Coffee grinder

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[[Image:Team6_CoffeeGrinder.jpg|thumb|220px|right|Hamilton Beach Coffee Grinder]]
 
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= Executive Summary =
 
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The purpose of this study is to identify potential areas of improvement for a consumer coffee grinder.
 
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The first step of this study was to conduct a user study in which we evaluated how the average consumer uses the product, taking into consideration how intuitive the product is, and to what degree the product meets the consumer's needs. We observed that the product is generally simple to use without reading the instructions, but after several uses in a short time frame, our perceived quality of the device was quite low. The product was loud and became very hot after many consecutive uses.
 
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The second step in this study was to dissect the product while noting the assembly procedure and making inferences about the materials used in the design. By noting each component's material, manufacturing process, and function, we are able to understand the intentions of the designers, the quality of the device, and it's impact on the environment.
 
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DFMA analysis revealed...
 
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FMEA analysis revealed...
 
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DFE analysis revealed...
 
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After conducting this in-depth analysis of the coffee grinder, we have identified several areas of potential improvement which include: ...
 
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= Primary Stakeholders and Product Needs =
 
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The primary stakeholders for this product are consumers, retailers, distributors and shippers, and manufacturers. The needs of these stakeholders are outlined below.
 
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'''Coffee Consumers:'''<br />
 
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*Longevity
 
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*Quiet operation
 
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*Aesthetically pleasing
 
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*Small footprint/Easy to store
 
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*Easy to clean
 
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*Dishwasher safe parts
 
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*Intuitive and fast operation
 
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*Versatility
 
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'''Retailers:'''<br />
 
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*Space efficient packaging
 
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*Light
 
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*Aesthetically pleasing
 
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*Low unit cost
 
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*High demand
 
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*Stackable
 
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'''Distributors and Shippers:'''<br />
 
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*Light
 
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*Durable packaging
 
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*Stackable
 
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'''Manufacturer:'''<br />
 
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*Easy mechanical assembly
 
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*High volume parts
 
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*Inexpensive materials
 
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*Low overhead costs
 
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= Product Function and Use=
 
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== User Study ==
 
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The coffee grinder is powered by a typical 110V power outlet. To free the power cord, pull down on the black cover on the bottom of the device. Unwrap the power cord, then replace the black cover. Unlock the top plastic cover by rotating it counter-clockwise.
 
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[[Image:Team6_UserStudy1.jpg|500 px|thumb|center|Cord storage system, opened]]
 
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Remove the inner cup and notice the marking lines on the side. These pertain to the number of cups of coffee you intend to brew. Fill the cup with whole coffee beans or raw spices to the desired level. Place the cup back in the device and lock the top cover. The device will not function if the cover is not locked in place.
 
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[[Image:Team6_UserStudy2.jpg|500 px|thumb|center|Top cover (left), back of coffee grinder (rear), cup with measurements (right), and brush (front)]]
 
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Select the quantity of coffee you desire (4, 8, 10, or 12 cups) using the switch on the front of the device. Turn the knob to the desired grind.  Press the on button. The device will stop automatically, or you can manually stop the device by pressing the button again.
 
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[[Image:Team6_UserStudy3.jpg|300 px|thumb|center|Front controls]]
 
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== Mechanical Function ==
 
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The coarseness and size selection control the motor speed (driving the blade) and the duration of operation. As one would expect, the larger quantities require longer run times. Interestingly, the finer grinds require slower motor speeds. We suspect that because the more coarse grinds run for a shorter time, a higher speed is required to get a good quality grind. We took some preliminary data to characterize the device.
 
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[[Image:Team6_GrindDetail.jpg|600 px|thumb|center|Three samples of different grinds. As you can see, it is difficult to differentiate the grinds by visual inspection.]]
 
