Archive | May 2013

Finally Done with Threaded Rod

ImageImageMy printer did a great job printing the rods, but now whenever I try printing something else it fails. I am getting a lot of warping, and prints aren’t sticking right, but I will be able to fix those problems with some tweaking. It is nice to have arguably the most difficult piece printed, and as I have never really used acetone to stick pieces together, I am very glad it worked as well as it did.

The goal right now is to build the whole machine first and get it all to work with standard Arduino values. This means I will probably stick with basic sweeps and knob controls before I start putting in the Rhino and Grasshopper parts. I was thinking of using the Firefly plugin as it is developed particularly for Arduino, but I am now thinking maybe I will just use the gHowl component (which I am more familiar with) and just run the Arduino through Processing.

The Pros and Cons of Rapid Prototyping

ImageI was able to design and print fifteen or twenty different ring types and sizes per day on my last project; but things are much slower now. Each 10 cm length of thread that I print takes just over 2.25 hours to print compared to the 8 minutes per ring. Today has been spent sitting around for over 7 hours waiting for three pieces to print, and I am less than half way there. It is a little bit frustrating knowing that I could easily buy a threaded rod for pretty cheap and get similar if not better results in a LOT less time.

What I can’t buy at a store is a nut that fits perfectly on it that I can customize to fit multiple purposes, which this project requires. I can also make the rod the exact size I want it rather than buying large and then figuring out some way to cut it down. By 3d printing all of the pieces, it also allows anybody who wants to build this to simply print out the parts rather than needing to find the exact piece that I bought. I love my 3d printer, and all of these new technologies, but I am really eager to BUILD, and yet today and probably most of tomorrow will be sit around and wait days.

Servo Motor and Threaded Rod

I have three servo motors at home, and while the long threaded rod will be used with the stepper motor (which should arrive tomorrow), I decided to test out how this would work as a proof of concept.

One of the big problems I still haven’t solved is how to make the pen go up and down, but I think this solves it. Instead of putting a stepper motor on the thread, I think I will just use a 180 degree servo motor and, once I double the height of the threads, I can use it to move the pen up and down. The current thread moves 2.5 cm per 180 degree rotation, so hopefully getting it up to 5 cm will be enough to give the pen the movement it needs.

I am worried that the servo motor wont be able to support the weight of the stepper motor, but I wont be able to find that out until I receive the stepper motor and get some more pieces printed. I don’t have a backup plan if it doesn’t work, so I really hope it will.

One last Glove Keyboard Video

I was just about to start taking apart my Glove Keyboard project so I could use the Arduino in my Tattoo Machine project when I realized that I never made a final Glove Keyboard video showing it working.

I never actually put the time into learning how to use it, so the video just goes through me pressing all of the combinations of buttons resulting in gibberish. The camera was being held between my neck and my chin and it does in fact fall about halfway through the video.

Notes:
1) The pinky finger on my right had has a large sized ring on it so that is why it is awkwardly placed. The connection on my original pinky finger ring must have come loose at some point in the last few days.
2) A few seconds after the video camera drops to my lap I switch the toggle allowing me to type in capital letters and more symbols, so there are only half as many key combinations as you see me pressing
3) This video finally shows me closing out of Processing and opening up the text file that it creates, but it only shows it for about a second at the very end of the video.

First Print

ImageI have already tested the threaded rod (as seen in my previous post) but with such a large project I thought it would be a good idea to test out some of the other pieces as well, even before I get really started. I have fairly small arms, so the piece I tested probably won’t fit other people.

My current design is 8 cm tall and 57 cm long, but I will need to change it to be about 11 cm tall and anywhere between 60 and 76 cm long. (I tend to work in inches and feet, but because my 3d printer works in millimeters, I have switched over to doing this entire project in mm’s and cm’s). I don’t want to make it any taller than 11 cm in order to ensure the pen can still reach the thinner portions of the arm.

