing the layout of the lid on the stl, so that it is horizontal, not vertical.</p>
Hello,<br><br>PLA is good for getting a surface you can easily sand and finish, but not so great for strength. ABS is much better for moving parts, but it smells pretty bad while printing, and is a lot harder to finish.<br><br>What software does your printer use? You should be able to flip the stl flat before printing (although you're right, I should save it out already flat). An important thing to note though is that sometimes it is better to print vertically as FDM printers will give a better finish to vertical surfaces.
<p>Remarkable work. I would like to print a large one, laid out like a line and printed out of wood filament. Yes--the wood filaments do exist and print in detail.</p><p>Do you have a video of the real thing printed and working?</p><p>Also, I noticed that some of the STLs don't render correctly on Chrome on this page. Those are the gears mostly. When you look at them statically and especially when you manipulate the 3D images, the walls and planes of the pieces don't make sense. It is like I'm looking at an Escher-esque incomplete solid.</p>
<p>Great! Would like to see your print running. I've designed and printed the same type of escapement. Not for the wrist but for the wall:</p><p><iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/HgZBPYJ2Y-w" width="500"></iframe></p><p><a href="http://www.thingiverse.com/thing:328569" rel="nofollow">http://www.thingiverse.com/thing:328569</a></p>
<p>This is awesome! <br><br>I was wondering what was wrong with all of the parts you didn't end up using? Was it the initial measurements or the printer, and if so, what kind of printer did you use?</p>
<p>Have you ever printed this watch? What kind of springs should I use for the winding and balance spring?</p>
I finally got the parts downloaded but now I'm having problems with the measurements of each part. I really would like to make this a wrist watch. Please help!?
Please help!! This looks amazing! I want to try sending it to a 3d print shop but i cant open the files! I have an ipad, is there a special program i need to do this?

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