Paper shredder
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==Functional Operation:== | ==Functional Operation:== | ||
There are three switches in the electrical circuit that must be activated to begin shredding. First, the shredder must be properly resting on the waste bin to toggle the safety switch, and then the off/auto/reverse switch that allows power to go to the shredder must be moved to "auto". Finally, the paper being put into the shredder compresses an air damper which trips the third switch and sends power to the AC motor. The damper slowly depresses and when it is fully extended the switch is released, terminating the shredding process. The AC motor drives a gear train that reduces the speed of the shaft rotation and increases the torque. The first two gears are helical gears in order to reduce noise. At the end of the gear train, two spur gears are meshed and attached to individual shafts with cross-hatching blades. The blades are in a wave shape that cuts paper into the desired diamond shaped shreds. The blades spin in opposite directions and the paper is fed in between the spinning blades. The shredded paper falls into basket. | There are three switches in the electrical circuit that must be activated to begin shredding. First, the shredder must be properly resting on the waste bin to toggle the safety switch, and then the off/auto/reverse switch that allows power to go to the shredder must be moved to "auto". Finally, the paper being put into the shredder compresses an air damper which trips the third switch and sends power to the AC motor. The damper slowly depresses and when it is fully extended the switch is released, terminating the shredding process. The AC motor drives a gear train that reduces the speed of the shaft rotation and increases the torque. The first two gears are helical gears in order to reduce noise. At the end of the gear train, two spur gears are meshed and attached to individual shafts with cross-hatching blades. The blades are in a wave shape that cuts paper into the desired diamond shaped shreds. The blades spin in opposite directions and the paper is fed in between the spinning blades. The shredded paper falls into basket. | ||
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==Media:== | ==Media:== |
Revision as of 00:59, 9 February 2007
Contents
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Purpose
The purpose of this information page is to analyze in entirety all manufacturing and working aspects of a paper shredder. Following the analysis, what is deemed the most crucial of all possible modifications will be prototyped. Our analysis will take into account Design for manufacturing and assembly as well as user considerations.
Product Study and Dissection
Conventional and Unconventional Purposes:
Shreds paper or credit cards placed correctly into feeder
- Increase security - not able to easily retrieve information from shredded items
- Facilitate disposal - reduce volume of garbage
- Substitute for a recycling bin - provide a seperate container for paper wastes
- Produce confetti - save money on party decorations
Inputs/Outputs:
- Material Inputs: Paper, Staples, Credit Cards (no ties)
- Information Inputs: Direction of motor rotation
- Energy Inputs: 120V AC
- Material Outputs: Shredded material inputs
- Information Outputs: Operation status
- Energy Outputs: Heat, Noise, Light
Stake Holders:
- Possible outsourced companies (computer chips, bulbs, motor)
- Raw materials suppliers
- Retail stores
- Transportation workers
- Stock holders
Operation Procedures:
- If stored without power cord plugged into electrical wall outlet
- Position basket in desired place (making sure it is close to an outlet)
- Place shredder assembly on top of basket
- Confirm the off/auto/reverse switch is in the off position
- Plug power cord from shredder assembly into the wall outlet
- If stored in the off position or continuing from un-powered storage
- Set off/auto/reverse switch to auto
- Identify the items for shredding, confirming acceptable destruction
- Documents(s)
- Credit Card
- Confirm dimensions of items to be shredded
- There is not more than a thickness of 8 pieces of paper
- There is not more than one credit card
- Orient items for better control when feeding them into the shredder
- Align documents
- Fold/unfold documents
- Orient credit card to be fed long-ways
- Confirm that the “ready light” is illuminated
- Feed item into proper opening
- Position document(s) in proper groove
- Position credit card in proper slot
- Action following feeding
- Let go of document(s) once feeder has caught them, allowing them to be pulled through automatically
- Continue pressing credit card downwards until no longer possible
- If finished shredding, return to desired storage conditions
- If placing in desired storage area
- Turn off shredder
- Unplug power cord from wall outlet
- Pick up shredder assembly or shredder assembly and basket, placing it where desired
- If leaving in desired spot
- Can leave in auto position, off position, or off position with power cord unplugged from wall outlet
- If placing in desired storage area
Specific User Considerations:
- Certain tasks difficult for people with a neural disorder and/or coordination difficulty
- Feeding tasks
- Switch control
- Bending over to feed items difficult for individuals with orthopedic (e.g. back) and/or balance problems
- Inconvenient and inefficient for large corporate tasks
- Main shredder assembly is heavy and possibly difficult to lift for weaker individuals
- Main shredder assembly must be lifted when emptying basket and setting up
- Main shredder assembly may often be moved depending on storage preference
Functional Operation:
There are three switches in the electrical circuit that must be activated to begin shredding. First, the shredder must be properly resting on the waste bin to toggle the safety switch, and then the off/auto/reverse switch that allows power to go to the shredder must be moved to "auto". Finally, the paper being put into the shredder compresses an air damper which trips the third switch and sends power to the AC motor. The damper slowly depresses and when it is fully extended the switch is released, terminating the shredding process. The AC motor drives a gear train that reduces the speed of the shaft rotation and increases the torque. The first two gears are helical gears in order to reduce noise. At the end of the gear train, two spur gears are meshed and attached to individual shafts with cross-hatching blades. The blades are in a wave shape that cuts paper into the desired diamond shaped shreds. The blades spin in opposite directions and the paper is fed in between the spinning blades. The shredded paper falls into basket.
