Team I: Prius

Ryan M. Pocratsky / Mechanical Design, Fabrication, and Assembly
Manasi K. Patil / Electrical Circuit Design and Fabrication
Sruthi Reddy Chintakunta / Controls and Microcontroller Programming
Shrey Aggarwal / Assembly

Project Specifications
·         Overall volume should be less than 8 ft3  
·         Dumping 10 cans in 10 seconds or less
·         Compression ration greater than or equal to 3
·         Crush 10 cans in under 2 minutes

Main design concept
The overall objective of this project is to make an aluminum can recycler for standard 12 fluid ounce cans. There are three main steps that need to be implemented: input of cans through a hopper to the crusher, crushing of the cans, and output of cans to a container.  Figure 1 shows the primary components inside the system.

Figure 1: System from inside the box and below the hopper
System Overview
Our system is subdivided into three subsystems: the hopper, chute, and crusher.

For the input mechanism, we used a hopper made out of galvanized sheet metal, with a 2 ft. by 2 ft. mouth, as seen in Figure 2. The hopper funnels towards one corner where there is an opening large enough for one can to enter the system. Above this hole is a sheet metal cover that prevents cans from stacking on-top of each-other and jamming at the hole.  A vibrating motor is attached below the hopper to help to cans move down the hopper into the chute quickly.

Figure 2: Hopper, on the top face of the can crusher
To ensure that only one can enters the crusher at a time, two pull-solenoids are used as gates in the chute. One is placed at the end of the chute before the crusher and the other is placed one can length above this solenoid inside the chute, as seen in Figure 3.  Solenoid Gate 1 is used to separate one can from the other cans in the chute.  Then, solenoid gate 2 is retracted long enough for the single can to fall into the crushing area.  If the first gate was not there, the retraction time required to allow only one can into the crushing area would be dependent on the number of cans in the chute.  Multiple cans in the chute apply additional force to the can behind gate 2, which cause it to fall faster than if one can was in the chute.  Implementing two solenoid gates makes the can delivery system perform more consistently, independent of the number of cans in the system.

Figure 3: Chute and solenoid gate positions
A sensor at the end of the chute indicates when a can is ready to be put into the crushing area.  Figure 4 shows the sensor and solenoid gate 2.  This sensor is used to indicate the position of the can in the system, which is used to control the state of the device.

Figure 4: Solenoid gate and light sensor at the end of the chut
For crushing we decided to use a pneumatic cylinder to supply the necessary pressure to crush a can because of its speed and simplicity. The can crushing area is shown in Figure 5.  The pneumatic cylinder selected has a force rating of 61 pounds at a supply pressure of 100 psi, with a maximum operating pressure rating of 250 psi. The supply pressure we used for the device is 125 psi.  Since the can will be under dynamic loading, the effective force of the cylinder will be approximately three times the rated force.  A force of 180 pounds is sufficient to crush a can. 

However, our experimental results indicate that the piston needs to actuate twice to reduce the can volume to the desired amount.  As the can is crushed, the piston is decelerating.  This causes the force applied to transition from dynamic loading to static loading.  Once crushing is initiated, a force greater than 61 pounds is required to crush the can to a third of its original volume.  Since the pneumatic cylinder actuates and retracts in less than a second, the time required to actuate twice is minimal compared to the given time requirements.
Figure 5: Crushing area showing the sensors and output hole
The cans are output through a hole in the base of the device, as shown in Figure 5.  Once the can is reduced to the desired volume, it falls through the opening.  Additionally, a safety sensor is located in the output hole to stop the system if anyone reaches into the system from the output hole.

How the System works
The flow chart of the system is shown in Figure 6.

Figure 6: General Flow Chart of the system
The flowchart above gives a basic overview of how a can thrown into the hopper will travel through the different subsystems to be crushed to a third of its original size.  While a can is being crushed, the system stops the motion of cans through the chute.

Safety Features
There are two safety features on the device, the output sensor and the shut-off switch.  As described above, the output sensor prevents the system from processing cans if an object is inserted in the output hold.  The shut-off switch kills power to the solenoids in the system.  The default of the pneumatic solenoid is closed, so the pneumatic actuator will be connected to the exhaust port.  Therefore, killing power to the solenoids will cause the piston to retract and prevent cans from traveling down the chute.


No comments:

Post a Comment