Automatic pet feeder

From DDL Wiki

Executive Summary

Stakeholders and Needs

Product Usage

Insert 3 D cell batteries, or plug a DC power convertor into the feeder. Align the hopper with the base to allow insertion, then twist to lock in position. Inser the bowl into the feeder base, connecting the hooks inside the base. Fill the hopper from the top with pet food and align the lid to the hopper using the arrows. Insert the lid and twist. Food must be dog or cat food, and cannot be a treat, canned food, or moist.

Turn the feeder on using the switch on the bottom. The feeder can be scheduled to provide three meals of varying sizes per day. Each meal is adjusted with 0.25 cup increments. To set meals and schedule, hold the ENTER button for 2 seconds. Using the up and down arrows, select the meal you would like to edit with the ENTER button. This will allow you to edit the time of the meal, followed by the meal size, if changes are desired. Once all meals are edited, press ENTER and the feeder will reenter the automated feeding mode. To manually feed the pet, hold the up arrow button and the feeder will provide a meal the size of the scheduled breakfast meal.

Mechanical Function

The fins in the feeder base rotate, able to move 1 cup of food in a full rotation.

The image above is a profile of the fin section of the feeder. The hopper containing the food is located directly above the fin section, thus providing the food from that location. The bowl is located at the bottom left of the diagram. The opening at the bottom left allows food to drop into the bowl.

The feeder base contains four sets of fins, each connected to an axis parallel to the floor. Gravity pulls pet food from the hopper into the fin section at the highest point of rotation. At the time of a meal, the motor rotates a worm gear, which rotates a gear in a timing belt system. One end of the belt receives rotation from the motor, and causes rotation of the fins. This provides food to the bowl since each quarter rotation transports 1/4 cup of food. Limit switches allow the motor to provide only the scheduled amount of food preset by the user. For example, if programmed to give 1/2 cup for lunch, the motor will stop rotating after the amount of two fin sections are dropped into the bowl. Keep in mind that the volume between two adjacent fins is 1/4 of a cup. The food is transported to an area where it can drop into the bowl hooked to the bottom of the base.

Mechanical Analysis

Bill of Materials

Part #	Name	Qty.	Material	Manufacturing	Weight	Function	Photo
01	lid	1	plastic	molding	203g	provide a cover for food storage to ensure freshness and prevent pet from eating from the top
02	hopper	1	plastic	molding	223g	reservoir of food used to feed
03	dish	1	plastic	molding	219g	holds portioned food for pet to eat
04	battery cover	1	plastic	molding	17g	protects and supports batteries
05	black screw	4	metal	purchased	<1g	hold parts together
06	gold screw	4	metal	purchased	<1g	hold parts together
07	silver screw	2	metal	purchased	<1g	hold parts together
08	display cover	1	clear plastic	molding	13g	second layer to protect digital display and to smooth the look of the outside of feeder
09	tiny gold screw	2	metal	purchased	<1g	hold parts together
10	tiny silver screw	6	metal	purchased	<1g	hold parts together
11	display buttons	1	plastic	molding	<1g	allow user to interface with electrical equipment from the outside of the feeder
12	screen plate	1	plastic	molding	8g	first layer to protect digital display screen
13	display faceplate	1	plastic	molding	31g	protects the electrical gear and digital plate and provides a finished look to the product
14	gold screw	3	metal	purchased	<1g	hold together the main gear apparatus
15	'eyeglass' black screw	2	metal	purchased	<1g	hold parts together
16	fastening bracket for #15	2	nylon	casting	<1g	provides a base for the #15 screws to attach to
17	pulley bands	2	plastic	casting	<1g	transfers energy from motor to gear base to turn spinner blades
18	worm gear assembly	1	asst.		7g	transfers energy and motion
19	silver screw (round head)	2	metal	purchased	<1g	hold parts together
20	silver screw (flat head)	4		metal	purchased	hold parts together
21	spinner cover half (no mount)	1	ABS	molding	53g	acts as a guide for the food into the dish and protects and houses the spinner apparatus
22	spinner blades	4	plastic	molding and cutting	<1g	portion out food and then turn to allow food to drop into dish
23	spinner axle	4	plastic	molding	6g	base for spinner blades and thing that is torqued to move blades
24	bushing/bearing	1	plastic	purchased	<1g	provide spacing and reduce friction
25	spinner gear	1	nylon	casting	5g	turn spinner axle
26	long silver screw	2	metal	purchased	<1g	hold parts together
27	motor mount	1	plastic	molded	7g	to provide a stable place for the motor to attach
28	spinner cover half (with mount)	1	plastic	molding	57g	acts as a guide for the food into the dish and protects and gives a mount for the spinner apparatus
29	base	1	plastic	molding	146g	mount for all of the machine. is the weight that keeps it upright and connects the pieces together
30	circuit board	1	asst.	asst. purchased	99g	all electrical equipment for using outlet power and telling motor when to move
31	limit switch	1	asst.	asst. purchased	<1g	limits motor movement
32	motor	1	asst. metal	asst. purchased	37g	provides transfer of electrical to mechanical energy for system
33	on/off switch	1	plastic	molding	<1g	user interface to shut machine off

Design for Manufacturing and Assembly

The dog feeder is already manufactured very simply and efficiently. The part count is low and only necessary parts were manufactured. The design is very simple. Most parts are plastic and thus easily manufactured with casting or molding, which is the method chosen. The material should not be changed because plastic is the most logical choice for reasons of cost and ease of manufacturing. Any change in material would spike the price of the machine.

Failure Modes and Effects Analysis

Design for Environment

Team Member Roles

Lauren Walch - DFMA and Bill of Materials (BOM)

References