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After my nephew got a spirograph I was inspired to build upon the idea and be able to create something more permanent with it. This is only the beginning of the project as I discovered when I thought I was done, so this may simply be a Part 1, but here is the first part.

Please vote for me in the 3D Printing Contest!!!

Step 1: Model the Parts

I work with Autodesk Inventor at work and am allowed to use it at home with our licensing, so I use it at home as well. There are many free software options but because I'm familiar with Inventor that's what I stick with for my personal stuff, too. With several interfacing parts, the method I like to use for modeling assemblies is to create one part file with each individual part betting a new solid. Inventor does a very good job with this method and it seems to be the most reliable parametric method within Inventor. In my experience projecting geometry part to part within an assembly file is not (at all) reliable.

My plan was to model an outside track, a geared follower and a Dremel mount that would go inside the geared follower. The Dremel mount was necessary to let the Dremel rotate without having to make every turn the geared follower made. After getting started with the modeling I realized that in order to fit the parts on the print bed of the printer I had access to the outside track would have to be in multiple pieces. To simplify the files I made the track into four identical pieces that locked together, so the number of teeth had to be divisible by four so they would split up evenly.

Inventor does not actually model threads when you put a thread feature in the model, so for the purpose of 3D printing you have to create the actual geometry of the threads.

The single part file ended up having three unique solids- a quarter of the outside track, the geared follower and the Dremel mount. I exported the solids into an assembly file to get unique parts from the one part file. After putting the other three quarters of track in the assembly to check fit, I created my .stl files of the three components.

The printers I have access to are Makerbots, so I use their free desktop software Makerware to create .thing files to use for printing. It took two files to fit all six pieces required.

Step 2: Print the Pieces

Once your files are ready it's time to print the parts. My parts printed somewhat well-well enough to use but certainly not perfectly. Printing them with a raft may help the print stick to the bed and not warp (and sometimes not so much) but it usually creates some extra cleanup.

I modeled in .5mm clearance between the teeth locking the outside track together and they required very little work to get them to fit, just some very minimal filing.

I tested the follower within the track and it worked well. My first file for the Dremel mount was a bit too tall, so I updated my model and printed another that worked much better.

Step 3: Assemble and You're Done...For Now.

Once you put the track together and Dremel mount on it's time to try it out. I didn't model mounting holes into the track because I didn't want holes in the workpiece, so I always planned to clamp them down. You need to adjust the bit in your Dremel to protrude through the mount in the geared follower to the depth you want it.

I did my initial test in plywood, and it was working well, but my bit was dulling rather quickly. I recommend putting a mark on the follower that lines up with the track four where you start-if you have to stop and start over again, you need to start in the same place in order to make sure your cut spirograph pattern lines up with itself.

What makes this not the last step is that during my way around the track, attempting to complete all the revolutions to complete the entire pattern my bit dug into the wood oddly. It turns out that the cutting produced enough heat to soften the plastic, which then allowed the Dremel mount to push into the follower.

In order to move forward, my next step is going to be to make the Dremel mount and the geared follower out of aluminum. I will print new parts scaled up by 2% for casting and use them as investment casting blanks. There is an Instructable "How to Sand Cast 3D Printed Objects" which has information on the process.

Thankfully the design concept works, and so now it's simply a matter of finishing my furnace preparations for the next phase of the project to be complete.

<p>Let me know when you're ready to sell these!!!</p>
<p>Me too please!</p>
I'm trying to get more prints made now to get some castings going. Hopefully soon : )
I'm not set up for production but I will see what I can do about making a few : )
May be invalute gears will be better?
They may be better, but thankfully the teeth seemed to work pretty well. I may try out the involute profile later on.
<p>Have you tried using the grout removal bit? it has a smaller head profile, and digs a flat bottom channel.</p>
I haven't tried one yet. The bit I ended up using had a triangular point and it was rather shallow and the actual cutting profile rather narrow by the time the mount was on the tool and it was in the geared follower. <br><br>I'm confident not using plywood would help-I didn't have any lumber on hand that size or glued up to that size but I think the heat can be an issue regardless so I definitely want to cast the pieces. I'm assuming for that to happen in the next week or two.
I know it would be a lot more work, but are you planning an outside gear track as well? I would greatly improve the versatility of your tool.
I was actually planning several other shapes-on oval, a triangle, rectangle, etc. but wanted to do the casting of these parts first since using the printed parts directly didn't work out.

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