Paper towel dispenser

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Contents

Executive Summary

Paper towel dispensers are used in the majority of public restrooms, the main alternative being a hot air blower. There are several types of dispensers available. The three most common types are infrared sensor dispensers that lowers a length of paper when it detects a hand motion, hand-lever-powered dispensers that lower a length of paper for each pull of a mechanical lever and lastly, the most common on the Carnegie Mellon Campus, is a dispenser where the user pulls on a hanging paper towel and a sheet is cut and available for hand drying.

The third dispenser is the one being analyzed for the purposes of this report, a Kimberly-Clark In-Sight Sanitouch Hard Roll Towel Dispenser. The report will begin with the basic functionality of the paper towel dispenser and a catalog of all the parts included in the total assembly. We evaluate the design of the dispenser by conducting Design for Manufacturing and Assembly (DFMA), Failure Mode and Effects Analysis (FMEA) and Design for Environment (DFE) and Mechanical Analysis (MA) analyses.

In the DFMA we concluded that for the most part the manufacturing and assembly processes were efficient, but some parts (such as the spindle housing) were unnecessary or used too much material. We also concluded that outsourcing the assembly process in an attempt to increase units and decrease selling price was something that needed to be considered.

In the FMEA we concluded that a few of the parts could result in a failure in the cutting mechanism.

In the DFE we concluded that most of the pollutants such as toxic waste and greenhouse gases, come from the generation and supply of energy. Another consideration is the plastic used in the dispenser and whether it is possible to recycle it after its life cycle. The paper towels are also very wasteful and costly, unless there is a way to recycle them or use paper overall.

In the MA we condluded that the combination of springs in the paper towel dispenser provide a resistant torque of 2.2 lb-in. The paper towel dispenser requires a minimal amount of force that can be applied by all types of users (children, elderly, etc.).

Stakeholders

There are six major stakeholders with regards to the paper towel dispenser: Manufacturer, retailer, customer, user, society. The main needs for the manufacturer are to reduce cost and create a reliable product. For the retailer, it is being able to sell a quality product. For the customer, it is making sure it is an affordable and reliable machine. For the user, cleanliness and ease of use are paramount. For the maintenance worker, ease of opening and replacing the paper towel are important. Society plays a role with regards to how the use of paper towel affects the ecosystem and earth in general. Listed below are the stakeholders and their respective needs.


Retailer

  • Storage
  • Reliability
  • Usability
  • Transporting
  • Protection against vandalism
  • Security against theft


Customer

  • Cost
  • Ease of installation
  • Ease of use
  • Reliability
  • Aesthetics
  • Safety


User

  • Ease of use / ergonomics
  • Speed of operation
  • Aesthetics
  • Cleanliness - making sure the machine does not spread germs
  • Safety


Maintenance Worker

  • Ease of towel replacement
  • Detection of empty roll
  • Ease of installation
  • Safety


Society

  • Environment
  • Reduction of paper towel use

Product Function

Objective

To provide a simple and effective way of obtaining a paper towel slip to dry your hands.


How to Operate

With both hands, pull straight down on the exposed part of the paper towel to operate and turn the spindle. If the dispenser is jammed and there is no exposed paper towel area to grab, locate the red knob on the right side of the product and turn it towards you.


How the Dispenser Operates

As you are pulling down on the paper towel, the spindle rotates along with it because if the friction created by the rubber skin over the spindle. Two springs are attached to a lever which is attached to the end of the spindle. When the spindle turns, the lever also turns to cause the springs to elongate. While this is occurring, there is also another piece attached to the spindle that provides the cutting function. It is a rod with a roller that follows a track created by the side panels that the spindle is attached to. When the roller meets a certain point on the track, it causes the cutter to rise out of the spindle for a moment to cut the paper towel. The cutter then returns its non-operating state when the roller comes to another point on the track that forces the cutter back in. Keep in mind that this is all occurring as the paper towel is being pulled by the user and the springs are still being displaced. As the springs come to its maximum displacement, it begins to retract quickly to make a nice swift cut. The process then continues until a jam occurs or until the paper towel roll becomes empty.