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'''Run Time in Seconds:'''
 
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{| class="wikitable" border="1"
 
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|-
 
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!  Quantity
 
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!  Percolator 
 
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!  Drip
 
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!  Espresso
 
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|-
 
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| 12 cups || 10 || 18 || 30
 
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|-
 
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| 10 cups || 10 || 16 || 30
 
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|-
 
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| 8 cups || 9 || 14 || 25
 
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|-
 
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| 4 cups || 9 || 13 || 20
 
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|}
 
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'''Motor Speeds in rpm for 12 Cup Setting:'''
 
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{| class="wikitable" border="1"
 
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|-
 
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! 
 
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!  Percolator 
 
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!  Percolator/Drip
 
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!  Drip
 
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!  Drip/Espresso
 
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!  Espresso
 
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|-
 
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| Speed [rpm] || 25,000 || 23,000 || 22,600 || 22,600 || 22,500
 
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|}
 
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[[Image:Team6_Blade.jpg|500 px|thumb|center|Close up of cup and blade]]
 
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[[Image:Team6_Testing.jpg|200 px|thumb|center|Measuring the motor speed]]
 
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=List of Parts=
 
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The following details the list of parts of a hands-free coffee grinder.
 
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[[Image:Team6 Labeled Exploded View.JPG|800 px|thumb|center|Coffee Grinder Exploded View]]
 
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== Bill of Materials ==
 
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{| class="wikitable" border="1"
 
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|-
 
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!  Part Number
 
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!  Name
 
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!  Quantity
 
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!  Mass (g)
 
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!  Function
 
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!  Material
 
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!  Manufacturing Process/ Purchased Component
 
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!  Image
 
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|-
 
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| colspan="8" align = center| '''Grinding Chamber Sub-Assembly'''
 
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|-
 
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| 1 || Lid || 1 || 66 || Contains coffee || Plastic || Blow Molded || [[Image:Team6_Part_1.jpg|100px|center]]
 
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|-
 
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| 2 || Flat Head Screws || 3 || <1 || Cup to Scatter Shield || Steel || Catalog Purchase ||[[Image:Team_6_Part_02.jpg|100px|center]]
 
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|-
 
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| 3 || Female Drive Adapter || 1 || 6 || Provides Torque to Blade Assy || Plastic || Injection Molding ||[[Image:Team_6_Part_03.jpg|100px|center]]
 
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|-
 
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| 4 || Rubber Nipples || 3 || <1 || Vibration Isolation & Noise Reduction || Rubber || Die Cut ||[[Image:Team_6_Part_04.jpg|100px|center]]
 
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|-
 
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| 5 || Plastic Washer || 1 || <1 || Reduces friction of Blade Assy || Plastic || Catalog Purchase ||[[Image:Team_6_Part_05.jpg|100px|center]]
 
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|-
 
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| 6 || Cup || 1 || 46 || Provides References for Coffee Bean Measuring || Plastic || Injection Molding ||[[Image:Team_6_Part_06.jpg|100px|center]]
 
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|-
 
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| 7 || Scatter Guard || 1 || 15 || Contains Coffee Beans behind the Blade || Tin || Stamped ||[[Image:Team_6_Part_07.jpg|100px|center]]
 
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|-
 
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| 8 || Dust Shield || 1 || 3 || Separates the Grinding Chamber and the Drive Assy || Plastic || Injection Molding ||[[Image:Team_6_Part_08.jpg|100px|center]]
 
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|-
 
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| 9 || Blade-Adapter Shaft || 1 || 2 || Transmits Torque from Part 3 to Part 13 || Plastic || Catalog Purchase ||[[Image:Team_6_Part_09.jpg|100px|center]]
 
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|-
 
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| 10 || Blade Gasket || 1 || <1 || Seals Blade Assy || Rubber || Injection Molding ||[[Image:Team_6_Part_10.jpg|100px|center]]
 
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|-
 
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| 11 || Blade Washer || 1 || <1 || Reduces friction of Blade Assy and Provides Axial Preload|| Steel || Catalog Purchase ||[[Image:Team_6_Part_11.jpg|100px|center]]
 
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|-
 
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| colspan="8" align = center| '''Blade Sub-Assembly'''
 
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|-
 
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| 12 || Blade Hub || 1 || 2 || Connects blade to drive shaft || Plastic || Injection Molding ||[[Image:Team_6_Part_12.jpg|100px|center]]
 
