DIY Final Project

The only requirements for this project were to make something that makes us happy, and to not make something too large that a 5-year old couldn’t carry it around. It took me quite a while to think of a project, but I finally settled on a pen roll. This was something that I had wanted to make for a while, but never got around to it, so I figured I may as well spend the time to get an assignment out of the way, too. It was also sort of a nice way to physically gather all the things that were given to us over the course of the class.

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First thing, as always… sketches. There are some irrelevant things on the page, but the two on the right are pertinent to the project. I like having round holes to slot in the writing implements. The wavy cutouts were also pretty appealing, but I was worried that the fold over the top of the pens would get in the way of nice rolling.

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There are some not-so-visible sketches at the top, but those were just more of the folding top design. This is where I start really thinking about how things are going to fit in the pen roll.

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This is the sort of final project sketch before I started fabricating. I did end up switching the position of the eraser and knife, because I was worried that the eraser would get in the way of removing the knife.

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There is a sort of assembly sketch for me to figure out the layering of all the parts. I had originally intended to skive and fold each of the round cutouts, but when I started actually fabricating, I decided against this, because it would have been too difficult, and I did not really have a proper skiving tool for this.

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Laid out everything on a slightly extended piece of paper. The leather I had to work with was just a little bit over 12 inches, so I extended the 8.5″x11″ accordingly. Layout is everything from here, because I only had enough leather for one attempt. The assignment was due the next day, and I had no room for a screw-up.

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I trade out all the parts that I wanted to go into the pen roll, along with centerlines, and stitching lines. I had to use a ballpoint on the right side of the layout, because it was taped over, and pencil wouldn’t draw on it. (I should have done the layout on the other side of the page, but oh well…)

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After taking down the paper layout to the first sheet of leather, I used a spacing tool to mark out all the stitching holes. This also had the added benefit of keeping the paper from sliding around the surface of the leather when I started cutting out the holes.

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All holes cut out! I actually had to re-hone my X-Acto knife between cutting each hole. I kept a stropping leather loaded with jeweler’s rouge on my desk for that purpose.

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Before stitching, I had to burnish all the inner edges of the circles that I had cut out. I used a burnishing tool (figures) and some stuff called Gum Tragacanth. Basically, the stuff dissolved the leather, and after it dried, the leather would be nice and fused together.

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I cut out a sheet of denim from a pair of torn jeans that I probably should have stopped wearing long ago. I made sure to trim the denim just shy of the perimeter stitching lines, because I did not want the denim to interfere with the burnishing later. I also used some flexible glue to tack the denim down to the back sheet of leather.

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There’s the strip that ends up going around the entire pen roll to keep it closed. The front of it is leather, and the back is another strip of denim. I used more glue to keep it together and limit the fraying of the denim. I stitched the lengths of the strip first, before mounting it to the rest of the pen roll.

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There it is anchored to the back piece of leather. The tie-off for the stitching ends of being hidden under the inner sheet of leather.

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After many, many more hours of stitching, I ended up with this. I decided to not have the partitioning stitches run all the way to the end of the perimeter, because there would have been stitching hole alignment issues. The gap allowed me to not have to take the alignment into consideration.

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Perimeter stitching finally done, along with trimming the edges. Last step was to burnish all the outer edges.

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The things that were given out in class were the 3 COPIC marks, one regular Sharpie, a fine tipped Sharpie, BIC Cristal, and two colored pencils. That’s not even including the sketchbook!

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Some minor issues with the edge not bring fully burnished, but that can always be fixed later.

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That’s it! I think that was a pretty good way to wrap up that class. Hopefully, I’ll get to be a TA next year and see what other awesome ideas students come up with.

Mastering Mockups

So the point of this project is to prototype how an object might look using paper, expanding foam (I actually didn’t end up using this), and design clay (industrial plasticine).

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First thing is always sketches! I actually spent a lot more time just looking at ladles than sketching out different designs. I was pretty much set on a design anyways, but sketching is sort of part of the project.

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With the terrible hand illustrations above, I tried to explain why I selected a ladle for the project. Basically, the curvature of the handle on most ladles (and flatware in general) is facing the wrong way. For almost any other hand tool, the convex side of a handle tends to fall into the fingers, while the the concave side usually is where the thumb rests. Ladles and flatware have to sort of stupid curvature, which makes them all really uncomfortable to use, especially when trying to pick up a small bowlful of soup.

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To make the paper mockup, I first had to go into CAD to make a hemisphere for the bowl part of the ladle.

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And a pretty rough near-pyramid for the bump in the handle.

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The hemisphere made in Solidworks was exported as an STL then imported into Meshlab. Using the “Quadric Edge Collapse Decimation” tool, I reduced the number of faces. With the new low-poly STL, I simplified bowl part along with the handle bump to Pepkura, which was used to generate unfolded paper models.

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The instructions for the assignment were to laser cut these, but with the end of semester drawing near, the line for the laser cutter was quite long. Instead, I just hand cut the parts.

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The cardstock doesn’t take to folding too well on its own, so I had to scribe everything first in order to fold it nicely.

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All folds were creased prior to gluing. I used a toothpick to apply a thin coat of glue on each of the tabs.