How to Replace Paper Towels when Roll Becomes Low or Empty

1. Use the Y-shaped key to unhinge the top of the dispenser.

2. Open the front housing to reveal the inside compartment.

3. Place a new paper towel roll with the towel faced inside (touching the back housing). Open the blue spindle housing by unhooking the plastic tabs.

4. Clip the paper towel to the white tube guide and turn the red knob towards you one revolution.

5. Remove the paper towel from the clips, pull it around the spindle drum, and feed it through the bottom thin paper guide.

6. Close the blue spindle housing and the main front housing and the product is ready to be used.

1. Use Key to Open Cover
1. Use Key to Open Cover
2. Inside Compartment
2. Inside Compartment
3. Open Blue Spindle Cover and Load Roll with Towel Faced Inside (cover is removed for usability ease)
3. Open Blue Spindle Cover and Load Roll with Towel Faced Inside (cover is removed for usability ease)
4. Clip the Paper Towels and Turn the Red Dial One Revolution
4. Clip the Paper Towels and Turn the Red Dial One Revolution
5. Remove Paper Towel from Clips and Pull it Around the Spindle and Feed Through Thin Paper Guide
5. Remove Paper Towel from Clips and Pull it Around the Spindle and Feed Through Thin Paper Guide
6. Close Cover (ready to use)
6. Close Cover (ready to use)


How the Spring Mechanism Attached to the Spindle Works

Initial State
Initial State
Quarter Turn (Spring being stretched)
Quarter Turn (Spring being stretched)
Half Turn (Maximum Spring Displacement)
Half Turn (Maximum Spring Displacement)
Final State (Returning to original state)
Final State (Returning to original state)

Please refer to Assembly Picture: Left Spindle Housing

Usability Study

After using and inspecting numerous paper towel dispensers in public restrooms on the Carnegie Mellon campus, we have encountered a few issues that have been suggested.


General Use

  • Paper towel gets jammed or stuck on the dispenser which requires to turn the red knob.
  • Paper towel portion is cut too short.
  • Should implement a paper towel replacement when the first roll is running low.
  • Pulling with one hand sometimes did not work.
  • Pulling too soft did not cut the paper towel.
Jammed Roll
Jammed Roll
Short Portion
Short Portion
Incomplete Cut
Incomplete Cut

Replacing the Paper Towel Roll

  • Ambiguous loading instructions.
  • Paper towel roll must be oriented the right way.
  • Difficult to feed paper towel roll through white tube guide.
  • May have problems aligning paper towel to be straight.
Ambiguous Loading Instructions
Ambiguous Loading Instructions

Mounting the Paper Towel Dispenser

  • Template to drill holes was included in the manufacturers box
  • Relatively simple and easy to mount
Mounting Instructions
Mounting Instructions
Mounting Template
Mounting Template


Please consult the following link for videos on how to replace the paper towel roll, mounting and paper towel dispenser, and other insightful videos on general use:

http://www.kcprofessional.com/us/download/dispensers/lm-videos/menu_str.swf

Assembly Pictures

Inside Compartment (Front View)



Left Spindle Housing


Mechanical Analysis

In Mechanical Analysis, we decided to determine the amount of force that is required to advance the paper towel roll one sheet. In turn, we can determine the amount of torque that is exerted as a resistance Torque inside of the paper towel dispenser. This resistance torque includes torques created by friction in the center of spindle, and also 2 even springs. Also, we found relationship between angle of rotation of spindle and torque required to advance further.


Free Body Diagram

Image:FBD_PTD.jpg

  • F pull: force exerted on the spindle to rotate
  • T resist: torque created by even hooked springs and friction in the center of spindle
  • Radius: 0.05m


Method

In order to find the relationship between angle of rotation of spindle(theta) and torque required to advance, we incremented theta by 45 degrees and reported forces. To find force, we attached a reference spring to the end of sheet of paper towel and pulled to measure the stretch of spring. Then we multiplied spring constant to change in length of the spring to calculate force required for specific angles. We measured the reference spring constant, by hanging a known mass(0.600 kg) onto the reference spring and dividing Force of mass due to gravity by the difference between the initial length and stretched length of the spring. Finally, the forces were multiplied by radius of spindle(0.05m) to give torques.


