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Students from the University of the North West submitted a project emphasising “green business” with their Waste Management System. The project showed great business acumen and covered most aspects of machine building.
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Competing Students - Hanno Snyman; Oswald van Ginkel
Email us for more information about these students or their Waste Managemement System.
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1. Introduction
Everyday more and more people are becoming aware of the need to recycle their waste. This is easy to do on a small scale, but there is a gap in larger implementations, such as a sport stadiums and entertainment venues. Typically all the trash from these types of venues gets gathered and then dumped into a single location without consideration for recycling purposes. Currently there are systems available for sorting trash, but by using innovative Festo and SEW Eurodrive products, we would be able to take waste management to the next level.
Imagine a system that does the same job as the best out there, but is a lot cheaper to build and uses less energy to do the same job.
2. The Design of the Waste Management System
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Our proposed machine is designed to sort bottles or containers according to four of the most common material types found in trash, for example glass, plastic, carton and tin.
For a machine to determine the type of element, it must perform a number of tests by checking the property of every item. All elements have unique characteristics, for instance the magnetism of ferrous metals or the lower density of carton.
We did some research to determine the kind of machines that are available to determine each element. Useful machines are x-ray scanners, infrared detectors and other light based distance and property measurement instruments, density testing machines and also sonar. The conclusion is that for a machine that only has to distinguish between four common elements, a lot of expensive energy consuming machines would have to be used.
So the question could be asked as how to simplify the sorting process in the long run. A very simple answer is, 'colour coding'.
If every element has a colour associated with it, for instance glass is blue and tin is red, then we can use a different inexpensive way of determining the element. If all bottles or containers get a colour ring at a certain height, then reading the colour will be possible.
The Festo colour sensor could be positioned in such a way that when the bottle moves by it on the conveyer belt, it will read the colour. Then the machine knows what type of material the bottle is made of. The next step is placing the bottle with similar material. This is achieved by using a pneumatic gripper that is mounted on a trolley that is powered by an electric motor.
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Overall Design of the Waste Management System
The Conveyor Belt
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2.1. The Conveyer Belt and Positioning Arms
The conveyer belt, powered by a SEW Eurodrive Movigear, is designed to transport the containers to the colour sensor and distance meter for sizing and finally to the gripper for sorting.
Before objects can be prepared for sorting, they must first be colour scanned, sized-up and orientated in such a way that they can be picked up easily. This can be achieved with the positioning arms. The positioning arms can be adjusted to suit a specific job as well. Any objects between 50mm and 300mm in diametercan be positioned with the positioning arms.
2.2. The Gripper and Pulley System
The gripper’s arms are designed to pick up objects that are lying down as well as standing upright. The arms have a rubber surface so that the objects can be picked up easily.
To achieve a high sorting rate, the trolley needs to move very fast. A consequence of a long, linear gripper module is that that the breaking mechanism of the trolley could generate substantial momentum (an estimated ~120Nm). A possible solution to this is placing eight wheels on the trolley, designed to clamp the trolley to the guiding rods.
The pulley system could ensure that there is a constant connection between the compressor and the linear module and gripper.
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Positioning Arms
The Gripper and Pulley System
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3. Unique Features
3.1. The Bottle Positioning System
Before every bottle is ready to be colour read and picked up, it must come to the colour sensor and gripper in a way that this task can be done successfully every time (the problem is that most bottles will probably be lying down on the conveyor).
The positioning arms are designed and situated in such a way that no matter how the bottle is placed on the conveyer belt, it will end parallel to the colour sensor and square to the gripper. With this design, colour reading, sizing and picking up the bottle can be achieved simply and easily.
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The Bottle Positioning System
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3.2. Colour Coding
Colour coding has been around a while, but using it to sort objects according to their element, we believe, is something new. This design could lower the cost and complexity of a sorting machine drastically. The energy usage is also significantly lower than conventional systems. The colour sensor is positioned along the left positioning arm, because all the objects have to pass it. The colour sensor is able to be adjusted up or down for optimum colour reading.
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Colour Coding Sensor
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3.3. The Pulley System
Why did we go so far as to design a pulley system that is a little bit complicated, instead of using the Festo spiral tube?
We know that the spiral tube could have handled the job, but we wanted to bring something into our design where the SEW Eurodrive and Festo products had to rely on each other to accomplish the job.
How it works: The same motor that operates the trolley is connected to the pulley that rolls up the air tube. Each pulley’s size in the pulley system was carefully determined. The end results are that the length of tube rolled down, is the same length the trolley car moves. The advantage of such system is that more than one wire, air or electrical, can be moved without getting entangled in the way of workers and thus being a health and safety hazard. The longevity of the cabling is also ensured. The system does it like clockwork and it is neat.
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3.4 Colour Positioning
This is the feature that makes the system versatile. Instead of pre-programming the trolley motor to stop when the trolley has traveled a certain distance, we make use of a colour positioning system. When the colour sensor on the conveyer belt reads a colour, for instance red, it sends that information to the colour sensor on the trolley. On the frame above every trash can, a colour card can be inserted that is easy to remove and replace.
The idea behind this is that when the trolley is transporting a red object, it reads the colour card above every trash can and compares it with the colour that was read earlier on the conveyer belt. When it reaches the red colour card, the trolley motor is stopped. With the colour positioning system, one trash can can be removed and the colour card could be inserted above another trash can and the sorting process could continue as usual. The design allows for the sorting frame to be made as long as required so that more than four trash cans could be placed next to each other.
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Colour Sensors and Positioning
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