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The handle bump seemed to be pretty good. This is the part of the project that probably should have been filled with expanding foam, but the volume was so little, and it was actually pretty stiff by itself, so I decided to skip out on the foam-filling part.

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The long handle was formed with two long strips of cardstock, scribed into approximate thirds. The outer piece was scribed just a little bit wider to compensate for the thickness of the paper when folded. The bimorph allows my to shape the hook at the end of the handle along with help to maintain the shape of the handle better than a single sheet of cardstock.

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Paper part seems to be coming along just fine.

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I probably spent a little too much time doing this. Design clay is very soft when heated, but once it is cooled, it retains its shape quite well. It cools sort of quickly, so after slapping on a bunch of clay and then carving down a bit, I had to put the entire part back into the hot box. I had to repeatedly put the part in, take it out to smooth, and heat again to get the final shape and finish.

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That’s it! Hopefully I’ll get some more design clay to work with in the future. It definitely was quite a bit of fun, and it’s nice and reusable.

The Desk Mount Dilemma

Despite the title suggesting that this is a desk mounted clamp, the professor gave to OK to create any sort of clamping device to hold an object. So instead of making another phone dock, I decided instead to make a bike mount for my phone.

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So as always, the project started with some sketching. Seeing as the clamping mechanism itself was the most important part, I decided to start my sketching with the mechanism. The screw-assembled pipe clamp mechanism is probable the simplest, go-to method, but I wanted a way to be able to take off the clamp and put it back on without tools. A cam-locking type device could have done the job, but I decided against it, because it required too many parts. The sketch on the right is similar to what I eventually settled on.

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The next step was to CAD it up and print it off on my 3D printer! Except…this first design ended up sucking pretty bad. The dimensions were all a little out of whack. First off, it didn’t fit around the handle bar, because the diameter of the clamp was too small. Also, the holes for the pins were much too tight, preventing any of the parts from pivoting. Even if it the parts did fit, the straight clipping pieces (the parts that look like a link in a bike chain) would not have had enough flex to allow the clipping pin to snap into place.

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So next, I decided to make a sort of hole sizing tool. I made a bunch of different diameter holes to figure out what would be the correct size for a pivot, and what would be good for a press fit.

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This time, instead of making all the holes the same size, I made all the holes on the outer faces of the clamp press git holes. The two inner holes allow for parts to pivot more freely. The pair of part for clipping are now bow-shaped instead of just straight, allowing for enough flex for the part to snap into place.

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Having learned my lesson with the poor fitment of the pin holes earlier, I printed off a smaller part to test fit around my phone. This was nice and snug, so I went ahead and made the full version next.

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All the pins were made with a Dremel and file. There isn’t much more satisfying than cleaning up a rough Dremel cut with a file and the brushing the file clean.

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And there’s the part! The standoff block that interfaces between the phone holding parts and the handlebar clamp also helps to offset the phone such that it site centered on the handlebars.

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There’s the clamp on my bike! The phone is inserted into the holder by sliding it in from the bottom. This ensures that if I do crash my bike, my phone will most likely stay with the bike instead of being ejected forward.

Hope you guys enjoyed looking through this again!

The Molding Mystery

I’ve played with silicone molding a couple times before, but this is the first two-part silicone mold that I made. There were some size limitations on the project, but it was otherwise pretty open-ended.

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It actually took me a while to find something to mold, and then I remembered these little pigs that I had laying around from testing my 3D printer. As is evident from the above image, this print went particularly poorly, as the top of the pig wasn’t completely filled, and the print layers are very obvious. If I tried to mold this, the silicone would seep in everywhere and would be disastrous.

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So the solution was J.B. Weld! I originally wanted to use Bondo, but I didn’t have any on hand, and the Bondo would have been pretty porous after sanding. I knew J.B. Weld sands pretty well, so I just used that instead. The finish was really lumpy, so more had to be done after it fully cured.

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After some 120 and 400 grit sandpaper, the piggy was pretty smooth, and all the holes were filled in.

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Before building forming the mold, I made some sketches to get an idea of where to part the mold and place the sprue.

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Piggy in mud! The first step was to bury half of the pig up to the parting line in clay. It’s a little tilted here to minimize the undercutting. The silicone is pretty flexible, so some undercutting near the parting line and near-vertical walls are acceptable.

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I used the end of a sharpie to poke some divots into the surface of the clay. These are for aligning the two halves of the mold later. Using some more clay, I sealed the edges of the foam core box built up around the clay block. It was sort of like caulking, but way more relenting. The next step was to mix and degas the silicon mixture and pour into the top of the box.

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After waiting 24 hours, I pulled everything out, removed the clay, and inverted the silicone block. I then placed a straw flush with the feet of the pig and built up some clay around it for the sprue.

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After both sides of the silicone mold were completed, I could remove the original pig and the straw. Next, I poured in the polyurethane casting resin. Ir seemed to come out pretty well. With some sanding and filing, and I was able to remove the sprue that was also cast. There are some bubbles on the feet, which I probably could have gotten rid of if I had degassed the part after pouring the resin.

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That’s it! The parting line is visible on the cast part, but it’s not too noticeable.

And as a mechanical engineer, I needed to get the orthogonal views of the pig. Thanks for checking this out!