Sunday, June 22, 2014

Gears with logos

The theme for the kids VBS (Vacation Bible School) this year is "Workshop of Wonders" by Cokesbury.  I participate every year with my kids but was extremely enthusiastic that the theme this year was for makers so my goal is to show off the 3D printer and make some things for the 50 or so kid participants.  It's no fun watching a 3D printer without having something to touch and even take home.  However, I am fairly new to 3D print design so this was only my second endeavor to design something of my own.

I was trying to think of a project where each student would get a gismo to take home but we could put them all together to build something as a group. This fit in with the theme quite nicely however most of my ideas were a little too complex to get off the ground.

I finally settled on building gears with logos and holes on one end so they could attach them to their backpacks.  I thought I could assemble all of the gears together to make one big machine the kids could play with that all worked together.  With this plan in mind I searched though thingiverse and youmagin for some designs I could use as a starting point.  I was really excited when I found this one by that can be used to make gears that fit into Lego technics. I have a ton of lego technics and I really liked the idea that the motivated students to integrate their gear with their own legos.

After some iteration, I ultimately ended up doing is importing the images into Inkscape and converting them to a dfx file which is a vector map using instructions I found on a couple of website. Here is an example image I loaded into Inkscape


Using this technique I was able to make a variety of gears and they worked well with lego. Here is a video of one of the gears working with my old first generation mindstorm:

This turned out to be a really flexible design and I was also able to someone elses openscad files to make other gears with different projects I found on thingiverse. For example here is one with a robot in a openscad file from thingiverse

Here is another one from an stl file I found on youmagin that originally was a keychain modification for the ultimaker (

I really like this design because it is easy for me to swap out different logos based on the event.  I uploaded my source files and these examples to github:

And posted a few on

Please let me know if you find this helpful and email me links to gears that you have made.

- Dirk

Milk Jug Bird Feeder

My eldest daughter wanted to make a birdhouse/feeder.  It was the middle of winter and I think she was thinking of building it out of wood. However, I realized what she really wanted to do was decorate it using some extra stickers she had.  So, we compromised and I cut out a hole in a washed out milkjug.  

She spent the afternoon decorating and had a lot of fun. 

Add a little birdseed and the project was complete.

Easy way to entertain a fidgety girl on a beautiful but cold afternoon.  The seeds ended up on the ground although I don't ever think I saw a bird.

- Dirk

Monday, June 16, 2014

Diet Coke and Mentos

As any true geek dad, I have always wanted to do the Diet Coke and mentos experiment.  However it is messy and the logistics of getting the mentos in the coke without getting crazy sticky is challenging.  I did a quick search of thingiverse and found a couple of wonderful solutions:
A short 3D print of the second one and all we needed was Diet Coke, Mentos, string, paperclip and space:

So much fun :)

- Dirk

Friday, June 13, 2014

Tripod Quick release mount

I got a tripod for my birthday this year.  It is a really nice one, but I lost the quick release mount.  Here is a picture with a quick release mount from another tripod. Obviously, it doesn't fit:

After some shopping online this one looks fairly good, but possibly not the right size.

So, I took some measurements and came up with this drawing

My goal is to see if I can print this out using a 3D printer. When I started this project I was planning to use the one in the engineering department where I work, but now I have an Ultimaker 2.  I know I need an stl file but I was not sure the best way to generate one. After some quick internet searching I found openscad.

I downloaded the software and found the wiki quick start page.  It did not take long to figure out the simple language.  I started by making a cube and then creating the top.  Then I made objects to cut out the inside and the bevels.  Here is the resulting model.  

The hardest part was to get the surface normals for the wedge shape object to face in the right direction.  However, once I drew out my points and used the right hand rule things settled in nicely.  Openscad outputs stl files so all I did was import it into the cura program to generate the gcode for my printer and save it to the SD card to print.  The first print was a little too close to my tolerances and I could not get it to fit inside the tripod.  However, with some simple modifications to the openscad file I was able to generate a quick release mount that I think looks quite nice and works well:

A future design would fix the bottom to the mount somehow. I posted the STL and OpenScad files on if you are interested in makeing your own:
- Dirk

Thursday, June 12, 2014

Party Pinata

I like to watch Curious George with my Kids.  That little monkey is a bit of a maker. I really like the episodes where he tries to build things.  In most cases he doesn't get his design right and has to debug and iterate on the design until he has what he wants. It is a very good lesson for our young makers.

In one episode George decides to make a pinata.  My youngest daughter LOVEs this episode and has been asking my wife and I to make a pinata for weeks.  A few weeks ago my wife relented and found a really nice youtube tutorial on-line:

We got the supplies suggested by the video and my wife and kids started paper machine a star shaped balloon and party hats.  The family ended up making two since the overall costs were about the same.

We filled them with candy and put one of them to the test this weekend at a family party:

The only problem we had was keeping the pinata attached to the string.  Ultimately, I had to tie the string around the whole thing to get it to stay.  I probably need to follow George's example by iterating and engineering a better process for the second one.

- Dirk