This is part 2/2 in a series of guest posts from Jay Doscher.
In the previous article we worked on designing a part on the computer. We sketched out the part on graph paper, designed it in Visio, then printed it out to make sure it fit on our project chassis. It will take a couple weeks or so to get the parts in the mail, and we're going to pick up the project after getting the parts back. You can see the paper print out below where we printed it out and cut it out on paper from last time.
It's especially important to make sure all your holes are where they need to be- this can get tricky on complex shapes. As you can see here we have printed out several holes. We can use a hobby knife to cut those out or simply poke out the holes with a pencil in a pinch.
As you can see above, we've taped the part to the project frame. (3M painter's tape works great for this exercise.) Here's a picture of the whole project with several of the parts taped to the frame. It looks a little bit messy, but it shows us exactly how it will all line up.
When we get the parts in the mail, it's important to check the parts individually- in this case it's easy to stack them up and sure enough, they are all in good shape. You can see a photo of one of the finished parts below. One important thing we did for this project was leave the screw holes a little smaller than needed- this meant that when the parts arrived, we could start testing with smaller screws, then drill out the holes to the size we needed. Since there is a high amount of precision from the part design, we can use the existing holes as guides for the larger diameter screw holes. This means the location of the holes stays very accurate even though we are drilling them out by hand.
You'll notice that all the holes line up exactly where we want them, and that the part matches the paper design we did a couple weeks before. One important advantage to working with ABS plastic is that it's easy to work with if we need to change small things. As you can see in the picture below, the part on the right has a couple new additions- we have drilled holes to make spots for some stand off screws, making room for a Raspberry Pi B+.
You can also see how the parts sitting next together show that they can interlock together. This would be extremely difficult to do without prototyping them in paper first, and would likely require very expensive software. Instead, we can rest easy knowing our parts will fit on our frame, just as we expect.
Finally, you can see the finished parts installed on the frame. The parts fit great, and as you can see they fit on a variety of places on the frame thanks to the versatile design. It's important to note that this process works the same for most plastics and even some metals. We could easily place the same order but use aluminum instead. It's important to take into consideration the different materials' properties, since tolerances and other attributes change with different materials types.
We hope you have found this article helpful. You see the full project build gallery over on the Polyideas website here. There you can find other projects that use the same process for prototyping with paper, then using Big Blue Saw to make the ideas a reality.