Build-a-Bird Day: #4—2/11/11

Today we focused on creating the remaining components of our model in SolidWorks, so that we would be ready to print our first iteration.  Our gears and ‘little red rotators’ were complete, so we moved onto finishing the base and building the small and large support rectangles.

The little rectangles are on the very edge, supporting the wings.  The large rectangles are behind the gears, supporting the turning mechanisms.

We based our measurements for the rectangles on the measurements from our sketch of the base, since they would need to be press fit-into holes on the base.

Little rectangle: First iteration

We realized that the placement of the holes on our large rectangles would be completely dependent on the exact distance between the center holes of the two gears when they were connected, so we decided to wait to add the holes until we could physically measure the distance on the gears.

At this stage, we thought our final count for laser-printed parts would be:

Base (1)
Small rectangles (2)
Large rectangles (2)
Gears (2)
Little red rotators (2)
Donuts to help with press-fitting (16)

How we hoped to use donuts--as press-fit pieces on either side of a rotating part

We decided to use piano wire not only to connect our little red rotators to our small rectangles, but also to connect our Delrin rod wings to our two gears.  We chose to leave the donuts for the end, since they would be the simplest to make.  At this point we had SolidWorks designs for all of the other parts (minus the holes in the large rectangles) so we were ready to print our first iteration!  We had originally planned to make our base out of ¼ inch Delrin, but we realized the extra strength was unnecessary, and in an effort to save Delrin, printed everything out on 1/8 inch Delrin instead.

Our first iteration:

Gears! Just look at those pearly whites

Base, little (red) rotators, and small rectangles

Unfortunately, we did not think the complete switch to 1/8 Delrin all the way though, and realized too late that certain pieces (little red rotators, small and large rectangles) still needed to be printed in ¼ Delrin, since we would be drilling into them later and would need the extra depth.  We also realized that we had miscalculated the size of our little rectangles, making them too narrow.

Small rectangle iteration #2: 'Fatter Little Rectangle'

We decided to use ¼ inch Delrin rods to press-fit into our gears, as well as for our birds ‘wings.’  We realized that the many donuts we had previously thought we would need had been rendered unnecessary by piano wire—since it is so thin,  we decided to simply bend the ends to keep them secure, instead of using the donuts.

When we tried our gear onto a 1/4 inch Delrin rod for size, we discovered that the two had a loose fit, rather than the tight fit we needed.  This turned out to be somewhat of a problem, since our gear plug-in forced us not only to rebuild the entire gear, but also only gave us certain center hole sizes to choose from.  We selected the next smallest size (unfortunately, considerably smaller), reprinted our gears and discovered (unsurprisingly) that the holes were far too small. 

One is too big, one is too small . . . which one will be just right?

 

We moved over to the drill press (a machine that we would quickly become very accustomed to using), and realized that if we drilled the hole to a size just under ¼ inch, we would be able to use a smaller drill bit to carve just enough  Delrin away to make our gear the perfect press fit size.

Lyn teaching us the ways of the drill press

Beautiful press-fit gear flower! Unfortunately we had used our gimpy gear as a tester . . .