Calculations


Determination of Reference Spring Constant

  • Initial length = 0.023 m
  • Length stretched when 0.600kg mass attached = 0.059 m

=> Reference Spring Constant = 0.600(9.8)/(0.059-0.023) = 163.3 N/m


State identification

The spindle was incremented by 45 degrees rotationand forces are measured at each state .

State 1: initial state State 2: 45 deg turn State 3: 90 deg turn
State 4: 135 deg turn State 5: 180 deg turn State 6: 225 deg turn
State 7: 270 deg turn State 8: 315 deg turn State 9: 360 deg turn


Summary of Data Analysis

This table summarizes data collected at each stated for calculating torques.

Image:PTD_table.jpg

Where:

  • Delta xi = Spring Lengthi - initial length = (Spring Lengthi) - 0.023) m
  • Forcei = (163.33)(Delta xi)N
  • Torquei = (0.05*Forcei)Nm

The maximum force was found out to be 6.860N and torque be 0.343Nm both occuring at when theta is 90 degrees from initial state.

Plot of Torque vs. theta

This plot shows relationship between Torque and theta. The plot implies that the relationship is much like a sine graph. Before reaching the maximum force, the force required is positive(spindle resists rotation in the direction of pulling) but after the maximum force, the force required goes to negative (spindle automatically rotates in the direction of pulling as even hooked springs contracts). This cycle continues every rotation.

Image:PTD_plot2.jpg


Mechanical Analysis Conclusion


As a result, the combination of springs in the paper towel dispenser provide a Maximum resistant torque of 0.343 Nm which occurs when theta is 90 degrees from initial state. In conclusion, the paper towel dispenser requires a minimal amount of force that can be applied by all types of users (children, elderly, etc.). For improvements, some possibilities may be to have different spring constants so it could be even easier, or possibly making the towel advance more after a towel has been pulled, so the next one is easier to grab.

Parts List

Part No. Name Function QTY Weight Material Manufacturing Process Image
01 Front Housing Protects device from exterior 1 935g Plastic Injection Molding
02 Front Housing Clip Holds housings together 1 13g Steel Bending, Punching
03 Front Housing Tab Secures housing clip 1 <1g Plastic Injection Molding
04 Rear Housing Holds mechanical components 1 986g Plastic Injection Molding
05 Paper Towel Holding Arm Holds paper towel roll 2 40g each Plastic Injection Molding
06 Phillips Head Screw (1/8 x 1/4 long) Secures device to rear housing 1 1g Steel Machined
07 Wall Mounting Screw (1/8 x 1.25 long) Secures housing to wall 4 3.5g each Steel Machined
08 Screw Anchor Holds screw in wall 4 ~0.25g Plastic Injection molding
09 Paper Guide Tube Guides paper towel to cutting cylinder 1 55g Plastic Injection molding
10 Spring (uneven hooks) Holds 09 in place 2 2g each Metal Extrusion
11 Spring (even hooks) Holds lever to spindle housing 2 1.5g each Metal Extrusion
12 Screw (3/32 x 5/8 long) holds turning wheel and lever to spindle housing 2 ~1g each Metal Extrusion
13 Red Screw Cap Hides screw in turning wheel 1 <1g Plastic Injection molding
14 Locking Spring Ensures correct wheel spin direction 1 4g Steel Extrusion
15 Red Turning Wheel Turns main spindle 1 30g Plastic Injection molding
16 Guide clips for 09 Guides paper on 09 2 2.5g each Plastic Injection molding
17 Screw (3/32 x 3/8 long) Holds lever assembly together and spindle housing 2 <1g each Metal Machined
18 Lever Arm Connects spring to spindle 1 1g Plastic Injection molding
19 Spring Connector Connects two springs to lever arm 1 <1g Plastic Injection molding
20 Rounded Spring Guide Angles spring to desired measurement 1 <1g Plastic Injection molding
21 Thin Paper Guide Guides paper out of device 1 24g Plastic Injection molding
22 Spindle Housing Front Final housing before paper leaves device 1 132g Plastic Injection molding
23 Spindle Housing Back Back of spindle housing 1 162g Plastic Injection molding
24 Spindle Housing (L) Left of spindle housing 1 105g Plastic Injection molding
25 Spindle Housing (R) Right of spindle housing 1 105g Plastic Injection molding
26 White Spindle Guide Holds spindle in line 3 2.3g each Plastic Injection molding
27 Screw (3/32 x 3/8 long) Connects spindle halves 2 <1g Metal Machined
28 Square nut For use with 27 2 <1g Steel Cast and drilled
29 White Teeth Guide/Arm Guides cutting teeth in spindle 2 3g each Plastic Injection molding
30 Cutting Teeth Cuts paper towel 1 75g Steel Cast, punched and bent
31 Spindle Top Half Holds cutting tool 1 125g Plastic Injection molding
32 Spindle Bottom Half Holds cutting tool 1 135g Plastic Injection molding
33 Metal Key Helps open housing 1 5g Steel Punched

