V. Conclusions

Timing Belts

     Though every precaution was taken to minimize friction throughout the system (oil impregnated brass bushings, nylon spacers, lubricant, lightweight parts) the amount of torque necessary to drive the system was greater than the timing belts could transfer.  The main issue here was belt width.  There simply was not enough contact area between the belts and the pulleys.  Also, the system was designed and constructed with the belts in tension.  An improved design would have been to create a tensioning system, at least for the first belt running from the motor to the Geneva driving wheel shaft.  The motor was able to provide the proper amount of torque, even at the very low speeds we were running it at.  However, the belt would skip between the motor and the first pulley, not allowing the 4-bar system to engage.

Toggle Position

     Another strain on the timing belts, in addition to the system's friction, was a toggle position in the straight line mechanism.  Though we designed the linkage arm carrying the cutting wheel to be as lightweight and short as possible, a toggle point created what amounted to an increase in torque load that further disrupted the motion of the MXL timing belts.

Acrylic Laser Cutting and Bonding

     We had tremendous success using acrylic as our principle material.  The laser cutters are extremely accurate and fast, making fabrication of not only our linkages but housing, platform and electronics box very easy.  We bonded the acrylic parts together with chemical solvent, which creates a strong bond and sets fairly quickly.  We saw the best results when parts were affixed with clamps, allowing the solvent to properly set and giving the best finish appearance.  

Potential Changes

     In maintaining the scope of our project, one slight change could alleviate the problems caused by the shorter timing belt.  By going to a mechanically geared drive directly to the Geneva mechanism, the slippage problem of the MXL belt would be solved.  The gears could be 3D printed, as the material properties of the FDM plastic would allow for accurate movement and translation of the rotary motion.