Thursday, December 25, 2014

3D Cookie Cutter app comparison

My oldest daughter is in her second year of Brownies.  My wife and I volunteered to lead a couple of their meetings with a maker theme.  I thought the 3D printer is always a hit and what better project for girl scouts than cookies (yes I realize this is cliche but it is still fun).  I did some searching on the internet and came up with a variety of ways the girl scouts could design cookie cutters.  However, I had a checklist of desires and none of them quite made the "cut" (I will stop now).  Here is what I was looking for:
  1. An option to upload and trace a picture. This is necessary because I do not have enough computers for the group. I saw a similar activity at the Detroit Maker Faire and I thought hand drawn images would be more natural.
  2. Ability to add both internal and external features on the cookies. What I would really like is two layers so the cutters could imprint on the cookie as well as cut through the cookie. 
  3. Ideally an online app so I do not have to download anything.  
  4. Obviously an easy way to output stl files I could use with my printer.

Online app for drawing outline of cookie cutters.  This makes for a fun group project because you can scan and upload hand drawings into the editor and trace them.  The downside is that this editor only does a cookie outline and not the insides. Here is an example we did:

Cookie Cutter Editor:
Downloadable cookie cutter editor. Uses a programming language called processing (written in java).  I could not get the MacOS stand alone version to work so I tried to download processing and run the source directly.  Still was missing some libraries so I gave up on it.  Looking at the examples I do not think it would work much better than CookieCaster and could not get any of the internal details I wanted anyway.


Thingiverse has one of their customizable apps.  This one was really nice because it could do some internal details. Seems to only have one height but having details is better than the other two.  However, this app also only had an option for online editing and no way to upload a picture.  It was also a difficult interface to master.  For example, it does not handle overlapping editing very well and was particularly hard to get right with my laptop's touchpad.  Here is an examples we made:

Although none of the apps seem like they would work, none of them really fit all of my criteria.  I am going to have the girl scouts use Cookie Caster since it is the one that works with pictures. Please stay tuned for future blog posts with details highlights from the girl scout projects.

- Dirk

Friday, November 28, 2014

Snowflake Lithophane

There is something magical about looking at a lithophane.  I like handing them to people with the light coming from the front.  Most of the time they are polite and say, "that's nice."  Then I have them hold the lithophane to let the light come in from the back and the image pops out.  "Wow," "cool" they say and the expressions on their faces are ones of awe and surprise.

For christmas this year, my wife came up with the idea of putting a picture of the kids inside of a lithophane inside of a 3D printed snowflake.

Took a while to figure out but got much easier when I found an openscad program to generate snowflakes I found on Thingiverse:

I picked a random seed that fit well with my idea and then I tried importing my the stl file from my lithophane program.  I could not quite git it to work. So, instead I decided to make the print in two parts and glue them together. I did some minor modifications to the openscad file add an area for the lithophane, the hole for a ribbon and in latter modifications a way to add the year:

You can download the stl file for the frame on youmagine:

Now I just print the lithophane separate from the frame and it turns out quite well.  Here is a video:
I am happy to share any of the code or you can just upload a photo and order one of these on our etsy store:

I wife has challenged me to do something similar with a heart for valentines day.  That should be fun.

- Dirk


I saw my first 3D printer when I was visiting the University of Notre Dame.  It was over 10 years ago, it was fairly expensive to operate and it printed in a kind of expensive wax.

Anyway, this was the first time I saw a lithophane.  It was a picture of Marilyn Monroe that just popped out if you held it so up to a light so that it is backlit.  It was just so cool that I really wanted to make some Lithophanes when I got my 3D printer.

Once I finally found some time I did some research and there were a few programs on the web which would make lithophanes for me.

I tried a few but nothing excited me so I just wrote one myself.   I am very pleased with the results:

If you just want a lithophane, we added them to my wife's etsy store:

If you already have a printer I am happy to send you the MATLAB code to generate these for yourself.  However, I must warn you that it is not very robust and I am reluctant to post it until I can add a bunch of error checking and a little better user interface.  It's also written in MATLAB, ideally I would like to change to something like Python but I am just quicker working with MATLAB.

Learning to use a sewing and embroidering machine

We are trying to turn our basement into a mini makerspace for the kids.  Quite a few years ago my wife bought a fancy sewing machine that does embroidery which I thought would make a fun addition.  My eldest daughter and I got playing with the machine and it is quite amazing.  In no time at all we were able to embroider a bow and make a cute little pillow.  I look forward to seeing what we will make next time.

- Dirk

Fairy House

Over the summer we spent some time up at our Aunt and Uncle's cottage.  Kids were picking up a lot of nature detritus to "keep" and my wife got the idea to make a Fairy House.  Turned out to be a really fun project.  I particularly like the paper lantern made from an old hornet's nest and the ladder.  The trick seems to be start with the big stuff and keep filling in the details until it looked right.  