DFMA Analysis

There are several different manufacturing processes involved. Most of the components in the paper towel dispenser are made of plastic so injection molding is the most common manufacturing process. There are still some metal parts used, those are manufactured through punching, stamping and bending processes.


Design For Manufacture

Housings

The various housings, as with many of the components of the paper towel dispenser, are made out of plastic. Even though the types of plastic are different for the different housings, the manufacturing process is the same: injection molding. As mentioned earlier, injection molding is the primary manufacturing process used in the paper towel dispenser. The evidence for injection molding is quite visible, there are multiple points for the plastic to be injected into a mold as well as vents. Each of the housings would have been molded independently and it does not appear that several of the same type of housing were molded together and then separated. The sides of the housings have been manufactured without any notable imperfections

Most of the housings are produced using sensible methods. The spindle housing (Part 22), however, uses far too much material.

For almost the entire lifetime of the dispenser, the spindle housing will not be exposed to anything outside the product because the front housing protects everything on the inside. The front housing is usually removed to change the paper towel roll and when this happens, the spindle housing is also removed. Therefore there is no economically justifiable reason to manufacture the spindle housing.

We tested the dispenser without the spindle housing attached to determine if it could function correctly without a part that we suspected was unnecessary. From our tests we observed that the paper made its way through the device exactly the same way as it would with the spindle housing attached. From our observations we are concluding that the spindle housing is not needed.

The spindle housing holds three plastic guides that prevent the paper towel from sliding off the spindle. These three guides could easily be held (in the same position and orientation as it is when connected to the spindle housing) by a thin bar that attaches to the left and right spindle housings.

Springs

There are several springs used in the paper towel dispenser. The springs are most likely manufactured from a separate company and purchased by Kimberly-Clark. Most springs are manufactured by coiling a stiff wire, hardening through heat treatment and finishing the spring by adding connection hooks to the ends. The hooks were produced through a bending or curling process. Seeing as how these springs are mass produced, the entire manufacturing process would be conducted by machinery.

Seeing as how the springs are most likely purchased from a separate vendor and are already very inexpensive, no change needs to be made in the manufacturing process.

Metal Clips and Cutting Teeth

The metal clips and cutting teeth were punched out of metal sheets and then shaped through a bending or stamping process. The punching process is easy to see as there is visible evidence with rough edges and corners of virtually all metal components. Even though steel is a very strong material, thin sheets are very easy to mechanically bend and stamp. The bending and stamping processes require a considerable force (though this is not a major concern because it is conducted by machinery) they do not jeopardize the physical properties of the material to a point where it would impact the reliability or use of the product.

Punching, stamping and bending are simple and efficient manufacturing processes, in terms of both cost and time, as there is no complicated casting involved and no expensive mold needed. The manufacturing of the metal clips and cutting teeth does not need to be improved.