Media:
For videos of user-trials and general operation, please visit the following: http://www.youtube.com/view_play_list?p=501153C70A89F93B
Components:
FMEA: Failure Mode and Effects Analysis
Item & Function | Failure Mode | Effects of Failure | S | Causes of Failure | O | Design Controls | D | RPN | Recmd Actions | Responsibility & Deadline | Actions Taken | S | O | D | RPN | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Motor
| Electrical failures: Short circuited | Product ceases to function reliably. Shredding no longer possible. | 8 | Intense heat and/or vibrations loosen connections, resulting in itermittant operation. | 4 | Run under extreme working conditions | 3 | 96 | Add solder to strengthen connections. Add dampening to decrease effect of vibrations | Motor manufacturer prior to purchase | - | 8 | 3 | 3 | 72 | |
Mechanical Failures: Wear. Fatigue. Fracture. | Inoperative. Noise. | 8 | Gear train shears helical gear. Thermal deformation from heat generation. Shredding unapproved items | 3 | Test at high rpm with strain gage and thermocouple | 5 | 120 | Treat motor axis to add strength | Motor manufacturer prior to purchase | - | 8 | 2 | 5 | 80 | ||
Main shafts | Mechainical Failures: Thermal. Creep. Corrosion. | Depending on degree of failure, blades may begin to clash or will function at a reduced capacity. Noise. Unstable. | 7 | Heat. Applied load from gear train. Shredding unapproved items | 2 | Feed solid items. Run under extreme conditions | 6 | 84 | Treat rod to increase strength. Increase diameter | Machinist(s) prior to installation | - | 7 | 1 | 6 | 42 | |
Helical gear | Mechainical Failures: Shearing. Thermal. Wearing. Plastic deformation to out of spec | Under complete mechanical failure, gear train will not be connected to the motor. Under partial failure, will have possible slippage which will result in inefficient operation and noise | 7 | Heat from motor. Vibrations. Forces from gear train. | 4 | Drive gear at high rpm and/or under intense working conditions | 3 | 84 | Thicker injection mold to make gear larger. Use stronger plastic. | Injection molder(s) prior to installation | - | 7 | 2 | 3 | 42 | |
Shredding cutoff time-delay
| Electrical failures: Short circuited | Product ceases to function reliably. Shredding no longer possible. | 8 | Intense heat and/or vibrations loosen connections, resulting in itermittant operation | 4 | Run under extreme working conditions | 3 | 96 | Add solder to strengthen connections. Add dampening to decrease effect of vibrations | Switch manufacturer prior to purchase | - | 8 | 3 | 3 | 72 | |
Mechanical Failures: Creep. Fatigue. Deformation. Shear. | 8 | Flat metal spring fatigues leading to fracture. Thermal deformation from heat generation. Plastic deformation from shredding unapproved items | 4 | Compress and expand spring repeatedly and under extreme conditions | 3 | 96 | Treat metal to strengthen. Increase thickness of spring. | Switch manufacturer prior to purchase | - | 8 | 2 | 3 | 48 | |||
Helical Blade | Mechainical Failures: Shearing. Fatigue. Thermal. Wearing. | Fracture of blade will result in inefficient, but continued, function. Bending of blade can result in wear against other blades, which can also result in a chain reaction leading to complete failure. | 7 | Bending and shearing can result from shredding unapproved items. Fracture and malfunctions can also result from malfunctions of other components such as the main shaft or gears. | 4 | Shred unapproved items. Work at high rpm. Shred lots of paper and/or credit cards | 5 | 140 | Thicker blades for strength. Smaller opening so unapproved items are harder to fit. | Blade stamping department | - | 7 | 2 | 5 | 70 |
DFX: Design for 'X'
DFE: Design for Environment
Possible Environmental Problems:
- Power usage
- Harmful products of manufacturing processes
- Pollution from production
- Leftover materials
