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Hamilton Beach Coffee Grinder

Executive Summary

The purpose of this study is to identify potential areas of improvement for a consumer coffee grinder.

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.

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.

DFMA analysis revealed...

FMEA analysis revealed...

DFE analysis revealed...

After conducting this in-depth analysis of the coffee grinder, we have identified several areas of potential improvement which include: ...

Primary Stakeholders and Product Needs

The primary stakeholders for this product are consumers, retailers, distributors and shippers, and manufacturers. The needs of these stakeholders are outlined below.

Coffee Consumers:

• Longevity
• Quiet operation
• Aesthetically pleasing
• Small footprint/Easy to store
• Easy to clean
• Dishwasher safe parts
• Intuitive and fast operation
• Versatility

Retailers:

• Space efficient packaging
• Light
• Aesthetically pleasing
• Low unit cost
• High demand
• Stackable

Distributors and Shippers:

• Light
• Durable packaging
• Stackable

Manufacturer:

• Easy mechanical assembly
• High volume parts
• Inexpensive materials
• Low overhead costs

Product Function and Use

User Study

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.

Cord storage system, opened

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.

Top cover (left), back of coffee grinder (rear), cup with measurements (right), and brush (front)

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.

Front controls

Mechanical Function

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.

Three samples of different grinds. As you can see, it is difficult to differentiate the grinds by visual inspection.

Run Time in Seconds:

Motor Speeds in rpm for 12 Cup Setting:

Close up of cup and blade

Measuring the motor speed

List of Parts

The following details the list of parts of a hands-free coffee grinder.