Intricate Plastic Components

The remaining plastic components are manufactured using injection molding. These components are considerably more difficult to manufacture as they have geometries that can only be produced through injection molding. Since the moldings are not very straight forward, they would be more expensive than the simpler moldings for the housing.

This is a complicated, economically inefficient process and it is the most expensive of all the components manufactured. Several of these components are unnecessarily complex, leading to expensive molds for injection molding.


DFM Guidelines

For the most part, the designers of this paper towel dispenser used good DFMA guidelines. DFM guidelines were applied in minimizing part count, keeping the design simple and ease of fabrication. The following is a list of the relevant applications of DFM guidelines that could have a noteworthy impact.

  • Minimize Part Count: This paper towel dispenser has several parts, as can be seen in the parts list mentioned earlier in this report. That being said, all the parts included serve a purpose that improves some aspect of the product. Very few fastners are needed as almost all of the plastic components can clip or snap into place without screws.
  • Standardize Components: Many components on the left and right sides are the same, but there are some areas where this could be improved. For example, the paper towel holders could be modified so there would be the same exact part on both sides. This would help to reduce cost because only one mold/machine would be needed to produce both sides.
  • Keep Designs Simple: The overall design is much more complicated than many other paper towel dispenser designs. However, the Kimberly-Clark model we chose to analyze is much more reliable than other dispensers and it is because of the more complex design. It would be hard to develop a simpler design that met the performance and reliability levels from this model.
  • Ease of Fabrication: Plastic is the ideal choice of material for the product because it is lightweight, strong enough and can be easily molded into the various geometries needed. For example, the housings need to be strong enough to manage day-to-day wear as well as be molded into unusual shapes. A tough plastic is an ideal material choice for this application.
  • Tight tolerances: Some of the pieces that snap into each other, such as the paper towel holders into the top of the left and right spindle housings, must be precisely placed or they will not connect. Tight tolerances are needed because slight imperfections will make it different for connections and this may cause an avoidable increase in price.

Overall, the designers applied the DFM guidelines reasonably well. There are some areas for improvement such as using the same part on the left and right sides of dispenser and possibly decreasing the tolerances on the places where the plastic components snap together. It is clear that the designers took manufacturing into consideration, but there is certainly significant room for improvement.



Design For Assembly

Kimberly-Clark paper towel dispensers are made in the United States of America. The assembly process is not simple. As the Parts List shows, there are many different parts and many different steps required to fully assemble the device. If any of the smaller pieces, such as the springs, are incorrectly assembled the system will not function properly. The customer purchases the dispenser fully assembled (with the exception of the mounting) so it must be in perfect working order. The customer will most likely not attempt to use the dispenser until on-site installation is completed. Customers and users will most likely be unable to fix any mistakes in the assembly process because the device, as visible below, is complex and can be confusing for someone who is not familiar with it.

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It is for this reason that Kimberly-Clark would have decided to assemble the paper towel dispensers in the USA where there is higher skilled labor than east Asia and there will be minimal transport cost as they are distributed from the USA as well.

Even though the mechanisms within the main assembly can be quite confusing at first glance, our team was able to decipher how everything worked after taking it apart. Based off of our groups disassembling experience, an assembly plant worker would be able to confidently assemble the entire product within a day or two of training.

The assembly process is most likely cost efficient as Kimberly-Clark should have done significant research into the different associated variables. It is important to consider moving the assembly overseas because labor is much cheaper in places like east Asia and South America. Paper towel dispensers are much more expensive than one would guess, so whether outsourcing assembly would increase profit by decreasing price and increasing units sold is something that needs to be considered.

DFA Guidelines For the most part, the designers of this paper towel dispenser used good DFMA guidelines. DFA guidelines were applied in minimizing part count, using subassemblies, being mistake-proof and minimizing fastners. The following is a list of the relevant applications of DFA guidelines that could have a noteworthy impact.