- Odd shapes make it difficult to transport product
- Heat production
- Noise production
Possible Environmental Improvements:
- Use alternative energy sources (solar power)
- Use less power if possible
- Use recyclable/recycled materials
- Reduce amount of material used
- Add heat sink and bigger fan
- Add noise dampening materials to inside of shredder
- Make parts shaped such that as many stamped parts as possible can be stamped on one sheet
- Make stackable parts
- Use leftover materials for other parts
DFMA: Design for Manufacturing and Assembly
DFA
- Clear Subassebmlies (Modularity)
- Plastic housing used as base for other components
- Pieces fit together and mate without fasteners
- Base has nesting features
- Base webbed to increase rigidity
- Electrical assembly is held between the top and bottom covers. This speeds up assembly by eliminating fasteners.
DFM
- Clever stamped blades allow for cross cutting and are cheap to manufacture vs. cast or machined blades.
- Most parts made by injection molding or stamping.
- No complex metal or plastic pieces.
Possible Areas of Improvement
- There are about 50 seperate blades which need to be put onto a shaft. It would be better if the blades were joinded together first then slid onto the shaft.
- Feeder lips made from two pieces. This could be redesigned to just one piece.
Design for Maintainability
- Blades are coated to resist corrosion
- Easy to assebmle and dissassemble
- Fasteners are repeat use, meaning screws are used instead of rivets or snap fasteners.
- Design is modular, parts are easily accessible.
- Overall design of product is simple
Design for Reliability
- White paper aligners ensure that paper is fed straight through blades
- Blades have notches on them that catch the paper to feed it through consistently
- The gears are very well lubricated to ensure consistent, quiet meshing
- Tolerances in the manufacturing of parts for proper alignment
- Blades appear to be corrosion resistant
Design for Safety
- The on/off/reverse switch is "child-proof."
- The user must press a button and slide the switch in order to move it.
- There is a protective cover over the blades so that fingers cannot fit inside the paper slot but paper and credit cards can.
- Electrical components are housed inside of the shredder.
- Shredder has a safety switch that does not allow shredding to occur unless the shredder is on basket.
- When shredder is on for a prolonged period of time, it shuts off auotomatically for a fixed amount of time for motor to cool.
Design for Usability / ergonomics
- Shredder mounts easily on top of basket
- On/off/reverse switch is on top of shredder for easy access
- Shredder has convenient slot for paper and convenient slot for credit cards
- Basket height is such that it can hold alot of paper but still fit under the user's desk
- Lightweight and portable
Design for Variety (product families)
Modification:
Areas of Possible Improvement:
- Improved shredding capability for added security
- Rotary blade in which confetti is funneled into
- Pulp making apparatus
- Water jet (maybe acetone)
- Stirrer
- Decrease heat generation (when shredder overheats, safety mechanism kills motor till it has cooled significantly)
- Fan and vents
- Way to empty basin without taking off top
- Wall-mounting capabilities
- Weight issues of shredder assembly which affect portability, sotrage, and emptying waste basket
- Use a lighter material than machined steel for main rods
- Titanium
- Plastic
- Composite
- Smaller motor
- Lighter blades
- Composite
- Titanium
- Use a lighter material than machined steel for main rods
- Decrease noise pollution of system
- Line shredder with sound-dampening material
- Foam
- Line shredder with sound-dampening material
- Improved feeding capabilities
- Large queue where can position multiple sheets that will automatically feed
- Examine a printer and fax feeder