Coffee Grinder Exploded View

Bill of Materials

Part Number	Name	Quantity	Mass (g)	Function	Material	Manufacturing Process/ Purchased Component	Image
Grinding Chamber Sub-Assembly
1	Lid	1	66	Contains coffee	Plastic	Blow Molded
2	Flat Head Screws	3	<1	Cup to Scatter Shield	Steel	Catalog Purchase
3	Female Drive Adapter	1	6	Provides Torque to Blade Assy	Plastic	Injection Molding
4	Rubber Nipples	3	<1	Vibration Isolation & Noise Reduction	Rubber	Die Cut
5	Plastic Washer	1	<1	Reduces friction of Blade Assy	Plastic	Catalog Purchase
6	Cup	1	46	Provides References for Coffee Bean Measuring	Plastic	Injection Molding
7	Scatter Guard	1	15	Contains Coffee Beans behind the Blade	Tin	Stamped
8	Dust Shield	1	3	Separates the Grinding Chamber and the Drive Assy	Plastic	Injection Molding
9	Blade-Adapter Shaft	1	2	Transmits Torque from Part 3 to Part 13	Plastic	Catalog Purchase
10	Blade Gasket	1	<1	Seals Blade Assy	Rubber	Injection Molding
11	Blade Washer	1	<1	Reduces friction of Blade Assy and Provides Axial Preload	Steel	Catalog Purchase
Blade Sub-Assembly
12	Blade Hub	1	2	Connects blade to drive shaft	Plastic	Injection Molding
13	Blade	1	3	Grinds Coffee	Stainless Steel	Stamped
Cord Housing Sub-Assembly
14	Tamper Proof Screw	1	<1	Connects cord housing assembly to main body	Steel	Purchased Part
15	Rubber Foot Pad	3	<1	Prevents Device from Slipping	Rubber	Stamped
16	Cord Reel Container	1	17	Contains Cord While Wound	Plastic	Blow Formed
17	Screw	3	<1	Mates Part 19 to Part 28	Steel	Purchased Part
18	Power Cord Reel Center	1	3	Cord Capstan	Plastic	Injection Molded
19	Power Cord Reel	1	26	Captures Cord	Plastic	Injection Molded
20	Internal Motor Gasket	2	3	Seals Motor Components	Rubber	Injection Molding
21	Screw For Part 22	2	1	Mates Part 22 to Part 28	Steel	Purchased Part
22	Power Cord Retention Clip	1	2	Positively Retains The Power Cord Inside The Housing	Plastic	Injection Molding
23	Tiny Spring	1	<1	Provides Preload to the Safety Mechanism	Steel	Purchased Part
24	Safety Paper	1	<1	Reduces Abrasion of Safety Switch	Plastic	Stamped
25	Electrical Switch Cover	1	1	Houses Electric Switch	Plastic	Injection Molded
26	Electrical Switch Lead	2	1	Provides Current to Electrical Switch	Copper	Purchased Part
27	Mechanical Switch	1	1	Actuates the Safety Switch	Plastic	Injection Molded
28	Motor Housing	1	47	Secures motor to device	Plastic	Injection Molded
AC Motor Sub-Assembly
29	Brushes	2	<1	Provides Current to Commutator	Carbon	Electronic Component
30	Motor Shaft Cap	1	<1	Transmits Torque from Part 42 to Part ??	Plastic	Injection Molded
31	Shaft Insulator	1	<1	Provides Mechanical and Electrical Insulation to the Shaft	Fiber	Stamped
32	Spring Washer	1	<1	Provides Axial Preload to locate the commutator with respect to the bushings	Copper	Purchased
33	Small Brown Washers	4	<1	Locates Part 42 Axially	Plastic	Stamped
34	Large Orange Washers	2	<1	Locates Part 42 Axially	Plastic	Stamped
35	Small Metal Washers	2	<1	Locates Part 42 Axially	Steel	Purchased
36	Bearing	2	2	Locates Part 42 Radially	Steel	Purchased
37	Brush Side Bracket	1	17	Locate Part 36 on Brush Side	Steel	Stamped and Bent
38	Non-Brush Side Bracket	1	16	Locate Part 36 on Non Brush Side	Steel	Stamped and Bent
39	Brush Housing	2	1	Constrains Part 29	Plastic	Injection Molded
40	Stator Coil	2	13	Provides Magnetic Poles	n/a	Electronic Component
41	Steel Inductor Plate	30	4	Enhances Magnetic Poles	Steel	Stamped
42	Rotor	1	77	Provides Motor Torque	n/a	Electrical Component
43	Circuit Board	1	28		Assembly	Electrical Component
56	Male Drive Adapter	1	15		Plastic	Injection Molded
Knob Sub-Assembly
44	Power Button	1	2	Allows user to operate grinder	Plastic	Injection Molded
45	Power Button Finger	1	<1	Translate power button movement to connect circuit	Plastic	Injection Molded
46	Knob	1	8	Allows user to adjust fineness of grind	Plastic	Injection Molded
47	Circuit Board Connector	1	<1	Connects fineness knob circuit	Copper	Stamped
48	Power Button Spring	1	<1	Returns power button after press	Steel	Purchased
49	Knob Screws	4	<1	Fastens knob sub-assembly	Steel	Purchased
50	Detent Springs	2	<1	Pushes ball bearings for discrete adjustment of knob	Steel	Purchase
51	Detent Bearings	2	<1	Allows for discrete adjustment of knob	Steel	Purchased
52	Detent Housing	1	2	Contains detent components in knob	Plastic	Injection Molded
53	Brush	1	3	Cleans coffee grinds	Plastic	Injection Molded
54	Body	1	74	Houses inner components	Plastic	Injection Molded
55	Power Cord	1		Supplies electrical current from outlet to grinder	Assembly	Purchased

Design For Manufacturing and Assembly (DFMA)

Design for Manufacturing [DFM]

For the most part we believe the coffee grinder was well designed for manufacturing. The majority of the components are injection molded plastic with few post machining operations. While there are a lot of components a vast majority of them came from the motor which we are fairly positive was a purchased component.

Design for Assembly [DFA]

The motor fits squarely into the motor housing and connects with two screws.

The coffee grinder has an astonishing number of parts, as can be seen 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.

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.

Failure Modes and Effects Analysis (FMEA)

Studying the failure modes of the coffee grinder

Design for Environment (DFE)

Studying the Design for Environment Execution of the Coffee Grinder

Team Members

Phil Aufdencamp - DFE Czar

Justin Barsano - DFMA Czar

Kristen Hauser - User Study, General Organization Czar

Brian Tang - FMEA Czar

References

Dieter, George E., and Linda C. Schmidt. Engineering Design. 4th Edition. New York, NY: McGraw-Hill, 2009. Print.