  • Minimize Part Count: There are several parts, but they are necessary for the performance and reliability of the product.
  • Use Subassemblies: The spindle is designed and assembled as a subassembly which significantly improves ease of assembly.
  • Mistake-Proof: Plastic components fit together in a very obvious fashion. We were able to disassemble and reassemble the dispenser without using any sort of guide or instructions.
  • Minimize Fastners: Most pieces snap into place without any extra pieces (nails, screws, etc.)
  • Provide Unobstructed Access: If the dispenser is assembled in a logical order it there will not be any issues with unobstructed access. However, if a mistake is made it could require the person assembling the device to take apart the dispenser to make a connection.

It is easy to see that the designers took the assembly process into consideration. Despite having a lot of parts and a relatively complex product to assemble, the designers were able to create a design that required a simple assembly process.

FMEA Analysis

Failure mode and effects analysis (FMEA) identifies potential problems of every component in the machinery, lists their effects on the system, and finally provides recommended actions to prevent such failures. The methodology for problem identification depends on ratings of Severity of a failure (S), Occurrence of Failure (O), and Detection of Failure (D). These scales are between 1 and 10 and they are rated in a way that less number of ratings indicates less significant problem and conversely higher rating means more serious failure or effect. The results of a FMEA Analysis (RPN) are calculated by multiplying S, O and D to signify seriousness of the problem.

Conclusion

Since our machine is a simple and easy mechanism, it does not require a significant amount of force to operate. Thus, it does not involve any component that undergoes serious stress or force, and under proper usage the mechanism is rigid enough: most parts have low Occurrence of Failure rating. Moreover, it is found that severity of failure of most components is low, but in cases of components with a high severity of failure, the detections are made easy (low Detection of Failure rating), keeping RPN rating to a small number. In conclusion our FMEA analysis, not many parts with high RPN, indicates the mechanism overall is reliable and we found only a few issues.

One issue we did find was the if the cutter was not perforating the paper. We found the culprit to be Part 10, the uneven springs. In the case we find, these springs were missing, which did not allow the paper towel guide (Part 09) to push down on the paper. This, in turn, did not provide enough force to keep the paper towel taught, and ultimately to perforate the paper.

Another issue we found, was a case where one of the Spring 11 were missing. In fact, the paper towel dispenser worked fine even with only one spring, meaning that the second spring may provide more force on a different part of the rotation of the spindle, but the single spring provides enough force to make it complete its rotation. Another consideration is if the spring is stretched quickly (i.e. a user pulls to fast) it often occurs that the next sheet of paper recedes back into the machine. We figured this is why the knob is needed on the side, which is a reliable solution to that problem. Also, pulling at different angles does not affect the way the paper leaves the spindle or gets cut. This is because the thin paper guide is there to make sure the paper is coming straight down off the spindle and not at an angle.

We found these occurrences to be very low in our observations of campus paper towel dispensers. Also, the detections are relatively high for the failure of Part 10.



Part No. Name Function Failure Mode Effects of Failure S Causes of Failure O Design Controls D RPN Recommended Actions Responsibility
01 Front Housing Protects device from exterior Fractures, Warped
  • Exposure of internal components
  • Possible injury to customer
7
  • Improper handling
  • Improper manufacturing
4
  • Material selection
2 56
  • Drop test
Reliability


02 Front Housing Clip Holds housings togetherBends
  • Housings fell apart
4
  • Improper handling
  • Improper assembling
2
  • Material Selection
  • Packaging
648
  • Select a stiffer material
Assembly and Reliablity


03 Front Housing Tab Secures housing clip Strips
  • Housing clip exposed
2
  • Improper assembling
  • Improper manufacturing
2
  • Material selection
  • Mold design
832
  • None
Assembly


04 Rear Housing Holds mechanical components Fractures
  • Unable to hold mechanical components
7
  • Improper handling
  • Improper manufacturing
4
  • Material Selection
1 28
  • Drop test
  • Select a stiffer material
Reliability
05 Paper Towel Holding Arm Holds paper towel roll Bends
  • Unable to hold paper towel roll due to misaligned components
6
  • Improper handling
  • Improper manufacturing
  • Incorrect design
3
  • Material selection
  • Mold design
236
  • Select a flexible and elastic material
Assembly and Manufacturing
08 Screw Anchor Holds screw in wall Fractures
  • Unable to hold mechanical components
  • Possible injury to customer
7
  • Improper handling
  • Poor upkeep
2
  • Material selection
456
  • Select a reliable material
Reliablity
09 Paper Guide Tube Guides paper towel to cutting cylinder Failed
  • Unable to hold paper towel stick to spindle
4
  • Improper manufacturing
3
  • Material selection
  • Mold design
224
  • Select a stiffer material
Manufacturing
10 Spring (uneven hooks)Holds 09 in place Deformed
  • Malfunctioning of mechanical spindle
8
  • Fatigue
2
  • Material selection
  • Improper assemblying
5 80
  • Select a stiffer material
  • Reduce stress on spring
  • Secure spring better
Assembly and Reliablity
11 Spring (even hooks) Holds lever to spindle housing Deformed
  • Malfunctioning of mechanical spindle
5
  • Improper handling
  • Fatigue
  • Improper use
5
  • Material selection
  • Improper assemblying
4 100
  • Select a stiffer material
  • Reduce stress on spring
Assembly and Reliablity
14 Locking Spring Hides screw in turning wheel Deformed
  • Unable to confine rotation direction of spindle
3
  • Improper handling
  • Fatigue
2
  • Material selection
  • Improper assemblying
4 24
  • Select a stiffer material
  • Reduce stress on spring
Assembly and Reliablity
16 Guide clips for 09 Guides paper on 09 Break
  • Unable to hold paper towel stick to spindle
4
  • Improper manufacturing
  • Improper design
3
  • Material selection
  • Mold design
224
  • Select a stiffer material
Assembly and Manufacturing
18 Lever Arm Connects spring to spindle Breaks
  • Malfunctioning of mechanical spindle
5
  • Improper handling
  • Improper manufacturing
2
  • Material selection
220
  • Select a stiffer material
Manufacturing and Reliablity
19 Spring Connector Connects two springs to lever arm Breaks
  • Malfunctioning of mechanical spindle
5
  • Improper manufacturing
  • Improper assemblying
2
  • Material selection
  • Mold design
330
  • Select a stiffer material
Assembly and Reliablity
20 Rounded Spring Guide Angles spring to desired measurement Breaks
  • Unable to adjust spring to a desired angle
2
  • Improper handling
  • Improper manufacturing
2
  • Material selection
728
  • None
Manufacturing
21 Thin Paper GuideGuides paper out of device Breaks
  • Paper ejected in inconsistent direction
  • User dissatisfaction
4
  • Improper handling
  • Improper manufacturing
3
  • Material selection
112
  • Select a stiffer material
Manufacturing
22 Front Spindle Housing Final housing before paper leaves device Fractures
  • User dissatisfaction
3
  • Improper assemblying
  • Improper manufacturing
2
  • Packaging
  • Material selection
  • Mold design
636
  • Select a stiffer material
Assembly and Manufacturing
23 Spindle Housing Back Back of spindle housing Fractures
  • User dissatisfaction
3
  • Improper assemblying
  • Improper manufacturing
2
  • Packaging
  • Material selection
  • Mold design
636
  • Select a stiffer material
Assembly and Manufacturing
24,25 Spindle Housing (L,R) Sides of spindle housing Breaks
  • Unable to hold spindle
5
  • Improper assemblying
  • Improper manufacturing
2
  • Packaging
  • Mold design
660
  • None
Assembly and Manufacturing
29 White Teeth Guide/ArmGuides cutting teeth in spindle Breaks
  • Malfunctioning of mechanical spindle
3
  • Improper assemblying
  • Improper manufacturing
3
  • Packaging
  • Mold design
636
  • None
Assembly and Manufacturing
30 Cutting Teeth Back of spindle housing Wears,Bends
  • Unable to cut papers
  • User dissatisfaction
4
  • Improper manufacturing
2
  • Material selection
  • Teeth design
216
  • Redesign teeth
Manufacturing
31,32 Spindle Back of spindle housing Warps,Breaks
  • Malfunctioning of machinery
5
  • Improper assemblying
  • Improper manufacturing
1
  • Material selection
  • Mold design
315
  • None
Assembly and Manufacturing

