Ice cube maker

From DDL Wiki

Jump to: navigation, search

Contents

Ice Cube Maker

Executive Summary

A preliminary evaluation of an existing ice cube maker gives us performance criteria against which to judge a new design. The current design requires a lengthy and possibly confusing installation with power and water hookups, so many consumers do not know how to install it themselves. The design itself includes twenty-two parts and subassemblies and is made up of electrical and mechanical systems, notably conductive and convective heat transfer and basic mechanical systems.

An Economic Input-Output Life Cycle Assessment (EIO-LCA) shows that the energy to produce the ice cube makers is the economic sector with the largest effect on greenhouse gasses emitted. Reducing the energy necessary to produce the ice cube maker lessens the environmental impact of the product, which is itself a luxury more than a necessity and should be extra-environmentally safe.

The product was designed to be manufactured using mostly plastic injection molding. The design was also made to be easy to assemble, with grooves to hold the cooling coil into the ice tray and drilled holes prepared well for the screws. There is even an electrical wiring guide molded into the inside of the cover. A thermal Finite Element Analysis (FEA) shows that the ice cube maker requires approximately five and a half hours for the ice cubes to fully freeze. Failure Mode and Effects Analysis shows that the part most sensitive to failure is the thermocouple. The thermocouple has several failure modes which will cause the system to be completely disabled. The largest failure concern comes from the very cold, wet environment in which the product must function, causing cracks in brittle plastic and possible electrical component damage.

Mode of Operation

Image:Cicruits.jpg


The automatic ice maker system functions on a looping mechanical/analog circuit algorithm. The entire system (showed graphically below) is synchronized and stepped by a central timing cam. This cam is assembled so that three electric switches are touching the cam, and are activated and deactivated as the AC motor revolves through the "program". According to external research, the default temperature that the ice temperature thermocouple is activated is 9 degrees Fahrenheit. The following is a flowchart outline of the freezing program.

Image:icecubemake_flowchart.jpg

Bill of Materials

In our disassembly we found that most of the parts fell into two categories: general parts that were purchased or those that were designed and manufactured especially for use in the ice maker. The standard parts that were purchased include components such as screws(22), motors(9), thermocouples(13), and relays(8). The specialized parts include components such as the ice tray(16), ice bin(18), ice ejector(6), and the ice shield(17).

The picture above left shows the ice maker pre-disassembly with visible parts labeled. The water inlet(21)located on the left is where the water entrance place of the water in the system and the cover assembly (1&2) on the right protects the electrical system as shown in the picture above right.


The two sides of the Outer plate (7), can be seen below. The "inner" side of the outer plate, the side which faces the inside cover(2), has the relays which act as a translator between the electrical and mechanical sides of the system. The "outer" side of the outer plate, the side which faces the outside cover(1), acts as a plane for the mechanical system and is the plane in which the gears(3&5) transfer the power from the motor(9) to the task of ejecting the ice by turning the ice ejector(6).

"inner" side: "outer" side:

The following picture shows the wires of the electrical system and the connection to the mechanical system:

The table shows an itemized list of the parts of the ice maker. Several of the components, including the relays and the motor, were purchased for use in the product and did not therefore need to be dissected further, as all that is applicable to this design process is their function and capacity. Additionally, some assemblies and parts were not disassembled in order to avoid destroying the parts.

Part # Part Name Qty Function Weight (Ounces) Material Manufacturing Process Photo
01 Outside Cover 1 Protect machinery 2 PVC Injection Molded
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/OutsideCover_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/OutsideCover_IceMaker.JPG/150px-OutsideCover_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
02 Inside Cover 1 Protect machinery 2 PVC Injection Molded
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/InsideCover_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/InsideCover_IceMaker.JPG/150px-InsideCover_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
03 Ice ejector gear 1 Connect the ice ejector to the switches 0.1 Plastic Injection Molded
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/IceEjectorGear_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/IceEjectorGear_IceMaker.JPG/150px-IceEjectorGear_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
04 Ice ejector timing shaft 1 Connect ice ejector gear to the ice ejector 0.4 Plastic Injection Molded
05 Ice ejector drive shaft 1 Transfer torque from the motor to the ice ejector 0.1 Plastic Injection Molded
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/IceEjectorDriveShaft_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/IceEjectorDriveShaft_IceMaker.JPG/150px-IceEjectorDriveShaft_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
06 Ice ejector 1 Rotate to push ice out of tray and into bin 1 Plastic Injection Molded
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/IceEjector_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/IceEjector_IceMaker.JPG/150px-IceEjector_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
07 Outer plate 1 Separate and support the mechanical components from the electrical wires 3 Steel Blanked and machine finished
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/OuterPlate_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/OuterPlate_IceMaker.JPG/150px-OuterPlate_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
08 Relay 3 Synchronize the mechanical and electrical elements 0.2 Plastic, Steel Purchased
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/Switch_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/Switch_IceMaker.JPG/150px-Switch_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
09 Motor 1 Power the ice maker 6 Steel, other Purchased
10 Arm 1 Senses when ice box is full to stop ice maker 0.1 Steel Machine bent
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/Arm_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/Arm_IceMaker.JPG/150px-Arm_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
11 Arm Spring 1 Transfers arm motion to CAM <0.1 Steel Purchased
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/Spring_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/Spring_IceMaker.JPG/150px-Spring_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
12 CAM 1 Stops ice ejector shaft from rotating 3.2 Steel Cast and finish machined
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/CAM_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/CAM_IceMaker.JPG/150px-CAM_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
13 Thermocouple 2 Switch on/off power to the heater 0.1 Various Purchased
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/Thermocouple1_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/Thermocouple1_IceMaker.JPG/150px-Thermocouple1_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/Thermocouple2_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/Thermocouple2_IceMaker.JPG/150px-Thermocouple2_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
14 Thermopaste enough Transfer heat <0.1 Thermal Paste Purchased
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/Thermopaste_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/Thermopaste_IceMaker.JPG/150px-Thermopaste_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
15 Heater 1 Heats tray to allow ice to be removed 3 Aluminum, Stranded Electrical Wire, Plastic Purchased
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/Heater_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/Heater_IceMaker.JPG/150px-Heater_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
16 Ice Tray 1 Holds water while it freezes to become ice 14.5 Teflon Coated Aluminum Cast, Coated
17 Ice shield 1 Keeps ice cubes from rotating back into the tray, guides ice cubes into bin 1.1 Plastic Injection Molded
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/IceGuard_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/IceGuard_IceMaker.JPG/150px-IceGuard_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
18 Ice Bin 1 Collects and stores ice cubes 16.5 PVC Injection Molded
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/IceBin_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/IceBin_IceMaker.JPG/150px-IceBin_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
19 Electrical Wires 6 Transfer electricity <0.1 Plastic & Stranded Electrical Wire Purchased
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/ElectricalWires_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/ElectricalWires_IceMaker.JPG/150px-ElectricalWires_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
20 Electrical Wire Cap X Joins wires together and covers the connection <0.1 Plastic Molded
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/ElectricalWireCap_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/ElectricalWireCap_IceMaker.JPG/150px-ElectricalWireCap_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
21 Water Inlet 1 Collects water and guides it into the ice tray 0.5 Plastic Injection Molded
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/WaterInlet_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/WaterInlet_IceMaker.JPG/150px-WaterInlet_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
22 Screws and bolts, nuts, & washers 17 Attach parts and keep them in place <0.1 Steel Purchased
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/Screws'n'Bolts_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/Screws'n'Bolts_IceMaker.JPG/150px-Screws'n'Bolts_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.
23 Valve Assembly 1 Aid and control water entrance into system 0.5 Plastic Purchased
Error creating thumbnail: convert: unable to open image `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/Screws'n'Bolts_IceMaker.JPG': No such file or directory @ error/blob.c/OpenBlob/2643.
convert: no images defined `/ux0/websites/wiki.ece.cmu.edu/wiki/virtual-hosts/ddl/images/thumb/Screws'n'Bolts_IceMaker.JPG/150px-Screws'n'Bolts_IceMaker.JPG' @ error/convert.c/ConvertImageCommand/3046.

EIO-LCA

The Economic Input-Output Life Cycle Assessment (EIO-LCA) website, www.eiolca.net, contains data on the most common contributors to greenhouse gases, toxic releases, and energy usage from industries and sections of those industries. Although there was not a category that specifically fit our product, our ice maker fit best in the category of “Household refrigerator and home freezer manufacturing.” The simulation pretended that an additional $1 million had been spent in this industry, then we examined the how much extra greenhouse gases would be released into the atmosphere. If the product were typical for its sector, the following table displays how many greenhouse gases would be emitted in to the atmosphere by spending an extra $1 million:


Sector GWP MTCO2E CO2 MTCO2E CH4 MTCO2E N2O MTCO2E CFCs MTCO2E
Total for all sectors 881. 671. 62.0 12.7 136.
Power generation and supply 231 228 0 0 2.
Industrial gas manufacturing 161. 46.1 0 0 115
Truck transportation 54.3 53.5 0.083 0.746 0
Household refrigerator and home freezer manufacturing 36.3 36.3 0 0 0
Waste management and remediation services 27.2 4.30 22.9 0.033 0
Plastics material and resin manufacturing 18.8 18.8 0 0 0
Oil and gas extraction 18.1 3.04 15.1 0 0

In manufacturing our ice maker, about a third of the greenhouse gasses emitted come from the creating the power necessary to create it. The metal necessary to create a freezer or refrigerator explain why Iron and steel mills are the next highest sector to output greenhouse gases. Our product, an ice maker has a very low metal content, so this does not make sense in the context of our specific product. Transportation of materials and finished product requires a significant amount of energy. The sector in which our product appears contributes a smaller amount of greenhouse gases, but the waste from the process contributes and even smaller amount. After these sectors we find that manufacturing the plastic components contributes as well as the process of extracting oil and gas (used in both the power generation and the creation of the plastics).


The cost of the ice maker is about 100 dollars and so with the economic input of $1 million dollars to the sector this accounts for about 10000 ice makers. Therefore in manufacturing one ice maker the total greenhouses gases emitted is approximately 0.0881 MTCO2.


The average ice maker is constantly making ice. Experimentally, we found that the average time to freeze an ice cube is five hours in the aluminum tray. The rotation of the ice ejector is fairly fast so the average cycle time is about five hours. The heater runs for about thirty seconds and then the motor runs for about thirty seconds per cycle. Combined they run for a minute and this translates to 4.8 minutes a day or 29.2 hours per year for each one individually. The life span of the product is around 20-25 years.


The heater requires 115 A at 165 V. This means that the heater requires 18.98kW per hour of use. The motor requires 0.67 A at 115 V. This means that the motor requires 77.05 W per hour of use. Together they require 19.05kW per h or 556.20 kWh per year. Per cycle the ice tray creates eight ice cubes, each ice cube of a mass of about 51 grams. As the 0.412 kg of water freezes into ice the temperature must change from the input of about 20 degrees Celsius to its freezing point of 0 degrees Celsius. As the specific heat capacity of water is 4.187 kJ/kgk, this requires 34.49 kJ. The phase change from liquid to solid requires additional energy, 137.56kJ, which is calculated using the latent heat of melting of 334kJ/kg. Overall the freezer must compensate for the energy necessary for freezing the ice, 172.05 kJ per cycle or 2.87 kWh per cycle which is 5023.8 kWh per year.


The EIO-LCA for the power generation and supply shows that 10500 MTCO2 are emitted per $1 million. With the average price of power at $0.10 this is 0.00105 MTCO2 emitted per kWh. The ice cube maker requires additional energy which was calculated to be 5580 kWh per year or 122760 kWh over an expected lifetime of 22 years. Over the lifetime of the product this is 128.898 MTCO2.


Therefore the most effective way to make our product more environmentally friendly would be in reducing the amount of energy required to make the ice. Unfortunately most of the additional energy require in using the ice maker to make ice comes from the additional energy the refrigerator must supply to the freezer to freeze the ice.

Design for Manufacturing and Assembly

The design of the system has been developed for easy and cost efficient manufacturing and assembling. Over all, there are three major families of components installed on the system: metals, plastic and accessories.

The most notable (and heavy) component of the system is the metal ice cube tray. The material selection of this part has allowed it to exhibit high thermal conductivity properties. The part has been highly engineered for metal casting efficiency. The process has been identified as molding based on the existence of notable ejector pin scars that remain on the part. On the core side of the mold, identified as the top side where the ice sits, are appropriate draft angles and wall thicknesses to be compatible with the metal injection molding process. This piece has a limited number of side actions, and thus is a remarkable example of an efficient injection molded component. There are no placed in the overall design where tight tolerances are necessitated, which is done intentionally to allow for fast and inexpensive manufacturing. The concept does not allow for multifunctional parts, all parts seem to serve only one function. Many of the screws share the same Phillips head driver socket, which allows for simple part acquisition and assembly.

Also a significant metal component is the tray sensor bar, but this was not molded, but rather is a bent aluminum extrusion that is assembled by threading the entire length of the bar through the outer wall side panel. The angles of bends were chosen appropriately so this would be possible.

The plastic components of this assembly also are all injection molded. The side panels and outer assembly, as well as the gears and brackets, are made with white ABS plastic and are created with high precision molding processes which made it a possibility to apply finely detailed trademark and identification labels inside the mold.

The accessories and wiring all consist of off-the-shelf components. The wiring is done with 16-gauge wire to allow for safe AC 110v handling, and the wire nuts are also off-the-shelf. The electric switches are all the same model, built from a third-party company, which greatly reduced engineering and assembly costs for the manufacturer of the assembly. The heating coil is constructed by bending a pre-made heating coil, which seems to have been made by an extrusion process of a selectively electricity conducting material.

The majority of the assembly process is simplified by accurately and strategically placed mounting and bracketing locations on the white ABS walls of the assembly. The assembly order most likely prioritized the wiring last, as the wire nut layout seemed to be the final thing connecting multiple sub-assemblies.

Our estimated assembly time for the assembly is around 20 minutes of experienced workers, probably done in stations. Because all parts are either purchased, molded, or bent (the ice level detector), there is little or no part fabrication involved in the process, and thus, the final assembly location and inexpensively and quickly produce this device.

Mechanical Analysis

Thermal FEA Analysis

We used an FEA thermal analysis to find that the system draws approximately 463 W/m^2. This flux value can be used to compare alternative designs. We used FEA analysis so that we can set a baseline for our future calculations. This will allow us to compare our material choices and ice cube shape to the design that we evaluated. Figure 1 shows the general setup of the model.

Analysis Methods

Figure 1 – Ice tray model
Figure 1 – Ice tray model
Figure 2- Heat flux of the tray
Figure 2- Heat flux of the tray
Figure 3(a) – Air Specific Heat
Figure 3(a) – Air Specific Heat
Figure 3(b) – Air Thermal Conductivity
Figure 3(b) – Air Thermal Conductivity
Figure 3(c) – Water Specific Heat
Figure 3(c) – Water Specific Heat
Figure 3(d) – Water Thermal Conductivity
Figure 3(d) – Water Thermal Conductivity

ANSYS Workbench was used to perform the analysis. A static thermal analysis is used to determine the thermal flux of the system. Figure 2 shows the flux obtained for the model.

This analysis makes several assumptions for boundary conditions. Conditions include:

  • Environment temperature - T∞ (°C)||-16.10
  • Water temperature - T0,water (°C) = 22.00
  • Water and Air have nonlinear thermal values which are obtained from "Heat Transfer: J.P. Holman". See Figure 3 for more details.
  • 1 atm of pressure is assumed for the entire system.
  • Aluminum properties are roughly constant with respect to temperature
    • k = 46 W/m K
    • c = kJ/kg K


Table 1 – Transient Thermal Analysis Details

Mesh Details
Number of Elements13606
Number of Nodes27231

Results

We found the flux of the system to be 463 W/m^2. This analysis gives us an objective value that we can use to compare other designs to. If a design draws more power than another design then it is likely to freeze ice faster. This static test was performed in lieu of a more complicated transient analysis because the overall goal was not to find the time that it takes ice to freeze. Instead, we needed to find a good objective measurement to compare designs against. This satisfies our need and time has been saved by performing this test instead of a transient test.

Major Stakeholders and Needs

Stakeholders are people, companies, or groups that are affected by the design and distribution of this product. Stakeholders may require certain design features from the product. Without these features the product may become uneconomic or unreasonable for them. Below is a list of stakeholders and their individual needs.

  • Customer
    • Affordable
    • Small
    • Cleanable
  • Parts manufacturers
    • Multiple-purpose parts
    • Easy Assembly
    • Standard materials
  • Appliance Stores
    • Small packaging
    • Marketable design
    • Lightweight for shipping
    • Stackable
  • General users
    • Automation
    • Adjustable controls
    • Accessibility in freezer
    • Quiet Operation
    • Easy Access
  • Installation
    • No special tools needed
    • Installation doesn’t damage freezer
    • No extra parts or plumbing needed
  • Transportation
    • Lightweight
    • Compact Packaging




FMEA

Failure Mode Effects and Analysis of this product, including the Severity (S), Probability of Occurence (O), and how likely the failure is to go undetected (D). Also included is what the various members of an engineering team can do to fix the problems and decrease chance of failure.

We found that one of the likely modes of failure would be the shorting of the electrical components. This is a fairly likely situation because there are motors, switches, heating elements, and other parts in a mechanism that operates in a very cold freezer freezing liquid. If the liquid was to get inside the main electrical compartment, it could short the electronics. The electronics could also overheat, preventing ice from freezing.

