Project: bead printer

Hey everyone!
My name is Michael and I have a project I'm working on: a fuse beads automatic "printer".
After I got my mechanical eng. degree I was looking for a project to prove to myself it was worth it. I guess being a maker was my secret ambition, and I felt I needed some project to be proud of. 
While babysitting my little cousins and doing some works with Perler beads, I thought to myself: hey! this is cool- I should try making something bigger! and so, as my works grew larger, I began to wonder- can I make it automatic?
What are fuse beads? 
These are small beads made from plastic that come in various colors, and can melt under a regular home iron. Its a kids toy- you place a pattern on a mat, iron it- and get cool results. google it!
What is it supposed to do? 
The idea is simple: place individual beads of various colors on a mat full of small spikes according to a pattern. sounds simple, doesn't it?
I think its good to first look at a 2 color (black-white) simple scheme and try to print it on a small part of the board. Once the mechanical part is finished, the real programming will start.
Some numbers: 
The beads are about 5[mm] in diameter and in height. A typical board is 30X30 spikes. A piece could usually contains 2-10 main colors.
Before you read my concept, I would like to know- how would you try to make this project? I have had this idea in my mind for over a year now, and I'm looking for new ideas.
The concept so far:
As I've mentioned, its been a long journey already. I am far from having a working prototype and am open to suggestions.
The "printer" I designed is similar to a CNC machine: a tube has 15 beads in it. The tube is moved above the board, placing the beads. Refill will be done manually since I wish to prove the mechanics first.
I made the printer with Lego and an NXT controller and engines, simply because I had it at home.
I tried making a 2 axis motion using a rack and gear (with transmission), moving a tube with beads in it. To my dread, the beads do not like falling off when placed on top of one another (in the tube), so I used a third engine, converting the rotary motion into linear one, applying a small force over the tube to prevent the beads from falling, moving them to the next position, than letting go.
I discovered the engines are not as accurate as I would have wanted, and the results are meh.
I will add some pictures at a later time as I need to re-assemble it.
Thanks a lot for reading, and I hope we can make this dream come true- lets have some fun!

caitlinsdad11 months ago

You should look into pick and place machines used in electronic circuit board manufacturing. They have preloaded cassettes of small parts that are accurately selected and positioned at a high speed. A lot of it probably depends on computer vision but you could probably work with mechanical sensors. Good luck.