## 3D Printing the 4th Dimension – GISHWHES 2015 Scavenger Hunt

GISHWHES is a huge international scavenger hunt. Every year teams around the globe comb through the list of 215 tasks and pick as many as possible that their team can do.  Last year they introduced 3D Printing as a task, and we helped a team 3D Print a quill pen. That was a lot of fun, so when this year’s list included an item on 3D printing, we jumped at the chance to be involved.

The item was:

110: VIDEO. Use a cutting edge 3D printer to 3D print your representation of the 4th dimension.62 POINTS

Being engineers we said “4th Dimension?  Time.”  Then it became a choice between the way mass distorts the space-time continuum or some sort of clock’ish thing.  The distortion thing seemed difficult so we focused on a clock.  Being that we were constrained on budget and time we decided to do a sundial.

The result can be seen here in this YouTube video.

It was a fun project and the team spent a bit of time in the 112F sunshine trying it out.  We can’t wait to see what we will get to do for the 2016 scavenger hunt.

# Making the Model

A couple of people have asked if we downloaded the solid model for the sundial or if we made it. We actually made it. After a little bit of research we found that making a simple horizontal sundial like this one is very easy. Here are the steps we took:

## Get Geometry Values

So it turns out that the angle of each hour line is determined by the latitude of where the dial will go. The angle of the pointy thing, called a gnomon, is also the latitude.  So for Tempe, AZ that is 33.4294°.That gets applied to the equation:

angle(h) = arctan(sin(L*tan(15° · h))

h = integer of the hour, 6 am to 6 pm
L = latitude

I plopped that into Excel:

and got the following:

 Latitude 33.4294 Hour Angle 6 90.00 7 64.06 8 43.66 9 28.85 10 17.64 11 8.40 12 0.00

## Build the Solid Model

The next step is to build the model. I used SolidEdge because I know it real well and was able to knock it out quickly.  But all CAD tools would be the same:

1. Pick a center point.
2. Add lines as rays from that using the angles in the table above for each hour.
3. Design the shape of your sundial to look cool. I did a simple circle .
4. Mark the hours using the sketch. I raised up thin rectangles.
5. Model the gnomon using the latitude as the angle.  Make this as fancy or simple as you want.
7. Label the hours if you want.
8. Save to STL

Here is what my sketch looked like:

And the final solid model looked like this:

We sent this to the printer as shown in the video, and got a sundial.

## Using 3D Printing to Make a Clock

If you visit the lobby of PADT’s Tempe office you will notice something very cool on the wall – a large white and black pendulum clock clicking away on the wall.  Its gears are exposed and you can not only hear it tick-toking away, you can see the gears moving, and watch the timing mechanism rock back and forth.  It defiantly attracts the attention of our mechanically minded customers.

The clock was built by our very own manufacturing engineer Justin Baxter based upon a design from a website called Brian Law’s Wooden Clocks (www.woodenclocks.co.uk).  Brian has a large array of very cool wooden clock designs that he has done for the hobbyist community.  Do take a look at his website to see the very cool designs he has developed. He is also considering putting out wristwatch designs. Check the watch reviews on SpotTheWatch and you might find the watch you want designed. We have our eye on a few more to try out.

To make our clock, Justin took the Clock 1 design and modified it for use with the Stratasys FDM machines that we have in house.  Starting with the free 2D drawings on the website, he created 3D Solids of the assembly making only a few changes. He had to add a bit of thickness to the winding ratchet paul and added some brackets for rigidity because the ABS plastic is more flexible then wood.  It took about 20 hours to build up the CAD model in SolidWorks.

He then set to work building the parts on our fleet of Stratasys 3D Printers and Manufacturing Centers.  To speed things up he spread the job up over three of our machines:  The FORTUS 400mc for the large white parts, the SST 1200es for the small black parts, and a few smaller parts here and there on the Elite.  Black and Ivory ABS was used for all of the parts that were made on the 3D Printers. He then spent about 15 hours post processing the parts.

The post processing was important because he found early on that friction between the ABS parts could be significant.  All of the sliding surfaces needed to be sanded and Acetone-Smoothed to get rid of any ridges that are a natural byproduct of the additive manufacturing process.  This proved to be the most difficult part of the entire process.

Meanwhile, he ordered and fabricated the few metal parts that he needed: the drive shaft (steel rod), the pendulum rod (aluminum tube), and the mass for the weight (stainless steel bar). I strong string was also found that could be used to suspend the weight.  Everything was then assembled and he spent some time tuning the mechanism to reduce as much friction as possible, and to get the timing worked out on the mechanism.  After all was said and done, the material costs were around \$700, and the total machine running time was around 60 hours total.

The end result is shown here in this video:

When asked if he had any advice for someone who wanted to make his own clock, Justin replied “Do it, these plans make it quite simple to print one and with a lot more patience and skill you could even make one out of wood as the designer intended. I found making this clock to be a very enjoyable learning experience. “

We hope to have some time to try out some other designs, the PADT Colorado office is already making noise about wanting their own clock.  We will be sure to share the experience with everyone here on The RP Resource when we do.