Fabrication

Overview

The Blast and Bounce mini sculpture concept is a modification of the original ball drop sculpture. To make things more complex, we replaced the catcher with a trampoline. Additionally, to develop another concept and test multiple ideas in one sculpture, the team added the launching mechanism to the top of the sculpture. To make for easy testing of the sculpture's consistency, the design was made to loop without any user input or replacement of balls.

Design Challenges and Solutions:

The ball was landing accurately but occasionally bounced off the funnel and exited the loop.
- We dampened the funnel by taping cardboard to it. This would absorb more of the marble's impact and reduce the amount it bounces.
The ball would slightly graze the speed sensor due to different drops through the basket.
- We straightened out the track completely so that even little bounces wouldn't cause the ball to hit the speed sensor.
The elevator belt was getting jammed.
- We noticed some links weren't moving properly so we replaced them. We also lubed the wheel so the links would fit much more smoothly.
We needed to connect the lego wheel to the DC motor.
- We ended up laser cutting a part to fit the motor and wheel.
The ball was hitting the trampoline's outsides.
- We adjusted offset in programming to reduce error as much as possible.
The trampoline cart was not moving fast enough to reach the calculated position before the ball bounced.
- We removed as much weight as possible from the cart, and positioned it in an ideal place.
More than one ball was being released.
- We found and tested various lego parts and motor movements until one ball was released at a time.
The ball would either get stuck in the plinko board or fall off.
- We added rubber bands to act as walls.

Programming

The program was built off of the original ball drop code, with the first iteration of the code only having cart movement functionality. After completing the tuning of values for the code to work properly, the trampoline part of the code was, for the most part, completely finished. This then leads us to the second version which used multitasking to run the trampoline cart task and a task dedicated to the human interface with the ball launcher. This version was quickly scrapped in favor of a new version which was a complete reworking into a single task format. The third and final version of the code with major changes is illustrated in the flow chart below:

MiniSculpture v0.2.c

Results

We visualized our sculpture through Working Model 2D simulations, as shown below.

trampoline.mp4

Dispensor (1).mp4

Iterations

Throughout the week that we had to complete our Mini-Sculpture, we had several iterations, each building upon the one before. These iterations are fully explained below.

Version 1:

This version focused primarily on the trampoline and belt lift systems, without a complete omission of the launcher idea. The primary reason for this omission is the difficulty of using non-standard DC motors and parts to create a flywheel. This, and all versions after it, loops for easy testing. This version was particularly useful in fine-tuning the trampoline cart's movement.

Version 2:

The major change with this version comes with the development of the ball counting and dispensing system. Within this version came many trials to get the ball counting to work since the light sensor was initially having difficulty detecting when a ball passed by. However, by adding a box around the area with the light sensor we were able to control the light levels and make the measurements more consistent and easy to read. The dispensing system also took many versions to get correct, as the specific shape to consistently get only one ball through at a time with the limited lego pieces we were using at the time proved to be a challenge. Ultimately, this version sets us up to get ready to test with the flywheel.

Version 2.5:

As a side project to develop concepts of making static parts of the track more interesting, we built and developed a Plinko board. This part does not add any additional functionality to the mini sculpture, but it is important in developing an interesting part of the sculpture and in using the laserCAM skills developed earlier.

Final Version:

With this version, we finally added the launching mechanism with two flywheels. However, a lot of tuning is needed to improve the accuracy of the flywheel launcher as the flywheels kept vibrating and shifting the track after each launch.

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