The gap in the upper arm piece is to allow for a rod to run along it like a track. This means that I don’t actually need the top piece as gravity will force it to stay flowing along the bottom, but I will keep it there just to make sure it doesn’t get out of line when I move it. I currently have them too thin, so they are very flexible, but I will be able to change that for the next print.

First Design

ImageImageImageImageI made a Rhino model which will serve as the basis for the rest of my design. I am currently planning on having three motors controlling the pen (shown as light blue boxes), two of which will stay at the far end of the machine. The third motor will need to move back and forth on the threaded screw to allow the pen to move back and forth.

I had originally imagined on putting your arm down a tube, but having the machine rest on a table seemed like it would be a little bit more practical. I was never intending on giving the pen the ability to move a full 360 degrees around the arm, but with the new design I am pretty much stuck with just 180 degrees of movement.

On the technical side I will be 3d printing my own thread (found on Thingiverse) for the threaded rod and running a steel rod through it for support. I plan on having a plywood base and back that I may or may not paint depending on the look I want to give it. I need to buy a stepper motor and the AdaFruit Motor Shield, and hopefully that will work well with the two servo motors I already own.

Case Studies

ImageI have spent a lot of time searching the internet, and this is one of the most similar concepts that I have found so far. Chris Eckert has created a beautifully designed piece which, while it looks better than anything I plan on creating, is essentially a limited version of what I am attempting.

His design doesn’t take into account the form of the human arm and is drawn on a flat plane where it assumes his arm is. This is limiting because it doesn’t allow for different size arms to use it, but also means that it can only draw on a very specific region of the arm. His design also uses predetermined symbols, rather than letting the user design exactly what they want on their arm.

Hopefully I can take some of what he has learned and apply it to my project. He has a blog which gives updated on the project on a week to week basis, but unfortunately it never goes into too much detail. The blog can be found here.

ImageKurt is another example of a similar project, but this one was created 8 years before Auto Ink came out. This design allows for the wearer of the tattoo machine to draw a symbol on a Palm Pilot and then that symbol would be drawn on the persons forearm. This design is a lot more similar to what I am proposing, just at a very rudimentary level.

Project 2: Digital Tattoo Machine

The premise of this project is to design and build a machine that you can fit your arm into, and once it scans your arm, it will use a skin safe marker to draw what ever you want onto it. The drawing would be applied in Rhino 3d, and then using Grasshopper and the Firefly plugin, would be exported to the Arduino as a bunch of coordinates and tell the pen exactly where to go.

There will be three motors controlling the position of the pen, one at the end of the machine that will rotate the pen 180 degrees around your arm, and another that will be connected to a threaded rod which the pen and final motor can move up and down the arm on. The last motor will move the pen either towards the arm or away from the arm allowing it to press down on the skin or hover over it.

This is all still very early design thinking, and as I run into problems, things will obviously change, but this is my plan as of now. While I was able to design the entire Glove Keyboard in exactly two weeks, I am giving myself just under 3 months to complete this task.

How to Put on the Glove Keyboard

This video sped up x4 to show how to put on the final Glove Keyboard. It would probably help to use some better quality double sided tape to keep the wrist pieces on. The total time (at 1x speed) is 9:33, and it was exhausting.

This is the final post for this project. I have made a fully functional Glove Keyboard that does both upper and lower case letters as well as numbers 0-9 and a hand full of important symbols and punctuation. I cannot press delete, enter, shift, alt, ctrl, or any other button that isn’t a letter but for what I was planning I think this is enough.

I could go further with this project, but this was really just supposed to be a practice and a learning experience which will help me with my future projects. Stay tuned for Project 2!

Final Design

ImageWhile I am waiting for the other wrist piece to print, I thought I would share some close up stills of my finished right hand. The wrist piece is connected to the breadboard via double sided tape and it feels pretty good. 

Overall the design is comfortable, and because I decided to remove the wire control pieces and just have the tips with buttons, I actually have the ability to bend my fingers a little bit.

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