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|-
 
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| 13 || Blade || 1 || 3 || Grinds Coffee || Stainless Steel || Stamped ||[[Image:Team_6_Part_13.jpg|100px|center]]
 
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|-
 
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| colspan="8" align = center| '''Cord Housing Sub-Assembly'''
 
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|-
 
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| 14 || Tamper Proof Screw || 1 || <1 || Connects cord housing assembly to main body || Steel || Purchased Part || [[Image:Team6_Part_14.jpg|100px|center]]
 
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|-
 
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| 15 || Rubber Foot Pad || 3 || <1 || Prevents Device from Slipping || Rubber || Stamped || [[Image:Team6_Part_15.jpg|100px|center]]
 
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|-
 
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| 16 || Cord Reel Container || 1 || 17 || Contains Cord While Wound || Plastic || Blow Formed || [[Image:Team6_Part_16.jpg|100px|center]]
 
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|-
 
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| 17 || Screw || 3 || <1 || Mates Part 19 to Part 28 || Steel || Purchased Part || [[Image:Team6_Part_17.jpg|100px|center]]
 
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|-
 
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| 18 || Power Cord Reel Center || 1 || 3 || Cord Capstan || Plastic || Injection Molded || [[Image:Team6_Part_18.jpg|100px|center]]
 
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|-
 
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| 19 || Power Cord Reel || 1 || 26 || Captures Cord || Plastic || Injection Molded || [[Image:Team6_Part_19.jpg|100px|center]]
 
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|-
 
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| 20 || Internal Motor Gasket || 2 || 3 || Seals Motor Components || Rubber || Injection Molding || [[Image:Team6_Part_20.jpg|100px|center]]
 
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|-
 
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| 21 || Screw For Part 22 || 2 || 1 || Mates Part 22 to Part 28 || Steel || Purchased Part || [[Image:Team6_Part_21.jpg|100px|center]]
 
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|-
 
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| 22 || Power Cord Retention Clip || 1 || 2 || Positively Retains The Power Cord Inside The Housing || Plastic || Injection Molding || [[Image:Team6_Part_22.jpg|100px|center]]
 
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|-
 
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| 23 || Tiny Spring || 1 || <1 || Provides Preload to the Safety Mechanism || Steel || Purchased Part || [[Image:Team6_Part_23.jpg|100px|center]]
 
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|-
 
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| 24 || Safety Paper || 1 || <1 || Reduces Abrasion of Safety Switch || Plastic || Stamped || [[Image:Team6_Part_24.jpg|100px|center]]
 
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|-
 
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| 25 || Electrical Switch Cover || 1 || 1 || Houses Electric Switch || Plastic || Injection Molded || [[Image:Team6_Part_25.jpg|100px|center]]
 
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|-
 
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| 26 || Electrical Switch Lead || 2 || 1 || Provides Current to Electrical Switch || Copper || Purchased Part || [[Image:Team6_Part_26.jpg|100px|center]]
 
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|-
 
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| 27 || Mechanical Switch || 1 || 1 || Actuates the Safety Switch || Plastic || Injection Molded || [[Image:Team6_Part_27.jpg|100px|center]]
 
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|-
 
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| 28 || Motor Housing || 1 || 47 || Secures motor to device || Plastic || Injection Molded || [[Image:Team6_Part_28.jpg|100px|center]]
 
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|-
 
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| colspan="8" align = center| '''AC Motor Sub-Assembly'''
 
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|-
 
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| 29 || Brushes || 2 || <1 || Provides Current to Commutator || Carbon || Electronic Component || [[Image:Team6_Part_29.jpg|100px|center]]
 
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|-
 
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| 30 || Motor Shaft Cap || 1 || <1 || Transmits Torque from Part 42 to Part ?? || Plastic|| Injection Molded || [[Image:Team6_Part_30.jpg|100px|center]]
 
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|-
 
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| 31 || Shaft Insulator || 1 || <1 || Provides Mechanical and Electrical Insulation to the Shaft || Fiber || Stamped || [[Image:Team6_Part_31.jpg|100px|center]]
 
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|-
 
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| 32 || Spring Washer || 1 || <1 || Provides Axial Preload to locate the commutator with respect to the bushings || Copper || Purchased || [[Image:Team6_Part_32.jpg|100px|center]]
 
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|-
 
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| 33 || Small Brown Washers || 4 || <1 || Locates Part 42 Axially || Plastic || Stamped || [[Image:Team6_Part_33.jpg|100px|center]]
 
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|-
 
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| 34 || Large Orange Washers || 2 || <1 || Locates Part 42 Axially || Plastic || Stamped || [[Image:Team6_Part_34.jpg|100px|center]]
 
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|-
 
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| 35 || Small Metal Washers || 2 || <1 || Locates Part 42 Axially || Steel || Purchased || [[Image:Team6_Part_35.jpg|100px|center]]
 
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|-
 
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| 36 || Bearing || 2 || 2 || Locates Part 42 Radially || Steel || Purchased || [[Image:Team6_Part_36.jpg|100px|center]]
 
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|-
 
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| 37 || Brush Side Bracket || 1 || 17 || Locate Part 36 on Brush Side || Steel || Stamped and Bent || [[Image:Team6_Part_37.jpg|100px|center]]
 
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|-
 
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| 38 || Non-Brush Side Bracket || 1 || 16 ||Locate Part 36 on Non Brush Side || Steel || Stamped and Bent || [[Image:Team6_Part_38.jpg|100px|center]]
 
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|-
 
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| 39 || Brush Housing || 2 || 1 || Constrains Part 29 || Plastic || Injection Molded || [[Image:Team6_Part_39.jpg|100px|center]]
 
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|-
 
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| 40 ||Stator Coil || 2 || 13 || Provides Magnetic Poles || n/a || Electronic Component || [[Image:Team6_Part_40.jpg|100px|center]]
 
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|-
 
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| 41 || Steel Inductor Plate || 30 || 4 || Enhances Magnetic Poles || Steel || Stamped || [[Image:Team6_Part_41.jpg|100px|center]]
 
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|-
 
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| 42 || Rotor|| 1 || 77 || Provides Motor Torque || n/a || Electrical Component || [[Image:Team6 part 42.jpg|100px|center]]
 
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|-
 
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| 43 || Circuit Board || 1 || 28 ||  || Assembly || Electrical Component || [[Image:Team6 part 43.jpg|100px|center]]
 
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|-
 
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| 56 || Male Drive Adapter|| 1 || 15 || || Plastic || Injection Molded || [[Image:Team6 Part 56.jpg|100px|center]]
 
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|-
 
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| colspan="8" align = center| '''Knob Sub-Assembly'''
 
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|-
 
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| 44 || Power Button || 1 || 2 || Allows user to operate grinder || Plastic || Injection Molded || [[Image:Team6 Part 44.jpg|100px|center]]
 
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|-
 
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| 45 || Power Button Finger || 1 || <1 || Translate power button movement to connect circuit || Plastic || Injection Molded || [[Image:Team6 Part 45.jpg|100px|center]]
 
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|-
 
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| 46 || Knob || 1 || 8 || Allows user to adjust fineness of grind || Plastic || Injection Molded || [[Image:Team6 Part 46.jpg|100px|center]]
 
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|-
 
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| 47 || Circuit Board Connector || 1 || <1 || Connects fineness knob circuit || Copper || Stamped || [[Image:Team6 Part 47.jpg|100px|center]]
 
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|-
 
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| 48 || Power Button Spring || 1 || <1 || Returns power button after press || Steel || Purchased || [[Image:Team6 Part 48.jpg|100px|center]]
 
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|-
 
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| 49 || Knob Screws || 4 || <1 || Fastens knob sub-assembly || Steel || Purchased || [[Image:Team6 Part 49.jpg|100px|center]]
 
