Mechanical and Machine Design

Part One: Mechanical Design

Getting the pieces together:

First I retrieved the dxf file from Nadya's site [modular] Machines that make: cardboard stages. But you might want to visit this site first. Then I imported the file into Coreldraw 5.0, prepared the stages for printing by: selecting, grouping, hairlining and arranging objects on the canvas to be recognized by the laser cutter (a 75watt Epilog Legend):

Laser Cutting Challenges:

I had to print the half stage you see on the Coreldraw canvas twice because my previous print settings were in err. One needs to turn off autofocus and use the manual-focus settings to ensure that the cardboard objects will be cut clean through, if not using the recommended settings in the laser cutter manual.

Manual Focus Steps:

Files weren't being printed out accurately or thoroughly in cardboard and using an X-acto knife wasn't optimal. Our boards were bowed (warped) but we chose not to waste material. Solutions: We learned how to manually focus the lens so that our stages would be thoroughly and accurately cut on the first print-out:
  1. 1. using masking tape to hold down the boards as tightly as possible
  2. 2. turning off the auto-focus in the print settings on the computer
  3. 3. turning off the x/y axis on the laser cutter and manually placing the lens at the most bowed (highest) point of the board
  4. 4. hitting the up switch 2-3 times to move the lens closer to the board
  5. 5. hit the reset button on the laser cutter
  6. Results:

Problems:

Some of the bolts were longer than needed for the motor, which made the housing weak and unstable for the entire stage that would encase the end effector.

Solutions:

My team mates helped me out by 3D printing washers with the z18 replicator and offering the suggestion of putting the bolts through the nuts first. Using a nut above the washer to secure the motor worked perfectly.

Part Two: Machine Design

Our team made the decision to create a fractal drawing machine upon the completion of our machine frames and stages. As none of us are well-versed in Python, I did extensive research to find a Python algorithm for a fractal tree. I wasn't very successful, as you have to find the parameter limits of your machine first, then calculate a series of (X,Y) arrays based on function that can be translated into Python to make the machine respond accordingly. Finding the function was easy but applying it within Python was frustrating because I'm not familiar with the language at all... I have the distinct prejudice that javascript and C are the only languages you really need to know, with C being the best. Here's a snapshot of our code:

Team Python Code

Powering Up the Machine in Sequence:

  • 1. Connect the boards
  • 2. then connect the motors
  • 3. then connect the 5volt USB cable
  • 4. then connect to the outlet or power cord
  • Finding Solutions to Programming
  • Challenges:
  • A shared lack of experience using Python within the team and inputting mathematical formulas into this coding language.
  • Solutions:
  • With some research and experimentation, a formula was found that could calculate a series of X,Y arrays in Python that the machine recognized and responded to: insert a new (a,b) vector as (a2 - b2 + x, 2ab + y) & Boolean reference
  • Securing the End-effector
  • Challenges:
  • The end-effector was installed inside the chamber housing the motor-mount (?) but wasn't completely secure with double-sided sticky tape. When the separate motors were tested the pencil drew at a 45 degree angle as opposed to a 90 degree angle as intended.
  • Solutions:
  • The end-effector was secured with double-sided carpet tape in the 4 corners of the chamber it was installed with - works fine.
  • Adjoining the Stages
  • Challenges:
  • How to combine the stages securely and quickly.
  • Solutions:
  • Using industrial velcro at the ends of stage Z to attach to the motor mount housings of stages X and Y.
  • ...and designing and milling out the power jack.
  • Insight:
  • It might be better to 3D print hinges that rotate on a ball (a non-subtractive design) that could be screwed in place of the velcro on the stages to allow for flexibility without sacrificing strength and endurance.
  • Hero Shots

    Completed frame and stage:

    Power Jack: