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Contents 1 Ice cube maker 1.1 Mode of Operation 1.2 Bill of Materials 1.3 LCA 1.4 Design for Manufacturing and Assembly 1.5 Mechanical Analysis 1.5.1 Thermal FEA Analysis 1.5.2 Analysis Methods 1.5.3 Results 1.6 Major Stakeholders and Needs

Ice cube maker

Basic introduction information.

How on earth do we get the "contents" box?

Mode of Operation

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.

Bill of Materials

Part #	Part Name	Qty	Function	Weight (Ounces)	Material	Manufacturing Process	Photo
01	Outside Cover	1	Protect machinery	2	PVC	Injection Molded
02	Inside Cover	1	Protect machinery	2	PVC	Injection Molded
03	Ice ejector gear	1	Connect the ice ejector to the switches	0.1	Plastic	Injection Molded
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
06	Ice ejector	1	Rotate to push ice out of tray and into bin	1	Plastic	Injection Molded
07	Outer plate	1	Separate and support the mechanical components from the electrical wires	3	Steel	Blanked and machine finished
08	Switch	3	Synchronize the mechanical elements	0.2	Plastic, Steel	Purchased
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
11	Arm Spring	1	Transfers arm motion to CAM	<0.1	Steel	Purchased
12	CAM	1	Stops ice ejector shaft from rotating	3.2	Steel	Cast and finish machined
13	Thermocouple	2	Switch on/off power to the heater	0.1	Various	Purchased	-
14	Thermopaste	enough	Transfer heat	<0.1	Thermal Paste	Purchased
15	Heater	1	Heats tray to allow ice to be removed	3	Aluminum, Stranded Electrical Wire, Plastic	Purchased
16	Ice Tray	1	Holds water while it freezes to become ice	14.5	Metal, Unknown	Casted
17	Ice shield	1	Keeps ice cubes from rotating back into the tray, guides ice cubes into bin	1.1	Plastic	Injection Molded
18	Ice Bin	1	Collects and stores ice cubes	16.5	PVC	Injection Molded
19	Electrical Wires	6	Transfer electricity	<0.1	Plastic & Stranded Electrical Wire	Purchased
20	Electrical Wire Cap	X	Joins wires together and covers the connection	<0.1	Plastic	Molded
21	Water Inlet	1	Collects water and guides it into the ice tray	0.5	Plastic	Injection Molded
22	Screws and bolts, nuts, & washers	17	Attach parts and keep them in place	<0.1	Steel	Purchased

**Note: Some assemblies and parts were not disassembled in order to avoid destroying the parts.

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 best method for reducing the ecological impact of our product is to decrease the amount of power used in the manufacturing process. Making this more efficient could potentially cut down significantly the amount of greenhouse gases emitted. Additionally, if the transportation of parts and finished product were made more efficient this would be better for the environment.

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 injection molding efficiency. The process has been identified as injection 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.

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 mostly injection molded. The side panels and outer assembly, as well as the gears and brackets, 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 12-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.

Mechanical Analysis

Thermal FEA Analysis

We used an FEA thermal analysis to find that it takes approximately 5.50 hours for an ice cube to freeze in an aluminum tray. 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.

Analysis Methods

ANSYS Workbench was used to perform the analysis. A Transient Thermal simulation was performed on the model illustrated below (Fig. 1).

The analysis made several assumptions but found a fairly reasonable answer compared to what we were able to get with simple analytical solutions. First, we modeled just one ice cube in one tray. This could have been expanded but computational time would have increased greatly. We assumed that because of the high conductivity of aluminum that the heat transfer would be dominated by the surroundings and each ice cube would have only a small effect on adjacent cubes. Second, we assumed material properties consistent with those found in Heat Transfer, 9th Edition (J. P. Holman). Third, we assumed that the thermal properties of water remain the same as it freezes. Details of the simulation can be seen below (Table 1).

Table 1 – Transient Thermal Analysis Details

Mesh Details
Number of Elements	17008
Number of Nodes	34039
Transient Analysis Details
Minimum Step Size	10
Maximum Step Size	100
Initial Conditions
T∞ (°C)	-16.10
T0,water (°C)	22.00
T0,air (°C)	-16.10
T0,tray (°C)	22.00
Results
Ice Freezing time (hours)	5:33
Computation time (hours)	0:38

Results

This analysis gives a good estimate of the time that it takes for our evaluated design to freeze. Even more importantly the analysis allows us to easily import our models and compare our design before building a prototype. This will allow us to validate our design before implementing it.

Below is an illustration (Fig. 2) that shows the temperature distribution at the moment that the ice cube becomes completely frozen. Another illustration (Fig. 3) shows the maximum temperature with respect to time.

Major Stakeholders and Needs

• Customer
  • need
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• Dogs
  • need
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