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|-
 
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| 50 || Detent Springs || 2 || <1 || Pushes ball bearings for discrete adjustment of knob || Steel || Purchase || [[Image:Team6 Part 50.jpg|100px|center]]
 
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|-
 
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| 51 || Detent Bearings || 2 || <1 || Allows for discrete adjustment of knob || Steel || Purchased || [[Image:Team6 Part 51.jpg|100px|center]]
 
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|-
 
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| 52 || Detent Housing || 1 || 2 || Contains detent components in knob || Plastic || Injection Molded || [[Image:Team6 Part 52.jpg|100px|center]]
 
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|-
 
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| 53 || Brush || 1 || 3 || Cleans coffee grinds || Plastic || Injection Molded || [[Image:Team6 Part 53.jpg|100px|center]]
 
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|-
 
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| 54 || Body || 1 || 74 || Houses inner components || Plastic || Injection Molded || [[Image:Team6 Part 54.jpg|100px|center]]
 
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|-
 
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| 55 || Power Cord || 1 || || Supplies electrical current from outlet to grinder || Assembly || Purchased || [[Image:Team6 Part 55.jpg|100px|center]]
 
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|}
 
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= Design For Manufacturing and Assembly (DFMA)=
 
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== Design for Manufacturing [DFM] ==
 
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{| class="wikitable" border="1"
 
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|-
 
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| colspan="8" align = center| '''Design For Manufacturing Analysis of Coffee Grinder'''
 
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|-
 
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| Minimize Part Count || blasfdlfas6dfkasflksadfa ||
 
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|-
 
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| Standardize Components || sdgsdfgsdfgdgsd ||
 
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|-
 
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| Commonize Product Line || dghfhghhdghhg ||
 
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|-
 
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| Standardize Design Features || sfgsfdgdfgsfdgdgf ||
 
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|-
 
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| Keep Designs Simple || sdfghjfdgsds sdf ||
 
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|-
 
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| Multifunctional Parts || sdfasdfsaf poop ||
 
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|-
 
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| Ease of Fabrication || twerytwhtwwher ||
 
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|-
 
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| Avoid Tight Tolerances || sdfghrdterf ||
 
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|-
 
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| Minimize Secondary & Finishing Operations || fsfgggdfgfdggsgf ||
 
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|-
 
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| Take Advantage of Special PRocess Properties || asvasiubfcsndfauisbvflais ||
 
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|-
 
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== Design for Assembly [DFA] ==
 
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[[Image:Team6_Motor_and_Housing.jpg|200px|thumb|right|Caption ]]
 
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The coffee grinder has an astonishing number of parts, as can be see in the Bill of Materials, however, there appear to be no redundant or unnecessary parts. The assembly sequence is very straightforward, with four major sub-assemblies: the cup and lid, the motor and motor housing, the circuit board and front controls, and the cord housing. The cup and lid assembly can be removed effortlessly and separately tested as one unit.The circuit board and customer-facing controls are also one unit and can be tested separately, although cannot be accessed without completely disassembling the device. There is only one way to connect the cup to the rest of the housing, which is inconvenient to the user. The cup could be improved such that it could lock to the rest of the housing in multiple configurations. The motor is sandwiched between two assemblies, the upper cup and blade assembly, and the lower power cord housing assembly. Ideally, the entire motor housing would be accessible from one side of the part, such that the assembly process is linear. Instead, the assembler must rotate the piece many ways in order to stack and secure the parts in the appropriate configuration. Also, the configuration is so specific that many interior parts, such as the motor housing, must be inserted a single way into the outer housing. An ideal design would allow for the parts to slide into place in a logical fashion. Most of the parts are either custom injection molded pieces or specific hardware, like washers and screws. Much of the hardware is consistent. For example, all of the screws take the same size Phillip's head screwdriver. A minimal amount of hardware is used to hold and connect sub-assemblies.
 
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In summary, it is apparent that much consideration went into minimizing the number of parts and optimizing the sub-assemblies, however, the assembly process still requires a non-ideal level of meticulousness and maneuvering.
 