- Dirk

Monday, September 1, 2014

Fish Tank Kids Coat Rack

This one was a lot of fun.  We have a coat area down by the back door landing.  I used those plastic hooks with the special double sided tape that allows you to remove the hooks without damaging the wall.  Unfortunate, the kids managed to pull the hooks off taking some paint and drywall with them. 

Anyway my plan was to print put some new hooks using my 3D printer.  I thought this would be the "cheap" way to  go.  I let my imagination get away with me and ended up with something a little more expensive but also something unique.

The design is quite simple and consists of two hooks I found on thingiverse; a fish:

And a round hook or bubble:

The overall affect is a fish tank with a bunch of fish skeletons swimming around.

The design is a little odd bit visually appealing and has a ton of places for the kids to hand stuff.

- Dirk

Monday, August 4, 2014

Vacation fort

We are spending time with the kids at our aunt and uncle's cabin in northern Michigan.  This is an old hunting cabin but it is not exactly roughing it.  There is air conditioning and internet.  

I am worried that the kids are spending too much time inside on the devices.  At some point yestuday I banned the devices and told my eldest to go out and build a fort:

She found some old ladders ready for the burn pile and built from there.

The fort turned out really well.  It is surprisingly strong and all of the kids are proud of what they built.

It is also a fun place to picknick lunch out of the hot afternoon sun.

- Dirk

Saturday, July 19, 2014

Bug bots

I like the simple fun of bushbots; little robots, typically made with toothbrush heads, that use a cell phone vibrating motor to scoot around a table (you can buy kits here:  I decided that this would be a great project for me to do with my kids.  Step one was to find the parts.
  1. Cell phone motors (pack of 50). 
  2. Batteries. Large pack ordered on amazon:
  3. Glue
  4. Double sided tape
  5. Toothbrushes
Between the motors and batteries, the price per brushbot was getting expensive.  So Instead of buying a bunch of toothbrushes I decided to see if I could print the body instead.  I came across the following design on thingiverse that did exactly what I wanted:

I ended up using only the "legs" and the body.  I also think it was also better to assemble the body upside down. In any case, I was able to print out these three parts and just let the kids assemble them using superglue:
Then we had to strip the wires for the motor (probably the trickiest part) and remove the sticker cover on the motor to stick it to the "bug".  
Add small pieces of double sided tape and lay down one of the wires on the tape. Then have the kids stick the battery on top of the tape and use a second piece of tape to secure the top wire. 
At this point the bug bots should start dancing.  We used an upside down paper plate as a "sumo" rink to see which bug bot could stay on the longest.  
Overall this activity was easily complete in 15 minutes and the kids had something to take home with them.  Special thanks to ekaggrat at thingiverse for posting his 3D designs which made this project possible.

- Dirk

Coffee table drawer

The kids have really done a number on our living room coffee table.  The top has been "distressed"  by biting, thrown toys and lots of drumming.
The drawers have also been used as steps to get up on top of the table.  Most of the hardware components have broken under this level of used.  
I decided that this would be a fun project for my 3D printer.  There are a lot of drawer guides in thingiverse. I downloaded a few drawer guild stl files but none of them really fit my dawers:

I ended up having to design my own using a pair of calipers and OpenScad.  I think they turned out great:

I also replaced 3 of the four drawer stops using another design developed in OpenScad:

After the flat part was printed I put it in a warm pan on the stove to soften the plastic a little so I could put an appropriate bend in it. Here is a link to my files if you are interested in working with them:

I also posted them on

Overall, I am happy with the results.  And I am comforted in knowing that I can replace the parts again if the kids get destructive again.

- Dirk

BackBlog - Teleporter video

We through a Star Trek themed surprise party for my wife and I thought it would be fun to see if I could make a transporter effect.
To start we took two pictures, one with everyone in an away team formation and one with just the background

I then wrote a simple program to add the two images together using a weighted sum.  This technique looked okay but I also wanted some noise.  I used the matlab imnoise function to create some sparkles. Inicially just a few, grow to a lot about halfway and then disparate as the people materialize.  

The trick is to get the speckles to only appear where there are people.  I could have tried some clever image subtraction trick to find the region that changed but it was just as quick for me to use GIMP to cut the people out and make a simple flag array using the following Matlab code.  I had to also use GIMP to paint over any white spots in the image. Fortunately for my image there was very little white. I ended up with the following (I guess I could also have just select the white and set everything else to black).

Now, potting All the components together and looping from 0 to 100 I was able to create a directory of images that I wanted and stitched the images together using ffmpeg.

To top it off,  I found a transporter like sound on the net and used my copy of Camtacia ( to put the audio and video together.
Here is my final product:


- Dirk

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