Paint Delivery Mechanism

What it was:

No change from Idea 2. However we decided not to use it for our next revised design (Design 4)

Why we changed it:

Given the availability of robust pump systems already in the market to transfer paint directly from the gallon to the nozzle, we decided that it would make more sense to buy a product from the market despite it’s cost. The spray gun of a commercial airless pump was also much lighter than a handheld paint sprayer and hence would allow for the use of smaller motors.

Vertical Movement Mechanism:

What it was:

In order to increase stability, we decided to use a scissor lift system instead. There were two variations of this that we explored. 

#1 A mini scissor lift, where the spray gun would be on the lift platform (Fig 1). The horizontal contraction of the scissor lift will be done using a piston pump system (Fig 2).

 

#2 A pulley system together with the lift. The scissor lift would extend to the entire length of the wall. Thereafter, a secondary platform (green) will be lowered from the top of the scissor lift. The platform will move up and down using a pulley system. The spray gun would be placed on the secondary platform. This is to minimise energy expenditure and increase precision as the scissor lift would require more energy to extend and retract

Why we changed it:

This method had too many components and would not be feasible to build in 3 months. It also required a larger number of motors, and had many hanging parts which would be difficult for the consumer to assemble. We decided that our mechanism in idea 4 would be more cost effective, efficient and simple than this idea. 

Base Mechanism

What It WAS:

We decided on using mecanum wheels as they allow the robot to move left & right, up & down, and rotate. Mecanum wheels (Fig 4), are omni directional wheels designed to allow the robot to move in any direction due to its ability for each wheel to turn independently. To move side to side, pairs of wheels oppose one another, acting like a worm gear. Each wheel would also be connected to its own motor, using hubs. As for the motors, we decided on stepper motors due to its ability to offer precision which we initially thought would have been a necessary function. 

why we changed it.

Given the fact that our painting robot would primarily only need to move in one direction, right to left while painting, it would not add much value to have the robot be able to rotate, and move front and back. Mecanum wheels are also expensive and controlling these wheels would require extensive coding. After much discussion we decided that the cost was greater than the value added. Hence, we decided on using simple unidirectional wheels for our robot to complete the task that is required.