DFE Analysis


The production of a product has an environmental impact from the creation of the parts that make up the product, to the time when the consumer throws the product in the garbage. In the Design for Environment, we try to reduce or eliminate any harmful byproducts they may result of the manufacture or use of the product. In our case, we studied the Economic Input-Output Life Cycle Assessment (EIO-LCA) of a paper towel dispenser using Carnegie Mellon's EIO-LCA site. This tool allows us to quantify the data involved with the environmental impact of manufacturing a paper towel dispenser. Specifically, we focused on conventional air pollutants, greenhouse gases, and toxic releases.

Each of the categories below were calculated using $1 million dollars of activity in the sector of "326199 All Other Plastics Product Manufacturing." Since most of the paper towel dispenser is made from plastic parts, we feel that this sector is appropriate. The data are from the Industry Benchmark US Dept of Commerce EIO model from 1997, a Producer Price Model.

We are concerned impact this product has on the environment; specifically, if Congress were to pass a CO2 tax, would this have a significant impact on the cost of production of the paper towel dispenser?

Conventional Air Pollutants

Below is a table of the release of conventional air pollutants from the top ten contributors in the supply chain, in units of metric tons (mt).

Image:PTD_Conventional_Air_Pollutants.JPG


In this chart of conventional air pollutants, you can see that 52% of air pollutants from the production of the paper towel dispenser comes from the generation and supply of energy. In addition, truck transportation plays a smaller, but still significant role in the production of air pollutants.

Image:PTD_Conventional_Air_Pollutants_Chart.JPG

Greenhouse Gases

Below is a table of the release of greenhouse gases from the top ten contributors in the supply chain, in units of metric tons of CO2 equivalent(MTC02E).

Image:PTD_GHG.JPG


In this chart, we focused on the emission of CO2 since this is what the government would tax. The generation and supply of energy plays a large role again, taking producing 46% of the CO2 emissions. Truck transportation and plastics material and resin manufacturing play a smaller role, but still impact the emissions to the environment.

Image:PTD_GHG_Chart.JPG

Toxic Releases

Below is a table of the release of toxic substances from the top ten contributors in the supply chain, in units of kilograms (kg).

Image:PTD_Toxic_Releases.JPG


The chart below shows that plastics plumbing fixturs and all other plastics products accounts for 45% of the toxic releases. Another significant part is played by plastics material and resin manufacturing at 18%.

Image:PTD_Toxic_Releases_Chart.JPG

EIO-LCA Paper Towel Dispenser

Below is a table showing the effects of production and use of a paper towel dispenser. This is based on an example given by Professor Michalek and thus, we used the example as a template for our project. We ignored the Distribution and End of Life sections. Since the actual use of the paper towel dispenser requires no electricity, the two components are the dispenser and paper towels.

In this example, the paper towels overwhelm the dispenser in terms of CO2 output. This is because the dispenser only needs to be made once, while the paper towels are constantly being thrown out and replaced.

Image:PTD_EIOLCAPTD2.JPG


DFE Conclusion

From the results of the EIO-LCA, we can see that there are many factors that contribute to the release of harmful waste and gases into the environmental. For example, the energy supply causes a large number of CO2 to be released in the air, this may be reduced by the use of renewable resources such as solar or wind. Truck transportation also plays a detrimental role towards the environment. It is difficult to just make trucks more efficient or burn cleaner, but maybe using a strategic network or green-powered locomotives to transport products can reduce the amount of emissions to the environment. We also realize that since most of the paper towel dispenser is made from plastic, it is not biodegradable and would be better if there were a way to recycle the plastic. Another point, is if it is possible to recycle the paper towels after they are used, instead of being sent to a landfill.

Team Member Roles

  • Eric Totong: Stakeholders, DFE
  • Chang Keun Jung: FMEA, Mechanical Analysis
  • James Li-Yang Lee: Usability Study, Assembly pictures, How it works
  • Nishan Kulatilaka: DFMA, Executive Summary, Parts list

References

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