The chill temperature of the freezer can cause several failures. Plastic could become brittle and crack at such low temperatures. Water could then get inside the component and freeze in unwanted places to inhibit the motion of the mechanical components.

The best course of action to avoid these failures would involve eliminating electrical components from the design. Also, the fewer mechanical components involved would decrease the risks of those parts freezing and failing.



Part # Part Name Function Failure Mode Effect S Cause O Design Controls D RPN Recommended Actions Responsibility Actions Taken
1 CoverProtect machineryPlastic CracksElectrical insides get cold, wet7Brittle from cold temperature2Use good strength plastic342Fatigue TestingMaterials Engineer
2 Inside CoverHolds machinery parts in placePlastic CracksParts don\'t work together6Brittle from cold temperature2Use good strength plastic560Fatigue TestingMaterials Engineer
3 Ice Ejector GearConnect the ice ejector to the switchesStripsIce doesn\'t get ejected4Brittle from cold temperature3Use good strength plastic784Fatigue TestingMaterials Engineer
4 Ice Ejector Timing ShaftConnect ice ejector gear to the ice ejectorBreaksIce doesn\'t get ejected4Brittle from cold temperature2Use good strength plastic540Fatigue TestingMaterials Engineer
5 Ice Ejector DriveshaftTransfer torque from the motor to the ice ejectorStallsIce doesn\'t get ejected5Brittle from cold temperature2Use good strength plastic550Fatigue TestingMaterials Engineer
6 Ice EjectorRotate to push ice out of tray and into binFailsIce cubes get back in tray9Brittle from cold temperature2Use good strength plastic354Fatigue TestingMaterials Engineer
7 Outer PlateSeparate and support the mechanical components from the electrical wiresPlastic CracksParts don\'t work together7Brittle from cold temperature2Use good strength plastic456Fatigue TestingMaterials Engineer
8 SwitchSynchronize the mechanical elementsFailsElements out of sync6Wet switch3Water shield7126Protective CoveringMechanical Engineer
9 MotorPower the ice makerFailsMachine has no power9Wet motor2Water shield7126Protective CoveringMechanical Engineer
10 ArmSenses when ice box is full to stop ice makerSticks in one placeFreezer does not detect ice build up5Freezes4Frequent motion480Make many ice cubes per hourMechanical Engineer
11 Arm SpringTransfers arm motion to CAMDoes not transfer motionCAM does not move5Freezes3Frequent motion690Make many ice cubes per hourMechanical Engineer
12 CAMStops ice ejector shaft from rotatingFailsAllows rotation4Freezes2Frequent motion432Make many ice cubes per hourMechanical Engineer
13 ThermocoupleSwitch on/off power to the heaterFailsPower not provided9Overheats2Operating range8144Use during range of temperaturesMechanical Engineer
14 ThermopasteTransfer heatDoesn\'t conduct heatNo thermal control7Gets wiped off3Protections6126Keep area clear during manufactureMechanical Engineer
15 HeaterHeats tray to allow ice to be removedOverheatsIce cubes melt8Circuit error5Water shield7280Protective CoveringMechanical Engineer
HeaterHeats tray to allow ice to be removedUnderheatsIce cubes stick5Circuit error4Water shield7140Protective CoveringMechanical Engineer
16 Ice TrayHolds water while it freezes to become iceMaterial CracksNew ice unable to be made9Brittle from cold temperature2Use good conducting material472Fatigue TestingMaterials Engineer
17 Ice ShieldKeeps ice cubes from rotating back into the tray, guides ice cubes into binIce cubes get back in trayNew ice unable to be made7Freezes3Frequent motion5105Make many ice cubes per hourMechanical Engineer
18 Ice BinCollects and stores ice cubesNot thereFreezer fills with ice cubes4Forgetful consumer4--116--Consumer
19 Electrical WiresTransfer electricityFailsNo power in unit4Brittle from cold temperature3High quality wires672Stronger, protected wiresControls Engineer
20 Electrical Wire CapJoins wires together and covers the connectionFalls offEasy to shock self3Brittle from cold temperature2Use good strength plastic424Fatigue TestingMaterials Engineer
21 Water InletCollects water and guides it into the ice trayDoes not provide enough waterCannot make ice cubes8Low water pressure2Good pipe diameter696Pipe Pressure TestMechanical Engineer
22 Screw, Nuts, Bolts, WashersAttach parts and keep them in placeShearsMechanism won\'t hold together6Too much shear stress3Screw thickness, material354Fatigue TestingMaterials Engineer
Personal tools