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= Failure Modes and Effects Analysis (FMEA) =
 
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{| class="wikitable" border="1"
 
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|+ FMEA Summary: Table summarizes likely failure modes and effects of various components of the coffee grinder.
 
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<br> (S)everity, Probability of (O)ccurence and (D)ectability of Failure ratings are assigned following the standards established in Tables 14.12, 14.13 and 14.14, respectively in Dieter and Schmidt.
 
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<br> Risk Priority Numbers (RPN) are generated by finding the product of SxOxD
 
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|-
 
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! '''Item and Function'''
 
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! '''Failure Mode'''
 
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! '''Effects of Failure'''
 
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! '''  S  '''
 
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! '''Causes of Failure'''
 
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! '''  O  '''
 
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! '''Design Controls'''
 
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! '''  D  '''
 
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! '''  RPN  '''
 
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! '''Recommended Actions'''
 
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|-
 
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|-
 
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|rowspan="2"| Lid Safety Switch
 
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|rowspan="2"| Switch stuck
 
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|rowspan="2"| Blade powers on when lid is off
 
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|rowspan="2"| 7
 
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| Sticktion
 
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| 2
 
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| Friction reducing shim
 
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| 8
 
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| 112
 
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|rowspan="2"| Create redundant fail-safe mechanisms
 
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|-
 
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|-
 
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| Return spring failure
 
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| 2
 
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| Positive mechanical engagement
 
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| 8
 
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| 112
 
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|-
 
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|-
 
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| rowspan="2"|Grinder blade
 
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| rowspan="2"|Fracture
 
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| rowspan="2"|Catastrophic failure of grinder resulting in a useless product
 
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| rowspan="2"|7
 
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| Misuse: grinding unintentional objects
 
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| 7
 
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| rowspan="2"|Product warnings and guidelines
 
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| rowspan="2"|
 
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|
 
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| rowspan="2"|Yield before breaking <br>Hardened lid
 
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|-
 
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|-
 
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|Manufacturing defects
 
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|2
 
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|
 
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|-
 
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|-
 
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| Power cord
 
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| Snapping
 
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| Faulty electrical wiring <br>Inoperable product
 
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| 5
 
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| Excessive force from pulling
 
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| 4
 
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| Reenforcing bracket
 
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| 7
 
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| 140
 
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| Better power cord directions
 
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|-
 
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|-
 
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| rowspan="2"| Lid and body
 
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| rowspan="2"| Crack or fracture
 
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| rowspan="2"|
 
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| rowspan="2"|
 
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| Unexpected loads e.g. leaning, dropping
 
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|
 
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| rowspan="2"| None
 
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| rowspan="2"|
 
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|
 
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| rowspan="2"|
 
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|-
 
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|-
 
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| Placing in dishwasher
 
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|
 
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|
 
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|-
 
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|-
 
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| Electric Motor
 
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| Burnt out motor
 
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| Inoperable grinder
 
-
| 6
 
-
| Excessive duty cycle
 
-
| 5
 
-
| None
 
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| 5
 
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| 150
 
-
| Temperature sensor to force mandatory cool down
 
-
|-
 
-
 
-
|-
 
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| User interface switches
 
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| Wearing of control mechanisms, breakage
 
-
| Uncontrollable grinder
 
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| 4
 
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| Fatigue wear
 
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| 5
 
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| None
 
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| 7
 
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| 140
 
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| Use fatigue resistant materials
 
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|-
 
-
 
-
 
-
|}
 
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= Design for Environment (DFE) =
 
-
 
-
= Team Members =
 
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Phil Aufdencamp - DFE
 
-
 
-
Justin Barsano - DFMA
 
-
 
-
Kristen Hauser - User Study, General Organization
 
-
 
-
Brian Tang - FMEA
 
-
 
-
= References =
 
-
Dieter, George E., and Linda C. Schmidt. Engineering Design. 4th Edition. New York, NY: McGraw-Hill, 2009. Print.
 

Revision as of 23:27, 2 February 2014

Retrieved from "https://wiki.ece.cmu.edu/ddl/index.php/Coffee_grinder"
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